Glucose regulates the cortical actin network through modulation of Cdc42 cycling to stimulate insulin secretion
Glucose regulates the cortical actin network through modulation of Cdc42 cycling to stimulate insulin secretion
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DOI：
10.1152/ajpcell.00093.2003
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发表时间：
2003-09-01
影响因子：
5.5
通讯作者：
Thurmond, DC
中科院分区：
文献类型：
--
作者：
Nevins, AK;Thurmond, DC
葡萄糖刺激的胰岛β细胞的胰岛素颗粒胞吐涉及皮质肌动蛋白重塑，导致聚合的肌动蛋白与质膜T-SNARE(靶膜可溶性N-乙基马来酰亚胺敏感因子附着蛋白受体)复合体相互作用的一过性中断。为了研究皮质肌动蛋白重塑的启动机制，我们使用肌动蛋白成核/稳定剂jasplakinolide来证明重塑是在刺激分泌途径中ATP敏感的K+通道附近的一步开始的。共聚焦免疫荧光显微镜显示，葡萄糖刺激的胰岛素分泌需要皮质肌动蛋白重塑。此外，葡萄糖介导了Rho家族GTPase CDc42的内源性激活状态，CDc42是肌动蛋白聚合的正向近端效应因子，导致刺激5min内CDc42-GTP的净减少。有趣的是，葡萄糖刺激导致了CDc42的快速和可逆的糖基化，这表明葡萄糖通过选择性的糖基化来失活CDc42，从而诱导皮质肌动蛋白重排。此外，组成活性形式的CDC42(Q61L)的表达抑制了葡萄糖刺激的胰岛素分泌，而主要的负性形式(T17N)的表达则没有作用，这表明葡萄糖刺激的胰岛素分泌需要CDC42循环到GDP结合状态。相反，KCl刺激的胰岛素分泌不受显性负性或结构性活性的CDC42表达的影响，并停止调节内源性CDC42的激活，这与葡萄糖依赖的皮质肌动蛋白重塑一致。这些发现表明，葡萄糖通过调节CDC42循环来调节皮质肌动蛋白网络，从而诱导胰岛β细胞分泌胰岛素。
Glucose-stimulated insulin granule exocytosis in pancreatic beta-cells involves cortical actin remodeling that results in the transient disruption of the interaction between polymerized actin with the plasma membrane t-SNARE (target membrane soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complex. To examine the mechanism underlying the initiation of cortical actin remodeling, we have used the actin nucleating/stabilizing agent jasplakinolide to show that remodeling is initiated at a step proximal to the ATP-sensitive K+ channels in the stimulus-secretion pathway. Confocal immunofluorescent microscopy revealed that cortical actin remodeling was required for glucose-stimulated insulin secretion. Furthermore, glucose was found to mediate the endogenous activation state of the Rho family GTPase Cdc42, a positive proximal effector of actin polymerization, resulting in a net decrease of Cdc42-GTP within 5 min of stimulation. Intriguingly, glucose stimulation resulted in the rapid and reversible glucosylation of Cdc42, suggesting that glucose inactivated Cdc42 by selective glucosylation to induce cortical actin rearrangement. Moreover, expression of the constitutively active form of Cdc42 (Q61L) inhibited glucose-stimulated insulin secretion, whereas the dominant negative form (T17N) was without effect, suggesting that glucose-stimulated insulin secretion requires Cdc42 cycling to the GDP-bound state. In contrast, KCl-stimulated insulin secretion was unaffected by the expression of dominant negative or constitutively active Cdc42 and ceased to modulate endogenous Cdc42 activation, consistent with glucose-dependent cortical actin remodeling. These findings reveal that glucose regulates the cortical actin network through modulation of Cdc42 cycling to induce insulin secretion in pancreatic beta-cells.