Regulation of protein synthesis by cholecystokinin in rat pancreatic acini involves PHAS-I and the p70 S6 kinase pathway.
OBJECTIVE
Cholecystokinin (CCK) stimulates protein synthesis in pancreatic acini at the translational level, although the signaling mechanisms involved remain uncharacterized. Two intermediates controlling translation are p70 S6 kinase and PHAS-I. We previously showed that CCK activates p70 S6K in pancreatic acini through phosphatidylinositol 3-kinase (PI 3K). In the present study we investigated the role of PI 3K, p70 S6K, and PHAS-I in mediating CCK-stimulated protein synthesis.


METHODS
Protein synthesis was measured by [35S]methionine incorporation into pancreatic protein using acini from rats with streptozotocin-induced diabetes. p70 S6 K activity was measured. PHAS-I was identified by Western analysis. PHAS-I/eIF-4E association was measured as the amount of PHAS-I recovered after purification of translation factor eIF-4E by 7-methyl guanosine triphosphate-Sepharose.


RESULTS
Rapamycin and PI 3K inhibitors, wortmannin and LY294002, blocked CCK-stimulated p70 S6K activity. Rapamycin inhibited basal protein synthesis and blocked the increase to all CCK concentrations. Wortmannin and LY294002 dose-dependently inhibited basal and CCK-stimulated protein synthesis and also blocked insulin-stimulated protein synthesis. CCK dose-dependently increased PHAS-I phosphorylation via a rapamycin- and LY294002-sensitive pathway and decreased the amount of PHAS-I associated with eIF-4E. Rapamycin and LY294002 eliminated this effect of CCK.


CONCLUSIONS
CCK stimulation of protein synthesis in pancreatic acini is sensitive to rapamycin and PI 3K inhibitors and involves PHAS-I phosphorylation and its association with eIF-4E.
Department of Physiology, University of Michigan, Ann Arbor, Michigan, USA.
M J
MJ
Bragado
G E
GE
Groblewski
J A
JA
Williams
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001839:Bombesin / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D002352:Carrier Proteins; D002766:Cholecystokinin / Q000494:pharmacology*; D002867:Chromones / Q000494:pharmacology; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D008297:Male; D008715:Methionine / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D010179:Pancreas / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D010448:Peptide Initiation Factors / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D011090:Polyenes / Q000494:pharmacology; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism*; D020123:Sirolimus; D013462:Sulfur Radioisotopes; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D000077191:Wortmannin
D000730:Androstadienes; D002352:Carrier Proteins; D002867:Chromones; C499526:Eif4ebp1 protein, rat; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D009025:Morpholines; D010448:Peptide Initiation Factors; D010750:Phosphoproteins; D011090:Polyenes; D011506:Proteins; D013462:Sulfur Radioisotopes; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D002217:Carbachol; D002766:Cholecystokinin; D008715:Methionine; D019893:Ribosomal Protein S6 Kinases; D013755:Tetradecanoylphorbol Acetate; D001839:Bombesin; D020123:Sirolimus; D000077191:Wortmannin