Research Service, John D. Dingell VA Medical Center, USA; Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI, USA.
Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.
Mol Cell Endocrinol. 2024 Jan 15;580:112104. doi: 10.1016/j.mce.2023.112104. Epub 2023 Oct 30.
Emerging evidence implicates novel roles for small G protein GDP dissociation stimulator (smgGDS) in G protein activation and subsequent targeting to relevant subcellular compartments for effector regulation. Given the well-established roles of small G proteins in insulin secretion, we undertook this investigation to determine the putative roles of smgGDS in insulin secretion. Immunoblotting studies revealed that both splice variants of smgGDS are expressed in human islets, rat islets and INS-1 832/13 cells. A significant inhibition (-52%) of glucose-stimulated insulin secretion (GSIS) was observed in INS-1 832/13 cells following siRNA-mediated depletion of smgGDS. In addition, insulin secretion elicited by a membrane depolarizing concentration of KCl (via increased calcium influx), forskolin (via increased cAMP generation) or IBMX (via inhibition of phosphodiesterase) was inhibited by -49%, -27%, and -28%, respectively. Subcellular distribution studies revealed no significant alterations in the abundance of smgGDS in the cytosolic and membrane fractions during the 45-min exposure of INS-1 832/13 cells to an insulinotropic concentration of glucose. Together, we present the first evidence of expression of smgGDS in human islets, rodent islets, and clonal β-cells. We also demonstrate novel regulatory roles of these proteins in insulin secretion derived from glucose metabolic events, including calcium- and cAMP-dependent signaling steps.
新的证据表明，小 G 蛋白 GDP 解离刺激因子（smgGDS）在 G 蛋白激活及其随后靶向相关亚细胞隔室以进行效应子调节中具有新的作用。鉴于小 G 蛋白在胰岛素分泌中的作用已得到充分确立，我们进行了这项研究，以确定 smgGDS 在胰岛素分泌中的可能作用。免疫印迹研究表明，smgGDS 的两种剪接变体均在人胰岛、大鼠胰岛和 INS-1 832/13 细胞中表达。在 INS-1 832/13 细胞中，通过 siRNA 介导的 smgGDS 耗竭，观察到葡萄糖刺激的胰岛素分泌（GSIS）显著抑制（-52%）。此外，通过增加钙离子内流的膜去极化浓度 KCl、通过增加 cAMP 生成的 forskolin 或通过抑制磷酸二酯酶的 IBMX 引起的胰岛素分泌分别被抑制了-49%、-27%和-28%。亚细胞分布研究表明，在 INS-1 832/13 细胞暴露于胰岛素刺激浓度的葡萄糖的 45 分钟内，smgGDS 在胞质和膜部分中的丰度没有明显变化。综上所述，我们首次证明了 smgGDS 在人胰岛、啮齿动物胰岛和克隆β细胞中的表达。我们还证明了这些蛋白在胰岛素分泌中的新的调节作用，这源自葡萄糖代谢事件，包括钙和 cAMP 依赖性信号步骤。
