Mastoparan-induced insulin secretion from insulin-screting βTC3 and INS-1 cells:: Evidence for its regulation by rho subfamily of G proteins

被引:40
作者
Amin, RH
Chen, HQ
Veluthakal, R
Silver, RB
Li, JS
Li, GD
Kowluru, A
机构
[1] Wayne State Univ, Coll Pharm & Hlth Profess, Dept Pharmaceut Sci, Detroit, MI 48201 USA
[2] Wayne State Univ, Dept Pharmacol, Detroit, MI 48201 USA
[3] Wayne State Univ, Dept Physiol, Detroit, MI 48201 USA
[4] Wayne State Univ, Dept Radiol, Detroit, MI 48201 USA
[5] Wayne State Univ, Dept Biomed Engn, Detroit, MI 48201 USA
[6] John D Dingell Vet Affairs Med Ctr, Cell Biochem Res Lab, Detroit, MI 48201 USA
[7] Natl Univ Singapore, Natl Univ Med Inst, Inst Cardiovasc Res, Singapore 117597, Singapore
[8] Natl Univ Singapore, Natl Univ Med Inst, John D Dingell Vet Affairs Med Ctr, Singapore 117597, Singapore
[9] Natl Univ Singapore, Natl Univ Med Inst, Argonne Natl Lab, Singapore 117597, Singapore
关键词
D O I
10.1210/en.2003-0106
中图分类号
R5 [内科学];
学科分类号
1002 ; 100201 ;
摘要
Mastoparan, a tetradecapeptide from wasp venom, stimulates insulin secretion from the islet beta-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 betaTC3 and INS-1 cells. Preincubation of betaTC3 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 beta-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.
引用
收藏
页码:4508 / 4518
页数:11
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