Regulation of protein synthesis by cholecystokinin in rat pancreatic acini involves PHAS-I and the p70 S6 kinase pathway.
BACKGROUND & AIMS: 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.[1]References
- Regulation of protein synthesis by cholecystokinin in rat pancreatic acini involves PHAS-I and the p70 S6 kinase pathway. Bragado, M.J., Groblewski, G.E., Williams, J.A. Gastroenterology (1998) [Pubmed]
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