Clip R-59: a novel regulator of Akt signaling

描述（由申请人提供）：我们研究了Akt， PI3K的直接效应器和胰岛素代谢作用的主要介质。在这些研究过程中，我们分离了作为Akt相互作用蛋白的ClipR-59，其表达在脂肪细胞分化过程中升高，在肥胖发展过程中降低。ClipR-59不涉及Akt的激活。相反，它调节Akt活化后的细胞区隔化，特别是Akt膜结合。ClipR-59对Akt膜关联的调节对葡萄糖转运至关重要，研究结果表明，强制表达ClipR-59促进脂肪细胞葡萄糖转运，而沉默ClipR-59则会损害脂肪细胞葡萄糖转运。脂肪细胞的葡萄糖摄取对维持全身葡萄糖稳态至关重要。由于肥胖的流行，II型糖尿病已成为流行病和主要的公共卫生负担。考虑到ClipR-59与Akt相互作用并调节葡萄糖转运，对ClipR-59的进一步研究值得进一步研究。我们目前的研究表明，a)小鼠脂肪组织中ClipR-59的表达导致脂肪量减少和葡萄糖耐量增加，这表明ClipR-59可能在维持全身葡萄糖稳态中发挥作用；b) ClipR-59的棕榈酰化，可能是由蛋白棕榈酰转移酶DHHC17介导的，是ClipR-59调节Akt细胞膜关联的关键，这意味着DHHC17调控ClipR-59棕榈酰化是ClipR-59调节Akt信号传导的重要机制；c) ClipR-59与AS160络合，AS160是一种连接胰岛素信号和Glut4囊泡的rabi - gap蛋白。由于ClipR-59也直接与Akt相互作用，因此ClipR-59可能作为支架蛋白将Akt信号连接到AS160。为了进一步研究ClipR-59的功能和调控，我们提出了以下具体问题的实验：确定脂肪组织中ClipR-59的强制表达对全身葡萄糖稳态的影响，以及对肥胖、胰岛素抵抗和糖尿病的发生和进展的影响；2. 通过调节ClipR-59棕榈酰化，确定蛋白棕榈酰转移酶DHHC17在Akt信号传导和脂肪细胞葡萄糖转运中的作用；和3。确定ClipR-59和AS160之间相互作用在脂肪细胞葡萄糖运输中的功能重要性。总体而言，本文提出的研究将证明由ClipR-59介导的特异性Akt胰岛素信号如何调节全身葡萄糖稳态和脂肪细胞功能，从而深入了解特异性Akt信号在胰岛素作用中的重要性。

DESCRIPTION (provided by applicant): We have studied Akt, the direct effector of PI3K and the primary mediator of insulin's metabolic actions. In the course of those studies, we isolated ClipR-59, whose expression is elevated during adipocyte differentiation and decreased during development of obesity, as an Akt interaction protein. ClipR-59 does not involve Akt activation. Instead, it modulates Akt cellular compartmentalization following Akt activation, in particular, Akt membrane association. The regulation of Akt membrane association by ClipR-59 is critical for glucose transport, as evidenced by the finding that forced expression of ClipR-59 promotes, whereas silencing of ClipR-59 impairs, adipocyte glucose transport. Adipocyte glucose uptake is essential for the maintenance of whole-body glucose homeostasis. Due to the prevalence of obesity, type II diabetes has become epidemic and a major public health burden. Given that ClipR-59 interacts with Akt and regulates glucose transport, further studies of ClipR-59 are warranted studies. Our current studies indicated that a) expression of ClipR-59 in adipose tissue in mice results in reduced fat mass and increased glucose tolerance, an indication that ClipR-59 might play a role in maintaining whole-body glucose homeostasis; b) palmitoylation of ClipR-59, likely mediated by protein palmitoyltransferase DHHC17, is critical for ClipR-59 to modulate Akt cellular membrane association, implying that regulation of ClipR-59 palmitoylation by DHHC17 constitutes an important mechanism by which ClipR-59 modulates Akt signaling; and c) ClipR-59 is complexed with AS160, a Rab-GAP protein that connects insulin signaling and Glut4 vesicles. Because ClipR-59 also interacts directly with Akt, ClipR-59 may function as a scaffold protein to connect Akt signaling to AS160. To further study the function and regulation of ClipR-59, we proposed the experiments to address following specific questions: 1. Determine the impact of forced expression of ClipR-59 in adipose tissue on whole-body glucose homeostasis and on the development and progression of obesity, insulin resistance, and diabetes; 2. Determine the role of protein palmitoyltransferase DHHC17 in Akt signaling and adipocyte glucose transport by modulating ClipR-59 palmitoylation; and 3. Determine the functional importance of the interaction between ClipR-59 and AS160 in adipocyte glucose transport. Overall, the studies proposed here will demonstrate that how specified Akt insulin signaling by ClipR-59 modulates whole body glucose homeostasis and adipocyte function thereby, providing insight knowledge into the importance of specified Akt signaling in insulin action. PUBLIC HEALTH RELEVANCE: Adipocytes plays an essential role in maintaining energy homeostasis via glucose uptake and adipokine production. The studies proposed are to investigate how specified insulin signaling through interaction between Akt and ClipR-59 modulates glucose transport and adipocyte function. Thus, this research will provide invaluable knowledge to understand the development of fat insulin resistance and identify novel drug target for treatment of type II diabetes.