Mechanism of Myosin Action in Glucose Uptake

 描述（由申请人提供）：2型糖尿病是美国最常见的糖尿病形式。导致2型糖尿病发展的主要因素是外周组织（主要是骨骼肌和脂肪组织）的胰岛素抵抗。 胰岛素介导的含胰岛素应答性葡萄糖转运蛋白（GLUT 4）的囊泡与质膜的易位和融合对于适当的葡萄糖稳态至关重要。因此，确定和表征的细胞因子和过程调节GLUT 4运输是至关重要的了解受损的胰岛素敏感性的分子机制。胰岛素信号传导部分通过调节肌动蛋白细胞骨架来协调GLUT 4囊泡的束缚、对接和融合。虽然肌动蛋白重组所需的GLUT 4囊泡运输，很少有人知道这些过程所需的细胞骨架重排的调节因素。该提案的主要目的是深入了解胰岛素刺激GLUT 4囊泡运输过程中细胞骨架动态重组的调节机制。基于肌动蛋白的运动蛋白的肌球蛋白家族，特别是肌球蛋白II（MyoII）已经显示出调节肌动蛋白丝重组以促进各种细胞类型中的囊泡运输。肌球蛋白II已被证明在“结构”中起作用，以帮助肌动蛋白细胞骨架的重组，以及在“马达”中起作用，以收缩肌动蛋白丝。我们的研究表明，MyoIIA亚型被激活，并与GLUT 4和丝状肌动蛋白（F-肌动蛋白）在质膜共定位后，胰岛素刺激，以促进GLUT 4介导的葡萄糖摄取。此外，我们表明，抑制MyoII活性损害了GLUT 4在质膜上的正确插入。由于肌动蛋白是一个不可分割的组成部分拴系GLUT 4囊泡在质膜以及囊泡融合事件，我们假设，MyoIIA促进肌动蛋白重组所需的GLUT 4囊泡拴系和融合与质膜。因此，本提案的具体目的是确定和表征MyoIIA在胰岛素刺激的GLUT 4囊泡在脂肪细胞中运输过程中调节肌动蛋白细胞骨架的机制。

 DESCRIPTION (provided by applicant): Type 2 diabetes is the most prevalent form of diabetes in the United States. The major contributing factor to the development of type 2 diabetes is insulin resistance of peripheral tissues, primarily skeletal muscle and adipose tissue. Insulin-mediated translocation and fusion of insulin-responsive glucose transporter (GLUT4)-containing vesicles to the plasma membrane is critical for proper glucose homeostasis. Thus, the identification and characterization of cellular factors and processes regulating GLUT4 trafficking are critical to understanding the molecular mechanisms underlying impaired insulin sensitivity. Insulin signaling coordinates the tethering, docking and fusion of GLUT4 vesicles in part by regulating the actin cytoskeletal. While actin reorganization is required for GLUT4 vesicle trafficking, little is known about the factors regulating the cytoskeletal rearrangements required for these processes. The broad aim of this proposal is to gain insight on the mechanisms regulating the dynamic reorganization of the cytoskeleton during insulin-stimulated GLUT4 vesicle trafficking. The myosin family of actin- based motor proteins, specifically myosin II (MyoII) has been shown to regulate actin filament reorganization to facilitate vesicle traffickig in various cell types. Myosin II has been shown to function in a "structural" role to aid in the reorganization of the actin cytoskeleton as well as in a "motor" role to contract actin filaments. Our studies show that the MyoIIA isoform is activated and colocalizes with GLUT4 and filamentous actin (F-actin) at the plasma membrane upon insulin stimulation to facilitate GLUT4-mediated glucose uptake. Furthermore, we show that inhibition of MyoII activity impairs the proper insertion of GLUT4 at the plasma membrane. Since actin is an integral component tethering GLUT4 vesicles at the plasma membrane as well as vesicle fusion events, we hypothesize that MyoIIA facilitates the actin reorganization required for GLUT4 vesicle tethering and fusion with the plasma membrane. Thus, the specific aims of this proposal are to identify and characterize the mechanisms by which MyoIIA regulates the actin cytoskeleton during insulin-stimulated GLUT4 vesicle trafficking in adipocytes.