REGULATION OF PROTEIN TRAFFICKING IN ADIPOCYTES

描述（由申请方提供）：Glut 4葡萄糖转运蛋白催化餐后全身葡萄糖处置的限速步骤。胰岛素刺激的Glut 4向质膜的再分布的中断是与2型糖尿病相关的外周胰岛素抵抗的近端原因。因此，阐明胰岛素刺激Glut 4向质膜急性重新分布的机制所涉及的精确分子途径可能对于了解胰岛素抵抗状态的发病机制具有相当重要的意义。调节的亚细胞运输Glut 4部分由胰岛素响应性AS 160/Rab 10 GTd 3循环决定，但需要其他未鉴定的因素来完全解释其基础细胞内隔离和胰岛素刺激的质膜运动。此外，指导其调节亚细胞运输的Glut 4的具体结构特征仍然知之甚少。我们已经确定了一个新的亚细胞靶向基序（LXXLXP）内的羧基末端12个残基的细胞质尾的Glut 4是共享的胰岛素响应性氨肽酶。与其他Glut 4靶向基序不同，LXXLXP基序（本文称为胰岛素应答基序）的改变对转运蛋白的稳态分布具有深远的影响，似乎完全消除了其基础再循环和胰岛素刺激的向细胞表面的易位。该提案的目标是通过描绘Glut 4调节的作用和推定的Akt调节的GT3活化蛋白AS 250在该过程中的作用来获得对Glut 4调节的基本见解。为了实现这一目标，将进行以下具体的目标：1）精确地定义Glut 4及其如何与其他已知的Glut 4靶向基序相互作用; 2）鉴定和表征Glut 4移动通过的新的亚细胞膜隔室;阐明AS 250复合物的功能，胰岛素如何影响其功能，并鉴定AS 250/KIAA 1219复合物的新组分。 公共卫生相关性：该项目旨在研究脂肪细胞中胰岛素如何调节葡萄糖转运的新方面。它直接关系到了解参与全身葡萄糖稳态调节的分子机制及其在胰岛素抵抗状态（如糖尿病、肥胖和代谢综合征）中的紊乱。

DESCRIPTION (provided by applicant): The Glut4 glucose transporter catalyzes the rate-limiting step in postprandial whole body glucose disposal. A disruption in the insulin-stimulated redistribution of Glut4 to the plasma membrane is the proximal cause of the peripheral insulin resistance associated with type 2 diabetes mellitus. Elucidation of the precise molecular pathways involved in the mechanism by which insulin stimulates the acute redistribution of Glut4 to the plasma membrane may thus be of considerable importance in understanding the pathogenesis of insulin resistant states. The regulated subcellular trafficking of Glut4 is partially dictated by the insulin- responsive AS160/Rab10 GTPase cycle, but additional unidentified factors are necessary to fully account for its basal intracellular sequestration and insulin-stimulated movement to the plasma membrane. Additionally, the specific structural features of Glut4 that direct its regulated subcellular trafficking remain poorly understood. We have identified a novel subcellular targeting motif (LXXLXP) within the carboxy-terminal 12 residues of the cytoplasmic tail of Glut4 that is shared with the insulin-responsive aminopeptidase. Unlike other Glut4 targeting motifs, alteration of the LXXLXP motif (herein referred to as IRM, insulin-responsive motif) has a profound effect on the steady-state distribution of the transporter and appears to completely abolish its basal recycling and insulin-stimulated translocation to the cell surface. The goal of this proposal is to gain fundamental insights into Glut4 regulation by delineating the role of the IRM and of a putative Akt-regulated GTPase activating protein, AS250, in this process. In order to accomplish this goal, the following specific aims will be undertaken: 1) to precisely define the IRM and how it interacts with other known Glut4 targeting motifs; 2) to identify and characterize novel subcellular membrane compartments through which Glut4 moves; and 3) to elucidate the function of the AS250 complex, how insulin affects its function, and identify novel components of the AS250/KIAA1219 complex. PUBLIC HEALTH RELEVANCE: This project proposes to investigate novel aspects of how glucose transport is regulated by insulin in fat cells. It is directly relevant to understanding the molecular mechanisms involved in the regulation of whole body glucose homeostasis and its derangement in insulin resistant states such as diabetes, obesity, and metabolic syndrome.