Wortmannin-sensitive activation of p70S6-kinase and MAP-kinase by the G protein-coupled receptor, G/CCKB.
The gastrin/CCKB (G/CCKB) G protein-coupled receptor has been shown to mediate the proliferative effects of gastrin on normal and neoplastic gastro-intestinal tissues. In the present study, we examined the signal transduction mechanisms coupled to this receptor. We report here that phosphorylation and activity of the p70S6K, whose major substrate is the ribosomal S6 protein, are enhanced in response to gastrin. These effects were completely reversed by a commonly used PI-3-kinase inhibitor, wortmannin, suggesting that p70S6K may be a downstream target of PI-3-kinase in a signaling cascade induced by gastrin. In addition, blocking PI-3-kinase activity by wortmannin partially decreased gastrin-induced MAPK activation (42% +/- 3) as well as the tyrosine phosphorylation of She (50% +/- 6), an upstream regulator of the Ras-dependent MAPK pathway. These results indicate that at least two signaling pathways lead to MAPK activation by gastrin, only one of which is sensitive to PI-3-kinase inhibitors.
Seva
C
C
INSERM U.151, Groupe de Recherche de Biologie et Pathologie digestive, Institut Louis Bugnard, CHU Rangueil, Toulouse, France. sevac@rangueil.inserm.fr
Kowalski-Chauvel
A
A
Daulhac
L
L
Barthez
C
C
Vaysse
N
N
Pradayrol
L
L
D000730:Androstadienes / Q000494:pharmacology*; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005755:Gastrins / Q000378:metabolism / Q000502:physiology*; D010190:Pancreatic Neoplasms; D019869:Phosphatidylinositol 3-Kinases; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors; D011090:Polyenes / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D043887:Receptor, Cholecystokinin B; D011949:Receptors, Cholecystokinin / Q000502:physiology*; D019893:Ribosomal Protein S6 Kinases; D012269:Ribosomal Proteins / Q000378:metabolism*; D020123:Sirolimus; D014407:Tumor Cells, Cultured; D000077191:Wortmannin; D018909:src Homology Domains / Q000187:drug effects
D000730:Androstadienes; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019204:GTP-Binding Proteins; D005755:Gastrins; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011090:Polyenes; D017346:Protein Serine-Threonine Kinases; D043887:Receptor, Cholecystokinin B; D011949:Receptors, Cholecystokinin; D019893:Ribosomal Protein S6 Kinases; D012269:Ribosomal Proteins; D020123:Sirolimus; D000077191:Wortmannin