在可兴奋细胞中，存在着与神经递质或激素释放相耦联的快速胞吞，是维持神经递质或者激素持续释放的先决条件，但是其发生分子机制、回收蛋白种类以及动力学过程并不清楚。申请人前期结果揭示了胰岛beta细胞存在两类快速回收机制，一类是依赖于网格蛋白的胞吞，是网格蛋白小窝沿着细胞质膜下的微管网络，在分泌位点附近的局部甘油二酯指引下运动到分泌位点的过程；另一类是不依赖于网格蛋白的胞吞，依赖于肌动蛋白的新聚合蛋白mDia1。本申请将基于这些前期结果，进一步阐明这两种快速胞吞耦合到胰岛素分泌的机制，研究不同囊泡蛋白通过不同胞吞途径分选、回收、再利用的差异。另一方面，基于相应的基因敲除小鼠模型，我们还将研究这些快速胞吞过程的缺失对胰岛细胞功能的影响以及它们对整体血糖调控的影响。这些研究将有可能揭示糖尿病发病过程中胰岛beta细胞数量和功能发生变化的新机制，也将为神经细胞上的类似热点研究提供研究思路和重要工具。

In excitable cells, tight spatiotemporal coupling of exocytosis with fast vesicle recycling processes is quintessential to sustain vesicle release and surface membrane protein homeostasis during intense stimulation. The molecule mechanisms underlying such spatiotemporal coupling have remained a mystery for decades. Our previous work have revealed two types of fast vesicle recycling pathways in pancreatic beta cells: one is a fast clathrin-mediated endocytosis (CME) , dependent on the hopping of clathrin-coated pits along cortical microtubules and guided by local diacylglycerol concentration elevation to vesicle fusion sites upon exocytosis; the anotehr is a fast, mDia1-dependent, clathrin-independent endocytosis (CIE). Base on these studies, we propose to study how these two endocytic processes are coupled to the insulin secretion, and how different cargo proteins are differentiated sorted, recycled and reused by different pathways. Furthermore, we will use knock-out mice models to study effects of deficiency of CME or CIE on primary beta cell function and blood glucose regulation of the whole animal. These studies will reveal a new type of mechanism underlying the beta-cell mass and function changed during diabetes progression, and shed light on similar processes in neurons.