血管内皮膜受体蛋白FGFR1的SUMO化修饰在血管生成中的作用和机制研究

Angiogenesis contributes fundamentally to physiological and pathological features of human beings. Typically, the key steps of new vessel generation include endothelial budding and tube formation, which is modulated by intricate signaling network of growth factors. However, the corresponding regulatory mechanisms are largely unknown. SUMOylation, a newly discovered post-translational modification of proteins by small ubiquitin-like modifier (SUMO), is now appreciated to be an essential process controlling various cellular functions. So far, most SUMOylation substrates are in categories of nuclear and peri-nuclear proteins. Notably, recent studies suggested potential involvement of SUMOylation in cardiovascular system physiology and correlated disease pathogenesis, in which vascular cells could be the exact biological targets. Our preliminary work demonstrates a specific SUMO conjugation on FGFR1, a membrane receptor on vascular endothelial cells, which is.mediated by SENP1 (major member of deSUMOylation enzyme family). And interference of such modification has significant effect on angiogenic character of endothelial cells. Based on the established role of endothelial FGFR1 in angiogenesis, we will systematically investigate the pathophysiological function of endothelial FGFR1 SUMOylation in angiogenesis by employing mice models. On the other hand, further investigation in vitro will determine the regulatory mechanism of SUMO modification on FGFR1 protein and related signalings, as well as corresponding angiogenic function of vascular endothelial cells. The accomplishment of the current project will help us to better understand the role of SUMOylation in angiogenesis from a new angle, which may provide new therapeutic target and theory for medical cure of related diseases.

血管生成的核心过程是血管内皮细胞的出芽生长和管腔形成，由复杂的生长因子信号网络调控，但是目前相关机制还存在诸多未知。SUMO化是新近发现的一类蛋白翻译后修饰形式，其修饰对象主要为核蛋白及核周边蛋白。最新研究及我们的工作（Circulation Research，Nature Commun等）发现，SUMO化修饰与血管功能维持密切相关，而且血管内皮细胞很可能是其调控的主要目标。我们的前期工作发现，血管内皮细胞膜蛋白-成纤维细胞生长因子I类受体(FGFR1)受SUMO系统特异性修饰。鉴于血管内皮FGFR1在血管生成中已知的重要地位，我们拟在体外和体内系统中深入探究SUMO化对血管内皮FGFR1及相关血管生成信号通路的调控机制，以及该修饰过程对血管生成的作用和功能;以期待从新的角度阐明血管系统的发生机理，并为相关血管生成疾病治疗提供新的理论依据。

血管生成的核心过程是血管内皮细胞的出芽生长和管腔形成，由复杂的生长因子信号网络调控，但是目前相关机制还存在诸多未知。SUMO化是新近发现的一类蛋白翻译后修饰形式，其修饰对象主要为核蛋白及核周边蛋白。最新研究及我们的工作发现，SUMO化修饰与血管功能维持密切相关，而且血管内皮细胞很可能是其调控的主要目标。我们的前期工作发现，血管内皮细胞膜蛋白-成纤维细胞生长因子I类受体(FGFR1)受SUMO系统特异性修饰。本研究在体外和体内系统中深入探究SUMO化对血管内皮FGFR1及相关血管生成信号通路的调控机制，以及该修饰过程对血管生成的作用和功能。首先我们鉴定了FGFR1蛋白的SUMO化修饰位点，并通过构建FGFR1 SUMO化缺失突变体--FGFR1-2KR 证实FGFR1 SUMO化缺失能够增强FGFR1蛋白自磷酸化并促进FGFR1蛋白二聚体的形成。体外细胞实验发现，血管内皮细胞中FGFR1 SUMO化缺失能够明显降低VEGFR2的磷酸化水平并影响其信号活性，进而抑制细胞的促血管生成能力。生化机制研究发现，FGFR1 SUMO化缺失能够显著增强FGFR1与其底物FRS2的结合能力，进而削弱了FRS2与VEGFR2蛋白的结合能力并抑制了VEGFA/VEGFR2信号活性。为验证体外数据的真实性，我们分别构建了正常FGFR1蛋白及FGFR1 SUMO化缺失突变体的基因敲入小鼠。体内实验发现FGFR1 SUMO化缺失突变新生小鼠的视网膜血管发育受到明显抑制，免疫染色证实在FGFR1 SUMO化缺失突变新生小鼠的新生血管中，血管内皮细胞的增殖能力显著降低，同时伴随顶端细胞数量减少、血管网络密度减低等缺陷表型。本研究首次阐述了FGFR1蛋白能够被SUMO化修饰，并且从体内、体外等多方面研究了血管生成过程中SUMO化修饰通过精细调控FGFR1信号通路活性从而参与调控VEGFR2信号通路的分子机制，为更好理解血管发育过程中FGFR1信号与VEGFR2信号的相互作用提供了理论基础。

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