载脂蛋白CIII对β细胞膜CaV1通道密度上调作用及其机理的研究

Apolipoprotein CIII (ApoCIII) hyperactivates β cell voltage-gated Ca2+ (CaV) channels and triggers Ca2+–dependent β cell apoptosis, thereby playing an important role in the development of diabetes. A recently-published study suggests that ApoCIII-induced hyperactivation of β cell CaV1 channels is likely to result from increases in CaV1 channel density in the β cell plasma membrane. However, there is a lack of experimental evidence for ApoCIII-induced upregulation of CaV1 channel density in the β cell plasma membrane. The overall goal of the present project is to explore possible upregulation of CaV1 channel density by ApoCIII in the β cell plasma membrane and its underlying mechanisms. The first specific aim is to clarify if ApoCIII stimulates protein kinase A and Src kinase to bring about phosphorylation of silent CaV1 channels already existing in the β cell plasma membrane and consequent activation of these previously silent channels. The second specific aim is to elucidate if ApoCIII recruits CaV1 channels to and increase their density in the β cell plasma membrane by promoting exocytostic trafficking of CaV1 channels. The third specific aim is to reveal if ApoCIII accumulates CaV1 channels and elevates their density in the β cell plasma membrane via inhibition of endocytic trafficking of CaV1 channels. Completion of this project will lead to unveil a totally new mechanism for the pathogenesis of diabetes and lay a solid foundation for the establishment of novel rational approaches for effectively preventing and treating diabetes.

载脂蛋白CIII超激活β细胞电压门控性钙（CaV）通道，触发钙依赖性β细胞凋亡，在糖尿病发病过程中起重要作用。研究提示载脂蛋白CIII超激活β细胞CaV1通道很可能是通过增加细胞膜CaV1通道密度实现的。但目前尚无载脂蛋白CIII对β细胞膜CaV1通道密度调节的实验证据。本项目总体目标是探明载脂蛋白CIII对β细胞膜CaV1通道密度的上调作用及其机理。第一个具体目标是揭示载脂蛋白CIII是否通过激活蛋白激酶A/Src酪氨酸激酶使已位于β细胞膜但无活动的CaV1通道磷酸化而转变为有活动的CaV1通道。第二个具体目标是查明载脂蛋白CIII是否通过促进β细胞胞吐，募集CaV1通道到细胞膜，引起β细胞膜CaV1通道密度上调。第三个具体目标是弄清载脂蛋白CIII是否通过抑制β细胞胞吞，阻止β细胞膜CaV1通道向细胞内回运，导致β细胞膜CaV1通道密度增加。完成本项目将揭示一种全新的糖尿病发病机理。