Insulin stimulated ubiquitin-like modification

描述（由申请人提供）：泛素样修饰是一种保守的生化机制，被细胞用于各种目的。这些包括蛋白质的靶向降解，受体的内吞作用，蛋白质定位的调节和信号转导。除了泛素本身调节胰岛素受体和IRS蛋白的作用外，泛素样修饰尚未被描述为在胰岛素信号传导中发挥突出作用。TUG被认为是胰岛素信号转导的靶标，并参与调节GLUT4葡萄糖转运蛋白的运输和脂肪细胞的葡萄糖摄取。根据提出的模型，在缺乏胰岛素的情况下，TUG通过在细胞内“系住”GLUT4转运蛋白，将它们排除在质膜之外，限制葡萄糖的摄取。胰岛素“解开”转运蛋白，重新分配GLUT4，增强葡萄糖向细胞的转运。胰岛素作用于TUG和GLUT4的机制尚不清楚。目前的建议将验证胰岛素刺激TUG快速和位点特异性切割以释放氨基末端片段TUGUL的假设，这是一种新的泛素样修饰剂。使用培养的3T3-L1脂肪细胞，Aim 1将使用几种生化和细胞生物学方法来测试胰岛素是否刺激TUG裂解，以及这是否是胰岛素动员GLUT4所必需的。目的2将验证TUGUL作为泛素样修饰剂的假设，并将研究假定的TUG C末端裂解产物的作用。Aim 3将研究胰岛素信号如何作用于TUG导致其加工。预计，这些目标的实现将开始定义胰岛素调节的泛素样修饰的新途径。此外，预计该结果将对理解胰岛素如何刺激葡萄糖摄取具有重要意义。2型糖尿病是一个主要的公共健康问题，部分原因是胰岛素刺激葡萄糖摄取能力的缺陷。预计胰岛素作用和葡萄糖摄取的拟议研究将有助于更好地了解可能导致2型糖尿病发展的机制。

DESCRIPTION (provided by applicant): Ubiquitin-like modification is a conserved biochemical mechanism that is used by cells for various purposes. These include targeted degradation of proteins, endocytosis of receptors, regulation of protein localization, and signal transduction. Apart from a role of ubiquitin itself to modulate insulin receptors and IRS proteins, ubiquitin-like modifications have not been described to play a prominent role in insulin signaling. TUG was identified as a target of insulin signaling, and is implicated regulating GLUT4 glucose transporter trafficking and glucose uptake in adipocytes. According to the proposed model, TUG acts by "tethering" GLUT4 transporters intracellularly in the absence of insulin, excluding them from the plasma membrane and limiting glucose uptake. Insulin "untethers" the transporters to redistribute GLUT4 and to enhance glucose transport into cells. The mechanism by which insulin acts on TUG and GLUT4 is not well understood. The present proposal will test the hypothesis that insulin stimulates rapid and site-specific cleavage of TUG to liberate an amino terminal fragment, TUGUL, that is a new ubiquitin-like modifier. Using cultured 3T3-L1 adipocytes, several biochemical and cell biological approaches will be used in Aim 1 to test whether insulin stimulates TUG cleavage, and whether this is required for insulin to mobilize GLUT4. Aim 2 will test the hypothesis that TUGUL functions as a ubiquitin-like modifier, and will study the role of the putative TUG C terminal cleavage product. Aim 3 will study how the insulin signal may act on TUG to cause its processing. It is anticipated that, together, accomplishment of these aims will begin to define a novel pathway for insulin regulated ubiquitin-like modification. Furthermore, it is anticipated that the results will have importance for understanding how insulin stimulates glucose uptake. Type 2 diabetes is a major public health problem that results in part from a defect in the ability of insulin to stimulate glucose uptake. It is anticipated that the proposed studies of insulin action and glucose uptake will lead to a greater understanding of mechanisms that may contribute to the development of type 2 diabetes.