剪切力通过钙离子/钙调蛋白和胆固醇调节血管内皮细胞TMEM16A钙激活氯通道的机制研究

Hypercholesterolemia and abnormal blood flow induce endothelial dysfunction, which causes many cardiovascular diseases. Elucidating the mechanisms by which calcium-activated chloride channels and flow-activated chloride channels in the vascular endothelial cell (EC) are regulated by cholesterol and blood flow contributes to the deep understanding of endothelial physiology and diseases.Transmembrane protein 16A (TMEM16A), a newly discovered calcium chloride channel, has been reported to be expressed in the endothelium, and exhibits a characteristic current that resembles that of the calcium-activated chloride channels and flow-activated chloride channel in the EC, suggesting that TMEM16A may be the chloride channel responsible for the calcium-activated chloride channels and flow- activated chloride channel in the EC. It has been reported that TMEM16A is regulated by Ca2+/calmodulin, and cholesterol inhibits TMEM16A in vascular smooth muscles. We have investigated the role of flow-induced shear stress in TMEM16A expressed in HEK cells, and found that shear stress activates TMEM16A via increasing intracellular Ca2+, and inhibits TMEM16A via cholesterol. However, it remains unclear whether this regulatory mechanism occurs in the EC. The purpose of this project is to investigate the mechanisms by which Ca2+/calmodulin and cholesterol regulate TMEM16A in the EC, and to explore the mechanisms by which shear stress activates TMEM16A via Ca2+/calmodulin and inhibits TMEM16A via cholesterol in the EC. We believe that achieving these goals will shed a new light on the physiological roles of TMEM16A in the EC, and targeting TMEM16A for the treatment of cardiovascular diseases such as atherosclerosis.

高胆固醇血症和异常血流流速诱导血管内皮功能异常而导致许多血管疾病。阐明胆固醇和血流剪切力对血管内皮细胞上表达的钙激活氯通道和剪切力激活氯通道的调节机制是深入了解血管内皮细胞的生理功能和相关疾病的基础。新发现的跨膜蛋白16A （TMEM16A）钙激活氯通道具有血管内皮细胞上表达的钙激活氯通道和剪切力激活氯通道相似的电流特性，提示TMEM16A构成血管内皮细胞上这些氯通道。课题组发现剪切力能通过提高钙离子激活和通过胆固醇抑制转染在HEK细胞上的TMEM16A氯通道,但是血管内皮细胞是否存在这种调节机机制还有待深入。本项目拟通过研究钙离子/钙调蛋白及胆固醇对TMEM16A通道的调节机制；探讨剪切力通过钙离子/钙调蛋白激活和通过胆固醇抑制内皮细胞上TMEM16A钙激活氯通道的机制。本课题为深入研究TMEM16A参与内皮细胞的生理功能以及靶向TMEM16A治疗疾病（如动脉粥状硬化）提供新思路。

高胆固醇血症和异常血流流速诱导产生的血管内皮功能异常是导致血管疾病（如动脉粥样硬化）的主要诱因。钙激活氯通道参与内皮细胞的生理和血管疾病的机制尚不清楚。我们应用Western blot、免疫组织化学、膜片钳等方法，并结合shRNA敲除TMEM16A，发现TMEM16A介导内皮细胞上的钙离子激活的氯电流。通过分析内皮细胞上TMEM16A钙激活氯电流特征，发现内皮细胞上TMEM16A钙激活氯电流具有缓慢的激活特性，这一激活特性与低表达的TMEM16A通道以及处于失活状态的TMEM16A通道的激活特性相似，表明内皮细胞上TMEM16A钙激活氯通道主要处于失活状态。我们进一步发现胆固醇不仅能降低TMEM16A表达，还能通过胆固醇结合位点直接抑制TMEM16A钙激活氯电流。进而我们发现剪切力抑制主动脉内皮细胞上的钙激活氯电流。清除胆固醇减少了剪切力抑制TMEM16A钙激活氯通道的作用，表明胆固醇介导剪切力抑制小鼠主动脉内皮细胞上钙激活氯电流。总之，本课题从分子水平阐明了胆固醇和血流剪切力对血管内皮细胞上表达的TMEM16A钙激活氯通道的调节机制，为深入了解TMEM16A参与内皮细胞的生理功能以及靶向TMEM16A治疗疾病（如动脉粥状硬化）提供新方向。本项目研究成果发表相关论文 7 篇，其中 5 篇论文发表在SCI杂志，总影响因子达21.81。本项目共培养博士研究生 3 名、硕士研究生 7 名。