Endophilin A2通过促进血管新生改善缺血性心肌损伤及机制研究

The endophilin A proteins are a family of src homology 3 (SH3) domain-containing proteins, but their functions in cardiovascular system remain unknown. Our previous study showed that endophilin A2 was the most abundantly expressed isoform compared with Endophilin A1 and Endophilin A3 in cardiovascular tissues and was significantly decreased in ischemic cardiac and skeletal muscle tissues. Moreover, we found that endophilin A2 interacted with VEGFR2. Knockout of endophilin A2 decreased VEGFR2 protein expression, but had no effect on VEGFR2 mRNA expression. Compared with wide type mice, blood flow and VEGFR2 expression in ischemic limbs was markedly impaired in endophilin A2 knockout mice, indicating endophilin A2 may play an important role in regulating VEGFR2 protein stabilization and angiogenesis. The present study aims to clarify the functional role of endophilin A2 in angiogenesis of myocardial infarction with endophilin A2 knockout mice or endothelium-specific transgenic mice. Furthermore, we will investigate the mechanisms by which endophilin A2 regulates VEGFR2 protein expression and angiogenesis. This work will provide evidences that endophilin A2 may play a critical role in regulating angiogenesis, suggesting endophilin A2 may be a novel therapeutic target for the treatment of ischemic diseases.

Endophilin是一类含SH3结构的蛋白，其在心血管系统的功能尚不清楚。我们发现心血管系统主要表达endophilinA2亚型，在缺血性心肌和骨骼肌中其表达下调。EndophilinA2缺失降低VEGFR2蛋白表达，但mRNA水平无变化，且两蛋白间存在相互作用。敲除endophilinA2显著抑制小鼠后肢缺血后血流恢复，提示endophilinA2可能是调控VEGFR2蛋白稳定性和血管生成的关键分子。在此基础上，本研究拟采用endophilinA2敲除和内皮特异性转基因小鼠，制备心肌缺血模型，首先明确endophilinA2对缺血性心肌损伤和血管新生的影响，并进一步从调控VEGFR2蛋白稳定性的角度揭示endophilinA2调控血管新生的分子机制。该工作将从调控血管新生的角度阐明endophilinA2的新功能，为评估endophilinA2是否是防治缺血性疾病的新靶点提供实验依据。

Endophilin是一类含SH3结构的蛋白，其在心血管系统的功能尚不清楚。我们发现敲除Endophilin A2抑制小鼠后肢缺血模型血流恢复速度，减少后肢血管CD31、α-SMA和VEGFR2的表达。相反，内皮特异性高表达Endophilin A2增加小鼠后肢缺血模型血流恢复速度，上调后肢血管CD31、α-SMA和VEGFR2的表达。高表达Endophilin A2可促进VEGF诱导的人脐静脉内皮细胞的迁移和管腔形成，而敲减Endophilin A2则显著抑制内皮细胞的迁移和管腔形成。Endophilin A2通过其自身的N-BAR结构域的200-245个氨基酸位点与VEGFR2结合，促进VEGFR2二聚体的形成，进而增加VEGFR2的自身磷酸化水平，促进VEGFR2/PI3K/AKT，VEGFR2/Src以及VEGFR2/PLCγ/MAPK信号通路活化。VEGF作用增强Endophilin A2与VEGFR2结合，提示VEGFR2的磷酸化水平可能是调控两者结合水平的重要因素。Endophilin A2则通过SH3结构域与Src相互结合，增强VEGF诱导的VEGFR2/Src复合物形成，进而促进Src信号通路转导。此外，Endophilin A2与PLCγ存在相互作用，Endophilin A2通过增加VEGF诱导的VEGFR2与PLCγ复合物形成，进一步促进VEGFR2/PLCγ/MAPK信号通路转导。综上所述，Endophilin A2一方面通过N-BAR结构域的200-245个氨基酸位点与VEGFR2结合，促进VEGF诱导的VEGFR2二聚体形成和受体自身磷酸化；另一方面则通过促进VEGFR2/Src以及VEGFR2/PLCγ复合物形成，增强VEGFR2/PI3K/AKT，VEGFR2/Src以及VEGFR2/PLCγ/MAPK信号转导，共同促进血管新生。