PSF蛋白募集泛素连接酶Hakai抑制HIF-1α/VEGF通路活性的机制研究

Neovascular age-related macular degeneration (AMD) is the leading cause of severe vision loss in elderly persons. Although most cases of neovascular AMD are caused by choroidal neovascularization (CNV), a subgroup of neovascular AMD, known as retinal angiomatous proliferation (RAP), is characterized by subretinal neovascularization arising from retinal vessels. however, the regulatory mechanisms underlying neovascular AMD remain elusive. Our preliminary studies revealed that intravetrial injection of recombinant adeno-associated virus (rAAV) encoding polypyrimidine tract binding protein-associated splicing factor (rAAV-PSF) dramatically inhibited CNV and RNV in the mouse model respectively. On the other hand, PSF also suppressed the proliferation of both retinal pigment epithelial (RPE) cells and retinal vessel endothelial cells (RVECs), and the up-regulation of VEGF expression induced by insulin-like growth factor-1 (IGF-1), Furthermore, transcriptional complex including PSF, HIF-1α and Hakai were occurred after IGF-1 stimulation. Based on these results, we hypothesize that PSF may inhibit CNV and RAP through negative regulation of IGF-1 induced VEGF up-regulation . We propose to utilize cell culture and animal model to test this hypothesis. Moreover, luciferase assay, Co-IP and ChIP assay will be performed to investigate whether PSF inhibits IGF-1 induced VEGF up-regulation and subsequent CNV and RAP through recruiting Hakai to gene transcription complex of VEGF, hence degrading the transcriptional activator HIF-1α to down-regulate transcriptional activity of VEGF. This study will elucidate the molecular mechanism of CNV and RAP inhibition via PSF, and provide potential target for gene therapy to neovascular AMD.

新生血管性AMD包括起源于脉络膜的脉络膜新生血管( CNV) 以及起源于视网膜的视网膜血管瘤样增生(RAP)，是一种严重影响中心视力的视网膜变性类疾病，其调控机制尚不完全清楚。前期发现：玻腔注射 rAAV-PSF 可抑制小鼠模型的CNV和RNV，并证实IGF-I刺激后，PSF 抑制RPE细胞和RVECs增殖及VEGF表达升高，并与HIF-1α和Hakai形成转录调节复合物。据此提出假设：PSF 通过拮抗IGF-I 诱发的VEGF 表达升高，负性调控CNV 和RAP。本项目将从体内和体外实验两个方面，通过报告基因实验、免疫共沉淀，ChIP 明确：IGF-I 刺激后PSF作为桥连蛋白，介导HIF-1与Hakai的特异性结合，协同Hakai完成对于HIF-1的靶向降解，从而抑制下游VEGF表达。为阐明PSF 抑制CNV 和RAP的分子机制奠定基础，为新生血管性AMD的基因治疗提供潜在靶点。

本课题依据项目计划书的安排如期进行，深入探讨PSF蛋白对于新生血管性疾病的作用及其潜在的分子机制，发现PSF蛋白可作为乏氧感受器，通过有效的抑制病理性VEGF的表达，进而影响视网膜血管内皮细胞的增殖，迁移及官腔形成这三大与血管新生密切相关的功能。在探讨PSF发挥作用分子机制的过程中，发现在乏氧PSF这一大前提之下，PSF可以通过募集Hakai来特异性降解进入细胞核内的HIF-1a，进而下调VEGF的表达。在本项目支持下迄今共发表15篇科学论文，其中SCI论文5篇，迄今已完成培养4名硕士研究生及3名博士研究生，其中一名研究生荣获国家级奖学金，一名研究生荣获第十届中国眼科学和视觉科学研究大会奖学金。