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.