MBL与FGFR4相互作用促进系膜细胞EMT在IgA肾病中的作用及其分子机制的研究

IgA nephropathy (IgAN) is the most common form of gloemrulonephritis. It is crucial to investigate the mechanisms of the generation and development and to find specific therapeutic targets in IgAN. Mannose-binding lectin （MBL） is involved in various diseases, but its role in IgAN has not been defined. Our previous studies have administrated that the high levels of urinary MBL and the deposition of MBL in kidney were associated with more severe clinical and histological manifestations and prognosis of IgAN. According to the similar trends of urinary levels and histological deposition of MBL, we inferred that the abnormal reactions of MBL in kidney caused severe renal injury. The experiments in vitro demonstrated that MBL could promote epithelial-mesenchymal transition (EMT) in human mesangial cells and interact with fibroblast growth factor receptor 4 (FGFR4), a membrance protein of mesangial cells, so we can hypothesize that the interaction between MBL and FGFR4 may promote epithelial-mesenchymal transition in mesangial cells to cause the severe injury in kidneys. On the basis of previous studies, we will verify the way of the interaction between MBL and FGFR4 with human mesangial cells as a tool cell line. Rat models of IgAN would be built to investigate the role of the interaction between MBL and FGFR4 promoting epithelial-mesenchymal transition in mesangial cells in IgA nephropathy. A high thoughput screening with proteomics and mass spectrometry analysis will be performed to define the interacting proteins with FGFR4. Moreover, we will further investigate the pathway of interaction between proteins to supply new therapeutic targets for IgAN.

IgA肾病（IgAN）是最常见的肾小球肾炎，探讨其发生发展机制、寻找特异性治疗靶点至关重要。甘露糖结合凝集素（MBL）参与多种疾病发生发展，但在IgAN中的作用及机制尚不清楚。课题组前期研究发现尿MBL及在肾组织的沉积与IgAN更严重的临床病理表现及预后有关，并根据尿液与肾组织沉积的一致性推测MBL在肾组织局部发生异常反应导致严重肾损害；体外实验发现MBL能促进系膜细胞上皮间质转化（EMT），并能与系膜细胞膜蛋白FGFR4相互作用，从而推测MBL与FGFR4相互作用促进系膜细胞EMT而致严重肾损伤。本研究将在既往基础上，以人肾系膜细胞为工具细胞，证实MBL与FGFR4相互作用方式，建立IgAN鼠模型，通过体内试验探讨MBL与FGFR4相互作用促进系膜细胞EMT在IgA肾病中的作用，利用蛋白质谱分析高通量筛选FGFR4相互作用蛋白，并探讨具体功能途径，以期为IgAN治疗提供新靶点。

IgA肾病是全世界范围内最常见的肾小球肾炎，占原发性肾小球肾炎的20-45%，其临床及病理表现多种多样，严重危害人类健康，并且IgA肾病的治疗缺乏针对病因及发病机制的特异性治疗手段。探讨IgA肾病发生发展机制，寻找特异性治疗靶点至关重要。甘露糖结合凝集素（MBL）参与多种疾病发生发展，但在IgAN中的作用及机制尚不清楚。前期研究发现尿MBL及在肾组织的沉积与IgAN更严重的临床病理表现及预后有关，并根据尿液与肾组织沉积的一致性推测MBL在肾组织局部发生异常反应导致严重肾损害；体外实验发现MBL能促进系膜细胞上皮间质转化（EMT），并能与系膜细胞膜蛋白人成纤维细胞生长因子受体4（FGFR4）相互作用，从而推测MBL与FGFR4相互作用促进系膜细胞EMT而致严重肾损伤。本课题进一步证实MBL与FGFR4在体内外肾系膜细胞中的相互作用；并初步证实FGFR4蛋白的Thr121和Thr107是形成与MBL相互作用的关键氨基酸。FGFR4的糖基化进程可以影响FGFR4与MBL相互作用。利用慢病毒系统建立FGFR4高表达的肾系膜细胞系，进而证实MBL与FGFR4相互作用影响肾系膜细胞的生长及迁移能力，可能促进系膜细胞的EMT。同时MBL与FGFR4相互作用可能促进人肾系膜细胞分泌IL-6和MCP-1。综上所述本课题证实了MBL与FGFR4相互作用可以促进系膜细胞EMT可能在IgA肾病中发挥重要作用，为IgA肾病的防治提供新的治疗靶点。