Clip R-59: a novel regulator of Akt signaling

描述(申请人提供)：我们已经研究了PI3K的直接效应因子和胰岛素代谢作用的主要介体Akt。在这些研究过程中，我们分离了ClipR-59作为Akt相互作用蛋白。ClipR-59在脂肪细胞分化过程中表达升高，在肥胖发生过程中表达下降。ClipR-59不涉及Akt激活。相反，它在Akt激活后调节Akt细胞的区域化，特别是Akt膜结合。ClipR-59对Akt膜结合的调节是葡萄糖转运的关键，ClipR-59的强制表达促进了葡萄糖的转运，而沉默ClipR-59则削弱了脂肪细胞的葡萄糖转运。脂肪细胞的葡萄糖摄取是维持全身葡萄糖稳态所必需的。由于肥胖症的流行，II型糖尿病已经成为流行病和主要的公共卫生负担。鉴于ClipR-59与Akt相互作用并调节葡萄糖转运，ClipR-59的进一步研究是有必要的。我们目前的研究表明：a)ClipR-59在小鼠脂肪组织中的表达导致脂肪质量减少和糖耐量增加，这表明ClipR-59可能在维持全身血糖动态平衡方面发挥作用；b)ClipR-59的棕榈酰化可能由蛋白质棕榈酰转移酶DHHC17介导，对ClipR-59调节Akt细胞膜结合至关重要，这意味着DHHC17对ClipR-59棕榈酰化的调控是ClipR-59调节Akt信号转导的重要机制；以及c)ClipR-59与AS160复杂，AS160是连接胰岛素信号和GLUT4囊泡的Rab-Gap蛋白。由于ClipR-59也与Akt直接相互作用，ClipR-59可能作为连接Akt信号与AS160的支架蛋白发挥作用。为了进一步研究ClipR-59的功能和调控，我们提出了以下几个具体问题的实验：1.确定ClipR-59在脂肪组织中强制表达对全身血糖稳态以及肥胖、胰岛素抵抗和糖尿病发生发展的影响；2.通过调节ClipR-59的棕榈酰化，确定蛋白质棕榈酰转移酶DHHC17在Akt信号和脂肪细胞葡萄糖运输中的作用；3.确定ClipR-59和AS160相互作用在脂肪细胞葡萄糖运输中的功能重要性。总之，这里提出的研究将证明ClipR-59特定的Akt胰岛素信号如何调节全身葡萄糖稳态和脂肪细胞功能，从而为深入了解特定Akt信号在胰岛素作用中的重要性提供深入的知识。 与公共健康相关：脂肪细胞通过葡萄糖摄取和脂肪因子的产生，在维持能量平衡方面起着至关重要的作用。这些研究是为了研究Akt和ClipR-59之间相互作用的特定胰岛素信号如何调节葡萄糖运输和脂肪细胞功能。因此，这项研究将为了解脂肪胰岛素抵抗的发展和寻找治疗II型糖尿病的新药物靶点提供宝贵的知识。

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.