Activation of G-protein regulate all of the following except -
Ans is 'd' i.e., Transcription factoro The activated G protein effects one of the following effect pathway (activated stimulatory G protein stimulates, or activated inhibitory G protein inhibits) -Adenylyl cyclase (AC)o Activation of AC results in increased synthesis and intracellular accumulation of cAMP (by stimulatory G protein). cAMP acts through cAMP dependent Protein Kinase 'A', which phosphorylate and alters the function of many enzymes, ion channels and structural proteins. Inhibitory G protein inhibits AC and has opposite effects.o Examples - Corticotropin releasing hormone (CRH), FSH, LH, TSHACTH (corticotropin), ADH, Vasopressin (V2 receptors), Parathormone, Catecholamines (fi, CL2) e.g., adrenaline (most actions), Glucagon, hCG, Calcitonin, Somatostatin, acetylcholine (M2), Dopamine (Dj, D2), Angiotensin II(epithelial cells), GABAb, Histamine (H2).Phospholipase IP3 - DAG systemo Activation of phospholipase (by stimulatory G protein) hydrolyses the membrane phospholipid phosphatidyl inositol 4, 5 bisphosphate (PIP2) to generate \hc second messenger inositol 1,4, 5 - triphosphate (IP3 ) and diacytglycerot (DAG). IP3 mobilizes Ca+2 from intracellular organelles increased cytosolic Ca+2 DAG enhances Protein Kinase 'c' activation by Ca+2. Ca+2 acts as third messenger in this type of transduction mechanism and mediates the physiological effects of drugs.o Example - Growth hormone releasing hormone (GHRH), Thyrotropin releasing hormone (TRH), GnRh, A DH/Vasopressin (VI receptor, vasopressor action), oxytocin, cholecystokinin, PDGF, Gastrin, Catecholamines (some actions via Of/ receptors), Angiotensin II (vascular smooth muscle), Substance P, Histamine - H1, muscarinic M1, M3C) Channel regulationo Activated G-proteins can open or close ion channels - Ca , K7 or NaLo Examples -(1)|Ca+2-b1-adrenergic, (2) -|Ca+2-Dopamine D2, GABAB,(3) |K+-Adrenergic a2, muscarinic M2, Dopamine D2, GABAB.
Adenyl cyclase activity
Ion channels
I Pi & DAG
Transcription factor
Endocrinology metabolism