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该疾病的特征，其定义为不能对正常循环水平的胰岛素作出反应。这种状态下的原发性病变涉及肌肉和脂肪细胞中葡萄糖摄取和储存的缺陷。胰岛素通过增加细胞表面促进性转运蛋白Glut 4的浓度来刺激这些细胞中的葡萄糖摄取。将研究参与这一过程的分子事件，特别注意激素作用特异性的潜在基础。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，以控制Glut 4的运输。之前的研究揭示了G蛋白TC 10在这一过程中的核心作用。在目标1中，我们将研究TC 10的激活和失活所涉及的生化过程，研究解释这种蛋白质独特性质的分子细节，并试图了解胰岛素如何通过控制关键的上游激活因子来调节它。我们还将研究如何通过使蛋白质失活来关闭其活性。在目标2中，我们将创建具有编码TC 10的基因的靶向缺失的小鼠，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质代谢，预计该基因的缺失可能会显着改变胰岛素的作用。最后，在目标3中，我们将评估TC 10下游的一个特定途径，该途径控制细胞中Glut 4蛋白向质膜的运输。该途径涉及另一种G蛋白Rab 31;我们假设该蛋白的活性通过TC 10激活受胰岛素负调控。我们将探讨一种新发现的Rab 31激活剂Gapex-5在这一过程中的作用，以及它对Rab 31的作用如何通过控制其细胞位置来调节。总之，这些方法将允许评估这种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.