Structural Basis of Highly Specific Interaction between Nephrin and MAGI1 in Slit Diaphragm Assembly and Signaling.
Structural Basis of Highly Specific Interaction between Nephrin and MAGI1 in Slit Diaphragm Assembly and Signaling.
复制标题
DOI：
10.1681/asn.2017121275
复制
发表时间：
2018-07
期刊：
影响因子：
--
通讯作者：
Z. Weng;Y. Shang;Zeyang Ji;F. Ye;Lin Lin-Lin;Rong-guang Zhang;Jinwei Zhu
中科院分区：
文献类型：
--
作者：
Z. Weng;Y. Shang;Zeyang Ji;F. Ye;Lin Lin-Lin;Rong-guang Zhang;Jinwei Zhu
狭缝隔膜是相对的足细胞之间的专门的粘附连接，建立防止蛋白质从毛细血管腔进入泌尿空间的最终过滤屏障。Nephrin是表达于裂孔隔膜中的关键结构和信号粘附分子，其含有进化上保守的非典型PDZ结合基序（PBM），据报道其与裂孔隔膜中的多种蛋白质结合。导致nephrin缺乏完整PBM的NPHS 1（编码nephrin的基因）中的几个突变与肾小球疾病相关。然而，肾蛋白-PBM介导的蛋白复合物的分子基础仍然不清楚。方法采用生物化学、生物物理学和细胞生物学相结合的方法，系统地研究了肾蛋白PBM和含PDZ结构域的蛋白质在狭缝隔膜中的相互作用。结果我们发现肾蛋白-PBM特异性结合支架蛋白膜相关鸟苷酸激酶家族的一个成员MAGI 1，但不结合另一个成员MAGI 2。MAGI 1-PDZ 3/nephrin-PBM复合物的结构表明，nephrin-PBM的-3位Gly是MAGI 1-PDZ 3识别的决定性特征，这与典型的PDZ/PBM结合模式形成鲜明对比。MAGI 2内的单个功能获得性突变使肾蛋白-PBM结合成为可能。此外，利用我们的结构分析，我们开发了一种高效的抑制肽，能够特异性阻断nephrin/MAGI 1相互作用。结论MAGI 1与nephrin-PBM相互作用具有高度特异性。一种新开发的，有效的抑制肽，阻断这种相互作用可能是有用的，为未来的功能研究在体内。我们的发现也为NPHS 1突变引起的疾病提供了可能的解释。
BACKGROUND The slit diaphragm is a specialized adhesion junction between opposing podocytes, establishing the final filtration barrier that prevents passage of proteins from the capillary lumen into the urinary space. Nephrin, the key structural and signaling adhesion molecule expressed in the slit diaphragm, contains an evolutionally conserved, atypical PDZ-binding motif (PBM) reported to bind to a variety of proteins in the slit diaphragm. Several mutations in NPHS1 (the gene encoding nephrin) that result in nephrin lacking an intact PBM are associated with glomerular diseases. However, the molecular basis of nephrin-PBM-mediated protein complexes is still unclear. METHODS Using a combination of biochemic, biophysic, and cell biologic approaches, we systematically investigated the interactions between nephrin-PBM and PDZ domain-containing proteins in the slit diaphragm. RESULTS We found that nephrin-PBM specifically binds to one member of the membrane-associated guanylate kinase family of scaffolding proteins, MAGI1, but not to another, MAGI2. The complex structure of MAGI1-PDZ3/nephrin-PBM reveals that the Gly at the -3 position of nephrin-PBM is the determining feature for MAGI1-PDZ3 recognition, which sharply contrasts with the typical PDZ/PBM binding mode. A single gain-of-function mutation within MAGI2 enabled nephrin-PBM binding. In addition, using our structural analysis, we developed a highly efficient inhibitory peptide capable of specifically blocking the nephrin/MAGI1 interaction. CONCLUSIONS MAGI1 interacts with nephrin-PBM with exquisite specificity. A newly developed, potent inhibitory peptide that blocks this interaction may be useful for future functional investigations in vivo. Our findings also provide possible explanations for the diseases caused by NPHS1 mutations.