衔接蛋白APPL2对胰岛β细胞生理功能的分子调节机制研究

项目名称： 衔接蛋白APPL2对胰岛β细胞生理功能的分子调节机制研究

项目编号： No.81471015

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 医药、卫生

项目作者： 郑竞业

作者单位： 香港理工大学深圳研究院

项目金额： 73万元

中文摘要： 细胞功能异常是2型糖尿病的早期病理特征。自噬功能障碍可能导致β细胞功能异常，但机制不明。衔接蛋白APPL1和APPL2是一对具有近似结构的信号分子，我们已经报道了APPL1调节β细胞功能的机制。我们近期发现，APPL2在胰腺β细胞表达丰富，在肥胖及糖尿病小鼠显著降低。APPL2下调通过抑制自噬加重棕榈酸对葡萄糖刺激胰岛素分泌的抑制作用；APPL2与微管相关蛋白轻链3（LC3）存在相互作用。我们推测代谢应激状态下APPL2通过诱导自噬保护β细胞功能。我们将通过已经建立的β细胞特异性APPL2敲除小鼠模型，并分别在动物，离体胰岛和体外培养β细胞水平阐明APPL2如何通过对自噬过程的调控影响β细胞功能；并通过腺病毒相关病毒基因转运系统，确认过表达APPL2是否可以缓解db/db 糖尿病小鼠β细胞损伤。本研究将阐明APPL2调控自噬及其对β细胞功能的作用机制，为2型糖尿病的防治提供新的靶点。

中文关键词： 2型糖尿病；胰岛β细胞；APPL2；自噬；β细胞功能障碍

英文摘要： Type 2 diabetes mellitus (T2DM) and its related complications are the top healthcare burdens worldwide. Pancreatic ?-cell dysfunction, characterized by defective glucose-stimulated insulin secretion (GSIS) and decline of ?-cell mass, has been considered as one of the earliest defect during the pathogenesis of T2DM. Recent evidence indicate that impairment of autophagy, a conserved degradative and defensive process responsible for cellular homeostasis under stress condition, leads to hyperglycemia and ?-cell dysfunction in mice, yet its molecular underpinnings are unclear. The adaptor proteins APPL1 and APPL2, a pair of signaling molecules with same domain organization and high sequence identity, have been shown to regulate glucose metabolism via adiponectin and insulin signaling. We and other recently demonstrate that APPL1 acts as a positive regulator of action and secretion of insulin. Overexpression of APPL1 protects mice from insulin resistance and glucose intolerance, whereas knockout of APPL1 produces an opposite phenotype. Such beneficial actions of APPL1 are largely attributed to its potentiating effect on GSIS by up-regulating the expression of exocytotic proteins in ?-cells. Like APPL1, APPL2 is abundantly expressed in pancreatic ?-cells, and its expression is dramatically reduced in dietary-induced obese and db/db diabetic mouse models. Knockdown of APPL2 expression potentiates the inhibitory effects of the saturated fatty acid palmitate on GSIS, accompanied with reduced autophagy flux in pancreatic ?-cells. On the contrary, overexpression of APPL2 enhances autophagic flux. Further analysis revealed that APPL2 is translocated to autophagosome upon autophagy induction. Interestingly, APPL2 interacts with microtubule-associated protein light chain 3 (LC3), an ubiquitin-like protein involves in transport and maturation of the autophagosome. Based on these results, we propose that APPL2 protects ?-cell functions by promoting autophagy in response to metabolic stress. In this study, we will test this hypothesis by characterizing the metabolic changes in ?-cell-specific APPL2 knockout mice generated in our laboratory. We will use both in vitro, ex vivo and in vivo approaches to elucidate how APPL2 modulates ?-cell mass and insulin secretion by controlling the autophagy process. Furthermore, we will investigate whether overexpression of APPL2 alleviates hyperglycemia and ?-cell failure in db/db diabetic mice by using adeno-associated virial gene transfer system. The results are expected to provide new insight into the fundamental mechanisms regulating ?-cell function and insulin secretion, and to shed new light on the pathogenesis of glucose dysregulation in T2DM. In addition, such information may be helpful for the development of novel therapeutics to combat T2DM in human.

英文关键词： T2DM;β cell;APPL2;Autophagy;β cell dysfunction