Regulatory Mechanisms of GLUT4 Exocytosis

项目总结 随着胰岛素抵抗和2型糖尿病在全球范围内的流行，迫切需要 了解胰岛素是如何在分子水平上维持血糖稳态的。胰岛素的一个主要功能 是促进肌肉和脂肪组织对葡萄糖的吸收，这是一个由葡萄糖转运体介导的过程 GLUT4.在胰岛素刺激下，GLUT4从细胞内的存储小泡重新定位到细胞表面 通过调节胞吐作用。GLUT4囊泡的胞吐作用需要SNARE蛋白为核心 聚变机械，以及一组聚变调节器。圈套或融合的功能丧失突变 监管机构废除了胰岛素触发的GLUT4胞吐作用，并扰乱了血糖动态平衡。此外， GLUT4囊泡融合蛋白的失衡与肥胖相关的胰岛素抵抗有关。 虽然陷阱和融合调节器的生理重要性是显而易见的，但人们对它的了解仍然很少。 它们如何协同作用来调节和调节GLUT4囊泡融合。这项提案的总体目标是 用新的和互补的方法回答这个关键问题。我们将首先定义分子 利用一种新型重组融合技术研究囊泡融合蛋白的作用机制和功能相互作用 系统。我们将同时使用重组蛋白和从小鼠脂肪细胞中分离的天然蛋白。我们会 然后在3T3-L1脂肪细胞和从3T3-L1分离的脂肪细胞中鉴定GLUT4囊泡融合蛋白 基因敲除老鼠。最后，我们将确定囊泡融合蛋白的活性是否以及如何 以高脂饮食喂养的小鼠为模型系统，建立胰岛素抵抗受损模型。如果成功完成， 这项研究将极大地拓宽我们对GLUT4胞吐调节机制的认识。 这些发现还将揭示与胰岛素等葡萄糖失衡相关的疾病。 耐药性和2型糖尿病，并将促进开发新的治疗策略 干预。

PROJECT SUMMARY As the epidemic of insulin resistance and type 2 diabetes emerges worldwide, there is an urgent need to understand how insulin maintains blood glucose homeostasis at the molecular level. A major function of insulin is to promote glucose uptake into muscle and adipose tissues, a process mediated by the glucose transporter GLUT4. Upon insulin stimulation, GLUT4 is relocated from intracellular storage vesicles to the cell surface through regulated exocytosis. The exocytosis of GLUT4 vesicles requires the SNARE proteins as the core fusion machinery, as well as a group of fusion regulators. Loss-of-function mutations of the SNAREs or fusion regulators abrogate insulin-triggered GLUT4 exocytosis and disrupt blood glucose homeostasis. Moreover, imbalances in the GLUT4 vesicle fusion proteins have been implicated in obesity-associated insulin resistance. While the physiological importance of the SNAREs and fusion regulators is clear, it remains poorly understood how they act in concert to mediate and regulate GLUT4 vesicle fusion. The overall goal of this proposal is to answer this key question using novel and complementary approaches. We will first define the molecular mechanisms and functional interactions of the vesicle fusion proteins using a novel reconstituted fusion system. We will use both recombinant proteins and native proteins isolated from mouse adipocytes. We will then characterize GLUT4 vesicle fusion proteins in 3T3-L1 adipocytes and in adipocytes isolated from knockout mice. Finally, we will determine whether and how the activities of the vesicle fusion proteins are impaired in insulin resistance, using high fat diet-fed mice as a model system. If successfully accomplished, this research will substantially broaden our knowledge about the regulatory mechanisms of GLUT4 exocytosis. The findings will also shed light upon the diseases associated with glucose imbalances such as insulin resistance and type 2 diabetes, and will facilitate the development of novel strategies for therapeutic intervention.