SR-BI羧基末端胞质区磷酸化调控HDL诱导的胞内信号转导及内皮保护功能

SR-BI can mediate HDL-induced intracellular signal transduction and endothelial protection. However, the exact mechanism linking between SR-BI and intracellular signaling molecules is still unclear. Our previous work showed that HDL could stimulate the serine phosphorylation of SR-BI receptor in endothelial cells, suggesting that SR-BI phosphorylation may play a role in HDL-induced endothelial protection. Here, we hypothesize that HDL can regulate the interaction between cytoplasmic domain of SR-BI and intracellular signaling molecules by stimulating the phosphorylation in C-terminal regions of the SR-BI cytoplasmic tail in endothelial cells, and then promote signal transduction and exert endothelial protection. This project will focus on: detection of the phosphorylation sites in the C-terminal cytoplasmic domain of SR-BI and its site-specific kinases stimulated by HDL; impact of SR-BI phosphorylation on the cholesterol flow, the interaction between SR-BI, Src and PDZK1, and the cascade activation of related signaling molecules; influence of SR-BI phosphorylation on HDL-induced endothelial protection like nitric oxide production , cell migration and anti-apoptosis function. This project would provide new experimental data to deeply understand the mechanism of SR-BI-mediated signal transduction.

SR-BI可介导HDL诱导的胞内信号转导及内皮保护功能。然而，SR-BI与胞内信号分子间的确切联结机制目前仍不清楚。课题组前期工作发现HDL可诱导内皮细胞SR-BI受体的丝氨酸磷酸化，提示SR-BI的磷酸化修饰可能在介导HDL内皮保护功能中发挥作用。结合文献及前期基础，课题组提出“HDL可通过促进内皮细胞SR-BI受体C-末端胞质区的磷酸化来调节受体胞质区与信号分子的相互作用及胞内信号转导，最终发挥内皮保护作用”的科学假说。本项目拟探明HDL刺激SR-BI受体C-末端胞质区磷酸化的位点及相关激酶；分析磷酸化对SR-BI介导胆固醇流动、SR-BI与Src、PDZK1相互作用及胞内信号分子活化的影响；分析SR-BI受体磷酸化对HDL诱导一氧化氮生成、细胞迁移及抗内皮细胞凋亡等内皮保护功能的影响。本项目的完成将为深入理解SR-BI的作用机理提供新的实验数据。

SR-B1可介导HDL诱导的胞内信号转导及内皮保护功能。然而，SR-B1与胞内信号分子间的确切联结机制目前仍不清楚。本课题的完成明确了SR-B1受体C-末端胞质区的S491位磷酸化位点，且这一磷酸化不受PKA蛋白激酶的调节。S491位点的突变对内皮细胞的增殖与凋亡、细胞迁移和一氧化氮的生成似乎没影响，这可能与内皮细胞中SR-B1受体的基础表达对外源表达SR-B1突变体的干扰有关。回顾文献相关报道膜受体的磷酸化可能会影响到膜受体蛋白的稳定性，随后课题组根据实施过程中所遇的问题进行合理性调整，我们观察了S491位点磷酸化对SR-B1受体蛋白的稳定性影响，发现SR-B1的磷酸化确实能提高SR-B1蛋白的稳定性。本项目的完成将为深入理解SR-B1的作用机理提供新的实验数据。