Adhesion Adhesion

Cell junctionsCell junctions

Dr. habil. Kőhidai LászlóDr. habil. Kőhidai LászlóAssoc. ProfessorAssoc. ProfessorDept. Genetics, Cell- and ImmunobiologyDept. Genetics, Cell- and ImmunobiologySemelweis UniversitySemelweis University

20201414 – ED – ED

Significance of cell-adhesion:Significance of cell-adhesion: formation of cell laformation of cell layersyers

Significance ofSignificance ofcell-adhcell-adhesesion:ion:

Formation of Formation of multiplemultiplelayers of cellslayers of cells

AdhesionAdhesion

„„Rolling”Rolling”

EntryEntry

MigrationMigration

Lymphocytes cross the endotLymphocytes cross the endothhelel

homing receptorhoming receptor

vascular addressinvascular addressin

Main groups of cell adhesion Main groups of cell adhesion moleculesmolecules

Main adhesion molecules expressedMain adhesion molecules expressed on the cells on the cells duringduring adhesion adhesion

CadhedrinsCadhedrinshomophhomophilil SelectinsSelectins heterophheterophilil IntegrinsIntegrins heterophheterophilil Adh. mol. with Adh. mol. with immunoglobulinimmunoglobulin homophhomophilildomaindomain

Ca2+

ECMECM i.e. integrini.e. integrin

i.c. linker prot.i.c. linker prot.

i.e. cadherini.e. cadherin

cyto-cyto-sskkele-ele-tonton

CaCa2+2+

CaCa2+2+

CaCa2+2+

HomophHomophilil connection connection Cell-cellCell-cell CaCa2+2+-dependent binding-dependent binding I.c. anchored to actin or I.c. anchored to actin or intermedier filamentumintermedier filamentum Significant role in Significant role in developmentdevelopment of vertebratesof vertebrates

catecatenninin

actin oractin orIFIF

CadherinCadherin

Tissue-specificity:Tissue-specificity:N - nerveN - nerveP - placentaP - placentaE - epithelialE - epithelial

Ig-likeIg-likedomainsdomains

CAM = Cell Adhesion MoleculesCAM = Cell Adhesion Molecules

5 pcs. Ig-type domain5 pcs. Ig-type domain Ca Ca 2+ 2+ indep. adhesionindep. adhesion HomophHomophii connection - typical connection - typical HeterophHeterophilil connection - rare connection - rare More than 20 variationsMore than 20 variations Expressed in the critical phase of Expressed in the critical phase of ddevelopment evelopment Tissue-specificity:Tissue-specificity:

N-CAM - neuronN-CAM - neuronL-CAM - liverL-CAM - liver

In melanomaIn melanoma – relation between – relation between ICAM-1 ICAM-1 density anddensity and the theMetastatic activity of the tumourMetastatic activity of the tumour

SelectinsSelectins

LeLecctin type proteins,tin type proteins,Carbohydrate speciCarbohydrate specifficityicity

Tissue-specificity:Tissue-specificity:E - epithelialE - epithelialL - lymphoidL - lymphoidP - placentaP - placenta

L selectin: it has role in the initial phase of adhesion; L selectin: it has role in the initial phase of adhesion; in newborns the level of L sel. is low – the low in newborns the level of L sel. is low – the low number of inflammations (?!)number of inflammations (?!)

SS

SS

IntegrinIntegrin CaCa2+2+-dependent binding-dependent binding HeterophHeterophilil connection connection Focal contactsFocal contacts Its i.c. linker proteins areIts i.c. linker proteins are i.e.. talin, i.e.. talin, -actinin, vinculin-actinin, vinculin RGD sequ. Is significant inRGD sequ. Is significant in e.c. bindinge.c. binding Partner molecules:Partner molecules: fibronectinfibronectin

lamininlaminincollagencollagen

DeficiencyDeficiency (()) – the adhesion of leukocytes affected, results – the adhesion of leukocytes affected, resultsthe increase ofthe increase of inflammations inflammations

Cell-cell junctionsCell-cell junctions

Junctional complexesJunctional complexes

• Tight junctionTight junction• Zonula adherensZonula adherens• DesmosomeDesmosome• Gap junctionGap junction• HemidesmosomeHemidesmosome• InterdigitationInterdigitation

Tight junction = zonula occludensTight junction = zonula occludens

Intercellular space Intercellular space

Lipid bilayer Lipid bilayer CytoplasCytoplasmmic faceic face

Transmembrane proteinsTransmembrane proteinsoccludinoccludin

0.6 0.6 mmmm

Negative staining to detect „insulating” effectNegative staining to detect „insulating” effect of tight junctionof tight junction

Transport accross tight junctionTransport accross tight junction

System of occludin – lines System of occludin – lines

Role of tight junctionRole of tight junction

• Mechanical connectionMechanical connection• BarrierBarrier• Inhibits: Inhibits:

entry of water-soluble moleculesentry of water-soluble moleculeslateral diffusion of membrane-componentslateral diffusion of membrane-components

• CaCa2+2+ is required for the connections of occludins is required for the connections of occludins• Permeability: inorganic small substancesPermeability: inorganic small substances

amino acidsamino acids monosaccharidesmonosaccharides

Septate junctionSeptate junction

• on the on the apicalapical part of the cells part of the cells• they form a they form a contincontinoousus belt (like z. adherens) belt (like z. adherens)• promote promote to stickto stick together the cells together the cells• actin is anchored actin is anchored in in this junction this junction

Desmosome = macula adherensDesmosome = macula adherens

Cell to cell, snap-like junctionCell to cell, snap-like junction

desmosomal cadherinsdesmosomal cadherinsi.e. desmoglein, desmocollini.e. desmoglein, desmocollin

cytoplasmatic plaquecytoplasmatic plaquedesmoplaquin, plactoglobindesmoplaquin, plactoglobin

intermedier filamentsintermedier filaments

actinactin

DesmosomeDesmosome

Components of desmosomesComponents of desmosomes

TEM structure of desmosomeTEM structure of desmosome

Intermedier Intermedier filamentsfilaments(i.e. keratin)(i.e. keratin)

Cytoplasmatic Cytoplasmatic plaqueplaque

cadherinscadherins

Submembraneous Submembraneous network network connecting connecting desmosomesdesmosomes

Gap junction Gap junction (1958, 1968)(1958, 1968)

• Bridges the 2-4 nm gap between the neighbour cellsBridges the 2-4 nm gap between the neighbour cells

• Hexagonal channelHexagonal channel is formed (connexon) is formed (connexon)

• The wall of the channel is composed by The wall of the channel is composed by 6 connexins6 connexins (4 helical components)(4 helical components)

• The distribution of channels is The distribution of channels is tissue- or cell-specifictissue- or cell-specific due to the difference of connexins due to the difference of connexins

• Accross channels Accross channels substancessubstances are transmitted are transmitted (max M(max MWW. 1000) by a regulated mechanism. 1000) by a regulated mechanism

Gap junctionGap junction

Gap junctionGap junction

Role of gap junction Role of gap junction

• TransportTransport ofof neurotransmitters, cAMP, neurotransmitters, cAMP, Ca Ca 2+2+

• SignalSignalinging in early embryo in early embryo

PlasmodesmataPlasmodesmata

Gap junction-like functionGap junction-like functionViral infection results Viral infection results in in the increase of pore diameterthe increase of pore diameter

sERsER

desmotubuledesmotubulecytoplasmcytoplasm

membranemembrane

cellwallcellwall

plasmodesmataplasmodesmata

PlasmodesmataPlasmodesmata

ERER

desmotubuledesmotubule

membranemembrane

HemidesmosomeHemidesmosome

Fixing of epithelial cells Fixing of epithelial cells tto the basal membraneo the basal membrane

Basal striationBasal striation

InterdigitationInterdigitation

Characteristic between epithelial cellsCharacteristic between epithelial cells

actin filamentactin filament actininactinin

vinculinvinculin

paxillinpaxillin

talintalin

integrinintegrinfibronectinfibronectin

Structure of focal contactStructure of focal contact

Focal contactsFocal contacts

actin actin

vinculinvinculin

Extracellular MatrixExtracellular Matrix

ExtracellulExtracellulaar matrix - Fr matrix - Fuunctionnction

• Influence oInfluence onn migration of migration of the the cells cells

• Regulation of activity of Regulation of activity of molecules releasedmolecules released

• Co-receptorsCo-receptors

Extracellular matrix – Building blocksExtracellular matrix – Building blocks

• Glycosaminoglycans (GAG-s)Glycosaminoglycans (GAG-s)

heparan sulheparan sulffatate - e - basal membr., cell surfacebasal membr., cell surface keratan sulkeratan sulffatate - e - cornea, bonecornea, bone chondroitin sulchondroitin sulffatate – e – cartilage, bone, heartcartilage, bone, heart hyaluronate - hyaluronate - synovial fluidsynovial fluid dermatan sulfate - dermatan sulfate - blood vessels, heartblood vessels, heart

• „ „Core-proteins”Core-proteins” aggrecan – decorinaggrecan – decorin

collagen – elastin - strucollagen – elastin - strucctureture fibronectin – laminin - adhesionfibronectin – laminin - adhesion

FibronectinsFibronectins

collagencollagen

cellcell

heparinheparin

Dimer composedDimer composed by differentby different channels –channels –alternaalternattive splicingive splicing

RGDRGD

FibronectinsFibronectins

• GlycoproteinsGlycoproteins• Dimer-structureDimer-structure• RGD (Arg-Gly-Asp)RGD (Arg-Gly-Asp)• Plasma fibronectinsPlasma fibronectins• GenGenee „K.O.” experiments „K.O.” experiments

ArgArg GlyGly

AspAsp

Basal laminaBasal lamina

Layers:Layers: lamina lucidalamina lucidalamina densalamina densalamina fibroreticularislamina fibroreticularis

CellCell

ConnectiveConnectivetissuetissue

ComponentsComponents:: IV. collagenIV. collagenlamininlamininperlecanperlecanentactinentactin

SEM image of basal laminaSEM image of basal lamina

basalbasalmembranemembrane

collagencollagenfibrilsfibrils

epithelialepithelialcellscells

Main proteins composing Main proteins composing the the basal laminabasal lamina

Collagen IVCollagen IV

PerlecanPerlecan

LamininLaminin

EntactinEntactin

CollagenCollagen

• FibrilsFibrils (diam.(diam.10-300 nm10-300 nm))• More than 15 typesMore than 15 types• I., II., III., V., XI. – formation of fibrilsI., II., III., V., XI. – formation of fibrils• IV., VII. – networkIV., VII. – network• IX., XII. – association of fibrilsIX., XII. – association of fibrils

Synthesis and association of collagen Synthesis and association of collagen filamentfilament

Pro, LysPro, Lys hydroxilationhydroxilation

assemblyassembly

formation of triple helixformation of triple helix

secretionsecretion

splitting of splitting of procollagen procollagen

building intobuilding into fibrillfibrill

organizationorganizationinto a fiberinto a fiber

glycosylationglycosylation

synthesis of synthesis of -chain-chain

Negative staining of collagen Negative staining of collagen fibrilsfibrils

gaps betweengaps betweencollagen moleculescollagen molecules

collagencollagen

SEM image of collagen fibrils SEM image of collagen fibrils

LamininLaminin

A chainA chain BB11 chain chain BB2 2 chainchain

Globular Globular domainsdomains

helixhelix

• each chain has more typeseach chain has more types• 18 isoforms of laminin18 isoforms of laminin• diversities in tissuesdiversities in tissues

ElastinElastin

strech strech relaxrelax

cross-linkscross-links

fibre of elastinfibre of elastin

AggrecanAggrecan

One complex of aggrecan:One complex of aggrecan:

• M.W. aboutM.W. about 101088

• Volume 2x10Volume 2x10-12-12 mlml (= bacterium)(= bacterium)

Complex of aggrecanComplex of aggrecan

Chondroitin sulChondroitin sulffatatee

LinkerLinkerproteinsproteins

CoreCoreprot.prot.

KeratinKeratin

sulsulffatatee

HyaluronanHyaluronan

1 1 mmmm

Matrix types produced by vertebrate cellsMatrix types produced by vertebrate cells

CCOOLLLLAAGGEENNEE

II ChS, DSChS, DS fibrobl.fibrobl.IIII fibronectinfibronectin ChSChS integrinintegrin chondrocytechondrocyteIIIIII HS, Hep.HS, Hep. hepatocytehepatocyte

epithelepithel

IVIV lamininlaminin HS, Hep.HS, Hep. laminin rec.laminin rec. epithel,epithel,endothel,endothel,regeneratingregenerating hepatocytehepatocyte

VV fibronectinfibronectin HS, Hep.HS, Hep. integrinintegrin restingresting fibrobl.fibrobl.VIVI fibronectinfibronectin HSHS integrinintegrin restingresting fibrobl.fibrobl.

AnchorAnchor Proteogly.Proteogly. ReceptorReceptor CellsCells

Abbr.: ChS – chondroitin sulfate; DS – dermatan sulfate; Abbr.: ChS – chondroitin sulfate; DS – dermatan sulfate; HS – heparan sulfate; Hep - heparin HS – heparan sulfate; Hep - heparin

Clinical approachesClinical approaches

Collagen Collagen

hydroxy-Pro hydroxy-Pro hydroxy-Lys hydroxy-Lys cross-linking cross-linking N-term. propeptideN-term. propeptide

- - poor wound healingpoor wound healing- - hyperextensibilityhyperextensibility- - musculo-skeletal musculo-skeletal deformitiesdeformities

Complexity of cell adhesion Complexity of cell adhesion

Interactions in focal contactInteractions in focal contactFimbrinFimbrinNexilinNexilin

TensinTensinA-ActininA-ActininTalinTalin

PaxillinPaxillinCaveolinCaveolin

ZyxinZyxinPalladinPalladinVinexinVinexinPonsinPonsin

Integrin, Syndecan-4, Leukocyte common antigenIntegrin, Syndecan-4, Leukocyte common antigen

Protein associated to actin Protein associated to actin filamentsfilaments

Zonula adherensZonula adherens::E – cadherin E – cadherin

CCatetin atetin VinVincculinulin-a-acctinintininPlactoglobinPlactoglobin

Adhesion plaqueAdhesion plaqueIntegrinIntegrin -a-acctinintininVinculinVinculinTalinTalin

Induction of integrinsInduction of integrins

PP PP PP PPactinactin

e.c. matrixe.c. matrix

activeactiveintegrinintegrin

Binding site in matrixBinding site in matrix

Binding site in cytosBinding site in cytoskkeletoneleton