基于X射线散射技术的细胞极性蛋白MAGI2介导的蛋白复合物形成液-液相分离的分子机制研究

肾病综合征是一类以大量蛋白尿为临床症状的肾脏疾病，主要因肾小球滤过功能异常引起。裂孔隔膜是肾小球足细胞之间的紧密连接，是肾小球最重要的滤过屏障之一。MAGUK家族支架蛋白MAGI2介导的蛋白复合物在裂孔隔膜的建立与维持中发挥重要作用，但其组装机制仍不明确。我们的前期研究发现，MAGI2及其介导的蛋白复合物能够自发的形成液-液相分离，提示MAGI2及其复合物可能通过形成相分离组装裂孔隔膜。液-液相分离是当今生物学领域的热点之一，但对其形成机制和物理特性的研究手段仍相对滞后。X射线散射技术是研究亚微观动态结构和特征的一种有效方法。本项目中，我们将综合运用体外重组及多种X射线散射技术，研究MAGI2及其复合物相分离的驱动条件、形成机制和物理特性。我们的工作将为基于X射线散射技术的液-液相分离的分子机制研究提供新的实验方案，并为肾小球滤过屏障的组装机制提供新的理论模型。

Nephrotic syndrome, a heterogeneous group of renal diseases characterized by heavy proteinuria, is caused by functional defects of glomerular filtration barrier. As one of the most important barriers, slit diaphragm is a specialized adhesion junction between adjacent glomerular podocytes. MAGUK family scaffold protein MAGI2-mediated protein complexes play critical roles in slit diaphragm assembly and maintenance, although the underlying mechanisms are still unclear. Our preliminary study discovered that MAGI2 and its complex can autonomously undergo liquid-liquid phase separation (LLPS), which suggests that the slit diaphragm may be formed via LLPS of MAGI2-mediated protein complex. LLPS has emerged as one of the hot topics in biology, though the research methods for study of the mechanism and physical properties of LLPS are limited. X-ray scattering technology is an effective method to study the submicroscopic dynamic structure. Here, we plan to investigate the molecular mechanisms and physical properties of LLPS of MAGI2 and its complex through combination of in vitro reconstitution and various X-ray scattering techniques. Our work will develop a novel strategy for structural studies of LLPS by X-ray scattering and may provide a new mechanism for assembly of glomerular filtration barrier.