Cellular aspects of molecular pharmacology

• 1.CELLULAR ASPECTS

2. Receptors G-protein coupled receptors Ion Channel Receptors Receptor-enzymes Cytosolic-nuclear receptors 3. G-protein coupled receptors 4. G-protein coupled receptor: GPCR Examples: Adrenergic receptors Muscarinic ACh receptors GABAB receptors Metabotropic Glutamate receptors Dopamine receptors Metabotropic Serotonin receptors 5. G-protein coupled receptor: GPCR More exampleshormones: Angiotensin receptor Bradykinin receptor Thrombin receptor FSH receptor LH receptor TSH receptor ACTH receptor 6. GPCR structure A single subunit with 7 transmembrane segments out in 7. A depiction of how GPCRs activate signaling 8. Ligand + GPCR GPCR* GPCR* abg a + bg signaling abg Heterotrimeric GTP-binding protein (G protein) GPCR G-protein coupled receptor signalin g Another depiction of how GPCRs activate signaling 9. Heterotrimeric GTP-binding proteins cycle between GTP- and GDP-bound state Binding of ligand to G-protein coupled receptor facilitates exchange of GTP for GDP, a and bg dissociate a b g GDP a b g GTP INACTIVE ACTIVE 10. Heterotrimeric G proteins Activated by binding of ligand to 7-transmembrane receptor (G-protein coupled receptor) Ligand binding causes dissociation of a and bg subunits Dissociation allows GDP to exchange for GTP GTP binding causes conformational change, a subunit can now interact with effector (e.g. AC) GTP is hydrolyzed to GDP, a subunit dissociates from effector Signal is terminated 11. Adenylate cyclase Membrane protein makes cAMP from ATP ATP cAMP 12. Three major families of G-proteins Gs couples to Adenylate Cyclase stimulates AC activity increases cAMP activates Protein Kinase A Gi couples to Adenylate Cyclase inhibits AC activity decreases cAMP inhibits Protein Kinase A Gq couples to Phospholipase C increases diacylgyclerol (DAG) increases IP3 increases intracellular Ca2+ 13. Gs Gi Gq b-adrenergic receptor ACTH receptor FSH receptor a2-adrenergic receptor M2 muscarinic receptor a1-adrenergic receptor M1, M3 muscarinic receptors Angiotensin receptor cAMP PKA activity cAMP PKA activity PLC activity DAG, IP3 Ca2+ PKC activity G-protein Receptor examples Signaling pathway 14. cAMP-dependent stimulation of glucose liberation from glycogen 15. bAR a b g GTP AC PKA cAMP-dependent stimulation of cardiac muscle contraction Ca2+ Ca2+ Ryanodine Receptor Sarcoplasmic reticulum bAR = b-adrenergic receptor 16. cAMP is constantly inactivated by phosphodiesterase (active) (inactive) Theophylline blocks the phosphodiesterase 17. Phospholipase C activation produces Diacylglycerol and IP3 PI 4,5 biphosphate (PIP2) Plasma membrane lipid plasma membrane Diacylglycerol (DAG) Inositol 1,4,5-triphosphate (IP3) cytosolic messenger plasma membrane 18. a1-adrenergic receptors acting on vascular smooth muscle: PLC IP3 Ca2+ calmodulin myosin light chain kinase Myosin-P contraction An example of the Gq signaling pathway 19. IP3 receptors: intracellular calcium channels 20. Controlling intracellular calcium levels IP3 receptors Ca2+ Intracellular Ca2+ levels are