<prompt> Activation of G-protein regulate all of the following except -Adenyl cyclase activityIon channelsI Pi DAGTranscription factor  <response>: 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 ACo 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 IIepithelial 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 Ca2 from intracellular organelles increased cytosolic Ca2 DAG enhances Protein Kinase c activation by Ca2. Ca2 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 DHVasopressin 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 -1Ca2-b1-adrenergic, 2 -Ca2-Dopamine D2, GABAB,3 K-Adrenergic a2, muscarinic M2, Dopamine D2, GABAB. 