The Role of G Proteins in Insulin Action

描述(由申请人提供)：毫无疑问，我们正处于糖尿病的全球流行之中。胰岛素抵抗被认为是这种疾病的一个特征，其定义是无法对正常的循环胰岛素水平做出反应。这种状态的主要损害包括肌肉和脂肪细胞对葡萄糖的吸收和储存的缺陷。胰岛素通过增加细胞表面促进转运体GLUT4的浓度来刺激这些细胞对葡萄糖的摄取。将研究这一过程中涉及的分子事件，并特别注意荷尔蒙作用的特异性的潜在基础。我们已经了解到，小G蛋白协调整合来自胰岛素受体的信号来控制GLUT4的运输。以前的研究已经揭示了G蛋白TC10在这一过程中的核心作用。在目标1中，我们将研究TC10的激活和失活所涉及的生化过程，研究解释该蛋白独特性质的分子细节，并试图了解胰岛素是如何通过控制关键的上游激活物来调节它的。我们还将研究它的活性是如何通过灭活蛋白质来关闭的。在目标2中，我们将创建编码TC10基因的定向缺失的小鼠，以探索这种G蛋白在生理环境中的作用。我们将评估这些小鼠的葡萄糖和脂肪代谢，预计该基因的缺失可能会显著改变胰岛素的作用。最后，在目标3中，我们将评估TC10下游控制GLUT4蛋白运输到细胞质膜的特定途径。这一途径涉及另一种G蛋白Rab31；我们假设该蛋白的活性受胰岛素通过TC10激活而负向调节。我们将探索新发现的Rab31激活剂GAPEX-5在这一过程中的作用，以及它对Rab31的影响是如何通过控制其细胞位置来调节的。总之，这些方法将允许评估这一新途径在胰岛素作用中的重要性，为未来研究其在糖尿病发展中的潜在作用奠定基础。

DESCRIPTION (provided by applicant): There is little doubt that we are in the midst of a worldwide epidemic of diabetes. Insulin resistance is recognized as a characteristic trait of the disease, defined by the inability to respond to normal circulating levels of insulin. The primary lesion in this state involves defects in the uptake and storage of glucose in muscle and fat cells. Insulin stimulates glucose uptake in these cells by increasing the concentration of the facilitative transporter Glut4 at the cell surface. The molecular events involved in this process will be investigated, with special attention to the underlying basis for the specificity of actions of the hormone. We have learned that small G proteins coordinately integrate signals from the insulin receptor to control the trafficking of Glut4. Previous studies have revealed a central role for the G protein TC10 in this process. In Aim 1, we will study the biochemical processes involved in the activation and inactivation of TC10, investigating the molecular details that explain the unique properties of this protein, and attempting to understand how it is regulated by insulin via the control of crucial upstream activators. We will also study how its activity is turned off by inactivating proteins. In Aim 2, we will create mice with a targeted deletion of the gene encoding TC10 to explore the role of this G protein in a physiological setting. We will evaluate glucose and lipid metabolism in these mice, anticipating that deletion of this gene may significantly alter insulin action. Finally, in Aim 3, we will evaluate a specific pathway downstream of TC10 that controls the trafficking of the Glut4 protein to the plasma membrane in cells. This pathway involves another G protein, Rab31; we hypothesize that the activity of this protein is negatively regulated by insulin through TC10 activation. We will explore the role of a newly discovered Rab31 activator named Gapex-5 in this process, and how its effect on Rab31 is regulated by control of its cellular location. Together, these approaches will allow for the evaluation of the importance of this novel pathway in insulin action, setting the stage for future investigations into its potential role in the development of diabetes.