The regulatory site of functional GTP binding protein coupled to the high affinity cholecystokinin receptor and phospholipase A2 pathway is on the G beta subunit of Gq protein in pancreatic acini.
A non-hydrolysable guanosine nucleotide analog, GTP[S] at 200 microM, stimulated amylase secretion which was inhibited by an anti-phospholipase A2 (PLA2) antibody in permeabilized pancreatic acini, indicating that the PLA2 pathway is linked to the GTP binding protein. A high affinity cholecystokinin (CCK) receptor agonist, CCK-OPE (10 microM), and a low affinity receptor agonist, CCK-8 (0.1 microM), both caused amylase secretion in permeabilized cells. The action of CCK-OPE was abolished by the G beta antibody but not by the G alpha-q,11 antibody, whereas the opposite was true of the CCK-8 response. Biscoclaurine alkaloid isotetrandrine (10 microM), a specific inhibitor of PLA2-coupled G proteins, abolished Ca2+ oscillations and amylase secretion induced by CCK-OPE (0.1-100 nM), but not by CCK-8 (10 pM) in intact acini. Gp antagonist-2A (10 microM), which inhibits the activation of Gq, also inhibited the actions of CCK-OPE (10 pM-1 microM) in intact acini. These observations indicate that the functional unit of the heterotrimeric G protein coupled to the high affinity CCK receptor appears to be different from that linked to the low affinity CCK receptor/Gq-alpha pathway. The regulatory site of this G protein coupled to the high affinity CCK receptor is on the beta subunit of Gq protein which elicits Ca2+ oscillations and monophasic amylase secretion via the PLA2 pathway.
Tsunoda
Y
Y
Department of Internal Medicine, University of Michigan, Ann Arbor 48109, USA.
Owyang
C
C
D000470:Alkaloids / Q000494:pharmacology*; D000681:Amylases / Q000378:metabolism; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D044182:Benzylisoquinolines; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002463:Cell Membrane Permeability; D002766:Cholecystokinin / Q000031:analogs & derivatives / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology*; D006706:Homeostasis; D066298:In Vitro Techniques; D007700:Kinetics; D046911:Macromolecular Substances; D008297:Male; D009991:Oscillometry; D010179:Pancreas / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D054467:Phospholipases A2; D051381:Rats; D017207:Rats, Sprague-Dawley; D011949:Receptors, Cholecystokinin / Q000378:metabolism*; D015398:Signal Transduction; D012844:Sincalide / Q000494:pharmacology* / Q000031:analogs & derivatives; D013997:Time Factors
D000470:Alkaloids; D000906:Antibodies; D044182:Benzylisoquinolines; D002121:Calcium Channel Blockers; D046911:Macromolecular Substances; D010446:Peptide Fragments; D011949:Receptors, Cholecystokinin; C067408:cholecystokinin (26-32), Tyr-Gly-Nle(28,31) phenethyl ester-; C009438:tetrandrine; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002766:Cholecystokinin; D010741:Phospholipases A; D054467:Phospholipases A2; D000681:Amylases; D019204:GTP-Binding Proteins; D012844:Sincalide; D002118:Calcium