This Article Full Text Full Text (PDF) All Versions of this Article: 144/10/4508    most recent Author Manuscript (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Amin, R. H. Articles by Kowluru, A. Search for Related Content PubMed PubMed Citation Articles by Amin, R. H. Articles by Kowluru, A.

Mastoparan-Induced Insulin Secretion from Insulin-Secreting ßTC3 and INS-1 Cells: Evidence for Its Regulation by Rho Subfamily of G Proteins

Departments of Pharmaceutical Sciences (R.H.A., H.-Q.C., R.V., A.K.) and Pharmacology (R.B.S.), Physiology, Radiology, and Biomedical Engineering, Wayne State University, and ß Cell Biochemistry Research Laboratory (R.H.A., H.-Q.C., A.K.), John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan 48201; and John D. Dingell Veterans Affairs Medical Center and Argonne National Laboratory (R.B.S.), and Cardiovascular Research Institute (J.L., G.L.), National University Medical Institutes, National University of Singapore, Singapore 117597

Address all correspondence and requests for reprints to: Anjan Kowluru, Ph.D., Department of Pharmaceutical Sciences, College of Pharmacy and Health Professions, Wayne State University, 259 Mack Avenue, Detroit, Michigan 48201. E-mail: akowluru{at}med.wayne.edu.

Mastoparan, a tetradecapeptide from wasp venom, stimulates insulin secretion from the islet ß-cells, presumably via activation of trimeric G proteins. Herein, we used Clostridial toxins, which selectively modify and inactivate the Rho subfamily of G proteins, to examine whether mastoparan-induced insulin secretion also involves activation of these signaling proteins. Mastoparan, but not mastoparan 17 (an inactive analog of mastoparan), significantly stimulated insulin secretion from ßTC3 and INS-1 cells. Preincubation of ßTC3 cells with either Clostridium difficille toxin B, which inactivates Rho, Cdc42, and Rac, or Clostridium sordellii toxin, which inactivates Ras, Rap, and Rac, markedly attenuated the mastoparan-induced insulin secretion, implicating Rac in this phenomenon. Mastoparan-stimulated insulin secretion was resistant to GGTI-2147, a specific inhibitor of geranylgeranylation of Rho G proteins (e.g. Rac), suggesting that mastoparan induces direct activation of Rac via GTP/GDP exchange. This was confirmed by a pull-down assay that quantifies the binding of activated (i.e. GTP-bound) Rac to p21-activated kinase. However, glucose-induced insulin secretion from these cells was abolished by toxin B or GGTI-2147, suggesting that the geranylgeranylation step is critical for glucose-stimulated secretion. Mastoparan significantly increased the translocation of cytosolic Rac and Cdc42 to the membrane fraction. Confocal light microscopy revealed a substantial degree of colocalization of Rac (and, to a lesser degree, Cdc42) with insulin in ß-cells exposed to mastoparan. Further, stable expression of a dominant negative (N17Rac) form of Rac into INS-1 cells resulted in a significant reduction in mastoparan-stimulated insulin secretion from these cells. Taken together, our findings implicate Rho G proteins, specifically Rac, in mastoparan-induced insulin release.

This article has been cited by other articles:

				P. McDonald, R. Veluthakal, H. Kaur, and A. Kowluru Biologically active lipids promote trafficking and membrane association of Rac1 in insulin-secreting INS 832/13 cells Am J Physiol Cell Physiol, March 1, 2007; 292(3): C1216 - C1220. [Abstract] [Full Text] [PDF]

				R. Veluthakal, H. Kaur, M. Goalstone, and A. Kowluru Dominant-Negative {alpha}-Subunit of Farnesyl- and Geranyltransferase Inhibits Glucose-Stimulated, but Not KCl-Stimulated, Insulin Secretion in INS 832/13 Cells Diabetes, January 1, 2007; 56(1): 204 - 210. [Abstract] [Full Text] [PDF]

				A. Kowluru and R. Veluthakal Rho Guanosine Diphosphate-Dissociation Inhibitor Plays a Negative Modulatory Role in Glucose-Stimulated Insulin Secretion Diabetes, December 1, 2005; 54(12): 3523 - 3529. [Abstract] [Full Text] [PDF]

				G. Parnaud, E. Hammar, D. G. Rouiller, and D. Bosco Inhibition of calpain blocks pancreatic {beta}-cell spreading and insulin secretion Am J Physiol Endocrinol Metab, August 1, 2005; 289(2): E313 - E321. [Abstract] [Full Text] [PDF]

				J. Li, K. L. O'Connor, G. H. Greeley Jr., P. J. Blackshear, C. M. Townsend Jr., and B. M. Evers Myristoylated Alanine-rich C Kinase Substrate-mediated Neurotensin Release via Protein Kinase C-{delta} Downstream of the Rho/ROK Pathway J. Biol. Chem., March 4, 2005; 280(9): 8351 - 8357. [Abstract] [Full Text] [PDF]

				J. Li, K. L. O'Connor, M. R. Hellmich, G. H. Greeley Jr., C. M. Townsend Jr., and B. M. Evers The Role of Protein Kinase D in Neurotensin Secretion Mediated by Protein Kinase C-{alpha}/-{delta} and Rho/Rho Kinase J. Biol. Chem., July 2, 2004; 279(27): 28466 - 28474. [Abstract] [Full Text] [PDF]

				Y. Uchizono, M. Iwase, U. Nakamura, N. Sasaki, D. Goto, and M. Iida Tacrolimus Impairment of Insulin Secretion in Isolated Rat Islets Occurs at Multiple Distal Sites in Stimulus-Secretion Coupling Endocrinology, May 1, 2004; 145(5): 2264 - 2272. [Abstract] [Full Text] [PDF]