Regulation of protein synthesis by cholecystokinin in rat pancreatic acini involves PHAS-I and the p70 S6 kinase pathway

• Published in: Gastroenterology (New York, N.Y. 1943) Vol. 115; no. 3; p. 733
• Main Authors: Bragado, M J, Groblewski, G E, Williams, J A
• Format: Journal Article
• Language: English
• Published: United States 01.09.1998
• Subjects: Androstadienes - pharmacology; Animals; Bombesin - pharmacology; Carbachol - pharmacology; Carrier Proteins; Cholecystokinin - pharmacology; Chromones - pharmacology; Diabetes Mellitus, Experimental - metabolism; Enzyme Inhibitors - pharmacology; Gene Expression Regulation - drug effects; Gene Expression Regulation - physiology; Kinetics; Male; Methionine - metabolism; Morpholines - pharmacology; Pancreas - cytology; Pancreas - metabolism; Pancreas - pathology; Peptide Initiation Factors - metabolism; Phosphoproteins - metabolism; Polyenes - pharmacology; Protein Biosynthesis; Proteins - genetics; Rats; Rats, Sprague-Dawley; Ribosomal Protein S6 Kinases - metabolism; Sirolimus; Sulfur Radioisotopes; Tetradecanoylphorbol Acetate - pharmacology; Wortmannin
• ISSN: 0016-5085
• DOI: 10.1016/S0016-5085(98)70153-2

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. 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. 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. 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.