Dominant-Negative α-Subunit of Farnesyl- and Geranyltransferase Inhibits Glucose-Stimulated, but Not KCl-Stimulated, Insulin Secretion in INS 832/13 Cells

Veluthakal, Rajakrishnan; Kaur, Hitchintan; Goalstone, Marc L.; Kowluru, Anjaneyulu

doi:10.2337/db06-0668

Cited by 47 publications

(84 citation statements)

References 43 publications

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“…Several studies have reported that insulin secretion stimulated by membrane-depolarizing agents such as KCl and arginine was not blunted in secretagogueinduced desensitized b-cells or islet b-cells isolated from diabetic patients (Rustenbeck et al 2004, Del Guerra et al 2005 . A recent report that prevention of prenylation of small G-proteins, which may be involved in insulin granule movement, inhibited GSIS but not KCl-stimulated insulin secretion supports the idea that b-cells with functional impairment at the step of Ca 2C influx or insulin exocytosis can respond to KCl (Veluthakal et al 2007).…”

Section: Discussionmentioning

confidence: 77%

Tumour necrosis factor-α-induced glucose-stimulated insulin secretion inhibition in INS-1 cells is ascribed to a reduction of the glucose-stimulated Ca2+ influx

Kim¹,

Choi²,

Lee³

et al. 2008

Journal of Endocrinology

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The present study was undertaken to determine how tumour necrosis factor-a (TNF-a) elicits the inhibition of glucosestimulated insulin secretion (GSIS) in rat insulinoma cells (INS)-1 b-cells. TNF-a pretreatment did not change the expression levels of insulin, PDX-1, glucose transporter 2, glucokinase, K ATP channels, Ca 2C channels, and exocytotic molecules and, furthermore, did not reduce the glucosestimulated ATP level. On the other hand, TNF-a reduced the glucose-stimulated influx of Ca 2C. The TNF-a treatment was thought to activate c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), and NF-kB inflammatory signals, since TNF-a increased phospho-JNK and phospho-p38 and reduced IkB levels. Inhibitors of these signaling pathways prevented the TNF-a-induced reduction of the Ca 2C influx and GSIS. Overexpression of MEKK3, a possible mediator from the TNF-a receptor to the JNK/p38 and NK-kB signaling cascade, increased the levels of phospho-JNK, phospho-p38, and NF-kB, and reduced the glucose-stimulated Ca 2C influx and GSIS. The reduction of the Ca 2C influx and GSIS in MEKK3-overexpressing INS-1 cells was also prevented by inhibitors of JNK, p38, and NF-kB. These data demonstrate that TNF-a inhibits GSIS by reducing the glucose-stimulated Ca 2C influx, possibly through the activation of JNK and p38 MAPK and NF-kB inflammatory signals. Thus, our findings suggest that the activation of stress and inflammatory signals can contribute to the inhibition of GSIS in the development of diabetes.

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Section: Discussionmentioning

confidence: 77%

Tumour necrosis factor-α-induced glucose-stimulated insulin secretion inhibition in INS-1 cells is ascribed to a reduction of the glucose-stimulated Ca2+ influx

Kim¹,

Choi²,

Lee³

et al. 2008

Journal of Endocrinology

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“…The medium was changed twice, and cells were subcloned weekly. Islets from normal SpragueDawley rats were isolated by collagenase digestion method described previously (41). All experiments, including isolation of pancreatic islets from normal Sprague-Dawley rats, were reviewed and approved by the Wayne State University Institutional Animal Care and Use Committee.…”

Section: Methodsmentioning

confidence: 99%

“…Pharmacological (i.e., generic as well as more selective inhibitors of geranylgeranylation of Rac1), as well as molecular biological (i.e., dominantnegative mutants of prenyltransferases; Ref. 22) studies from our laboratory have clearly implicated Rac1 in islet function, including insulin secretion (17,15,41). The identity of the farnesylated protein, which is required for nutrient-induced ROS generation, remains to be determined.…”

Section: R759 G-protein-dependent Rosmentioning

confidence: 99%

Phagocyte-like NADPH oxidase generates ROS in INS 832/13 cells and rat islets: role of protein prenylation

Syed

Kyathanahalli

Kowluru

2011

American Journal of Physiology-Regulatory, Integrative and Comp

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Syed I, Kyathanahalli CN, Kowluru A. Phagocyte-like NADPH oxidase generates ROS in INS 832/13 cells and rat islets: role of protein prenylation. Am J Physiol Regul Integr Comp Physiol 300: R756-R762, 2011. First published January 12, 2011 doi:10.1152/ajpregu.00786.2010.-Recent evidence suggests that an acute increase in the generation of phagocyte-like NADPH-oxidase (Nox)-mediated reactive oxygen species (ROS) may be necessary for glucose-stimulated insulin secretion. Using rat islets and INS 832/13 cells, we tested the hypothesis that activation of specific G proteins is necessary for nutrient-mediated intracellular generation of ROS. Stimulation of ␤-cells with glucose or a mixture of mitochondrial fuels (mono-methylsuccinate plus ␣-ketoisocaproic acid) markedly elevated intracellular accumulation of ROS, which was attenuated by selective inhibitors of Nox (e.g., apocynin or diphenyleneiodonium chloride) or short interfering RNA-mediated knockdown of p47 phox , one of the subunits of Nox. Selective inhibitors of protein prenylation (FTI-277 or GGTI-2147) markedly inhibited nutrient-induced ROS generation, suggesting that activation of one (or more) prenylated small G proteins and/or ␥-subunits of trimeric G proteins is involved in this signaling axis. Depletion of endogenous GTP levels with mycophenolic acid significantly reduced glucose-induced activation of Rac1 and ROS generation in these cells. Other immunosuppressants, like cyclosporine A or rapamycin, which do not deplete endogenous GTP levels, failed to affect glucose-induced ROS generation, suggesting that endogenous GTP is necessary for glucose-induced Nox activation and ROS generation. Treatment of INS 832/13 cells or rat islets with pertussis toxin (Ptx), which ADP ribosylates and inhibits inhibitory class of trimeric G proteins (i.e., G i or Go), significantly attenuated glucoseinduced ROS generation in these cells, implicating activation of a Ptx-sensitive G protein in these signaling cascade. Together, our findings suggest a prenylated Ptx-sensitive signaling step couples Rac1 activation in the signaling steps necessary for glucose-mediated generation of ROS in the pancreatic ␤-cells. G protein; pancreatic islets; Rac1 activation; pertussis toxin; inosine monophosphate dehydrogenase GLUCOSE-INDUCED INSULIN SECRETION (GSIS) involves a series of metabolic and cationic events, leading to translocation of insulin-laden secretory granules from a distal site toward the plasma membrane for fusion and release of insulin into circulation. It is widely accepted that vesicular transport and fusion involves interplay between signaling proteins, including vesicle-associated membrane proteins on the secretory granule and docking proteins on the plasma membrane (23,28,33). Furthermore, interaction between these proteins is widely felt to require cytoskeletal remodeling, which is under the fine control of small molecular mass G proteins belonging to the Rho subfamily (e.g., Cdc42 and Rac1; see Ref. 17 for a recent review). Several effector proteins for these sm...

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“…The extent of Rac1 activation (i.e., GTP-bound form) was determined using a commercially available kit (Cytoskeleton, Denver, CO) described earlier (22,39). Scrambled or PHP-siRNA transfected INS 832/13 cells were incubated with low (2.5 mM) or high glucose (20 mM) for 15 min at 37°C.…”

Section: Methodsmentioning

confidence: 99%

“…The cells were incubated with Krebs-Ringer bicarbonate buffer for 2 h prior to stimulation with low (2.5 mM) or high glucose (20 mM), mitochondrial fuels (MMS; 15 mM), and KIC (5 mM), KCl (40 mM), or Mas (0 -15 M) for 45 min at 37°C. Insulin released into the medium was quantified by ELISA as described earlier (22,39).…”

Section: Methodsmentioning

confidence: 99%

Regulation of glucose- and mitochondrial fuel-induced insulin secretion by a cytosolic protein histidine phosphatase in pancreatic β-cells

Kamath

Kyathanahalli

Jayaram

et al. 2010

American Journal of Physiology-Endocrinology and Metabolism

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localization of a cytosolic protein histidine phosphatase (PHP; ϳ16 kDa) in INS 832/13 cells, normal rat islets, and human islets. siRNA-mediated knockdown of PHP markedly reduced glucose-or mitochondrial fuel-induced but not KCl-induced insulin secretion. siRNA-mediated knockdown of PHP also attenuated mastoparan-induced insulin secretion, suggesting its participation in G protein-sensitive signaling steps, leading to insulin secretion. Functional assays revealed that the ␤-cell PHP catalyzes the dephosphorylation of ATP-citrate lyase (ACL). Silencing of PHP expression markedly reduced ACL activity, suggesting functional regulation of ACL by PHP in ␤-cells. Coimmunoprecipitation studies revealed modest effects of glucose on the interaction between PHP and ACL. Confocal microscopic evidence indicated that glucose promotes association between ACL and nm23-H1, a known kinase histidine kinase, but not between PHP and ACL. Furthermore, metabolic viability of INS 832/13 cells was resistant to siRNA-PHP, suggesting no regulatory roles of PHP in cell viability. Finally, long-term exposure (24 h) of INS 832/13 cells or rat islets to high glucose (30 mM) increased the expression of PHP. Such increases in PHP expression were also seen in islets derived from the Zucker diabetic fatty rat compared with islets from the lean control animals. Together, these data implicate regulatory roles for PHP in a G protein-sensitive step involved in nutrient-induced insulin secretion. In light of the current debate on putative regulatory roles of ACL in insulin secretion, additional studies are needed to precisely identify the phosphoprotein substrate(s) for PHP in the cascade of events leading to nutrient-induced insulin secretion. nm23-H1; adenosine 5=-triphosphate-citrate lyase IT IS WELL ESTABLISHED THAT in the majority of cell types transduction of extracellular signals involves ligand binding to a receptor, often followed by the activation of one or more GTP-binding proteins (G proteins) and their effector systems (7). The pancreatic ␤-cell is unusual in that glucose, the major physiological agonist, lacks an extracellular receptor. Instead, events consequent to glucose metabolism promote insulin secretion via the generation and/or altered distribution of diffusible second messengers such as calcium, cAMP, and lipid hydrolytic products of various phospholipases (5,28,32,34,36). It is noteworthy that a selective increase in intracellular calcium not only initiates insulin secretion but also regulates various enzymes such as protein kinases, phosphodiesterases, adenylyl cyclases, and phospholipases, thereby facilitating insulin secretion. In the context of protein kinases, in addition to calcium-dependent protein kinase(s), several other kinases, including calmodulin-, cyclic nucleotide-, and phospholipiddependent protein kinases, tyrosine kinases, and mitogen-

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Dominant-Negative α-Subunit of Farnesyl- and Geranyltransferase Inhibits Glucose-Stimulated, but Not KCl-Stimulated, Insulin Secretion in INS 832/13 Cells

Cited by 47 publications

References 43 publications

Tumour necrosis factor-α-induced glucose-stimulated insulin secretion inhibition in INS-1 cells is ascribed to a reduction of the glucose-stimulated Ca2+ influx

Tumour necrosis factor-α-induced glucose-stimulated insulin secretion inhibition in INS-1 cells is ascribed to a reduction of the glucose-stimulated Ca2+ influx

Phagocyte-like NADPH oxidase generates ROS in INS 832/13 cells and rat islets: role of protein prenylation

Regulation of glucose- and mitochondrial fuel-induced insulin secretion by a cytosolic protein histidine phosphatase in pancreatic β-cells

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