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Rap1 promotes multiple pancreatic islet cell functions and signals through mammalian target of rapamycin complex 1 to enhance proliferation.

Authors: Kelly, P  Bailey, CL  Fueger, PT  Newgard, CB  Casey, PJ  Kimple, ME 
Citation: Kelly P, etal., J Biol Chem. 2010 May 21;285(21):15777-85. doi: 10.1074/jbc.M109.069112. Epub 2010 Mar 25.
Pubmed: (View Article at PubMed) PMID:20339002
DOI: Full-text: DOI:10.1074/jbc.M109.069112

Recent studies have implicated Epac2, a guanine-nucleotide exchange factor for the Rap subfamily of monomeric G proteins, as an important regulator of insulin secretion from pancreatic beta-cells. Although the Epac proteins were originally identified as cAMP-responsive activators of Rap1 GTPases, the role of Rap1 in beta-cell biology has not yet been defined. In this study, we examined the direct effects of Rap1 signaling on beta-cell biology. Using the Ins-1 rat insulinoma line, we demonstrate that activated Rap1A, but not related monomeric G proteins, promotes ribosomal protein S6 phosphorylation. Using isolated rat islets, we show that this signaling event is rapamycin-sensitive, indicating that it is mediated by the mammalian target of rapamycin complex 1-p70 S6 kinase pathway, a known growth regulatory pathway. This newly defined beta-cell signaling pathway acts downstream of cAMP, in parallel with the stimulation of cAMP-dependent protein kinase, to drive ribosomal protein S6 phosphorylation. Activated Rap1A promotes glucose-stimulated insulin secretion, islet cell hypertrophy, and islet cell proliferation, the latter exclusively through mammalian target of rapamycin complex 1, suggesting that Rap1 is an important regulator of beta-cell function. This newly defined signaling pathway may yield unique targets for the treatment of beta-cell dysfunction in diabetes.


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CRRD Object Information
CRRD ID: 10003134
Created: 2015-05-04
Species: All species
Last Modified: 2015-05-04
Status: ACTIVE


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