Small gtp-binding proteins in insulin secretion
نویسنده
چکیده
Glucose-stimulated insulin secretion [GSIS] involves interplay between small G-proteins and their regulatory factors. Herein, we tested the hypothesis that Arf nucleotide binding site opener [ARNO], a guanine nucleotide-exchange factor [GEF] for the small G-protein Arf6, mediates the functional activation of Arf6, and that ARNO/Arf6 signaling axis, in turn, controls the activation of Cdc42 and Rac1, which have been implicated in GSIS. Molecular biological [i.e., expression of inactive mutants or siRNA] and pharmacological approaches were employed to assess the roles for ARNO/Arf6 signaling pathway in insulin secretion in normal rat islets and INS 832/13 cells. Degrees of activation of Arf6 and Cdc42/Rac1 were quantitated by GST-GGA3 and PAK-1 kinase pull-down assays, respectively. ARNO is expressed in INS 832/13 cells, rat islets and human islets. Expression of inactive mutants of Arf6 [Arf6-T27N] or ARNO [ARNO-E156K] or siRNA-ARNO markedly reduced GSIS in isolated b-cells. SecinH3, a selective inhibitor of ARNO/Arf6 signaling axis, also inhibited GSIS in INS 832/13 cells and rat islets. Stimulatory concentrations of glucose promoted Arf6 activation, which was inhibited by secinH3 or siRNA-ARNO, suggesting that ARNO/Arf6 signaling cascade is necessary for GSIS. SecinH3 or siRNA-ARNO also inhibited glucose-induced activation of Cdc42 and Rac1 suggesting that ARNO/Arf6 might be upstream to Cdc42 and Rac1 activation steps, which are necessary for GSIS. Lastly, co-immunoprecipitation and confocal microscopic studies suggested increased association between Arf6 and ARNO in glucosestimulated b-cells. These findings provide the first evidence to implicate ARNO in the sequential activation of Arf6, Cdc42 and Rac1 culminating in GSIS. Published by Elsevier Inc. Abbreviations: Arf6, ADP-ribosylation factor 6; ARNO, Arf nucleotide binding site opener; GAP, GTPase activating protein; GDI, GDP-dissociation inhibitor; GEF, guanine nucleotide-exchange factor; GGA3, Golgi-localized c-ear homology domain Arf-binding protein-3; GSIS, glucose-stimulated insulin secretion; PA, phosphatidic acid; PIP2, phosphatidylinositol-4,5-bisphosphate; PLD, phospholipase-D. * Corresponding author. Tel.: +1 313 576 4478; fax: +1 313 576 1112. E-mail address: [email protected] (A. Kowluru).
منابع مشابه
Small GTP-binding proteins in parietal cells: candidate modulators of parietal cell membrane dynamics.
The stimulated fusion of intracellular H/K-ATPase-containing tubulovesicles with a target canalicular membrane surface is central to the process of acid secretion. A super-family of small GTP-binding proteins (smGTPBPs) has been implicated in many aspects of intracellular dynamics and vesicle membrane trafficking. We have investigated the presence of smGTPBPs in isolated rabbit parietal cells. ...
متن کاملRegulatory roles for small G proteins in the pancreatic -cell: lessons from models of impaired insulin secretion
Kowluru, Anjaneyulu. Regulatory roles for small G proteins in the pancreatic -cell: lessons from models of impaired insulin secretion. Am J Physiol Endocrinol Metab 285: E669–E684, 2003;10.1152/ajpendo. 00196.2003.—Emerging evidence suggests that GTP-binding proteins (G proteins) play important regulatory roles in physiological insulin secretion from the islet -cell. Such conclusions were drawn...
متن کاملExpression, localization and functional role of small GTPases of the Rab3 family in insulin-secreting cells.
We examined the presence of small molecular mass GTP-binding proteins of the Rab3 family in different insulin-secreting cells. Rab3B and Rab3C were identified by western blotting in rat and in human pancreatic islets, in two rat insulin-secreting cell lines, RINm5F and INS-1, as well as in the hamster cell line HIT-T15. In contrast, Rab3A was detected in rat pancreatic islets as well as in the ...
متن کاملBlockade of mevalonate production by lovastatin attenuates bombesin and vasopressin potentiation of nutrient-induced insulin secretion in HIT-Tt5 cells Probable involvement of small GTP-binding proteins
Small G-proteins (SMGs) require isoprenylation for their association with membranes. We have examined protein isoprenylation, subcellular distribution of SMGs, cytosolic Ca2l changes and insulin secretion in HIT-T1 5 cells after treatment with lovastatin, which inhibits the production of isoprenoids by blockling mevalonate production by 3-hydroxy-3-methylglutaryl-CoA reductase. Numerous protein...
متن کاملGlucose- and GTP-dependent Stimulation of the Carboxyl Methylation of CDC42 in Rodent and Human Pancreatic Islets and Pure b Cells Evidence for an Essential Role of GTP-binding Proteins in Nutrient-induced Insulin Secretion
Several GTP-binding proteins (G-proteins) undergo posttranslational modifications (isoprenylation and carboxyl methylation) in pancreatic b cells. Herein, two of these were identified as CDC42 and rap 1, using Western blotting and immunoprecipitation. Confocal microscopic data indicated that CDC42 is localized only in islet endocrine cells but not in acinar cells of the pancreas. CDC42 undergoe...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2015