ArpC3-mediated actin remodeling in insulin granule exocytosis and diabetes

项目摘要 胰岛素分泌不足是糖尿病的标志。在这一过程中，β细胞的皮质肌动蛋白最近被 被认为是糖尿病发病机制的关键因素。来自2型糖尿病（T2 D）的β细胞 患者表现出与皮质肌动蛋白重塑相关的显著信号改变， 异常将胰岛素分泌恢复到正常水平。皮质肌动蛋白最初被认为是一种简单的屏障， 阻止胰岛素分泌，但最近的研究挑战了这一观点，并暗示了积极的作用。越来越多的证据 进一步表明皮质肌动蛋白是β细胞中多种代谢信号的汇聚点和效应器。 然而，其重塑的分子和纳米结构基础仍然没有得到解决。处理这个问题 对于了解胰岛素分泌的调节和开发新的治疗方法， 恢复2型糖尿病患者的β细胞功能。本研究将研究编码Arp 2/3亚基的基因ArpC 3， 决定肌动蛋白丝分支和皮质重塑的复合物。虽然多种信号通路 由于Arp 2/3的活性与胰岛素分泌的关系密切，因此Arp 2/3下游调节胰岛素分泌的机制仍不清楚。 基于该领域的最新进展和我们在β细胞成像和功能测定方面的新数据，我们假设 ArpC 3依赖的肌动蛋白聚合通过驱动局部皮质肌动蛋白调节胰岛素胞吐作用， 拆卸-重新组装周期。通过这种重塑，皮质肌动蛋白丝可以积极协调 颗粒运输和胰岛素分泌的关键步骤。我们已经召集了一个调查小组 糖尿病，β细胞生物学，囊泡运输和超分辨率显微镜的专业知识来验证这一假设。 我们将重点关注三个具体目标。首先，确定ArpC 3介导的皮质肌动蛋白重塑的体内作用， 胰岛素分泌和葡萄糖稳态。我们已经生成了一个新的小鼠模型，其中ArpC 3被删除 选择性地在成年β细胞中消除Arp 2/3活性和皮质肌动蛋白分支。其次，定义ArpC 3函数 皮质肌动蛋白纳米重塑及其在胰岛素颗粒募集、对接和胞吐中的作用。第三、 评估皮质肌动蛋白分支在人β细胞中的作用及其在T2 D患者中的功能障碍。的结果 这项工作将填补皮层肌动蛋白重塑和胰岛素分泌之间长期存在的知识空白， 对皮质肌动蛋白功能障碍诱导的T2 D发病机制的机制见解。

PROJECT SUMMARY Insulin secretion deficiency is a hallmark of diabetes. In this process, the cortical actin of β cells has recently been recognized as a critical player contributing to diabetes pathogenesis. β cells from type-2 diabetes (T2D) patients show significant signaling alteration associated with cortical actin remodeling, and restoring such abnormality rescues insulin secretion to normal levels. Cortical actin is thought initially as a simple barrier to prevent insulin secretion, but recent studies challenge this view and imply an active role. Mounting evidence further indicates that cortical actin is a converging point and effector of multiple metabolic signals in β cells. However, the molecule and nanostructure basis of its remodeling remains unresolved. Addressing this question becomes imperative to understanding the regulation of insulin secretion and developing new therapeutics to restore β cell function in T2D. This proposal will investigate ArpC3, a gene encoding a subunit of the Arp2/3 complex that dictates actin filament branching and cortical remodeling. Although multiple signaling pathways converge on Arp2/3, the mechanism downstream Arp2/3 activity to regulate insulin secretion remains unknown. Based on recent progress in the field and our new data on β cell imaging and functional assays, we hypothesize that ArpC3-dependent actin polymerization regulates insulin exocytosis by driving the local cortical actin disassembly-reassembly cycles. Through this remodeling, cortical actin filaments may actively coordinate the critical steps of granule trafficking and insulin secretion. We have assembled a team of investigators with expertise in diabetes, β cell biology, vesicle trafficking, and super-resolution microscopy to test this hypothesis. We will focus on three specific aims. First, determine the in vivo role of ArpC3-mediated cortical actin remodeling in insulin secretion and glucose homeostasis. We have generated a new mouse model where ArpC3 is deleted selectively in adult β cells to ablate Arp2/3 activity and cortical actin branching. Second, define ArpC3 function in cortical actin nano-remodeling and its role in insulin granule recruitment, docking, and exocytosis. Third, evaluate the role of cortical actin branching in human β cells and its dysfunction in T2D patients. The results from this work will fill a long-standing knowledge gap between cortical actin remodeling and insulin secretion, providing mechanistic insights into T2D pathogenesis induced by cortical actin dysfunction.