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Mechanisms Sensing and Modulating SignalsArising From Cell Swelling

Martin Jakab1, Johannes Fürst1, Martin Gschwentner1, Guido Bottà2,Maria-Lisa Garavaglia1,2, Claudia Bazzini2, Simona Rodighiero2,Giuliano Meyer2, Sonja Eichmüller1, Ewald Wöll3, Sabine Chwatal1,Markus Ritter1 and Markus Paulmichl1,2

1 Institute of Physiology, University of Innsbruck, 2 Department of Physiology and Biochemistry, Universitàdegli Studi di Milano, 3 Department of Internal Medicine, University of Innsbruck

Markus Paulmichl or Markus RitterInstitut für Physiologie, Universität InnsbruckFritz Pregl-Str. 3, A-6020 Innsbruck (Austria/Europe)Tel. +43 512 507 3766, Fax +43 512 507 2853E-Mail [email protected], or: [email protected]

Introduction

The canonical strategy for the cells of different or-ganisms to defend against swelling of the cytoplasm isto promote cellular water efflux via osmosis, therebyleading to a reduction of the excess cellular volume. Thisis called regulatory volume decrease (RVD) and is af-fected by the release of organic and/or inorganic intra-

Key WordsCell volume regulation • Swelling • RVD • hypotonic-ity • RVDC • Signal transduction • Ion channels

AbstractCell volume alterations are involved in numerous cel-lular events like epithelial transport, metabolic proc-esses, hormone secretion, cell migration, prolifera-tion and apoptosis. Above all it is a need for everycell to counteract osmotic cell swelling in order to avoidcell damage. The defence against excess cell swell-ing is accomplished by a reduction of the intracellularosmolarity by release of organic- or inorganicosmolytes from the cell or by synthesis of osmoticallyless active macromolecules from their specificsubunits. Despite the large amount of experimentaldata that has accumulated, the intracellular mecha-nisms underlying the sensing of cell volumeperturbations and the activation of volume compen-satory processes, commonly summarized as regula-tory volume decrease (RVD), are still only partly re-vealed. Moving into this field opens a complex sce-nario of molecular rearrangements and interactionsinvolving intracellular messengers such as calcium,phosphoinositides and inositolphosphates as well as

phosphorylation/dephosphorylation processes andcytoskeletal reorganization with marked cell type- andtissue specific variations. Even in one and the samecell type significant differences regarding the activatedpathways during RVD may be evident. This makes itvirtually impossible to unambigously define commonsensing- and sinaling pathways used by different cellsto readjust their celll volume, even if all these path-ways converge to the activation of comparatively fewsets of effectors serving for osmolyte extrusion, in-cluding ion channels and transporters. This review isaimed at providing an insight into the manifold cellu-lar mechanisms and alterations occuring during cellswelling and RVD.

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cellular osmolytes. To achieve this goal, ions, amino ac-ids, sugars or alcohols are released from the cytosol byspecific transport molecules embedded in the cell mem-brane or via exocytosis. Another strategy to reduce in-tracellular osmolarity is to generate osmotically less ac-tive macromolecules from a pool of abundantly avail-able molecular subunits. A crucial and still open ques-tion is, how cytoplasmatic swelling is transduced intocellular osmolyte reduction. The influence of cell swell-ing on cellular processes is manifold including alteredlevels of intracellular messengers, alterations of the in-tracellular pH, phosphorylation/dephosphorylation proc-esses and cytoskeletal rearrangements with a consider-able cell type-dependent variance regarding the observedcellular responses. This review will focus on mechanismsand cellular processes sensing and modulating signalsthat arise from cell swelling.

Phosphoinositides and inositolphosphates

Phosphoinositide (PI) metabolism is mainly affectedby activation of the phosphatidylinositol-3-kinase (PI-3K) and by promoting hydrolysis of phosphatidylinositol-(4,5)-bisphosphate (PI(4,5)P2) (Fig. 1). PI-3K generatesfour different lipid products: phosphatidylinositol-3-phosphate (PI(3)P), phosphatidylinositol-(3,4)-bisphosphate (PI(3,4)P2), phosphatidylinositol-(3,5)-bisphosphate (PI(3,5)P2) and phosphatidylinositol-(3,4,5)-trisphosphate (PI(3,4,5)P3). The latter is mainlyformed from PI(4,5)P2. Hydrolysis of PI(4,5)P2 by phos-pholipase C (PLC) leads to the formation of inositol-(1,4,5)-trisphosphate (Ins(1,4,5)P3) and 1,2-diacylglycerol (DAG) [1, 2]. These signaling moleculesare tightly interrelated and connected to an array of down-stream transduction- and effector molecules.

The mechanisms by which PI-3K is activated mightarise from a direct action of the volume stimulus on theenzyme, via volume sensitive ion channels, G-proteinsand/or auto/paracrine stimulation of cell membranereceptors. It is important to note, that the phosphoryla-tion of PI on the 3’position of the inositol ring by PI-3Kdepends strongly on the membrane curvature, suggest-ing that its activity is regulated by mechanical membranedeformation and could hence be modified by cell swell-ing [3].

PI-3K activates several transduction pathways likethe protein kinase B (PKB/Akt)-PDK1-BAD cascade in-volved in regulation of apoptosis, the targets of rapamycin

(TOR)-p70/S6 kinase, E4-bindig protein cascade in-volved in regulation of cell proliferation, the proteintyrosin kinase BTK, the GRP-1 exchange factor for pro-teins of the ARF family, activation of mitogen activatedkinases (MAPK) and of PKC [2, 4].

In liver cells, swelling eliceted by hypotonicity aswell as by uptake of amino acids or by insulin has beenshown to stimulate PI-3K [5]. In Mz-Cha-1 humancholangiocarcinoma cells, cell swelling is followed byactivation of PI-3K, ATP release and a Cl- conductancein the cell membrane. The ATP release is inhibited byPI-3K inhibitors and volume-sensitive current activationis inhibited by intracellular dialysis with antibodiesagainst PI-3K. Similarly, in normal rat cholangiocytemonolayers, cell swelling stimulates luminal Cl- secre-tion via a PI-3K pathway. Intracellular application of thesynthetic lipid PI-3K products PI(3,4)P2 and PI(3,4,5)P3activates Cl- currents under isotonic conditionsresembeling those observed after cell swelling. This in-dicates that swelling-induced activation of PI–3K andthe generation of lipid messengers modulatecholangiocyte ATP release, Cl- secretion and bile forma-tion [6]. These PIs are barely detected in resting livercells, but they are rapidly produced in response to cellswelling. The PI-3K product PI(3,5)P2 was first identi-fied as a nonabundant phospholipid whose levels increasein response to hyperosmotic stress close to concentra-tions of other PIs. This suggests that PI(3,5)P2 plays amajor role in osmotic stress response, perhaps via regu-lation of vacuolar volume [7]. In monkey COS-7 cellshypotonic stimulation leads to the formation of PI(3,5)P2via PI-3P-5K [8]. Since PI(3,5)P2, PI(3,4)P2, PI(4,5)P2and PI(3,4,5)P3 can bind pleckstrin homology (PH) do-mains of different proteins, including actin associatedproteins [9], these PIs can act as an important link be-tween different signalling pathways involved in the com-plex scenario activated by cell swelling.

In neutrophil granulocytes PI-3K and PI(3,4,5)P3 arerequired for the respiratory burst mediated by theNADPH-oxidase complex [10]. Cell swelling has beenshown to trigger respiratory burst per se and to exert apriming effect on the triggering of respiratory burst withdifferent stimuli [11]. Hypertonicity exerts an oppositeeffect [12, 13]. Induction of oxidative burst by hypoto-nicity was also investigated in detail in suspended to-bacco cells. In these cells respiratory burst requires theactivation of stretch-activated channels, Ca2+ as well ascellular Cl- exit via Cl- channels and it is blocked by in-hibitors of Cl- channels, inhibitors of PKC, cyclin-

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dependent kinases and MAP kinases [4]. One of the func-tional consequences of the respiratory burst is an intrac-ellular acidosis with subsequent activation of the Na+/H+ exchanger and cell swelling, which is a prerequisitfor chemotaxis in neutrophil granulocytes [14].

Besides the activation of PI-3K, PIs are alsosubstrates for PLC and PI-directed phospholipase D(PLD). These enzymes modify the amount of membranePIs and convert them to DAG and soluble inositolpolyphosphates, which act as second messengers. In somecells, the activities of PLC and PLD have been shown tobe susceptible to cell swelling: MDCK cells respond tocell swelling with a rapid dissociation of PLC-!1 fromthe plasma membrane and this is paralleled by PI break-down [15]. Thus, cell swelling can promote the hydroly-sis of PI(4,5)P2 and the generation of Ins(1,4,5)P3.Ins(1,4,5)P3 is rapidly metabolised to Ins(1,3,4,5)P4 bythe Ins(1,4,5)P3 3-kinase. Both Ins(1,4,5)P3 andIns(1,3,4,5)P4 have profound effects on cellular Ca2+

homeostasis as outlined below. In addition, by its link-age to actin, PI(4,5)P2 hydrolysis will lead to a remodelingof the cytoskeleton (see below).

Ins(1,4,5)P3 is converted to Ins(1,3,4,5) P4 and toIns(1,3,4)P3, which inhibits the Ins(3,4,5,6)P4-1-kinase.Thus an increase of Ins(1,4,5)P3 may lead to a rise in thelevel of Ins(3,4,5,6)P4. In colonic T84 epithelial cellsIns(3,4,5,6)P4 inhibits a Ca2+/CaMKII-sensitive Cl- chan-nel, but the molecular identity of this channel within thenative cell is yet unknown.

Ins(1,4,5,6)P4 has been brought in conjunction withCl- transport, since the Salmonella virulence proteinSopB, which exhibits inositol polyphosphatase activityand which is able to generate Ins(1,4,5,6)P4, stimulatescellular Cl- influx when overexpressed in human embry-onic kidney (HEK) 293 cells [1]. The effect ofIns(1,4,5,6)P4, Ins(3,4,5,6)P4 and Ins(1,3,4,5,6)P5 on theanion channels/currents activated during RVD (RVDC)has been investigated in endothelial (CPAE) cells: TheRVDC amplitude is strongly reduced in cells loaded withIns(3,4,5,6)P4 or Ins(1,4,5,6)P4, while Ins(1,3,4,5,6)P5 iswithout effect. Both Ins(3,4,5,6)P4 and Ins(1,4,5,6)P4 in-hibit a GTP-"S induced current with properties similarto RVDC. The authors speculate of that the effects ofIns(3,4,5,6)P4 may represent an inhibitory pathway forRVDC in endothelial cells after sustained receptor-me-diated activation of PLC [16]. There is, however, no ex-perimental evidence for such a mechanism (Figs. 1, 3).

Arachidonic acid and eicosanoids

Arachidonic acid (AA) – the most abundanteicosanoid - is released from cell membranephospholipids by the action of phospholipases (PLA2,PLC, PLD/diglyceride lipase) (Fig. 2). It is rapidlymetabolised to prostaglandins, prostacyclins andthromboxanes by cycloxygenase (COX), to leukotrienesand HETE by 5-lipoxygenase (5-LOX), to hepoxylinsby 15-lipoxygenase (15-LOX) and to epoxyeicosatrienoicacid and hydroxyeicosatetraenoic acid by cytochromeP-450 (epoxygenase). AA and its derivatives are formedin response to hormone-, neurotransmitter-, or growthfactor stimulation and exert their physiological effectsas intracellular or parakrine messengers. In various cellsystems changes of RVDC properties upon cell swellinghave been correlated with altered intracellular eicosanoidconcentrations [17, 18].

PLD catalyses the hydrolysis of phosphatidylcholineto generate the lipid second messenger phosphatidic acid(PA). PLD activity in mammalian cells is activated byligands of G-protein coupled receptors, receptor- andnon-receptor tyrosin kinases. PLD activity can hence bemodulated by several stimuli generated during osmoticstress. In MDCK cells elevation of intracellular Ca2+ (Cai)leads to the activation of PLD resulting in the formationof PA and DAG [19]. Two mammalian PLD enzymes(PLD1 and PLD2) have been cloned and their intracel-lular regulators identified as ARF and Rho proteins,PKC# as well as PI(4,5)P2 [20]. Although in mamma-lian cells no reports on the influence of cell swelling onPLD activity are available yet, in the protozoon Leish-mania donovani PLD activity is reported to increase uponboth cell swelling and cell shrinkage[21]. Two isoforms,PLD1 and PLD2, are present and an analysis of their invitro activities revealed that either hypotonicity or hyper-tonicity causes an increase in PLD1 activation but a re-duction in PLD2 activity with predominance for PLD1.The enzymatic activity during acute hyposmotic shockis accompanied by tyrosyl phosphorylation of the PLD1isoform, suggesting osmotic control by protein tyrosinekinase [21].

For PLA2 a mechanosensor function is discussed,since its activity depends on the degree of lateral packingin the membrane and hence on membrane stretch inducedby osmotic forces [22]. Taking into account that PLA2and 5-lipoxygenase are both activated by Ca2+, cellswelling-induced rises of intracellular Ca2+ might providea trigger for the activation of these enzymes. PLA2-

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induced phospholipid breakdown is enhanced by cellswelling in human platelets [23], Ehrlich ascites tumorcells (EATC) [24] and human neuroblastoma cells [25].

Fig. 1. Phosphoinositide- andinositolphosphate metabolites canact as transmitters and effectors ofcell-swelling-induced signals. Themetabolic pathways and the targetsinvolved in the cell volumeregulatory response vary amongdifferent organisms and cells.

Fig. 2. Arachidonic acid andeicosanoids can act as transmittersand effectors of cell-swelling-induced signals. The signalingcascades involved in the cell volu-me regulatory response vary amongdifferent organisms and cells.Phospholipase A2 (PLA2) may beactivated as a direct response tomembrane stretch. Beside directactions of the lipids, elevatedintracellular calcium frequentlyacts as a second messenger.

In EATCs hypotonic exposure induced the translocationof cytoplasmic PLA2# to the nuclear fraction, which isfollowed by increased AA release [26]. Inhibition of

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PLA2 impedes RVD in different cell types such as humanplatelets [23], neuroblastoma cells [25], mouse distalcolon cells [27], rat cerebral cortex [28] and collectingduct principal cells [29]. In the latter cell type theinhibition of PLA2 blunts the activation of cell volumeregulatory Ca2+-activated K+ channels, which - on theother hand - are activated by AA. In pigmented ciliaryepithelial cells [30] and bovine chromaffin cells [31]PLA2-inhibition prevents the activation of the RVDC.In MDCK cells PLA2 is also involved in the synthesisof the organic osmolyte glycerophosphorylcholine (GPC)that is derived from choline via PC and its activationappears to result from a caffeine sensitive, ryanodine-inhibitable increase of Cai [32].

Direct effects of AA on cell volume regulatorypathways have been described. The mechanosensitiveK+ channels TREK-1, TREK-2 and TRAAK are openedby membrane stretch as well as by AA and other poly-unsaturated fatty acids [33, 34]. In heart cells and ratneuronal cells it activates mechanosensitive K+ channels[35, 36]. In contrast, AA inhibits RVDC in a variety ofcells, most likely by direct action on the channels [37-39].

The involvement of lipoxygenase products in theRVD response has been tested in a variety of cells [18].Hepoxilin A3 activates volume regulatory K+ channelsin platelets [40]. LTD4 activates volume regulatory K+-and Cl- channels in EATCs [41]. In these cells as well asin fish erythrocytes volume regulatory taurine release isstimulated by LTD4. In trout renal proximal tubule cells,colonic epithelium, chromaffin cells, MDCK cells andhuman fibroblasts lipoxygenase products are alsoinvolved in RVD. In EATCs the swelling-inducedincreased formation of LTD4 is accompanied by adecreased formation of PGE2, which may lead to aninhibition of Na+channels [18]. Volume regulatory K+

channels are activated by PGE2 in ciliary epithelial cells[42]. Ketoconazole, a blocker of lipoxygenase- andcytochrome P-450 enzyme systems, inhibits the releaseof organic osmolytes from renal papillary cells, MDCKcells and C6 glioma cells [43-45]. Since in C6 cells thiseffect can not be reversed by addition of HETEs, thiseffect on osmolyte flux is most likely not due to aninhibition of epoxygenase, but rather due to a direct blockof an efflux pathway. In agreement with this findingketoconazole inhibits RVDC and swelling-inducedcellular taurine release either directly or by drug-induceddepletion of cellular ATP [46]. In Necturus gall bladderketoconazole leads to a net electrolyte influx bystimulating NaCl entry, which counteracts RVD and leads

to cell swelling [47]. In EATCs obtained from mice withan enhanced dietary intake of polyunsaturated fatty acids,increased formation of leukotrienes, net loss of Cl- andaccelerated RVD during hypotonic exposure are observed[18, 39, 48].

Membrane stretch

Increased cell membrane tension may lead to theactivation of mechanosensitive- or stretch-activated ionchannels (SACs) (Fig. 3). SACs are ubiquitous in plantand animal cells where they act as transducers for forcesderived from osmotic gradients and shear stress [49].SACs are most commonly cation selective (permeableto Ca2+ and monovalent cations like Na+ and K+),however, also anion selective SACs have been described.Most of the SACs are not voltage gated or dependent onintracellular Ca2+ and are inhibited by Gd3+ [50]. Sincethe activation of cation selective SACs leads to Na+- andCa2+ influx at negative membrane potentials, they areobviously not directly contributing to RVD but rathertend to cause cell swelling. The signals promoting RVDcould, however, arise from the Ca2+ influx into the cellvia SAC and include, for instance, the activation of Ca2+-activated K+ and Cl- channels [39]. In rabbit ventricularmyocytes Gd3+ reduced the amount of swelling inhypotonic solutions and induced RVD, which was notobserved in the absence of the blocker [51]. This is incontrast to the inhibition of RVD observed in renal A6cells upon Gd3+-block of Ca2+ influx through SAC [52].In cell-attached patches from Necturus proximal tubule,basolateral K+ selective channels with similar singlechannel kinetics could be activated by either pipettesuction or cell swelling [53]. In the amphibian proximaltubule a voltage-gated stretch-activated K+ channel hasbeen described in the basolateral membrane [54]. Excisedmembrane vesicles from Xenopus oocytes exhibit volu-me as well as stretch-sensitive SAC. The volumesensitivity of these channels might involve membraneadhered cytoskeletal elements but the used techniqueexcludes the involvement of freely diffusible messengers[55]. In the yeast Saccharomyces cerevisiae the MID1gene product (Mid1) is required for Ca2+ influx into thecell. Functional expression of Mid1 conferred sensitivityto mechanical stress on Chinese hamster ovary (CHO)cells, which resulted in an increased Ca2+ conductanceand elevated Cai. These increases depended on thepresence of extracellular Ca2+ and were inhibited by Gd3+.Single-channel analysis demonstrated, that Mid1 can act


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as a Ca2+-permeable, cation-selective stretch-activatedchannel with a conductance of 32 pS [56]. Membranestretch, AA and polyunsaturated fatty acids (see above)open the K+ channels TREK-1, TREK-2 and TRAAK,which are outwardly rectifying in physiological K+

gradients and have unitary conductances of 100 pS(TREK-1/2) and 45 pS (TRAAK). Mechanical activationof TRAAK is induced by a convex curvature of the pla-sma membrane (negative pressure in the inside-out patchclamp configuration or positive pressure in the outside-out configuration) and can be mimicked by trinitrophenol- induced membrane crenation. Cytoskeletal elementsinteract with TRAAK since the disruption of thecytoskeleton potentiates TRAAK channel opening bymembrane stretch. Membrane depolarization activatesTRAAK and the channel is blocked by Gd3+ [33, 34, 57-59]. Stretch-sensitive Cl- channels with an almost linearIV relation of single channel currents and a unitaryconductance of about 140–170 pS were demonstrated ina small group of cultured human corpus cavernosummuscle cells [60]. Membrane stretch elicited an ATPdependent, outwardly rectifying Cl- current withoutvoltage-dependent gating in murine microglia, which wasblocked by the Cl- channel blockers DIDS, SITS andNPPB. Each of these Cl- channel blockers reversiblyinhibited the transformation of microglia from theiramoeboid into the ramified phenotype; it is thereforesuggested that functional stretch-activated Cl- channelsare required for the induction of ramification but not formaintaining the ramified shape [61].

Intracellular calcium (Cai) levels

The role of Cai in RVD has been investigated invarious cell types and tissues under diverse experimen-tal conditions. Cell swelling leads to an increase of Caiin some cells, whereas it does not alter Cai in others [62-67]. In MDCK cells for example, changes in Cai wereonly detected after a 50% reduction of the extracellularosmolarity, while moderate cell swelling did not meas-urably increase Cai. Ca2+-activated K+ channels, however,were fully activated by moderate cell swelling, indicat-ing localised Cai elevations near the cell membrane [68].A general problem of fluorescence aided Cai measure-ments is the fact, that concentration changes of Cai, evenif they are functionally significant, could be underesti-mated or even escape detection. Cell swelling promotesboth the Ca2+ entry into cells and the release of Ca2+ fromintracellular stores. In hepatocytes osmotic swelling

transiently increases Ins(1,4,5)P3 [69] and swelling, in-duced by the uptake of amino acids has also been shownto lead to a sustained elevation of Ins(1,4,5)P3 [70]. Simi-larly, Ins(1,4,5)P3 and Ins(1,3,4,5)P4 increase Ca2+ in rab-bit proximal tubule cells [71]. Mechanical stimulationof airway epithelial cells leads to an increase in Cai par-tially due to release of Ca2+ from Ins(1,4,5)P3-sensitivestores [72]. In contrast, Ca2+ release from internal storesduring RVD in IMCD cells proved not to be mediated byIns(1,4,5)P3 [73, 74]. In TALH cells, swelling promotesCa2+-induced Ca2+-release [75]. Several pathways forswelling-induced Ca2+ entry have been described. Stretch-activated ion channels (SACs) serve for Ca2+ entry inosteoclasts [76]. HTC rat hepatoma cells elevate Cai bycapacitative Ca2+ entry (CCE) [77]. In MDCK cells ca-pacitative CCE-independent (most likely SACs) and CCEseem to provide influx pathways that can be upregulatedby overexpression of the oncogene bcl-2 [68, 78]. Fur-thermore, dihydropyridine sensitive pathways [79] andNa+/Ca2+ exchange [80] serve to increase Cai. RVD- andCai responses of quiescent, non-proliferating and prolif-erating prostate cancer cells are different, probably dueto differences in the cytosolic content and organisationof F-actin. In multicellular spheroids of prostate cancercells only proliferating cells exhibited RVD and Cai tran-sients. The latter were independent from extracellularCa2+, and inhibition of the endoplasmatic reticulum (ER)Ca2+-ATPase abolished swelling-induced Cai transientsand RVD, indicating that Ca2+ release from intracellularstores is necessary for RVD in these cells. Both the risein Cai and RVD were dependent on intact microfilaments[81]. In accordance with this finding, the block of theER Ca2+ pump in LNCaP prostate cancer epithelial cellsby thapsigargin leads to an impaired RVD response. Thisimpairment of RVD could be attributed to an inhibitionof the swelling-dependent Cl- current, which seems tobe caused by a yet unknown inhibitory effect of Ca2+

ions entering the cells from the extracellular medium viastore-operated Ca2+ channels (SOCs). In the absence ofthapsigargin, however, the swelling-dependent Cl- cur-rent and RVD response of these cells is independent ofintra- and extracellular Ca2+ levels [82].

Cai may also increase as a result of ATP releaseduring RVD, subsequently followed by an auto/paracrineactivation of purinergic receptors [30, 83-86]. The in-crease in Cai may support RVD by activating Ca2+-acti-vated K+ channels [62, 87], by remodeling the cytoskel-eton (see below) or by promoting exocytosis of osmolytes[88]. In intestinal epithelial cells increased Cai causedby cell swelling plays a permissive role for the activa-



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Fig. 3. Cell volu-me regulatory pa-thways and targetsactivated by stretchof the cell membra-ne. Stretch-activa-ted ion channels(SAC) may be acti-vated as a direct re-sponse to membra-ne stretch.

Fig. 4. Interaction of intracellular calcium, intracellular pH, membrane potential and autokrine/paracrine ATP binding on cell swellingregulated ion transport. The depicted pathways represent a synopsis of strategies utilized by different cells or organsims. The cellularresponses of different cells to swelling may vary considerably. This indicates that swelling signals are not transduced by a uniformelyoperating cellular machinery, but that each cell rather utilizes an individual set of pathways to achieve volume reduction.


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tion of RVDC [89], whereas in human cervical cancercells hypotonicity-induced elevation of Cai by entry fromthe extracellular medium is a prerequisite for normalRVD [90]. In the latter cell type the hypotonicity-inducedCa2+ signalling and the swelling-dependent Cl- and tau-rine release were found to require myosin light chainkinase (MLCK) activity, but did not correlate with MLCphosphorylation, which implies that MLCK controls Ca2+

signalling by an MLC phosphorylation-independentmechanism [90].

Extra- and/or intracellular Ca2+ is critical for thecation over anion selectivity of native RVDC. Similarlythe cation over anion selectivity of reconstituted IClnion channel protein, a molecular candidate for RVDC, isCa2+-dependent [91-93]. Hypotonicity-induced secondmessenger independent Ca2+ release via a passive leakpathway from internal, non-mitochondrial stores has beenshown in A7r5 cells [94]. Indirect evidence indicates thatcellular Ca2+, extruded during swelling-induced increaseof Cai via Ca2+-ATPases, may act as an autocrine/paracrine signal by binding to the extracellular Ca2+/poly-valent cation receptor (CaR), which in turn leads to a G-protein mediated increase in cellular cAMP and subse-quent activation/facilitation of RVDC [86]. Ha-rasoncogene expressing NIH 3T3 fibroblasts exhibit stimu-lated Ins(1,3,4,5)P4 sensitive and CCE mediated Ca2+

influx and develop oscillations of Cai upon mitogenicstimulation, which are inhibited by hypotonic cell swell-ing [95-97].

Protein phosphorylation

Cell swelling and mechanical stress induce phos-phorylation cascades involving phospholipid-dependentprotein kinase C (PKC), PKA, protein tyrosine kinases(PTKs), mitogen activated serine/threonine kinases(MAPKs), PI-3K and others [39]. In many cases phos-phorylation events seem to be the molecular switch forRVDC activation, in other cases the phosphorylation ofchannel proteins involved in RVD, of accessory proteinsand/or cytoskeletal elements – though not needed forcurrent activation per se – can exert a modulatory effecton channel function. Elevation of cytosolic DAG uponcell swelling has been observed in skate red blood cells,EATCs and hepatocytes. Regarding the effect of PKCon RVDC a number of partly controversial reports havebeen published. Depending on the cell type studied, PKCeither exerted an activating or inhibiting effect on RVDC,or was found to have no effect on RVDC at all [5, 38,39]. In canine atrial myocytes activation of PKC by the

porbol ester 4$-phorbol 12,13-dibutyrate (PDBu) causedstimulation of the swelling-induced Cl- current, an ef-fect which was inhibited by bisindolylmaleimide I [98].PKC inhibition or stimulation by a phorbol ester signifi-cantly reduced or stimulated hyposmotically-inducedtaurine release from rat cerebral cortical neurons, respec-tively [28]. Hypotonicity-stimulated Cl- currents in pig-mented ciliary epithelial cells were abolished by PLC-,PLA2- as well as PKC-block. Since the block of PLA2not only prevented the development of the current butalso inhibited the current once activated by hypotonic-ity, the PLC-PKC-pathway obviously regulates thePLA2-eicosanoid pathway in these cells [99]. In HeLacells RVDC are not modulated by PKC-dependent phos-phorylation. Transient expression of human multidrugresistance/P-glycoprotein (MDR/P-gp), however, confersPKC sensitivity on these channels, suggesting a regula-tory role of P-gp on the endogenous Cl- channel in HeLacells [100]. The PKC blocker staurosporine activatesRVDC in nonpigmented ciliary epithelial cells under isos-motic conditions [101] and the PKC-activator PDBu in-hibits RVDC in rat brain endothelial cells [102].

Several external stress signals including osmoticstress are known to activate PTKs such as Pyk2, whichcan directly phosphorylate ion channels or KCEcotransport or further activate the MAP kinase pathway[103-105]. A role of tyrosine phosphorylation in the vol-ume-related signaling is also suggested for a variety ofother PTKs, which phosphorylate in response to cellswelling, such as p125FAK, p56lck and p72syk, but the ob-servations made in different cell types vary considerably.Studies on astrocytes, vascular endothelial cells, dogatrial myocytes, human prostate- and cervical cancer cellsand intestine 407 cells have shown a potent inhibitoryeffect of the PTK blockers genistein, herbimycin A ortyrphostins on glutamine, Cl- and taurine fluxes and, cor-respondingly, a current potentiation by the tyrosine phos-phatase inhibitor orthovanadate [106-113]. p56lck is sen-sitive to cell volume [114-116]. In p56lck-deficient lym-phocytes the osmotic activation of the swelling-activatedCl- current was found to be impaired. Retransfection ofp56lck or intracellular application of the kinase led tocurrent activation even in the absence of cell swelling[117]. In accordance with these findings Pedersen et al.[118] could show an inhibition of the osmosensitive tau-rine efflux by genistein and its potentiation by vanadatein NIH3T3 mouse fibroblasts. Interestingly, in L-fibro-blasts, another mouse fibroblast cell line, the inhibitionof protein tyrosin phosphatases results in the suppres-sion of both RVD and volume-sensitive Cl- current [119].



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Similarly, pervanadate was found to suppress this cur-rent in bovine chromaffin cells [120].

The family of MAPKs gives rise to parallel, inter-related enzymatic pathways, which are activated by ex-tracellular signals including growth factors and stresssignals like heat shock, UV radiation and osmotic per-turbations. The three commonly described phosphoryla-tion cascades lead to the activation of p38 kinase, extra-cellular signal regulated protein kinases 1 and 2 (Erk1/Erk2) and the stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK). Hypoosmotic stress hasbeen shown to activate several MAPKs [39, 106, 121-124], but these activations seem to predominantly affectlate-phase volume regulation via induction of gene tran-scription. Investigations of short-term effects of MAPKactivation on RVDC have yielded controversial results.In human cervical cancer cells the volume-responsiveErk1/Erk2 pathway, which is linked to the activation ofK+- and Cl- channels and taurine, is PKC-dependent. RVDin these cells is independent of p38 activation [111]. Simi-larly, in human Intestine 407 cells the inhibition of thep38 MAP kinase cascade does not prevent theosmosensitive anion efflux and cytokine-mediated p38activation does not increase the efflux [125]. In this celltype, stimulation of the swelling-induced ion efflux isindependent of Ras/Raf-mediated Erk1/Erk2 activation,as revealed by hypotonicity-provoked isotope efflux stud-ies [126]. In astrocytes the inhibition of MAPKK (MEK)reversibly inhibits the activation of RVDC [108] and inrat hepatocytes the inhibition of p38 leads to a dimin-ished volume-regulatory K+ efflux and an impairment ofRVD [124].

The activation of volume-sensitive Cl- currents bythe intracellular application of the non-hydrolyzable GTPanalog GTP-"-S in the absence of cell swelling, whichwas shown in earlier studies on bovine chromaffin cells[31, 127] and more recently in bovine endothelial cells[16, 109, 128] and neuroblastoma cells [129], pointstowards the involvement of GTP-binding proteins in thevolume regulatory response. The apparent role of G-proteins in RVD can be, at least partly, attributed to theactivity of small monomeric Rho GTPases and theirdownstream effectors, which – besides regulating genetranscription – influence actin cytoskeletalreorganization, actomyosin contractility and theformation of stress fibers and focal adhesions [130, 131].Tilly et al. [132] found a reduction of the osmosensitiveanion efflux from Intestine 407 cells by recombinantClostridium botulinum C3 exoenzyme, which blocks Rhoby ADP ribosylation, and a transient reorganization of

the F-actin cytoskeleton upon cell swelling along withan increased phosphorylation of p125 focal adhesionkinase (p125FAK) and an increased PI-3K activity. Furtherevidence for the involvement of the Rho pathway wasobtained in calf pulmonary endothelial (CPAE) cells,where the GTP-"-S-activated Cl- current is impaired byClostridium C3 toxin and by Y-27632, a blocker of Rhokinase (ROK) which is a downstream effector of Rho[128]. Moreover, myosin light chain (MLC)phosphorylation, which is directily increased by Rho/ROK, was identified as a crucial step in the activation ofthe swelling-activated Cl- current [133]. The Rhopathway, however, rather exerts a permissive effect onthe swelling-activated Cl- current in CPAE cells, sincethe activation of the Rho pathway by transfecting CPAEcells with constitutively active isoforms of a Rho-activating heterotrimeric G# protein subunit, Rho orROK was not sufficient to activate the current [134]. InNIH3T3 mouse fibroblasts, however, expression ofconstitutively active RhoA and Rac1 increased theswelling-activated K+- and taurine efflux and the RVDrate. The swelling-activated Cl- current was inhibited byblocking ROK with Y-27632 but, in contrast to CPAEcells, this current was augmented after MLC kinase block[118]. Estevez et al. [129] confirmed the block of theGTP-"-S-acitvated Cl- current by Clostridium C3exoenzyme in N1E115 neuroblastoma cells and furtherfound an inhibition of the current by cholera toxin; theseresults together with the finding that metabolic inhibitionand the block of adenylate cyclase did not block RVDC,led to the conclusion that in this cell type Rho GTPaseand heterotrimeric G#s/G$" regulate the swelling-activated Cl- current via phosphorylation-independentmechanisms.

Differential screening for cell volume sensitivetranscripts led to the cloning of the human homologueof the rat serum- and glucocorticoid-regulated serine/threonine kinase (SGK) from a human hepatoma cell line[135]. Transcription of h-SGK depends on the cellhydration state in a way that cell shrinkage increases andcell swelling reduces its transcription. Cell hydrationdependent levels of h-sgk mRNA and protein have beendetected in virtually all cell lines and tissues investigatedso far, including shark rectal gland [136], humanintestinal mucosa cells [137], pancreatic acinar and ductalepithelium [138], as well as in cerebral neurons and glialcells [139]. In HepG2 hepatoma cells the transcriptonalcontrol of h-SGK upon cell-shrinkage could recently belinked to the p38/MAPK kinase pathway [140].Coexpression of the mouse SGK in Xenopus oocytes with


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the three subunits of the epithelial Na+ channel ENaCresults in a significantly enhanced Na+ current. SGKincreases the expression of ENaC in renal collecting ductcells at the cell surface; it phosporylates Nedd4-2, whichexerts ubiquinates and that initiates the degradation ofENaC. Thus SGK activates ENaC by antagonising thisinhibitory effect of Nedd4-2 [141, 146].

Ca2+/calmodulin kinase-dependent phosphorylationseems to be necessary for RVDC or K+ channel activa-tion in various cell types but a lack of effect or even anactivation of channels involved in RVD by calmodulinantagonists has been shown as well [18, 38, 39, 147].STAT1 and 3 protein phosphorylation was also shownto be upregulated by cell swelling but so far no link toRVD was shown [148].

Autocrine regulation of RVD by hormonesand transmitters

As outlined above, in HTC hepatoma cells, cellswelling leads to ATP efflux, autocrine stimulation ofP2 receptors, and increases in anion permeability andCl- efflux, which contribute to RVD. The activation ofthe Cl- channels occurs through stimulation of P2receptors. Inhibition of PI-3K significantly inhibits bothRVD and activation of Cl- currents. Intracellular appli-cation of PI(3,4)P2 and PI(3,4,5)P3 activates Cl- currentsresembling those observed during RVD [6, 149, 150]. Inairway epithelial cells, CFTR-independent Ca2+-activatedCl- conductance is regulated by the P2Y2 receptor andmechanical stimulation induces ATP release independ-ent of CFTR. Thus ATP may function as an autocrinesignaling factor promoting Cl- secretion in these cells[151]. Similarly, in various other cell types mechanicalstrain induced ATP release was independent of CFTR[86, 152]. The swelling-induced ATP release might oc-cur via DIDS and/or NPPB inhibitable anion channels[30, 153-156] or by alternative pathways, propably byexocytosis. In human intestine 407 cells, hypoosmoticstress-induced release of ATP is inhibited by low intra-cellular Ca2+ concentrations and by cytochalasin B,whereas the swelling-induced anion efflux is potentiated.This indicates that in these cells the swelling-inducedATP release is independent of RVDC activation. Fur-thermore auto/paracrine ATP signaling does not activateRVDC in human intestine 407 cells, however, the ATPsignaling via P2Y receptors is responsible for swelling-induced Erk1/2 activation [89, 157] and can potentiatethe rise of Cai in response to hypotonic swelling by stimu-

lating cellular Ca2+ entry via volume-sensitive cationchannels and by release from intracellular stores [86]. Inrat hepatocytes and HTC hepatoma cells, the volume-sensitive ATP release is inhibited by Gd3+. The inhibi-tory effect is interpreted as a direct and reversible inter-action of the lanthanide with an ATP-release channel[158]. In human tracheal epithelial cells, ATP releasedby cell swelling is hydrolyzed to adenosine by specificectoenzymes. Adenosine then binds to purinergicreceptors, which leads to Cl- channel activation [159].Mechanical stimulation of isolated hepatocytes can evokeintracellular Ca2+ signals in the stimulated cell as well asin neighbouring hepatocytes and bile duct epithelia hav-ing no direct contact to the stimulated cells. This signalingis mediated by release of ATP or other nucleotides intothe interstitium [156]. A similar way of paracrine Ca2+

wave propagation elicited by mechanically stimulatedATP release via anion channels has been described forprostate cancer cells [83]. In rat hepatoma cellsoverexpressing MDR/P-gp, the rate of volume recoverywas augmented, most likely due to enhanced MDR/P-gp-dependent ATP release [160].

Intracellular- and extracellular pH

Most cells respond to swelling with an intracellularacidification. Guinea pig jejunal villus enterocytes di-vert from this behavior and respond only to a substantialcell volume increase (15% to 20%) with intracellularacidification, while modest (physiological) swelling leadsto intracellular alkalinization [161]. Similarly, rabbitproximal tubule cells respond to physiologic cell swell-ing with intracellular alkalinization [162]. The follow-ing mechanisms can influence intracellular (pHi) andextracellular (pHo) during RVD: (i) HCO3

- exit via chan-nels [87, 163-166], (ii) enhanced Cl-/HCO3

- exchange[167], (iii) release of H+ ions from intracellular pools[80, 168], (iv) enhanced formation of H+ ions duringmetabolism [169], (v) reduced H+ ion exit due to swell-ing-induced inhibition of Na+/H+ exchange [170], (vi)stimulated H+ exit via Na+/H+ exchange which may beactivated by the swelling-induced intracellular acidosis[171, 172] and (vii) stimulation of voltage gated H+ chan-nels [173].

Cell volume regulatory changes in pHi may havedistinct cellular effects [174]. Various K+ channels aresensitive to protons [175-185]. Alkaline pHo acceleratesand acidic pHo slowes the RVD response in EATCs. In-tra- and extracellular alkalinisation increases the current



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amplitude of volume-sensitive K+channels (IKswell)whereas acidification has an inhibitory effect. The mag-nitude of RVDC is not affected by changes in pHi or pHo[186]. Intracellular acidosis has been shown to inhibitvolume-activated charybdotoxin-sensitive K+ channels[161, 172] or to activate charybdotoxin-insensitive K+

channels via a Ca2+-calmodulin kinase II-dependent path-way [161]. IKswell is increased by high pHo and de-creased by low pHo. Accordingly, RVD is accelerated atalkaline pHo and attenuated at acidic pHo [48, 187, 188].The TASK (TWIK-related acid sensitive K+ channel)family of K+ channels is highly sensitive to changes inpHo with current inhibition at acidic pHo [34, 177].TREK-1 and TREK-2, members of the two-pore domainmechanosensitive K+ channels are opened by membranestretch, arachidonic acid (AA), temperature and volatileanesthetics, as well as by internal acidification. Lower-ing pHi shifts the pressure-activation relationship towardspositive values and leads to channel opening at atmos-pheric pressure. The pHi-sensitive, mechanosensitive andAA-activated parts of the protein are located at identicalpositions in the C-terminus [33, 189-191]. It is impor-tant to note, that pHi may influence cellular metabolism[62, 168], which in turn, is able to change the concentra-tion of intracellular osmolytes. The major role, however,of a decreased pHi after swelling cells can be envisionedto be the protonation of negatively charged amino acids,necessary for the osmotic balance of the cell by allow-ing a net efflux of positive charge in order to drive os-mosis. This is important, since the total amount of nega-tive charge available to compensate the cation efflux islimited in most cells [18]. Protonation of specific aminoacids determines also the function of ion channels andother proteins involved in RVD: The water permeabilityof Xenopus laevis oocytes expressing the water channelaquaporin 0 (AQP0) is increased at pHo of 6.5 due toprotonation of an external histidine residue [192]. Theselectivity of the ICln ion channel protein [193] is alsodependent on the pH by favouring anion over cation per-meation under acidic conditions [92, 93, 193].

Cell membrane potential and temperature

Due to the activation of ion conducting pathways,cell swelling leads to profound changes of the cell mem-brane potential (PD). PD determines the direction of theion fluxes depending on the respective equilibriumpotentials. This has profound implications on the efficacyof the mechanisms, which enable RVD. Usually,

activation of K+ channels leads to hyperpolarization,whereas the activation of anion or unselective cationchannels leads to depolarization of the cell membrane.Cell swelling has been shown to hyperpolarize and/ordepolarize various cell types [39]. In intestinal- and renalepithelial cells, activation of K+ channels causes atransient hyperpolarization, which is followed by asustained depolarization due to activation of anionchannels [164, 194]. The K+ channels are inwardlyrectifying so that K+ exit through these channels duringRVD may be limited by the cell membrane depolarization[87]. In contrast, the opening of the mechanosensitiveK+ channel TRAAK is facilitated upon depolarization toPD values more positive than -25 mV [58]. Inlymphocytes depolarization during RVD activates n-typeK+ channels [195, 196]. Depolarization of the cell mem-brane may activate voltage-sensitive Ca2+channels inpancreatic $-cells and vascular smooth muscle cells [62].In human red blood cells a non-selective cationconductance (NSC) is activated by cell shrinkage andinhibited by cell swelling. The changes of the membra-ne potential lead to passive Cl- fluxes across the mem-brane, which may contribute to RVD. Since thisconductance is sensitive to intracellular Cl- (highintracellular Cl- inhibits the conductance), a feedbackmechanism exists in the regulation of NSC conductance,and Cl- could therefore act as a voltage and/or volumesensor [197]. During RVD in trout red cells the cell mem-brane potential and the pHi remained remarkablyconstant, which was accomplished by a balanced gainand loss of Cl- and cations combined with a massiveefflux of zwitterionic taurine in a constant stoichiometry[198].

The influence of the ambient temperature on RVDwas shown in trout renal proximal tubule cells [199]. Inchick cardiomyocytes volume recovery after hypotonicexposure was missing when cells were kept at room tem-perature. This lack of RVD was attributed to a delayedswelling-induced rise of Cai observed in cells at roomtemperature, compared to myocytes kept at 37°C whichexhibited normal RVD [200]. In excised membranepatches from lymphocytes the activation of Cl- channelswas found to be strongly temperature dependent. At 30°Cthe percentage of patches with active channels was in-creased, the total time to channel activation was lowerand the channel open probability was higher comparedto patches kept at 20°C [201]. In dog atrial myocytes thelag-time between step changes in cell size and swelling-induced Cl- current activation was temperature depen-dent in a way that current activation was faster at 36°C


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compared with room temperature. Moreover, the currentswere evoked in a higher percentage of cells at 36°C thanat room temperature [202]. In MDCK cells and NIH 3T3fibroblasts the resting PD is below the Cl- equilibriumpotential at room temperature, which leads to a Cl- in-flux counteracting RVD. Increasing the temperature to37 °C, however, shifts the PD to values more negativethan the equilibrium potential of Cl-, which enables Cl-

efflux and supports RVD [203]. The two-pore domainmechanosensitive K+ channel TREK-1 is opened gradu-ally and reversibly by heat with an approximately 7-foldincrease of the current amplitude upon a temperature riseof 10°C. This thermal effect on the opening of TREK-1is reversed by PGE2 and cAMP via PKA-mediated phos-phorylation [189].

Cytoskeleton and protein to membranetransposition

In a variety of cell types, swelling leads to theremodeling of the cytoskeleton (Fig. 5). Actin stress fibersare depolymerized forming submembranous F-actin frag-ments. In many but not all cell types, RVD is inhibitedby cytochalasins, which prevent actin assembly [38, 39,204, 205]. Cytoskeletal assembly is regulated by anumber of actin-binding proteins (ABPs) like gelsolin,profilin and cofilin, which sever actin filaments, cap theirbarbed ends, bind actin monomers and thereby inhibitthe addition of new subunits to the actin filaments, a proc-ess that supports actin depolymerization. In humanmelanoma cells the involvement of ABPs in RVD hasbeen directly demonstrated [206]. The absence of ABPin these cells leads to an inhibition of RVD via inactiva-tion of swelling-dependent K+ channels, an effect thatcan be reversed by genetically rescuing ABP expression[206]. ABPs also bind to PI(4,5)P2, which sequestratesABPs, lowers their affinity for actin subunits and sup-ports filament growth by releasing free G-actin anduncapping the barbed ends of actin filaments. In addi-tion, actin cross-linking by the stimulation of #-actininis favoured and the attachment of actin to the cell mem-brane made possible. Actin is connected to the plasmamembrane by several actin-associated proteins, whichthemselves are attached to the cell membrane via bind-ing of their PH domains to PI(4,5)P2 molecules in theinner leaflet of the cell membrane. Hydrolysis ofPI(4,5)P2 by PLC thus supports actin depolymerizationby releasing sequestrated ABPs, while enhanced forma-tion of PI(4,5)P2 strongly induces actin polymerization.

The activity of the PI(4,5)P2 synthesising enzyme PI(4)P-5-kinase is enhanced by the ras-related GTPase p21(Rho),a key regulator of actin organisation [207-211]. PI(4,5)P2levels rapidly decrease after a hypotonic challenge inthe green alga Dunaliella salina. This is paralleled by anenhanced DAG synthesis [212, 213]. PI(4,5)P2 hydroly-sis by PLC leads to the formation of the second messen-gers DAG and Ins(1,4,5)P3, both of which are involvedin cytoskeletal organisation. DAG modulates actin dy-namics via activation of PKC [197, 214, 215], whileIns(1,4,5)P3 releases Ca2+ from internal stores (see be-low). In astrocytes hypotonic stress induces a twofoldincrease in PI hydrolysis. RVD is blocked by inhibitionof PLC and accelerated by PLC - agonist - stimulated PIhydrolysis [216]. In MDCK cells swelling leads to a rapiddissociation of PLC-!1 from the cell membrane to thecytosol with a parallel PI breakdown [15]. PI(4,5)P2 hy-drolysis may also occur as a consequence of autocrineand/or paracrine purinergic receptor stimulation follow-ing swelling-induced release of intracellular ATP (seeabove). Beside PI, Cai acts as a key regulator of actinassembly via binding to ABP like gelsolin, villin, severin,fragmin, adservin and scinderin. Cai can promote bothactin polymerization and depolymerization, dependenton the cell type, the level and spatio-temporal pattern ofCai elevations, the expression profile of ABPs and otherregulating factors [217]. In many cells Cai levels rise inresponse to cell swelling or autocrine/paracrinepurinergic receptor stimulation upon swelling-inducedrelease of intracellular ATP.

The cytoskeleton can be involved in cell volumeregulation in several ways: (i) It can act as a volume sen-sor by transducing the swelling-induced mechanical de-formation of the membrane to intracellular volume regu-latory mechanisms [218]. It has been suggested that thesubmembraneous F-actin network may confer mechani-cal resistance to the unfolding of cell membraneinvaginations. Upon swelling these invaginations unfoldand by remodeling of the actin meshwork alterations ofprotein-protein interactions lead to the activation ofRVDC [38]. (ii) It can directly modify the activity ofRVDC and transporters. Regulation by the cytoskeletonhas been shown for Na+ channels [219-224], cardiac L-type and T-type Ca2+ channels [225, 226], K+ channels[58, 190, 227-229], Cl- channels/CFTR [230-236],stretch-activated channels [237, 238] and NHE3 [237,239-242]. (iii) The cytoskeleton can modulate secondmessenger systems involved in the signal transductionduring RVD. NIH 3T3 fibroblasts expressing the trans-forming Ha-ras oncogene show profound alterations of



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RVD ion transport, in close relation to an intensecytoskeletal remodeling. Oncogene expression inducesa breakdown of the actin stress fiber network by gener-ating oscillatory elevations of Cai. This is paralleled bya shift of the cell volume regulatory set-point towardslarger volumes and activation of ion transport mecha-nisms serving for volume increase [96, 97, 239, 243-248].Cytoskeletal disruption is believed to alter the spatialdistribution of PLC and Ins(1,4,5)P3 receptors. This inturn impairs PLC-dependent Ca2+ signaling and abolishesCa2+ mobilisation by ATP and other agonists [249]. Ac-tin may function as an intracellular Ca2+ store by bindingCa2+ ions. Ca2+ release from F-actin can be triggered bydepolymerization of F-actin followed by dissociation ofCa2+ from Ca2+-ADP-actin monomer complexes.Depolymerization of F-actin during cell swelling couldtherefore lead to the increased Ca2+ levels observed dur-

ing RVD in some cells [250]. Cell swelling directly acti-vates the adenylate cyclase (AC) in mouse S49 lymphomacells by a mechanism that requires intact actin. A com-plete inhibition of the AC however, is without conse-quence on the initial volume expansion or the extent ofRVD after a hypotonic shock [251, 252], indicating thatactivation of AC is not directly involved in the activa-tion of RVDC. In the human liver cancer cell line HepG2actin reorganizes itself in response to hypoosmolarity ina manner that involves the PI-3K/PKB/AP-1 signalingcascade and phosphorylation of focal adhesion kinase(FAK) and this is dependent on an intact actin cytoskel-eton [253]. (iv) The cytoskeleton could act as a diffusionbarrier. Actin gelation might impede the osmotically in-duced water flux [254, 255], an effect that could be im-portant in cells with microvilli. Microfilaments in theshaft region of microvilli exert an efficient diffusion bar-

Fig. 5. Cytoskeletal remodelling in response to cell swelling. The cytoskeleton can act as both a volume sensor and anelement of signal transduction. Cell swelling can exert profound effects on the cytoskeletal architecture by triggeringpolymerization and/or depolymerization of actin due to modulation of key regulators of cytoskeleton.


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rier and separate the microvillar tip compartment fromthe cytosol. The tip compartment is believed to act as asensor for extracellular osmolarity changes and ion com-position. Due to the differential distribution of ion- andwater channels between the microvillar membrane andthe remaining cell membrane, both compartments re-spond differently to changes in the ambient osmolarity.Anisotonicity leads to swelling of either the tip compart-ment or the cytosol. This leads to surface enlargement atthe expense of the microvillar membrane, to ion and waterfluxes between the two compartments due to shorteningof the microvillar diffusion barrier and to volume regu-latory ion fluxes [256]. (v) The cytoskeleton can partici-pate in macromolecular crowding (see bolw) and (vi) itis involved in the regulation of the exocytotic release oforganic osmolytes [110]and propably ATP [89]. (vii)Cytoskeletal remodeling might also create local osmoticgradients, leading to osmotically driven water fluxes [211,257] and (viii) it can generate mechanical forces by pro-moting actin-myosin interaction [39]. (ix) Furthermore,the electroosmotic properties of actin could influencethe processing and conduction of electrical signals withinthe intracellular compartment [258].

An important feature of the cytoskeleton is to sortand target molecules to specific domains within the cellmembrane. This protein sorting is infuenced by hypoto-nicity in polarized cells [259]. In rat hepatocytes, forexample, cell swelling induces the translocation of Na+/taurocholate cotransporter bearing vesicles to the cellmembrane via a PI-3K sensitive pathway [88, 260]. IClnis another protein, which is directed to the cell mem-brane during cell swelling. This protein, cloned fromMDCK cell cDNA library, results in a nucleotide sensi-tive, outwardly rectifying Cl- current closely resemblingthe biophysical properties of RVDC when it is expressedin Xenopus oocytes [261]. This suggests that it mightform a molecular part of RVDC. Functional reconstitu-tion of purified ICln in lipid bilayers has unravelled achannel function of ICln with a relative K+ over Cl- per-meability matching the one of RVDC in native cells [91-93]. Knock down of the ubiquitously expressed proteinby specific antisense oligonucleotides suppresses RVDC[262-264] and overexpression of ICln enhances RVDC[264]. However, a considerable part of the ICln-proteinpool resides diffusely dispersed in the cytosol and only aminor fraction of the protein can be identified in the cellmembrane of cultured cells like NIH 3T3 fibroblasts,MDCK cells and reticulocytes [265]. In the kidney, IClnis mainly inserted in the apical membrane of the proxi-mal tubule and both in the cytosol and the membrane of

distal tubules [266, 267] indicating, that the distributionof ICln depends on the cell type and that it is subject tocellular regulation. Hypotonic cell swelling leads to thetransposition of ICln from the cytosol to the cell mem-brane in fibroblasts as well as skate- and neonatal ratheart cells [266, 268, 269]. In C6 glioma cells adapted toa hypertonic culture conditions and in human nonpig-mented ciliary epithelial cells, this shift upon a moder-ate reduction of the extracellular osmolarity cannot beobserved [270, 271]. Using fluorescence resonance en-ergy transfer (FRET) the cytosol to membrane shift ofICln can be confirmed in living NIH 3T3 fibroblasts[272]. Enhanced ICln abundance in the cell membraneis accompanied by stimulated cellular anion permeabil-ity and coincides with accelerated activation of RVDC[273]. In neonatal rat heart cells, taurine efflux parallelsICln transposition, indicating that ICln regulates a path-way for osmolytes or forms the pathway itself. This issupported by the finding that ICln, when functionallyreconstituted in lipid bilayers, is permeable to theosmolytes taurine and glutamate (Fürst, Ritter &Paulmichl, unpublished results). In addition, interactionsof ICln with cytoskeletal proteins like actin have beendemonstrated using a variety of biochemical methods[265, 274, 275]. ICln also interacts with erythrocyte pro-tein 4.1 [276], a human homologue of yeast Skb1 [277]and the non-muscle isoform of the myosin light chain[278] bind to ICln. Hence ICln might be involved in hy-potonicity induced cytoskeletal remodeling. Some ofthese cytoskeletal proteins might also be responsible forthe swelling-induced shift of ICln into the cell membrane.

Macromolecular crowding

Macromolecular crowding is the term used to de-scribe the phenomenon, that the total concentration ofmacromolecules in the cytosol is high enough that a sig-nificant proportion of the volume is physically occupied.This means that the solution deviates from ideality. Ran-dom movements are restricted and the occupied volumeis therefore not accessable to other molecules. Since com-pact (as opposed to unfolded) molecules and molecularassemblies (as opposed to their subunits) exclude lessvolume to other macrosolutes it is believed that molecu-lar crowding per se provides a nonspecific force that af-fects protein folding [279] as well as protein associationkinetics and has therefore profound effects on the activ-ity of individual proteins or protein complexes. The func-tion of proteins therefore strongly depends on the total



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cellular macromolecular concentration and hence on thecell volume [280, 281]. Changes in macromolecularcrowding due to changes in cell volume could serve asvolume sensor and trigger cell volume regulatory mecha-nisms, e.g. by the reversible association of ion transportproteins with cytosolic regulatory proteins [18, 282, 283].Macromolecular crowding has been shown to determinethe set point of cell volume regulation in erythrocytes[282, 284-286]. In these cells the swelling-induced dilu-tion of the cytosol is thought to greatly decrease the ac-tivity of a kinase, which is sensitive to the surroundingprotein concentration. The active kinase inhibits volumeregulatory KCl cotransport. Inhibition of this kinase willactivate the transporter, promote cell volume regulatoryKCl exit and thus RVD [280, 287]. The function andassociation of proteins is dependent on the ionic strengthand can be modulated by macromolecular crowding as ithas been conclusively shown for E.coli DNA polymer-ase [288], or the presence of urea. This may also be thereason for the activation or inhibition of several cell vol-ume regulatory ion transport mechanisms [289-294]. In-creasing the ionic strength can shift the volume regula-tory set point of erythrocytes towards smaller volumes[295], while in CHO cells [296] the volume regulatoryset-point decreased with lowered ionic strength. Highconcentrations of urea are thought to exert an inhibitoryeffect on the transcription of the cell volume regulatedserine-threonine protein kinase sgk-1 in human hepatomacells and shark rectal glands [135, 136].

Metabolism

Several metabolic pathways are known to be sensi-tive to cell volume. Cell swelling-induced alterations inthe concentrations of metabolites may thus contribute tocell volume regulation. Cell swelling increases glyco-gen synthesis and inhibits glycolysis, thus decreasing theconcentration of osmotically active carbohydrates. RVDCactivation is an important step in volume dependent regu-lation of glycogen synthesis since loss of Cl- ions leadsto an activation of glycogen synthase phosphatase andglucose-6-phosphatase, thus activating glycogen synthe-sis [297-299]. Cell swelling inhibits proteolysis andstimulates protein synthesis. Furthermore, cell swellinghas a weak stimulatory effect on lipogenesis.

Whole-cell-, perforated patch- and cell-attachedpatch clamp studies on insulinoma cells and rat pancre-atic $-cells revealed a swelling- and D-glucose-depend-ent Cl- conductance with properties of the outwardly rec-

tifying swelling-dependent Cl- current described in othercell types [300-302]. The stimulatory action of D-glu-cose was found for concentrations above 5 mM and ismost likely due to its metabolic conversion to L-lactate,which accumulates in significant quantities and causescell swelling followed by current activation [301]. Be-sides providing a pathway for RVD, these channels, bygiving rise to a depolarizing current upon glucose stimu-lation in a concentrations range where KATP channelsare already maximally inhibited, would further increasethe electrical activity of $-cells and insulin release [302].

The metabolic effects of cell volume are mediatedin part by alterations of lysosomal pH, which modifiesthe activity of acidic lysosomal proteases. Cell volumechanges interfere with a great number of other metabolicfunctions, which may in turn modify cellular osmolar-ity. The overall contribution of these changes to cell vol-ume regulatory changes in osmolarity seems to be mod-est. The influence of cell volume on various metabolicpathways is, however, of fundamental importance for theregulation of metabolic function [39, 168, 303-307].

Conclusions

The obvious presence of multiple volume sensingentities makes it impossible to enrol a simple, linear anduniversal sequence of cellular events aiming at the per-formance of RVD. Cells from different tissues andorganisms utilize their individual sets of sensors,modulators and effectors to achieve the major goal interms of acute cell volume regulation: the reduction ofthe intracellular osmotic activity as the driving force forcellular water exit. Even single cells can react to cellswelling with different patterns of cellular responses,depending on the cause and the extent of cell swellingand on the ambient conditions prevailing in the cells’environment. The ability to counteract lethal cell swellingand the close interrelation of cell volume regulatorymechanisms to signaling cascades regulating other cellfunctions puts them amongst the most fundamentalbiologic achievements. We just started to identify themultiple players involved in RVD on a molecular basisand much work is left in order to fully understand thecomplex scenario activated by cell swelling. A detailedknowledge of these mechanisms raises, however, theperspective of developing precise tools for harnessingthese pathways, thus opening a wide array of biologicpossibilities and new therapeutic strategies.


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Abbreviations

AA (Arachidonic acid), ABP (Actin bindingprotein), ATP (Adenosine 5’-triphosphate), AQP0(Aquaporin 0), Cai (Intracellular Ca2+ concentration),CaMKII (Calmodulin-dependent kinase II), cAMP(Adenosine 3’:5’-cyclic monophosphate), CCE(Capacitative Ca2+ entry), CFTR (Cystic fibrosistransmembrane receptor), CHO cells (Chinese hamsterovary cells), COX (Cycloxygenase), CPAE cells (Calfpulmonary artery endothelial cells), DAG(Diacylglycerol), DAGK (Diacylglycerol kinase), DGL(Diglyceride lipase), DIDS (4,4’-diisothiocyanatostilbene-2,2’-disulfonic acid), EATCs(Ehrlich ascites tumor cells), ENaC (Epithelial Na+

channel), Erk1/2 (Extracellular signal regulated proteinkinase 1 or 2), FAK (Focal adhesion kinase), FLAP (5-lipoxygenase activating protein), FRET (Fluorescenceresonance energy transfer), GPC(Glycerophosphorylcholine), GTP (Guanosine 5’-triphosphate), GTP-"S (Guanosine 5’-O-(3-thiotriphosphate)), HETE (Hydroxyeicosatetraenoicacid), ICln (Nucleotide-sensitive Cl- current; proteinlinked to this current), IKswell (Volume-sensitive K+

current), IMCD cells (Inner medulla collecting ductcells), Ins(1,4,5)P3 (Inositol-1,4,5-trisphosphate),Ins(1,3,4,5)P4 (Inositol-1,3,4,5-tetrakisphosphate),Ins(1,4,5,6)P4 (Inositol-1,4,5,6-tetrakisphosphate),Ins(3,4,5,6)P4 (Inositol-3,4,5,6-tetrakisphosphate),Ins(1,3,4,5,6)P5 (Inositol-1,3,4,5,6-pentakisphosphate),LOX (Lipoxygenase), LTD4 (Leukotriene D4), MAPK(Mitogen-activated protein kinase), MAPKK (MEK)(Mitogen-activated protein kinase kinase), MDCK cells(Madin-Darby canine kidney cells), MDR P-gp(Multidrug resistance protein P-glycoprotein), MLC(Myosin light chain), MLCK (Myosin light chain kinase),NADPH (#-nicotinamide adenine dinucleotidephosphate), Nedd (Neural precursor cell expresseddevelopmentally down-regulated), NHE1/3 (Na+/H+

exchanger type 1 or 3), NPPB (5-nitro-2-(3-phenylpropylamino)benzoic acid), NSC (Non-selectivecation conductance), PA (Phosphatidic acid), PAP(Phosphatidic acid phosphatase), PD (Cell membranepotential), PDBu (4$-phorbol 12,13-dibutyrate), PGE2(Prostaglandin E2), PH domain (Pleckstrin homologydomain), pHi/pHo (Intracellular/extracellular pH), PI(Phosphoinositide), PI-3K (Phosphatidylinositol-3-

kinase), PI-3P-5K (Phosphatidylinositol-3-phosphate-5kinase), PI(3)P (Phosphatidylinositol-3-phosphate),PI(3,4)P2 (Phosphatidylinositol-3,4-bisphosphate),PI(3,5)P2 (Phosphatidylinositol-3,5-bisphosphate),PI(4,5)P2 (Phosphatidylinositol-4,5-bisphosphate),PI(1,4,5)P3 (Phosphatidylinositol-1,4,5-trisphosphate),PI(3,4,5)P3 (Phosphatidylinositol-3,4,5-trisphosphate),PIPK (Phosphatidylinositol-phosphate kinase), PKA(Protein kinase A), PKB (Protein kinase B), PKC (Proteinkinase C), PLA2 (Phospholipase A2), PLC(Phospholipase C), PLD (Phospholipase D), PTK(Protein tyrosine kinase), RVD (Regulatory volumedecrease), RVDC (Regulatory volume decrease current(channel)), SAC (Stretch-activated channel), SAPK/JNK(Stress-activated protein kinase/c-Jun N-terminal kinase),SGK (Serum- and glucocorticoid-regulated serine/threonine kinase), SITS (4-acetamido-4’-isothiocyanatostilbene-2,2’-disulfonic acid), SOC (Store-operated Ca2+ channel), STAT (Signal transducer andactivator of transcription), TALH cells (Thick ascendingloop of henle cells), TASK (TWIK(two-pore weakinward rectifier K+)-related acid-sensitive K+ channel),TRAAK (TWIK-related arachidonic acid-stimulated K+

channel), TREK (TWIK-related K+ channel), VOC(Voltage-operated Ca2+ channel)

Acknowledgements

The authors gratefully acknowledge the helpfuldiscussion with Profs. R. Kinne and F. Lang. This articlewas supported in part by the Austrian Science Foundation(FWF, grant numbers P12337, P13041, P12467 andP14102), the Austrian National Bank (grant numbers8444 and 6994) the Gastein Foundation (grant numberFP41/FP46) to MP and MR and the Max KadeFoundation to JF.



251

References

1 Irvine RF, Schell MJ: Back in the water:the return of the inositol phosphates.2001;2:327-338.

2 Takenawa T, Itoh T: Phosphoinositides, keymolecules for regulation of actincytoskeletal organization and membranetraffic from the plasma membrane. BiochimBiophys Acta 2001;1533:190-206.

3 Hubner S, Couvillon AD, Kas JA, BankaitisVA, Vegners R, Carpenter CL, Janmey PA:Enhancement of phosphoinositide 3-kinase(PI 3-kinase) activity by membranecurvature and inositol-phospholipid-binding peptides. Eur J Biochem1998;258:846-853.

4 Cazale AC, Rouet-Mayer MA, Barbier-Brygoo H, Mathieu Y, Lauriere C:Oxidative Burst and Hypoosmotic Stress inTobacco Cell Suspensions. Plant Physiol1998;116:659-669.

5 Kim RD, Stein GS, Chari RS: Impact ofcell swelling on proliferative signaltransduction in the liver. J Cell Biochem2001;83:56-69.

6 Feranchak AP, Roman RM, Doctor RB,Salter KD, Toker A, Fitz JG: The lipidproducts of phosphoinositide 3-kinasecontribute to regulation of cholangiocyteATP and chloride transport. J Biol Chem1999;274:30979-30986.

7 Bonangelino CJ, Nau JJ, Duex JE,Brinkman M, Wurmser AE, Gary JD, EmrSD, Weisman LS: Osmotic stress-inducedincrease of phosphatidylinositol 3,5-bisphosphate requires Vac14p, an activatorof the lipid kinase Fab1p. J Cell Biol2002;156:1015-1028.

8 Dove SK, Cooke FT, Douglas MR, SayersLG, Parker PJ, Michell RH: Osmotic stressactivates phosphatidylinositol-3,5-bisphosphate synthesis [see comments].Nature 1997;390:187-192.

9 Lemmon MA, Ferguson KM: Signal-dependent membrane targeting bypleckstrin homology (PH) domains.Biochem J 2000;350:1-18.

10 Wymann MP, Sozzani S, Altruda F,Mantovani A, Hirsch E: Lipids on the move:phosphoinositide 3-kinases in leukocytefunction. Immunol Today 2000;21:260-264.

11 Miyahara M, Watanabe Y, Edashige K,Yagyu K: Swelling-induced O2- generationin guinea-pig neutrophils. Biochim BiophysActa 1993;1177:61-70.

12 Fahrner SL, Shackford SR, Bourguignon P,Bednar M, Shatney-Leach L: Effect ofmedium tonicity and dextran on neutrophilfunction in vitro. J Trauma 2002;52:285-292.

13 Kubo S, Matsumoto T, Mochida O,Sakumoto M, Mizuone Y, Kumazawa J:Inhibition of chemiluminescence responseof human polymorphonuclear leukocytes bythree different stimulations in hyperosmoticcondition comparable to the renal medulla.Ren Fail 1996;18:69-74.

14 Ritter M, Schratzberger P, Rossmann H,Wöll E, Seiler K, Seidler U, Reinisch N,Kahler CM, Zwierzina H, Lang HJ, LangF, Paulmichl M, Wiedermann CJ: Effect ofinhibitors of Na+/H+-exchange and gastricH+/K+ ATPase on cell volume, intracellularpH and migration of humanpolymorphonuclear leucocytes. Br JPharmacol 1998;124:627-638.

15 Fujii M, Ohtsubo M, Ogawa T, Kamata H,Hirata H, Yagisawa H: Real-timevisualization of PH domain-dependenttranslocation of phospholipase C-delta1 inrenal epithelial cells (MDCK): response tohypo-osmotic stress. Biochem Biophys ResCommun 1999;254:284-291.

16 Nilius B, Prenen J, Voets T, Eggermont J,Bruzik KS, Shears SB, Droogmans G:Inhibition by inositoltetrakisphosphates ofcalcium- and volume-activated Cl- currentsin macrovascular endothelial cells. PflugersArch 1998;435:637-644.

17 Hoffmann EK: Intracellular signallinginvolved in volume regulatory decrease.Cell Physiol Biochem 2000;10:273-288.

18 Hoffmann EK, Dunham PB: Membranemechanisms and intracellular signalling incell volume regulation. Int Rev Cytol1995;161:173-262.

19 Peterson MW, Walter ME: Calcium-activated phosphatidylcholine-specificphospholipase C and D in MDCK epithelialcells. Am J Physiol 1992;263:C1216-24.

20 Cockcroft S: Signalling roles of mammalianphospholipase D1 and D2. Cell Mol LifeSci 2001;58:1674-1687.

21 Blum JJ, Lehman JA, Horn JM, Gomez-Cambronero J: Phospholipase D (PLD) ispresent in Leishmania donovani and itsactivity increases in response to acuteosmotic stress. J Eukaryot Microbiol2001;48:102-110.

22 Lehtonen JY, Kinnunen PK: PhospholipaseA2 as a mechanosensor. Biophys J1995;68:1888-1894.

23 Margalit A, Livne AA, Funder J, Granot Y:Initiation of RVD response in humanplatelets: mechanical-biochemicaltransduction involves pertussis-toxin-sensitive G protein and phospholipase A2.J Membr Biol 1993;136:303-311.

24 Thoroed SM, Lauritzen L, Lambert IH,Hansen HS, Hoffmann EK: Cell swellingactivates phospholipase A2 in Ehrlichascites tumor cells. J Membr Biol1997;160:47-58.

25 Basavappa S, Pedersen SF, Jorgensen NK,Ellory JC, Hoffmann EK: Swelling-inducedarachidonic acid release via the 85-kDacPLA2 in human neuroblastoma cells. JNeurophysiol 1998;79:1441-1449.

26 Pedersen S, Lambert IH, Thoroed SM,Hoffmann EK: Hypotonic cell swellinginduces translocation of the alpha isoformof cytosolic phospholipase A2 but not thegamma isoform in Ehrlich ascites tumorcells. Eur J Biochem 2000;267:5531-5539.

27 Mignen O, Le Gall C, Harvey BJ, ThomasS: Volume regulation following hypotonicshock in isolated crypts of mouse distalcolon. J Physiol 1999;515:501-510.

28 Estevez AY, O’Regan MH, Song D, PhillisJW: Hyposmotically induced amino acidrelease from the rat cerebral cortex: role ofphospholipases and protein kinases. BrainRes 1999;844:1-9.

29 Ling BN, Webster CL, Eaton DC:Eicosanoids modulate apical Ca(2+)-dependent K+ channels in cultured rabbitprincipal cells. Am J Physiol1992;263:F116-126.

30 Mitchell CH, Carre DA, McGlinn AM,Stone RA, Civan MM: A releasemechanism for stored ATP in ocular ciliaryepithelial cells. Proc Natl Acad Sci USA1998;95:7174-7178.

31 Doroshenko P: Second messengersmediating activation of chloride current byintracellular GTP gamma S in bovinechromaffin cells. J Physiol 1991;436:725-738.

32 Kim DK, Jung KY: Caffeine causesglycerophosphorylcholine accumulationthrough ryanodine- inhibitable increase ofcellular calcium and activation ofphospholipase A2 in cultured MDCK cells.Exp Mol Med 1998;30:151-158.

33 Lesage F, Terrenoire C, Romey G,Lazdunski M: Human TREK2, a 2P domainmechano-sensitive K+ channel with multi-ple regulations by polyunsaturated fattyacids, lysophospholipids, and Gs, Gi, andGq protein-coupled receptors. J Biol Chem2000;275:28398-28405.

34 Lesage F, Lazdunski M: Molecular andfunctional properties of two-pore-domainpotassium channels. Am J Physiol2000;279:F793-801.

35 Kim D, Sladek CD, Aguado-Velasco C,Mathiasen JR: Arachidonic acid activationof a new family of K+ channels in culturedrat neuronal cells. J Physiol 1995;484:643-660.

36 Kim D: A mechanosensitive K+ channel inheart cells. J Gen Physiol 1992;100:1021-1040.

37 Estevez AY, O’Regan MH, Song D, PhillisJW: Effects of anion channel blockers onhyposmotically induced amino acid releasefrom the in vivo rat cerebral cortex.Neurochem Res 1999;24:447-452.


252

38 Okada Y: Volume expansion-sensingoutward-rectifier Cl- channel: fresh start tothe molecular identity and volume sensor.Am J Physiol 1997;273:C755-C789.

39 Lang F, Busch GL, Ritter M, Volkl H,Waldegger S, Gulbins E, Haussinger D:Functional significance of cell volumeregulatory mechanisms. Physiol Rev1998;78:247-306.

40 Margalit A, Sofer Y, Grossman S, ReynaudD, Pace-Asciak CR, Livne AA: HepoxilinA3 is the endogenous lipid mediatoropposing hypotonic swelling of intacthuman platelets. Proc Natl Acad Sci U S A1993;90:2589-2592.

41 Hoffmann EK: Leukotriene D4 (LTD4)activates charybdotoxin-sensitive and -insensitive K+ channels in ehrlich ascitestumor cells. Pflugers Arch 1999;438:263-268.

42 Civan MM, Coca-Prados M, Peterson-Yantorno K: Pathways signaling theregulatory volume decrease of culturednonpigmented ciliary epithelial cells. InvestOphthalmol Vis Sci 1994;35:2876-2886.

43 Furlong TJ, Moriyama T, Spring KR:Activation of osmolyte efflux from culturedrenal papillary epithelial cells. J Membr Biol1991;123:269-277.

44 Bagnasco SM, Montrose MH, Handler JS:Role of calcium in organic osmolyte effluxwhen MDCK cells are shifted fromhypertonic to isotonic medium. Am JPhysiol 1993;264:C1165-1170.

45 McManus M, Serhan C, Jackson P, StrangeK: Ketoconazole blocks organic osmolyteefflux independently of its effect onarachidonic acid conversion. Am J Physiol1994;267:C266-271.

46 Ballatori N, Wang W: Nordihydroguaiareticacid depletes ATP and inhibits a swelling-activated, ATP-sensitive taurine channel.Am J Physiol 1997;272:C1429-1436.

47 Kersting U, Napathorn S, Spring KR:Necturus gallbladder epithelial cell volumeregulation and inhibitors of arachidonicacid metabolism. J Membr Biol1993;135:11-8.

48 Hoffmann EK: Intracellular SignalingInvolved in Volume Regulatory Decrease.Cell Physiol Biochem 2000;10:273-288.

49 Yang XC, Sachs F: Mechanically sensitive,nonselective cation channels. EXS1993;66:79-92.

50 Yang XC, Sachs F: Block of stretch-activated ion channels in Xenopus oocytesby gadolinium and calcium ions. Science1989;243:1068-1071.

51 Suleymanian MA, Clemo HF, Cohen NM,Baumgarten CM: Stretch-activated channelblockers modulate cell volume in cardiacventricular myocytes. J Mol Cell Cardiol1995;27:721-728.

52 Urbach V, Leguen I, O’Kelly I, Harvey BJ:Mechanosensitive calcium entry andmobilization in renal A6 cells. J Membr Biol1999;168:29-37.

53 Sackin H: A stretch-activated K+ channelsensitive to cell volume. Proc Natl Acad SciUSA 1989;86:1731-1735.

54 Sackin H: Regulation of renal proximaltubule basolateral potassium channels. ProgClin Biol Res 1990;334:231-249.

55 Schutt W, Sackin H: A new technique forevaluating volume sensitivity of ionchannels. Pflugers Archiv 1997;433:368-375.

56 Kanzaki M, Nagasawa M, Kojima I, SatoC, Naruse K, Sokabe M, Iida H: Molecularidentification of a eukaryotic, stretch-activated nonselective cation channel.Science 1999;285:882-886.

57 Bang H, Kim Y, Kim D: TREK-2, a newmember of the mechanosensitive tandem-pore K+ channel family. J Biol Chem2000;275:17412-17419.

58 Maingret F, Fosset M, Lesage F, LazdunskiM, Honore E: TRAAK is a mammalianneuronal mechano-gated K+ channel. J BiolChem 1999;274:1381-1387.

59 Patel AJ, Honore E, Maingret F, Lesage F,Fink M, Duprat F, Lazdunski M: Amammalian two pore domain mechano-gated S-like K+ channel. EMBO J1998;17:4283-4290.

60 Fan SF, Christ GJ, Melman A, Brink PR: Astretch-sensitive Cl- channel in humancorpus cavernosal myocytes. Int J Impot Res1999;11:1-7.

61 Eder C, Klee R, Heinemann U: Involvementof stretch-activated Cl- channels inramification of murine microglia. JNeurosci 1998;18:7127-137.

62 Lang F, Busch GL, Volkl H: The diversityof volume regulatory mechanisms. CellPhysiol Biochem 1998;8:1-45.

63 McCarty NA, O’Neil RG: Calciumsignaling in cell volume regulation. PhysiolRev 1992;72:1037-1061.

64 Tinel H, Kinne-Saffran E, Kinne RK:Calcium signalling during RVD of kidneycells. Cell Physiol Biochem 2000;10:297-302.

65 Kinne RK, Tinel H, Kipp H, Kinne-SaffranE: Regulation of sorbitol efflux in differentrenal medullary cells: similarities anddiversities. Cell Physiol Biochem2000;10:371-378.

66 Strbak V, Greer MA: Regulation of hormonesecretion by acute cell volume changes:Ca(2+)-independent hormone secretion.Cell Physiol Biochem 2000;10:393-402.

67 Anfinogenova YJ, Rodriguez X,Grygorczyk R, Adragna NC, Lauf PK,Hamet P, Orlov SN: Swelling-induced K(+)fluxes in vascular smooth muscle cells aremediated by charybdotoxin-sensitive K(+)channels. Cell Physiol Biochem2001;11:295-310.

68 Wöll E, Ritter M, Haller T, Völkl H, LangF: Calcium entry stimulated by swelling ofMadin-Darby canine kidney cells. Nephron1996;74:150-157.

69 vom Dahl S, Hallbrucker C, Lang F,Haussinger D: Role of eicosanoids, inositolphosphates and extracellular Ca2+ in cell-volume regulation of rat liver. Eur JBiochem 1991;198:73-83.

70 Baquet A, Meijer AJ, Hue L: Hepatocyteswelling increases inositol 1,4,5-trisphosphate, calcium and cyclic AMPconcentration but antagonizesphosphorylase activation by Ca2(+)-dependent hormones. FEBS Lett1991;278:103-106.

71 Suzuki M, Kawahara K, Ogawa A, MoritaT, Kawaguchi Y, Kurihara S, Sakai O:[Ca2+]i rises via G protein duringregulatory volume decrease in rabbitproximal tubule cells. Am J Physiol1990;258:F690-696.

72 Felix JA, Woodruff ML, Dirksen ER:Stretch increases inositol 1,4,5-trisphosphate concentration in airwayepithelial cells. Am J R Cell Mol Biol1996;14:296-301.

73 Fischer R, Schliess F, Haussinger D:Characterization of the hypo-osmolarity-induced Ca2+ response in cultured ratastrocytes. Glia 1997;20:51-58.

74 Tinel H, Wehner F, Kinne RK: Arachidonicacid as a second messenger forhypotonicity-induced calcium transients inrat IMCD cells. Pflugers Arch1997;433:245-253.

75 Tinel H, Kinne-Saffran E, Kinne RH:Calcium-induced calcium releaseparticipates in cell volume regulation ofrabbit TALH cells. Pflugers Arch2002;443:754-261.

76 Tsuzuki T, Okabe K, Kajiya H, Habu T:Osmotic membrane stretch increasescytosolic Ca(2+) and inhibits boneresorption activity in rat osteoclasts. Jpn JPhysiol 2000;50:67-76.

77 Roe MW, Moore AL, Lidofsky SD:Purinergic-independent calcium signalingmediates recovery from hepatocellularswelling: implications for volumeregulation. J Biol Chem 2001;276:30871-30877.

78 Shen MR, Yang TP, Tang MJ: A novelfunction of Bcl-2 overexpression inregulatory volume decrease: enhancingswelling-activated calcium entry andchloride channel activity. J Biol Chem2002;22:22.

79 Bulow A, Johansson B: Membrane stretchevoked by cell swelling increases contractileactivity in vascular smooth muscle throughdihydropyridine-sensitive pathways. ActaPhysiol Scand 1994;152:419-427.

80 Souza MM, Gross S, Boyle RT, LiebermanM: Na+/K+-ATPase inhibition duringcardiac myocyte swelling: involvement ofintracellular pH and Ca2+. Mol CellBiochem 2000;210:173-183.

81 Sauer H, Ritgen J, Hescheler J, WartenbergM: Hypotonic Ca2+ signaling and volumeregulation in proliferating and quiescentcells from multicellular spheroids. J CelPhysiol 1998;175:129-140.



253

82 Lemonnier L, Prevarskaya N, Shuba Y,Vanden Abeele F, Nilius B, Mazurier J,Skryma R: Ca2+ modulation of volume-regulated anion channels: evidence forcolocalization with store-operated channels.Faseb J 2002;16:222-224.

83 Sauer H, Hescheler J, Wartenberg M:Mechanical strain-induced Ca(2+) wavesare propagated via ATP release andpurinergic receptor activation [seecomments]. Am J Physiol Cell Physiol2000;279:C295-307.

84 Dezaki K, Tsumura T, Maeno E, Okada Y:Receptor-mediated facilitation of cell vo-lume regulation by swelling- induced ATPrelease in human epithelial cells. Jpn JPhysiol 2000;50:235-241.

85 Shinozuka K, Tanaka N, Kawasaki K,Mizuno H, Kubota Y, Nakamura K,Hashimoto M, Kunitomo M: Participationof ATP in cell volume regulation in theendothelium after hypotonic stress. ClinExp Pharmacol Physiol 2001;28:799-803.

86 Okada Y, Maeno E, Shimizu T, Dezaki K,Wang J, Morishima S: Receptor-mediatedcontrol of regulatory volume decrease(RVD) and apoptotic volume decrease(AVD). J Physiol 2001;532:3-16.

87 Weiss H, Lang F: Ion channels activated byswelling of Madin Darby canine kidney(MDCK) cells. J Membr Biol1992;126:109-114.

88 Kinne RK, Czekay RP, Grunewald JM,Mooren FC, Kinne-Saffran E:Hypotonicity-evoked release of organicosmolytes from distal renal cells: systems,signals, and sidedness. Ren PhysiolBiochem 1993;16:66-78.

89 Van der Wijk T, Tomassen S, De Jonge H,Tilly B: Signalling mechanisms involved involume regulation of intestinal epithelialcells. Cell Physiol Biochem 2000;10:289-296.

90 Shen MR, Furla P, Chou CY, Ellory JC:Myosin light chain kinase modulateshypotonicity-induced Ca2+ entry and Cl-channel activity in human cervical cancercells. Pflugers Arch 2002;444:276-285.

91 Fürst J, Bazzini C, Jakab M, Meyer G,König M, Gschwentner M, Ritter M,Schmarda A, Botta G, Benz R, Deetjen P,Paulmichl M: Functional reconstitution ofICln in lipid bilayers. Pflugers Arch2000;440:100-115.

92 Fürst J, Gschwentner M, Ritter M, BottàG, Jakab M, Mayer M, Garavaglia L,Bazzini C, Rodighiero S, Meyer G,Eichmüller S, Wöll E, Paulmichl M:Molecular and Functional Aspects ofAnionic Channels activated duringRegulatory Volume Decrease in mammaliancells. Pflügers Archiv 2002;in press.

93 Garavaglia L, Rodighiero S, Bertocchi C,Manfredi R, Furst J, Gschwentner M, RitterM, Bazzini C, Botta G, Jakab M, Meyer G,Paulmichl M: ICln channels reconstitutedin heart-lipid bilayer are selective tochloride. Pflugers Arch 2002;443:748-753.

94 Missiaen L, De Smedt H, Parys JB, SienaertI, Vanlingen S, Droogmans G, Nilius B,Casteels R: Hypotonically induced calciumrelease from intracellular calcium stores. JBiol Chem 1996;271:4601-4604.

95 Hashii M, Nozawa Y, Higashida H:Bradykinin-induced Cytosolic Ca2+Oscillations and Inositol Tetrakisphosphate-induced Ca2+ Influx in Voltage-clampedras-transformed NIH/3T3 Fibroblasts. J BiolChem 1993;268:19403-19410.

96 Ritter M, Wöll E: Modification of cellularion transport by Ha-ras oncogeneexpression: Steps towards malignanttransformation. Cell Physiol Biochem1996;6:245-270.

97 Ritter M, Wöll E, Waldegger S, HäussingerD, Lang HJ, Scholz W, Scholkens B, LangF: Cell shrinkage stimulates bradykinin-induced cell membrane potentialoscillations in NIH 3T3 fibroblastsexpressing the ras-oncogene. Pflugers Arch1993;423:221-224.

98 Du XY, Sorota S: Protein kinase Cstimulates swelling-induced chloridecurrent in canine atrial cells. Pflugers Arch1999;437:227-234.

99 Mitchell CH, Zhang JJ, Wang L, Jacob TJ:Volume-sensitive chloride current inpigmented ciliary epithelial cells: role ofphospholipases [see comments]. Am JPhysiol 1997;272:C212-222.

100 Hardy SP, Goodfellow HR, Valverde MA,Gill DR, Sepulveda V, Higgins CF: Proteinkinase C-mediated phosphorylation of thehuman multidrug resistance P-glycoproteinregulates cell volume-activated chloridechannels [published erratum appears inEMBO J 1995 Apr 18;14(8):1844]. EMBOJ 1995;14:68-75.

101 Coca-Prados M, Anguita J, Chalfant ML,Civan MM: PKC-sensitive Cl- channelsassociated with ciliary epithelial homologueof pICln. Am J Physiol 1995;268:C572-579.

102 von Weikersthal SF, Barrand MA, HladkySB: Functional and molecularcharacterization of a volume-sensitivechloride current in rat brain endothelialcells. J Physiol 1999;516:75-84.

103 Lev S, Moreno H, Martinez R, Canoll P,Peles E, Musacchio JM, Plowman GD,Rudy B, Schlessinger J: Protein tyrosinekinase PYK2 involved in Ca(2+)-inducedregulation of ion channel and MAP kinasefunctions. Nature 1995;376:737-745.

104 Tokiwa G, Dikic I, Lev S, Schlessinger J:Activation of Pyk2 by stress signals andcoupling with JNK signaling pathway.Science 1996;273:792-794.

105 Lauf PK, Zhang J, Gagnon KB, Delpire E,Fyffe RE, Adragna NC: K-Cl cotransport:immunohistochemical and ion flux studiesin human embryonic kidney (HEK293)cells transfected with full-length and C-terminal-domain-truncated KCC1 cDNAs.Cell Physiol Biochem 2001;11:143-160.

106 Tilly BC, van den Berghe N, Tertoolen LG,Edixhoven MJ, de Jonge HR: Proteintyrosine phosphorylation is involved inosmoregulation of ionic conductances. JBiol Chem 1993;268:19919-19922.

107 Sorota S: Tyrosine protein kinase inhibitorsprevent activation of cardiac swelling-induced chloride current. Pflugers Arch1995;431:178-185.

108 Crepel V, Panenka W, Kelly ME, MacVicarBA: Mitogen-activated protein and tyrosinekinases in the activation of astrocyte volu-me-activated chloride current. J Neurosci1998;18:1196-1206.

109 Voets T, Manolopoulos V, Eggermont J,Ellory C, Droogmans G, Nilius B:Regulation of a swelling-activated chloridecurrent in bovine endothelium by proteintyrosine phosphorylation and G proteins. JPhysiol 1998;506:341-352.

110 Shuba YM, Prevarskaya N, Lemonnier L,Van Coppenolle F, Kostyuk PG, Mauroy B,Skryma R: Volume-regulated chlorideconductance in the LNCaP human prostatecancer cell line. Am J Physiol Cell Physiol2000;279:C1144-1154.

111 Shen MR, Chou CY, Browning JA, WilkinsRJ, Ellory JC: Human cervical cancer cellsuse Ca2+ signalling, protein tyrosinephosphorylation and MAP kinase inregulatory volume decrease. J Physiol2001;537:347-362.

112 Pasantes-Morales H, Franco R, Torres-Marquez ME, Hernandez-Fonseca K,Ortega A: Amino acid osmolytes inregulatory volume decrease andisovolumetric regulation in brain cells:contribution and mechanisms. Cell PhysiolBiochem 2000;10:361-370.

113 Ritchie JW, Baird FE, Christie GR, StewartA, Low SY, Hundal HS, Taylor PM:Mechanisms of glutamine transport in ratadipocytes and acute regulation by cellswelling. Cell Physiol Biochem2001;11:259-270.

114 Uhlemann AC, Muller C, Madlung J,Gulbins E, Lang F: Inhibition of CD95/Fas-induced DNA degradation by osmotic cellshrinkage. Cell Physiol Biochem2000;10:219-28.

115 Lepple-Wienhues A, Szabo I, Wieland U,Heil L, Gulbins E, Lang F: Tyrosine kinasesopen lymphocyte chloride channels. CellPhysiol Biochem 2000;10:307-312.

116 Lang F, Ritter M, Gamper N, Huber S,Fillon S, Tanneur V, Lepple-Wienhues A,Szabo I, Bulbins E: Cell volume in theregulation of cell proliferation and apoptoticcell death. Cell Physiol Biochem2000;10:417-428.

117 Lepple-Wienhues A, Szabo I, Laun T, KabaNK, Gulbins E, Lang F: The tyrosine kinasep56lck mediates activation of swelling-induced chloride channels in lymphocytes.J Cell Biol 1998;141:281-286.


254

118 Pedersen SF, Beisner KH, Hougaard C,Willumsen BM, Lambert IH, Hoffmann EK:Rho family GTP binding proteins areinvolved in the regulatory volume decreaseprocess in NIH3T3 mouse fibroblasts. JPhysiol 2002;541:779-796.

119 Thoroed SM, Bryan-Sisneros A,Doroshenko P: Protein phosphotyrosinephosphatase inhibitors suppress regulatoryvolume decrease and the volume-sensitiveCl- conductance in mouse fibroblasts.Pflugers Arch 1999;438:133-140.

120 Doroshenko P: Pervanadate inhibits volu-me-sensitive chloride current in bovinechromaffin cells. Pflugers Arch1998;435:303-309.

121 Niisato N, Post M, Van Driessche W,Marunaka Y: Cell swelling activates stress-activated protein kinases, p38 MAP kinaseand JNK, in renal epithelial A6 cells.Biochem Biophys Res Commun1999;266:547-550.

122 Zhang Z, Yang XY, Cohen DM:Hypotonicity activates transcriptionthrough ERK-dependent and - independentpathways in renal cells. Am J Physiol1998;275:C1104-1112.

123 Schliess F, Sinning R, Fischer R,Schmalenbach C, Haussinger D: Calcium-dependent activation of Erk-1 and Erk-2after hypo-osmotic astrocyte swelling.Biochem J 1996;320:167-171.

124 vom Dahl S, Schliess F, Graf D, HaussingerD: Role of p38(MAPK) in cell volumeregulation of perfused rat liver. Cell PhysiolBiochem 2001;11:285-294.

125 Tilly BC, Gaestel M, Engel K, EdixhovenMJ, de Jonge HR: Hypo-osmotic cellswelling activates the p38 MAP kinasesignalling cascade. FEBS Lett1996;395:133-136.

126 van der Wijk T, Dorrestijn J, Narumiya S,Maassen JA, de Jonge HR, Tilly BC:Osmotic swelling-induced activation of theextracellular-signal- regulated proteinkinases Erk-1 and Erk-2 in intestine 407cells involves the Ras/Raf-signallingpathway. Biochem J 1998;331:863-869.

127 Doroshenko P, Penner R, Neher E: Novelchloride conductance in the membrane ofbovine chromaffin cells activated byintracellular GTP gamma S. J Physiol1991;436:711-724.

128 Nilius B, Voets T, Prenen J, Barth H,Aktories K, Kaibuchi K, Droogmans G,Eggermont J: Role of Rho and Rho kinasein the activation of volume-regulated anionchannels in bovine endothelial cells. JPhysiol 1999;516:67-74.

129 Estevez AY, Bond T, Strange K: Regulationof I(Cl,swell) in neuroblastoma cells by Gprotein signaling pathways. Am J PhysiolCell Physiol 2001;281:C89-98.

130 Takai Y, Sasaki T, Matozaki T: Small GTP-binding proteins. Physiol Rev 2001;81:153-208.

131 Bishop AL, Hall A: Rho GTPases and theireffector proteins. Biochem J 2000;348:241-255.

132 Tilly BC, Edixhoven MJ, Tertoolen LG,Morii N, Saitoh Y, Narumiya S, de JongeHR: Activation of the osmo-sensitivechloride conductance involves P21rho andis accompanied by a transientreorganization of the F-actin cytoskeleton.Mol Biol Cell 1996;7:1419-1427.

133 Nilius B, Prenen J, Walsh MP, Carton I,Bollen M, Droogmans G, Eggermont J:Myosin light chain phosphorylation-dependent modulation of volume- regulatedanion channels in macrovascularendothelium. FEBS Lett 2000;466:346-350.

134 Carton I, Trouet D, Hermans D, Barth H,Aktories K, Droogmans G, Jorgensen NK,Hoffmann EK, Nilius B, Eggermont J:RhoA exerts a permissive effect on volu-me-regulated anion channels in vascularendothelial cells. Am J Physiol Cell Physiol2002;283:C115-125.

135 Waldegger S, Barth P, Raber G, Lang F:Cloning and characterization of a putativehuman serine/threonine protein kinasetranscriptionally modified during anisotonicand isotonic alterations of cell†volume.PNAS 1997;94:4440-4445.

136 Waldegger S, Barth P, Forrest JNJ, GregerR, Lang F: Cloning of sgk serine-threonineprotein kinase from shark rectal gland - agene induced by hypertonicity andsecretagogues. Pflugers Arch1998;436:575-580.

137 Waldegger S, Klingel K, Barth P, Sauter M,Rfer ML, Kandolf R, Lang F: h-sgk serine-threonine protein kinase gene astranscriptional target of transforminggrowth factor beta in human intestine.Gastroenterol 1999;116:1081-1088.

138 Klingel K, Warntges S, Bock J, Wagner CA,Sauter M, Waldegger S, Kandolf R, LangF: Expression of cell volume-regulatedkinase h-sgk in pancreatic tissue. Am JPhysiol Gastrointest Liver Physiol2000;279:G998-G1002.

139 Warntges S, Friedrich B, Henke G,Duranton C, Lang A, Waldegger S,Meyermann R, Kuhl D, Speckmann J,Obermuller N, Witzgall R, Mack F, WagnerJ, Wagner A, Broer S, Lang F: Cerebrallocalization and regulation of the cell volu-me-sensitive serum- and glucocorticoid-dependent kinase SGK1. Pflugers Arch2002;443:617-624.

140 Waldegger S, Gabrysch S, Barth P, FillonS, Lang F: h-sgk serine-threonine proteinkinase as transcriptional target of p38/MAPkinase pathway in HepG2 human hepatomacells. Cell Physiol Biochem 2000;10:203-208.

141 Snyder PM, Olson DR, Thomas BC: Serumand glucocorticoid-regulated kinasemodulates Nedd4-2-mediated inhibition ofthe epithelial Na+ channel. J Biol Chem2002;277:5-8.

142 Pearce D: The role of SGK1 in hormone-regulated sodium transport. TrendsEndocrinol Metab 2001;12:341-347.

143 Naray-Fejes-Toth A, Canessa C, CleavelandES, Aldrich G, Fejes-Toth G: sgk is analdosterone-induced kinase in the renalcollecting duct. Effects on epithelial na+channels. J Biol Chem 1999;274:16973-16978.

144 Debonneville C, Flores SY, Kamynina E,Plant PJ, Tauxe C, Thomas MA, MunsterC, Chraibi A, Pratt JH, Horisberger JD,Pearce D, Loffing J, Staub O:Phosphorylation of Nedd4-2 by Sgk1regulates epithelial Na(+) channel cellsurface expression. EMBO J 2001;20:7052-7059.

145 Bohmer C, Wagner CA, Beck S, MoschenI, Melzig J, Werner A, Lin JT, Lang F,Wehner F: The shrinkage-activated Na(+)conductance of rat hepatocytes and itspossible correlation to rENaC. Cell PhysiolBiochem 2000;10:187-194.

146 Wagner CA, Ott M, Klingel K, Beck S,Melzig J, Friedrich B, Wild KN, Broer S,Moschen I, Albers A, Waldegger S,Tummler B, Egan ME, Geibel JP, KandolfR, Lang F: Effects of the serine/threoninekinase SGK1 on the epithelial Na(+)channel (ENaC) and CFTR: implicationsfor cystic fibrosis. Cell Physiol Biochem2001;11:209-218.

147 MacLeod RJ, Hamilton JR: Ca(2+)/Calmodulin kinase II and decreases inintracellular pH are required to activateK(+) channels after substantial swelling invillus epithelial cells. J Membr Biol1999;172:59-66.

148 Meisse D, Dusanter-Fourt I, Husson A,Lavoinne A: Cell swelling activates STAT1and STAT3 proteins in cultured rathepatocytes. FEBS Lett 1999;463:360-364.

149 Feranchak AP, Roman RM, SchwiebertEM, Fitz JG: Phosphatidylinositol 3-kinasecontributes to cell volume regulationthrough effects on ATP release. J Biol Chem1998;273:14906-14911.

150 Wang Y, Roman R, Lidofsky SD, Fitz JG:Autocrine signaling through ATP releaserepresents a novel mechanism for cell vo-lume regulation. Proc Natl Acad Sci U S A1996;93:12020-12025.

151 Watt WC, Lazarowski ER, Boucher RC:Cystic fibrosis transmembrane regulator-independent release of ATP. Its implicationsfor the regulation of P2Y2 receptors inairway epithelia. J Biol Chem1998;273:14053-14058.

152 Grygorczyk R, Hanrahan JW: CFTR-independent ATP release from epithelialcells triggered by mechanical stimuli. AmJ Physiol 1997;272:C1058-1066.

153 Elgavish A, Elgavish GA: Evidence for thepresence of an ATP transport system inbrush-border membrane vesicles isolatedfrom the kidney cortex. Biochim Et BiophysActa 1985;812:595-599.



255

154 Lange J, Schlieps K, Lange K, Brandt U,Knoll-Kohler E: Detection of the ATP-dependent nonmitochondrial calcium storein a cell surface-derived vesicle fractionfrom isolated rat hepatocytes. Exp Cell Res1996;228:189-196.

155 Lange K, Brandt U: Rapid uptake ofcalcium, ATP, and inositol 1,4,5-trisphosphate via cation and anion channelsinto surface-derived vesicles from HIT cellscontaining the inositol 1,4,5-trisphosphate-sensitive calcium store. FEBS Lett1993;325:205-209.

156 Schlosser SF, Burgstahler AD, NathansonMH: Isolated rat hepatocytes can signal toother hepatocytes and bile duct cells byrelease of nucleotides. Proc Natl Acad SciUSA 1996;93:9948-9953.

157 Van der Wijk T, De Jonge HR, Tilly BC:Osmotic cell swelling-induced ATP releasemediates the activation of extracellularsignal-regulated protein kinase (Erk)-1/2but not the activation of osmo-sensitiveanion channels. Biochem J 1999;343:579-586.

158 Roman RM, Feranchak AP, Davison AK,Schwiebert EM, Fitz JG: Evidence forGd(3+) inhibition of membrane ATPpermeability and purinergic signaling. AmJ Physiol 1999;277:G1222-1230.

159 Musante L, Zegarra-Moran O, MontaldoPG, Ponzoni M, Galietta LJ: Autocrineregulation of volume-sensitive anionchannels in airway epithelial cells byadenosine. J Biol Chem 1999;274:11701-11707.

160 Roman RM, Wang Y, Lidofsky SD,Feranchak AP, Lomri N, Scharschmidt BF,Fitz JG: Hepatocellular ATP-binding cas-sette protein expression enhances ATPrelease and autocrine regulation of cell vo-lume. J Biol Chem 1997;272:21970-21976.

161 MacLeod RJ, Hamilton JR: Increases inintracellular pH and Ca(2+) are essential forK(+) channel activation after modest‘physiological’ swelling in villus epithelialcells. J Membr Biol 1999;172:47-58.

162 Breton S, Marsolais M, Lapointe JY,Laprade R: Cell volume increases ofphysiologic amplitude activate basolateralK and CI conductances in the rabbitproximal convoluted tubule. J Am SocNephrol 1996;7:2072-2087.

163 Kersting U, Wojnowski L, Steigner W,Oberleithner H: Hypotonic stress-inducedrelease of KHCO3 in fused renal epitheloid(MDCK) cells. Kidney Int 1991;39:891-900.

164 Ritter M, Paulmichl M, Lang F: Furthercharacterization of volume regulatorydecrease in cultured renal epitheloid(MDCK) cells. Pflügers Arch 1991;418:35-39.

165 Völkl H, Lang F: Ionic requirement forregulatory cell volume decrease in renalstraight proximal tubules. Pflugers Arch1988;412:1-6.

166 Völkl H, Paulmichl M, Lang F: Cell volu-me regulation in renal cortical cells. RenPhysiol Biochem 1988;3-5:158-173.

167 Livne A, Hoffmann EK: Cytoplasmicacidification and activation of Na+/H+exchange during regulatory volumedecrease in Ehrlich ascites tumor cells. JMembr Biol 1990;114:153-157.

168 Waldegger S, Busch GL, Kaba NK, ZempelG, Ling H, Heidland A, Haussinger D, LangF: Effect of cellular hydration on proteinmetabolism. Miner Electrolyte Metab1997;23:201-205.

169 Kuchkina NV, Orlov SN, Pokudin NI,Chuchalin AG: Volume-dependentregulation of the respiratory burst ofactivated human neutrophils. Experientia1993;49:995-997.

170 Ritter M, Fürst J, Wöll E, Chwatal S,Gschwentner M, Lang F, Deetjen P,Paulmichl M: Na+/H+ Exchangers: LinkingOsmotic Dysequilibrium to Modified CellFunction. Cell Physiol Biochem 2001;11:1-18.

171 Hallows KR, Restrepo D, Knauf PA:Control of intracellular pH duringregulatory volume decrease in HL-60 cells[published erratum appears in Am J Physiol1995 Mar;268(3 Pt 1):section C followingtable of contents.]. Am J Physiol1994;267:C1057-1066.

172 MacLeod RJ, Hamilton JR: Activation ofNa+/H+ exchange is required for regulatoryvolume decrease after modest\“physiological volume increases in jejunalvillus epithelial cells. J Biol Chem1996;271:23138-23145.

173 Morihata H, Nakamura F, Tsutada T, KunoM: Potentiation of a voltage-gated protoncurrent in acidosis-induced swelling of ratmicroglia. J Neurosci 2000;20:7220-7722.

174 Ganapathy V, Leibach FH: Protons andregulation of biological functions. KidneyInternational. Sppl 1991;33:S4-10.

175 Duprat F, Lesage F, Fink M, Reyes R,Heurteaux C, Lazdunski M: TASK, ahuman background K+ channel to senseexternal pH variations near physiologicalpH. EMBO J 1997;16:5464-5471.

176 Kim Y, Bang H, Kim D: TBAK-1 andTASK-1, two-pore K(+) channel subunits:kinetic properties and expression in ratheart. Am J Physiol 1999;277:H1669-1678.

177 Kim Y, Bang H, Kim D: TASK-3, a newmember of the tandem pore K(+) channelfamily. J Biol Chem 2000;275:9340-9347.

178 Pedersen KA, Jrgensen NK, Jensen BS,Olesen SP: Inhibition of the humanintermediate-conductance, Ca2+-activatedK+ channel by intracellular acidification.Pflugers Arch 2000;440:153-156.

179 Reyes R, Duprat F, Lesage F, Fink M,Salinas M, Farman N, Lazdunski M:Cloning and expression of a novel pH-sensitive two pore domain K+ channel fromhuman kidney. J Biol Chem1998;273:30863-30869.

180 Riquelme G, Diaz M, Sepulveda FV:Possible thiol group involvement inintracellular pH effect on low-conductanceCa(2+)-dependent K+ channels. Am JPhysiol 1997;273:C230-238.

181 Schulte U, Hahn H, Wiesinger H,Ruppersberg JP, Fakler B: pH-dependentgating of ROMK (Kir1.1) channels involvesconformational changes in both N and Ctermini. J Biol Chem 1998;273:34575-34579.

182 Terai T, Furukawa T, Katayama Y, HiraokaM: Effects of external acidosis on HERGcurrent expressed in Xenopus oocytes. JMol Cell Cardiol 2000;32:11-21.

183 Vereecke J, Carmeliet E: The effect ofexternal pH on the delayed rectifying K+current in cardiac ventricular myocytes.Pflugers Archiv 2000;439:739-751.

184 Zhu G, Chanchevalap S, Cui N, Jiang C:Effects of intra- and extracellularacidifications on single channel Kir2.3currents. J Physiol 1999;516:699-710.

185 Zhu G, Liu C, Qu Z, Chanchevalap S, XuH, Jiang C: CO(2) inhibits specific inwardrectifier K(+) channels by decreases in intra-and extracellular pH. J Cell Physiol2000;183:53-64.

186 Hougaard C, Jorgensen F, Hoffmann EK:Modulation of the volume-sensitive K+current in Ehrlich ascites tumour cells bypH. Pflugers Arch 2001;442:622-633.

187 Kramhoft B, Lambert IH, Hoffmann EK,Jorgensen F: Activation of Cl-dependent Ktransport in Ehrlich ascites tumor cells. AmJ Physiol 1986;251:C369-379.

188 Pasantes-Morales H, Murray RA, Lilja L,Moran J: Regulatory volume decrease incultured astrocytes. I. Potassium- andchloride-activated permeability. Am JPhysiol 1994;266:C165-171.

189 Maingret F, Lauritzen I, Patel AJ, HeurteauxC, Reyes R, Lesage F, Lazdunski M, HonoreE: TREK-1 is a heat-activated backgroundK(+) channel. EMBO J 2000;19:2483-2491.

190 Maingret F, Patel AJ, Lesage F, LazdunskiM, Honore E: Mechano- or acidstimulation, two interactive modes ofactivation of the TREK-1 potassiumchannel. J Biol Chem 1999;274:26691-26696.

191 Maingret F, Patel AJ, Lesage F, LazdunskiM, Honore E: Lysophospholipids open thetwo-pore domain mechano-gated K(+)channels TREK-1 and TRAAK. J BiolChem 2000;275:10128-10133.

192 Nemeth-Cahalan KL, Hall JE: pH andcalcium regulate the water permeability ofaquaporin 0. J Biol Chem 2000;275:6777-6782.

193 Fürst J, Jakab M, Konig M, Ritter M,Gschwentner M, Rudzki J, Danzl J, MayerM, Burtscher CM, Schirmer J, Maier B,Nairz M, Chwatal S, Paulmichl M:Structure and function of the ion channelICln. Cell Physiol Biochem 2000;10:329-34.


256

194 Hazama A, Okada Y: Ca2+ sensitivity ofvolume-regulatory K+ and Cl- channels incultured human epithelial cells. J Physiol1988;402:687-702.

195 Grinstein S, Smith DJ: Calcium-independent cell volume regualtion inhuman lymphocytes. J Gen Physiol1990;95:97-120.

196 Deutsch C, Chen LQ: Heterologousexpression of specific K+ channels in Tlymphocytes: functional consequences forvolume regulation. Proc Natl Acad Sci USA1993;90:10036-10040.

197 Huber BE, Gamper N, Lang F: Chlorideconductance and volume-regulatorynonselective cation conductance in humanred blood cell ghosts. Pflugers Arch2001;441:551-558.

198 Guizouarn H, Motais R, Garcia-Romeu F,Borgese F: Cell volume regulation: the roleof taurine loss in maintaining membranepotential and cell pH. J Physiol 2000;523Pt 1:147-154.

199 Kanli H, Norderhus E: Cell volumeregulation in proximal renal tubules fromtrout (Salmo trutta). J Exp Biol1998;201:1405-1419.

200 Souza MM, Boyle RT: A moderate decreasein temperature inhibits the calciumsignaling mechanism(s) of the regulatoryvolume decrease in chick embryocardiomyocytes. Braz J Med Biol Res2001;34:137-141.

201 Garber SS: Outwardly rectifying chloridechannels in lymphocytes. J Membr Biol1992;127:49-56.

202 Sorota S, Du XY: Delayed activation ofcardiac swelling-induced chloride currentafter step changes in cell size. J CardiovascElectrophysiol 1998;9:825-831.

203 Gschwentner M, Jungwirth A, Hofer S,Woll E, Ritter M, Susanna A, Schmarda A,Reibnegger G, Pinggera GM, Leitinger M,Frick J, Deetjen P, Paulmichl M: Blockadeof swelling-induced chloride channels byphenol derivatives. Br J Pharmacol1996;118:41-48.

204 Lang F, Ritter M, Völkl H, Häussinger D:The biological significance of cell volume.Ren Physiol Biochem 1993;16:48-65.

205 Moustakas A, Theodoropoulos PA,Gravanis A, Haussinger D, Stournaras C:The cytoskeleton in cell volume regulation.Contrib Nephrol 1998;123:121-134.

206 Cantiello HF, Prat AG, Bonventre JV,Cunningham CC, Hartwig JH, Ausiello DA:Actin-binding protein contributes to cellvolume regulatory ion channel activation inmelanoma cells. J Biol Chem1993;268:4596-4599.

207 Czech MP: PIP2 and PIP3: complex rolesat the cell surface. Cell 2000;100:603-606.

208 Janmey PA: The cytoskeleton and cellsignaling: component localization andmechanical coupling. Physiol Rev1998;78:763-781.

209 Janmey PA, Xian W, Flanagan LA:Controlling cytoskeleton structure byphosphoinositide-protein interactions:phosphoinositide binding protein domainsand effects of lipid packing. Chem PhysLipids 1999;101:93-107.

210 Sekimata M, Kabuyama Y, Emori Y,Homma Y: Morphological changes anddetachment of adherent cells induced byp122, a GTPase-activating protein for Rho.J Biol Chem 1999;274:17757-17762.

211 Stossel TP: On the crawling of animal cells.Science 1993;260:1086-1094.

212 Einspahr KJ, Peeler TC, Thompson GAJ:Rapid changes in polyphosphoinositidemetabolism associated with the response ofDunaliella salina to hypoosmotic shock. JBiol Chem 1988;263:5775-5779.

213 Ha KS, Thompson GAJ: Biphasic changesin the level and composition of Dunaliellasalina plasma membrane diacylglycerolsfollowing hypoosmotic shock.Biochemistry 1992;31:596-603.

214 Keenan C, Kelleher D: Protein kinase C andthe cytoskeleton. Cell Signal 1998;10:225-232.

215 Toker A: Signaling Through Protein KinaseC. Front Biosci 1998;3:d1134-1147.

216 Bender AS, Neary JT, Norenberg MD: Roleof phosphoinositide hydrolysis in astrocytevolume regulation. J Neurochem1993;61:1506-1514.

217 Janmey PA: Phosphoinositides and calciumas regulators of cellular actin assembly anddisassembly. Annu Rev Physiol1994;56:169-191.

218 Papakonstanti EA, Vardaki EA, C. S: ActinCytoskeleton: A Signaling Sensor in CellVolume Regulation. Cell Physiol Biochem2000;10:257-264.

219 Berdiev BK, Prat AG, Cantiello HF,Ausiello DA, Fuller CM, Jovov B, BenosDJ, Ismailov II: Regulation of epithelialsodium channels by short actin filaments. JBiol Chem 1996;271:17704-17710.

220 Cantiello HF, Stow JL, Prat AG, AusielloDA: Actin filaments regulate epithelial Na+channel activity. Am J Physiol1991;261:C882-888.

221 Prat AG, Bertorello AM, Ausiello DA,Cantiello HF: Activation of epithelial Na+channels by protein kinase A requires actinfilaments. Am J Physiol 1993;265:C224-233.

222 Prat AG, Holtzman EJ, Brown D,Cunningham CC, Reisin IL, Kleyman TR,McLaughlin M, Jackson GRJ, Lydon J,Cantiello HF: Renal epithelial protein (Apx)is an actin cytoskeleton-regulated Na+channel. J Biol Chem 1996;271:18045-18053.

223 Smith PR, Saccomani G, Joe EH, AngelidesKJ, Benos DJ: Amiloride-sensitive sodiumchannel is linked to the cytoskeleton in renalepithelial cells. Proc Natl Acad Sci USA1991;88:6971-6975.

224 Zuckerman JB, Chen X, Jacobs JD, Hu B,Kleyman TR, Smith PR: Association of theepithelial sodium channel with Apx andalpha-spectrin in A6 renal epithelial cells.J Biol Chem 1999;274:23286-23295.

225 Lader AS, Kwiatkowski DJ, Cantiello HF:Role of gelsolin in the actin filamentregulation of cardiac L-type calciumchannels. Am J Physiol 1999;277:C1277-1283.

226 Pascarel C, Brette F, Le Guennec JY:Enhancement of the T-type calcium currentby hyposmotic shock in isolated guinea-pigventricular myocytes. J Mol Cell Cardiol2001;33:1363-1369.

227 Ehrhardt AG, Frankish N, Isenberg G: Alarge-conductance K+ channel that isinhibited by the cytoskeleton in the smoothmuscle cell line DDT1 MF-2. J Physiol1996;496 ( Pt 3):663-676.

228 Jing J, Peretz T, Singer-Lahat D,Chikvashvili D, Thornhill WB, Lotan I:Inactivation of a voltage-dependent K+channel by beta subunit. Modulation by aphosphorylation-dependent interactionbetween the distal C terminus of alphasubunit and cytoskeleton. J Biol Chem1997;272:14021-14024.

229 Maguire G, Connaughton V, Prat AG,Jackson GRJ, Cantiello HF: Actincytoskeleton regulates ion channel activityin retinal neurons. Neuroreport 1998;9:665-670.

230 Bretscher A: Regulation of cortical structureby the ezrin-radixin-moesin protein family.Curr Opin Cell Biol 1999;11:109-116.

231 Cantiello HF: Role of the actin cytoskeletonin the regulation of the cystic fibrosistransmembrane conductance regulator. ExpPhysiol 1996;81:505-514.

232 Haussler U, Rivet-Bastide M, Fahlke C,Muller D, Zachar E, Rudel R: Role of thecytoskeleton in the regulation of Cl-channels in human embryonic skeletalmuscle cells. Pflugers Arch 1994;428:323-330.

233 Lascola CD, Nelson DJ, Kraig RP:Cytoskeletal actin gates a Cl- channel inneocortical astrocytes. J Neurosci1998;18:1679-1692.

234 Suzuki M, Miyazaki K, Ikeda M,Kawaguchi Y, Sakai O: F-actin networkmay regulate a Cl- channel in renal proximaltubule cells. J Membr Biol 1993;134:31-39.

235 Shen MR, Chou CY, Hsu KF, Hsu KS, WuML: Modulation of volume-sensitive Cl -channels and cell volume by actin filamentsand microtubules in human cervical cancerHT-3 cells. Acta Physiol Scand1999;167:215-225.

236 Zhang J, Larsen TH, Lieberman M: F-actinmodulates swelling-activated chloridecurrent in cultured chick cardiac myocytes.Am J Physiol 1997;273:C1215-1224.

237 Mills JW, Schwiebert EM, Stanton BA: Thecytoskeleton and membrane transport. CurrOpin Nephrol Hypertens 1994;3:529-534.



257

238 Sachs F: Biophysics of mechanoreception.Membr Biochem 1986;6:173-195.

239 Lang F, Ritter M, Woll E, Weiss H,Haussinger D, Hoflacher J, Maly K,Grunicke H: Altered cell volume regulationin ras oncogene expressing NIH fibroblasts.Pflugers Arch 1992;420:424-427.

240 Cantiello HF: Role of actin filamentorganization in cell volume and ion channelregulation. J Exp Zool 1997;279:425-435.

241 Henson JH: Relationships between the actincytoskeleton and cell volume regulation.Microsc Res Tech 1999;47:155-162.

242 Szaszi K, Grinstein S, Orlowski J, KapusA: Regulation of the epithelial Na(+) /H(+)exchanger isoform by the cytoskeleton. CellPhysiol Biochem 2000;10:265-272.

243 Lang F, Friedrich F, Kahn E, Wöll E,Hammerer M, Waldegger S, Maly K,Grunicke H: Bradykinin-inducedoscillaitons of cell membrane potential incells expressing the Ha-ras oncogene. J BiolChem 1991;266:4938-4942.

244 Ritter M, Dartsch P, Waldegger S, Haller T,Zwierzina H, Lang HJ, Lang F: Effects ofbradykinin on NIH 3T3 fibroblastspretreated with lithium. Mimicking eventsof Ha-ras oncogene expression. Biochim EtBiophys Acta 1997;1358:23-30.

245 Ritter M, Woll E, Haller T, Dartsch PC,Zwierzina H, Lang F: Activation of Na+/H(+)-exchanger by transforming Ha-rasrequires stimulated cellular calcium influxand is associated with rearrangement of theactin cytoskeleton. E J Cell Biology1997;72:222-228.

246 Ritter M, Wöll E, Häussinger D, Lang F:Effects of bradykinin on cell volume andintracellular pH in NIH 3T3 fibroblastsexpressing the ras oncogene. FEBS Lett1992;307:367-370.

247 Wöll E, Ritter M, Offner F, Lang HJ,Schölkens B, Häussinger D, Lang F: Effectsof HOE 694 - a novel inhibitor of Na+/H+exchange - on NIH 3T3 fibroblastsexpressing the ras oncogene. E J Pharmacol1993;246:269-273.

248 Wöll E, Ritter M, Scholz W, Häussinger D,Lang F: The role of calcium in cellshrinkage and intracellular alkalinization bybradykinin in Ha-ras oncogene expressingcells. FEBS Lett 1993;322:261-265.

249 Ribeiro CM, Reece J, Putney JWJ: Role ofthe cytoskeleton in calcium signaling inNIH 3T3 cells. An intact cytoskeleton isrequired for agonist-induced [Ca2+]isignaling, but not for capacitative calciumentry. J Biol Chem 1997;272:26555-26561.

250 Lange K, Brandt U: Calcium storage andrelease properties of F-actin: evidence forthe involvement of F-actin in cellularcalcium signaling. FEBS Lett1996;395:137-142.

251 Watson PA: Direct stimulation of adenylatecyclase by mechanical forces in S49 mouselymphoma cells during hyposmoticswelling. J Biol Chem 1990;265:6569-6575.

252 Watson PA, Giger KE, Frankenfield CM:Activation of adenylate cyclase duringswelling of S49 cells in hypotonic mediumis not involved in subsequent volumeregulation. Mol Cell Biochem 1991;104:51-56.

253 Kim RD, Darling CE, Roth TP, RicciardiR, Chari RS: Activator protein 1 activationfollowing hypoosmotic stress in HepG2cells is actin cytoskeleton dependent. J SurgRes 2001;100:176-182.

254 Ito T, Suzuki A, Stossel TP: Regulation ofwater flow by actin-binding protein-induced actin gelatin. Biophys J1992;61:1301-1305.

255 Ito T, Zaner KS, Stossel TP: Nonideality ofvolume flows and phase transitions of F-actin solutions in response to osmotic stress.Biophys J 1987;51:745-753.

256 Lange K: Regulation of cell volume viamicrovillar ion channels. J Cell Physiol2000;185:21-35.

257 Ritter M: Cell volume regulatory iontransport in cell migration. Contrib Nephrol1998;123:135-157.

258 Cantiello HF, Patenaude C, Zaner K:Osmotically induced electrical signals fromactin filaments. Biophys J 1991;59:1284-1289.

259 Reid JM, O’Neil RG: Osmomechanicalregulation of membrane trafficking inpolarized cells. Biochem Biophys ResCommun 2000;271:429-434.

260 Webster CR, Blanch CJ, Phillips J, AnwerMS: Cell swelling-induced translocation ofrat liver Na+/Taurocholate cotransportpolypeptide is mediated via thephosphoinositide 3-kinase signalingpathway. J Biol Chem 2000;275:29754-29760.

261 Paulmichl M, Li Y, Wickman K, AckermanM, Peralta E, Clapham D: New mammalianchloride channel identified by expressioncloning. Nature 1992;356:238-241.

262 Gschwentner M, Nagl UO, Woll E,Schmarda A, Ritter M, Paulmichl M:Antisense oligonucleotides suppress cell-volume-induced activation of chloridechannels. Pflugers Arch 1995;430:464-470.

263 Chen L, Wang L, Jacob TJ: Association ofintrinsic pICln with volume-activated Cl-current and volume regulation in a nativeepithelial cell. Am J Physiol1999;276:C182-192.

264 Hubert MD, Levitan I, Hoffman MM,Zraggen M, Hofreiter ME, Garber SS:Modulation of volume regulated anioncurrent by I(Cln). Biochim Et Biophys Acta2000;1466:105-114.

265 Schwartz RS, Rybicki AC, Nagel RL:Molecular cloning and expression of achloride channel-associated protein pIClnin human young red blood cells: associationwith actin. Biochem J 1997;327 ( Pt 2):609-616.

266 Laich A, Gschwentner M, Krick W, NaglUO, Fürst J, Hofer S, Susanna A, SchmardaA, Deetjen P, Burckhardt G, Paulmichl M:ICln, a chloride channel cloned from kidneycells, is activated during regulatory volu-me decrease. Kidney Int 1997;51:477-478.

267 Tao GZ, Komatsuda A, Miura AB,Kobayashi A, Itoh H, Tashima Y: pIClnpredominantly localizes at luminal surfacemembranes of distal tubules and Henle’sascending limbs. Biochem Biophys ResCom 1998;247:668-673.

268 Musch MW, Luer CA, Davis-Amaral EM,Goldstein L: Hypotonic stress inducestranslocation of the osmolyte channelprotein pICln in embryonic skate (Rajaeglanteria) heart. J Exp Zool 1997;277:460-463.

269 Musch MW, Davis-Amaral EM,Vandenburgh HH, Goldstein L:Hypotonicity stimulates translocation ofICln in neonatal rat cardiac myocytes.Pflugers Arch 1998;436:415-422.

270 Emma F, Breton S, Morrison R, Wright S,Strange K: Effect of cell swelling on mem-brane and cytoplasmic distribution of pICln.Am J Physiol 1998;274:C1545-1551.

271 Sanchez-Torres J, Huang W, Civan MM,Coca-Prados M: Effects of hypotonicswelling on the cellular distribution andexpression of pI(Cln) in humannonpigmented ciliary epithelial cells.Current Eye Res 1999;18:408-416.

272 Ravasio A, Ritter M, Chwatal S, Jakab M,Eichmüller S, Burtscher C, Fürst J,Paulmichl M: Probing the swelling inducedshift of the ICln ion channel protein byfluorescence resonance enrgy transfer(FRET) Pflügers Arch (Abrstract)2002;443.

273 Burtscher C, Jakab M, Gschwentner M,Ravasio A, Laich A, Chwatal S, SchirmerJ, Eichmüller S, Fürst J, Dossena S, RitterM, Paulmichl M: Hypotonicity inducedcytosol to membrane shift of the ICln ionchannel and acceleration of regulatory vo-lume decrease currents by repeated cellswelling Pflügers Arch (Abstract).2002;443.

274 Krapivinsky GB, Ackerman MJ, GordonEA, Krapivinsky LD, Clapham DE:Molecular characterization of a swelling-induced chloride conductance regulatoryprotein, pICln. Cell 1994;76:439-448.

275 Li Y-Y, Tao G-Z, Nagasawa H, Tazawa H,Kobayashi A, Itoh H, Tashima Y: pICln andcytosolic F-actin constitute a heteromericcomplex with a constant molecular mass inrat skeletal muscles. J Biochem (Tokyo)1999;126:643-649.

276 Tang CJ, Tang TK: The 30-kD domain ofprotein 4.1 mediates its binding to thecarboxyl terminus of pICln, a proteininvolved in cellular volume regulation.Blood 1998;92:1442-1447.


258

277 Krapivinsky G, Pu W, Wickman K,Krapivinsky L, Clapham DE: pICln bindsto a mammalian homolog of a yeast proteininvolved in regulation of cell morphology.J Biol Chem 1998;273:10811-10814.

278 Emma F, Sanchez-Olea R, Strange K:Characterization of pI(Cln) bindingproteins: identification of p17 andassessment of the role of acidic domains inmediating protein-protein interactions.Biochim Et Biophys Acta 1998;1404:321-328.

279 van den Berg B, Wain R, Dobson CM, EllisRJ: Macromolecular crowding perturbsprotein refolding kinetics: implications forfolding inside the cell. EMBO J2000;19:3870-3875.

280 Burg MB: Macromolecular crowding as acell volume sensor. Cell Physiol Biochem2000;10:251-256.

281 Minton AP: Implications ofmacromolecular crowding for proteinassembly. Curr Opin Struct Biol2000;10:34-39.

282 Minton AP, Colclasure GC, Parker JC:Model for the role of macromolecularcrowding in regulation of cellular volume[published erratum appears in Proc NatlAcad Sci USA 1993 Feb 1;90(3):1137].Proc Natl Acad Sci USA 1992;89:10504-10506.

283 Zimmerman SB, Minton AP:Macromolecular crowding: biochemical,biophysical, and physiologicalconsequences. Annu Rev Biophys BiomolStruct 1993;22:27-65.

284 Colclasure GC, Parker JC: Cytosolic proteinconcentration is the primary volume signalin dog red cells. J Gen Physiol 1991;98:881-892.

285 Colclasure GC, Parker JC: Cytosolic proteinconcentration is the primary volume signalfor swelling-induced [K-Cl] cotransport indog red cells. J Gen Physiol 1992;100:1-10.

286 Parker JC, Colclasure GC: Macromolecularcrowding and volume perception in dog redcells. Mol Cell Biochem 1992;114:9-11.

287 Al-Habori M: Macromolecular crowdingand its role as intracellular signalling of cellvolume regulation. Int J Biochem Cell Biol2001;33:844-864.

288 Zimmerman SB, Harrison B:Macromolecular crowding increasesbinding of DNA polymerase to DNA: anadaptive effect. Proc Natl Acad Sci USA1987;84:1871-1875.

289 Dunham PB: Effects of urea on K-Clcotransport in sheep red blood cells:evidence for two signals of swelling. Am JPhysiol 1995;268:C1026-1032.

290 Hallbrucker C, vom Dahl S, Ritter M, LangF, Haussinger D: Effects of urea on K+fluxes and cell volume in perfused rat liver.Pflugers Arch 1994;428:552-560.

291 Kaji DM, Diaz J, Parker JC: Urea inhibitsNa-K-2Cl cotransport in medullary thickascending limb cells. Am J Physiol1997;272:C615-621.

292 Kaji DM, Gasson C: Urea activation of K-Cl transport in human erythrocytes. Am JPhysiol 1995;268:C1018-1025.

293 Lim J, Gasson C, Kaji DM: Urea inhibitsNaK2Cl cotransport in human erythrocytes.J Clin Invest 1995;96:2126-2132.

294 Parker JC: Urea alters set point volume forK-Cl cotransport, Na-H exchange, and Ca-Na exchange in dog red blood cells. Am JPhysiol 1993;265:C447-452.

295 Parker JC, Dunham PB, Minton AP: Effectsof ionic strength on the regulation of Na/Hexchange and K-Cl cotransport in dog redblood cells. J Gen Physiol 1995;105:677-699.

296 Cannon CL, Basavappa S, Strange K:Intracellular ionic strength regulates the vo-lume sensitivity of a swelling-activatedanion channel. Am J Physiol1998;275:C416-422.

297 Meijer AJ, Baquet A, Gustafson L, vanWoerkom GM, Hue L: Mechanism ofactivation of liver glycogen synthase byswelling. J Biol Chem 1992;267:5823-5828.

298 Pederson BA, Nordlie MA, Foster JD,Nordlie RC: Effects of ionic strength andchloride ion on activities of the glucose-6-phosphatase system: regulation of thebiosynthetic activity of glucose-6-phosphatase by chloride ion inhibition/deinhibition. Arch Biochem Biophys1998;353:141-151.

299 Baquet A, Hue L, Meijer AJ, van WoerkomGM, Plomp PJ: Swelling of rat hepatocytesstimulates glycogen synthesis. J Biol Chem1990;265:955-959.

300 Best L, Sheader EA, Brown PD: A volu-me-activated anion conductance in insulin-secreting cells. Pflugers Arch1996;431:363-370.

301 Best L, Miley HE, Brown PD, Cook LJ:Methylglyoxal causes swelling andactivation of a volume-sensitive anionconductance in rat pancreatic beta-cells. JMembr Biol 1999;167:65-71.

302 Best L: Evidence that glucose-inducedelectrical activity in rat pancreatic beta-cellsdoes not require KATP channel inhibition.J Membr Biol 2002;185:193-200.

303 Haussinger D: Control of protein turnoverby the cellular hydratation state. Ital JGastroenterol 1993;25:42-48.

304 Haussinger D, Lang F, Gerok W: Regulationof cell function by the cellular hydrationstate. Am J Physiol 1994;267:E343-355.

305 Schliess F, Haeussinger D: Cell hydrationand insulin signalling. Cell PhysiolBiochem 2000;10:403-408.

306 Weiergraeber O, Haeussinger D:Hepatocellular hydration: Signaltransduction and functional implications.Cell Physiol Biochem 2000;10:409-416.

307 Graf J, Haussinger D: Ion transport inhepatocytes: mechanisms and correlationsto cell volume, hormone actions andmetabolism. J Hepatol 1996;24 Suppl 1:53-77.



mechanisms sensing and modulating signals arising from cell swelling

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