CCK activates p90rsk in rat pancreatic acini through protein kinase C.
The presence of the 90-kDa ribosomal S6 protein kinase (p90(rsk)) in isolated rat pancreatic acini was demonstrated by Western blotting and immunoprecipitation with anti-p90(rsk). Cholecystokinin (CCK) activated p90(rsk) activity in a time- and dose-dependent manner and increased its phosphorylation. The threshold concentration of CCK was 10 pM and the maximal effect was seen at 1 nM. An increase in p90(rsk) was observed 1 min after 1 nM CCK stimulation, reaching a maximum at 10 min, when p90(rsk) activity was increased 5.4-fold. Carbachol and bombesin, but not vasoactive intestinal peptide, also activated p90(rsk). CCK-induced activation of p90(rsk) appears to be mediated by protein kinase C (PKC), since 12-O-tetradecanoylphorbol-13-acetate increased p90(rsk) activity 5.3-fold. GF-109293X, a potent inhibitor of PKC, strongly inhibited CCK-evoked p90(rsk) activity. Treatment of acini with ionomycin or 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid had no effect, indicating that mobilization of intracellular Ca2+ by CCK is not important in p90(rsk) activation. Although there were some quantitative differences in the extent of inhibition, the specific inhibitors [rapamycin, wortmannin, mitogen-activated protein kinase (MAPK) kinase inhibitor PD98059, and GF-109293X] had parallel effects on p90(rsk) and p42(mapk) activities, consistent with a model in which p90(rsk) can be regulated in acini by MAPK.
Bragado
M J
MJ
Department of Physiology, University of Michigan, Ann Arbor 48109-0622, USA.
Dabrowski
A
A
Groblewski
G E
GE
Williams
J A
JA
D000818:Animals; D002766:Cholecystokinin / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects; D008297:Male; D010179:Pancreas / Q000201:enzymology*; D010716:Phosphatidylinositols / Q000378:metabolism; D010766:Phosphorylation; D011090:Polyenes / Q000494:pharmacology; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011949:Receptors, Cholecystokinin / Q000502:physiology; D019893:Ribosomal Protein S6 Kinases; D015398:Signal Transduction; D020123:Sirolimus
D010716:Phosphatidylinositols; D011090:Polyenes; D011949:Receptors, Cholecystokinin; D002766:Cholecystokinin; D017346:Protein Serine-Threonine Kinases; D019893:Ribosomal Protein S6 Kinases; D011493:Protein Kinase C; D020123:Sirolimus