Mechanism of Myosin Action in Glucose Uptake

 描述(申请人提供)：2型糖尿病是美国最常见的糖尿病类型。导致2型糖尿病发展的主要因素是周围组织，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反应性葡萄糖转运体(GLUT4)的囊泡转位和融合到质膜上是维持葡萄糖平衡的关键。因此，识别和表征调节GLUT4转运的细胞因子和过程对于理解胰岛素敏感性受损的分子机制至关重要。胰岛素信号在一定程度上通过调节肌动蛋白细胞骨架来协调GLUT4小泡的连接、对接和融合。虽然肌动蛋白重组是GLUT4囊泡运输所必需的，但人们对调控这些过程所需的细胞骨架重排的因素知之甚少。这项建议的主要目的是深入了解在胰岛素刺激的GLUT4囊泡运输过程中细胞骨架动态重组的调节机制。肌球蛋白家族是以肌动蛋白为基础的运动蛋白，特别是肌球蛋白II(MyoII)，它可以调节肌动蛋白细丝的重组，促进不同细胞类型的囊泡运输。肌球蛋白II已被证明具有帮助肌动蛋白细胞骨架重组的“结构性”作用，以及收缩肌动蛋白细丝的“马达”作用。我们的研究表明，在胰岛素刺激下，MyoIIA亚型被激活并与GLUT4和丝状肌动蛋白(F-actin)共存于质膜，以促进GLUT4介导的葡萄糖摄取。此外，我们发现抑制MyoII活性会损害GLUT4在质膜上的正确插入。由于肌动蛋白是连接GLUT4小泡在质膜上以及小泡融合事件的不可或缺的组成部分，我们假设MyoIIA促进了GLUT4小泡拴系和与质膜融合所需的肌动蛋白重组。因此，这项建议的具体目的是确定和表征MyoIIA在胰岛素刺激的GLUT4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.