at the University of Pécs and at the University of Debrecen
Identification number: TÁMOP-4.1.2-08/1/A-2009-0011
NON-GENOMIC
STEROID RECEPTOR
SIGNALING PATHWAYS
Tímea Berki and Ferenc Boldizsár Signal transduction
Medical Biotechnology Master’s Programmes
at the University of Pécs and at the University of Debrecen
Identification number: 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
Dexamethasone Cortisol
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
GR signaling pathways
RE Plasma membrane
Nucleus Other cytoplasmic
signaling proteins Hormone
mReceptor
Mitochondrion
Gene expression
?
cReceptor Cytoplasm
HSP90
GR signaling pathways
• Genomic (“classical”)
• Direct membrane effect
• Membrane GR
• Interaction with cytoplasmic signaling proteins
• Mitochondrial translocation
Genomic steroid actions
GRE
Milliseconds (?) Hours-days Seconds-minutes (?)
Multiple co- regulators
TFs
Nucleus Dimerization
Binding Molecular
assembly
?
? Levels of
regulation
CBG binding in blood MDR in the membrane
Metabolism and nuclear receptor fate
Transcription GRE RE
RNAs Proteins
TFs G-ptotein
coupled receptor
Ion channel Ionotropic receptor
Ion pump
Nucleus
MR/GR
Steroid G-protein Neurotransmitter
Slow Medium slow Rapid
Transmembrane currents Phosphorylation events
Calcium levels
Plasma membrane
Cytoplasm
Glucocorticoid
mGR
cGR Specific cGR dependent effects
Specific mGR
dependent effects Nonspecific GC effects
GRE TF
nGRE pGRE
Transrepression Transactivation
Genomic GC effects Nongenomic GC effects
Genomic and non-genomic GC
effects
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
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.
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???
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
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
Ligand induced mitochondrial GR translocation in DP thymocytes
DIC
CD4
CD8 GR
CM X- Ros
GR+
CMX-
Ros DIC
CD4
CD8 GR
CM X- Ros
GR+
CMX- Ros
Kontroll DX
Number of mitochondria-GR colocalised pixels
*
0 100 200 300 400
500 Ctrl DX
Mitochondrial GR translocation
Mitochondrion
cReceptor
HSP90
Membrane potential ↓
DNA Bcl-2 family
Other proteins
APOPTOSIS
Transcription factors
Summary of genomic and non- genomic glucocorticoid effects
RE Plasma membrane
Nucleus Other cytoplasmic
signaling proteins Hormone
mReceptor
Mitochondrion
Gene expression
?
cReceptor Cytoplasm
HSP90
