Bragado MJ, Groblewski GE, Williams JA. Regulation of protein synthesis by cholecystokinin in rat pancreatic acini involves PHAS-I and the p70 S6 kinase pathway.
Gastroenterology 1998;
115:733-42. [PMID:
9721171 DOI:
10.1016/s0016-5085(98)70153-2]
[Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
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.
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