Guanine nucleotides activate multiple signaling pathways in permeabilized gastric chief cells. Evidence for GTP gamma S-induced calcium-independent pepsinogen secretion.
Nonhydrolyzable guanine nucleotide analogues were used to evaluate the role of guanine nucleotide binding (G) proteins in regulating pepsinogen secretion from streptolysin O-permeabilized chief cells from guinea pig stomach. In the presence of 100 nM calcium, 100 microM guanosine 5'-(beta,gamma-imido)triphosphate or guanosine 5'-3-O-(thio)triphosphate (GTP gamma S) caused a 2- to 4-fold increase in pepsinogen secretion. GTP gamma S stimulated secretion in the absence of calcium (up to 10 mM EGTA). With or without added calcium, GTP analogues caused a 2- to 3-fold increase in cAMP, whereas guanosine 5'-O-2-(thio)diphosphate and calcium alone had no effect on cAMP levels. GTP analogue-induced activation of phospholipase C was evidenced by a calcium-independent increase in cytidine diphospho-1,2-diacylglycerol levels (50% above basal). Phorbol ester- and GTP gamma S-stimulated phosphorylation of a 72-kDa acidic protein was abolished by an inhibitor of protein kinase C (CGP 41251). However, GTP gamma S-induced pepsinogen secretion was only partially inhibited by adding CGP 41251 or a protein kinase C inhibitor peptide. These results indicate that guanine nucleotides activate major signaling pathways in gastric chief cells. Nevertheless, GTP gamma S can induce pepsinogen secretion independently of changes in calcium, cAMP, or activation of protein kinase C.
Raffaniello
R D
RD
Department of Medicine, State University of New York, Brooklyn 11203-2098.
Raufman
J P
JP
D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D001426:Bacterial Proteins; D002118:Calcium / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D002463:Cell Membrane Permeability; D000242:Cyclic AMP / Q000378:metabolism; D003567:Cytidine Diphosphate Diglycerides / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D005753:Gastric Mucosa / Q000166:cytology / Q000378:metabolism*; D006150:Guanine Nucleotides / Q000494:pharmacology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006168:Guinea Pigs; D008297:Male; D010435:Pepsinogens / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D015398:Signal Transduction; D019311:Staurosporine / Q000031:analogs & derivatives*; D013301:Streptolysins; D010738:Type C Phospholipases / Q000378:metabolism
D000470:Alkaloids; D001426:Bacterial Proteins; D003567:Cytidine Diphosphate Diglycerides; D006150:Guanine Nucleotides; D010435:Pepsinogens; D010703:Phorbol Esters; D013301:Streptolysins; C025964:streptolysin O; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002217:Carbachol; D000242:Cyclic AMP; D011493:Protein Kinase C; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D019311:Staurosporine; C059539:midostaurin; D002118:Calcium