Manifestation of Novel Social Challenges of the European Unionin the Teaching Material ofMedical Biotechnology Master’s Programmesat the University of Pécs and at the University of DebrecenIdentification number: TÁMOP-4.1.2-08/1/A-2009-0011
NON-GENOMIC STEROID RECEPTOR SIGNALING PATHWAYS
Tímea Berki and Ferenc BoldizsárSignal transduction
Manifestation of Novel Social Challenges of the European Unionin the Teaching Material ofMedical Biotechnology Master’s Programmesat the University of Pécs and at the University of DebrecenIdentification number: TÁMOP-4.1.2-08/1/A-2009-0011
TÁMOP-4.1.2-08/1/A-2009-0011
Glucocorticoid action
• The name glucocorticoid (glucose + cortex + steroid) derives from their role in the regulation of the metabolism of glucose, their synthesis in the adrenal cortex, and their steroidal structure.
• The glucocorticoid receptor is present in all vertebrate cell type
DexamethasoneCortisol
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Basics
• Some steroid effects can be detected within minutes eg. ion-currents change, membrane changes, phosphorylation changes
• Treatment of acute conditions: asthma, allergies, shock – high dose steroids exert rapid effects
• Apoptosis-inducing capacity
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GR signaling pathways
RE
Plasma membrane
Nucleus
Other cytoplasmic signaling proteins
Hormone
mReceptor
Mitochondrion
Gene expression
?
cReceptor
Cytoplasm
HSP90
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GR signaling pathways
• Genomic (“classical”)• Direct membrane effect• Membrane GR• Interaction with cytoplasmic signaling
proteins• Mitochondrial translocation
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Genomic steroid actions
GRE
Milliseconds (?) Seconds-minutes (?)Hours-days
Multiple co-regulators
TFs
Nucleus
Dimerization
Binding
Molecular assembly
?
?
Levels ofregulation
CBG bindingin blood
MDR in themembrane
Metabolism andnuclear receptor fate
Transcription GRE RE
RNAs
Proteins
TFs
G-ptoteincoupled receptor
Ion channel Ionotropic receptor
Ion pump
Nucleus
MR/GRSteroid G-protein Neurotransmitter
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Slow Medium slow Rapid
Transmembrane currentsPhosphorylation events
Calcium levels
Plasma membrane
Cytoplasm
Glucocorticoid
mGR
cGR
Specific cGRdependent effects
Specific mGRdependent effects Nonspecific GC
effects
GRE
TF
nGRE pGRE
Transrepression Transactivation
Genomic GC effects Nongenomic GC effects
Genomic and non-genomic GC effects
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Evidences
• Binding of corticosteroids to the glucocorticoid receptor (GR) stimulates PIP3K and protein kinase AKT, leading to eNOS activation and vasorelaxation
• Membrane associated GR has been shown to mediate lymphocytolysis
• In addition, some glucocorticoids have been shown to rapidly inhibit the release of the inflammatory prostaglandin PGE2
• A multi-protein complex composed of the unliganded glucocorticoid receptor, Hsp90, and the tyrosine kinases LCK and FYN is recruited to the antigen activated T cell receptor (TCR). This GR complex is necessary for TCR signalling. On binding of glucocorticoids to GR, this multi-protein complex dissociates blocking TCR signalling
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Direct membrane effects
• Human RBC• High-dose steroid treatment influenced the membrane lipid
mobility in mammary cancer cell line • Increased membrane lipid mobility in LPS treated B
lymphocytes • Inhibited membrane transport of Na+ and Ca2+, and increased
the H+ uptake into the mitochondria • In canine kidney epithel cell system there is a direct effect of
DX on tight junction formation • 20 min cortisol treatment caused changes in the excitability of
principal basolateral amygdala neurons
GCs, especially at high doses, could change plasma membrane physico-chemical properties due to their lipid soluble nature.
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Membrane GR
• Rodent and human lymphoid cell lines • Amphibian brain • Correlation between the mGR expression and the cell
cycle-dependent GC-induced apoptosis sensitivity of a human leukaemia cell line
• Presence of the mGR correlates with GC-resistance of a cell type (Sionov)
• Human blood monocytes and B cells • mGR+ monocyte frequency increased in rheumatoid
arthritis, SLE and ankylosing spondylitis patients
What pathways are activated by the mGR???
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Evidences for mitochondrial GR
• Upon ligand binding the glucocorticoid receptor can directly translocate to the mitochondria in both lymphoid and non-lymphoid cells where it can initiate the apoptotic cascade
• Ligand-induced mitochondrial GR translocation showed a close correlation with the GC-induced apoptosis sensitivity of several cell types
• In CD4+CD8+ (DP) thymocytes the GR translocates to the mitochondria rather than to the nucleus upon short-term in vitro GC treatment correlating with the high GC-induced apoptosis sensitivity of this cell type
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Mitochondrial GR actions
In the mitochondria, the GR might act through diverse mechanisms:• Act as mitochondrial transcription factor• Interaction with other mitochondrial transcription
factors• Interaction with pro- and anti-apoptotic proteins (eg.
Bcl-2 family proteins)• Decreasing the mitochondrial membrane potential
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Ligand induced mitochondrial GR translocation in DP thymocytes
DICCD4CD8 GR
CMX-Ros
GR+CMX-Ros DIC
CD4CD8 GR
CMX-Ros
GR+CMX-Ros
Kontroll DX
Number of mitochondria-GR colocalised pixels
*
0
100
200
300
400
500Ctrl
DX
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Mitochondrial GR translocation
Mitochondrion
cReceptor
HSP90
Membranepotential ↓
DNA Bcl-2 family
Otherproteins
APOPTOSIS
Transcriptionfactors
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Summary of genomic and non-genomic glucocorticoid effects
RE
Plasma membrane
Nucleus
Other cytoplasmic signaling proteins
Hormone
mReceptor
Mitochondrion
Gene expression
?
cReceptor
Cytoplasm
HSP90