不同亚细胞定位的TRPM2离子通道对胰岛素分泌的调控机制研究

TRPM2是胰岛中表达的一种非电压依赖性阳离子通道，主要通透钙、钠离子。TRPM2基因敲除小鼠的胰岛素分泌水平与野生型个体相比表现出显著的下降，但是相应的生理学机制还没有得到阐明。胰岛β细胞中的TRPM2通道在细胞膜和溶酶体上都有分布，分别介导胞外钙内流和溶酶体钙释放，二者都引起细胞质的钙水平上升。本项目的初步研究发现胰岛素促分泌剂格列本脲能够选择性激活溶酶体TRPM2通道，而对细胞膜TRPM2通道没有刺激作用，这可能是该药物的一种新的作用机制。本项目将以此为出发点研究细胞膜和溶酶体定位的TRPM2通道对β细胞胰岛素分泌的调控作用差异，使用的主要研究工具为TRPM2特异性通道封闭抗体（从胞外阻断细胞膜TRPM2通道）和溶酶体定位的TRPM2功能失活突变体（抑制溶酶体TRPM2通道），通过比较不同定位的TRPM2通道对不同时相胰岛素分泌的影响，分析其作用的具体机制，为糖尿病研究提供新的思路。

TRPM2 is a voltage-independent cation channel expressed in pancreatic islets and mainly permeable to Ca2+ and Na+. The insulin secretion of TRPM2-knockout mice is significantly reduced compared to that of wildtype mice. TRPM2 channels are distributed at the plasma membrane and lysosomes, and mediate Ca2+ influx from extracellular space and lysosomal Ca2+ release, respectively, both of which lead to the rise of cytosolic Ca2+. Preliminary study of this project revealed that the insulin secretion-promoting drug glybenclamide can selectively activate lysosomal TRPM2 channels, but has no stimulating effect on TRPM2 channels at the plasma membrane, which may be a new pharmacological mechanism of this drug. Based on these observations, the difference in the regulatory roles of plasma membrane and lysosomal TRPM2 channels on insulin secretion from pancreatic β cells will be studied in this project. Important research tools including TRPM2-selective pore-blocking antibody (blocking plasma membrane TRPM2 channels from extracellular side) and TRPM2 dominant negative variant specifically localized in lysosomes (inhibiting lysosomal TRPM2 channels) will be used in this project. Detailed regulatory mechanisms will be analyzed by comparing the effects of differently localized TRPM2 channels on insulin secretion at different phases， which may provide novel insight into diabetes studies.