MAGI-2 orchestrates the localization of backbone proteins in the slit diaphragm of podocytes
MAGI-2 orchestrates the localization of backbone proteins in the slit diaphragm of podocytes
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DOI：
10.1016/j.kint.2020.09.027
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发表时间：
2021-01-25
影响因子：
19.6
通讯作者：
Asanuma, Katsuhiko
中科院分区：
文献类型：
--
作者：
Yamada, Hiroyuki;Shirata, Naritoshi;Asanuma, Katsuhiko
足细胞是肾小球内高度特化的细胞，对超滤至关重要。足细胞足突之间的狭缝隔膜作为最终的过滤屏障，以防止血清蛋白渗漏到尿液中。裂膜主要由Nephrin和Neph 1组成，这些骨架蛋白的定位对于维持肾小球滤过屏障的完整性至关重要。然而，调节这些骨架蛋白定位的机制仍然难以捉摸。在这里，我们专注于膜相关的鸟苷酸激酶倒2（MAGI-2）的作用，以调查的机制，协调本地化的裂膜骨架蛋白。MAGI-2下调与人肾小球疾病如局灶节段性肾小球硬化或伊加肾病中裂膜骨架蛋白表达减少一致。小鼠足细胞特异性MAGI-2缺陷消除了Nephrin和Neph 1的定位，独立于其他支架蛋白。虽然缺乏小带occuldens-1下调内源性Neph 1的表达，MAGI-2恢复Neph 1在培养的足细胞的细胞边缘的表达。此外，MAGI-2的过表达保留了Nephrin定位于细胞间连接。免疫共沉淀和下拉测定也揭示了MAGI-2的PDZ结构域对于足细胞中MAGI-2和狭缝隔膜骨架蛋白之间的相互作用的重要性。因此，在细胞间连接中的Nephrin和Neph 1的定位和稳定化主要通过MAGI-2的PDZ结构域以及其他裂膜支架蛋白来调节。因此，这些发现可能阐明了一种维持骨架蛋白的机制。
Podocytes are highly specialized cells within the glomerulus that are essential for ultrafiltration. The slit diaphragm between the foot processes of podocytes functions as a final filtration barrier to prevent serum protein leakage into urine. The slit-diaphragm consists mainly of Nephrin and Neph1, and localization of these backbone proteins is essential to maintaining the integrity of the glomerular filtration barrier. However, the mechanisms that regulate the localization of these backbone proteins have remained elusive. Here, we focused on the role of membrane-associated guanylate kinase inverted 2 (MAGI-2) in order to investigate mechanisms that orchestrate localization of slit-diaphragm backbone proteins. MAGI-2 downregulation coincided with a reduced expression of slit-diaphragm backbone proteins in human kidneys glomerular disease such as focal segmental glomerulosclerosis or IgA nephropathy. Podocyte-specific deficiency of MAGI-2 in mice abrogated localization of Nephrin and Neph1 independently of other scaffold proteins. Although a deficiency of zonula occuldens-1 downregulated the endogenous Neph1 expression, MAGI-2 recovered Neph1 expression at the cellular edge in cultured podocytes. Additionally, overexpression of MAGI-2 preserved Nephrin localization to intercellular junctions. Co-immunoprecipitation and pull-down assays also revealed the importance of the PDZ domains of MAGI-2 for the interaction between MAGI-2 and slit diaphragm backbone proteins in podocytes. Thus, localization and stabilization of Nephrin and Neph1 in intercellular junctions is regulated mainly via the PDZ domains of MAGI-2 together with other slit-diaphragm scaffold proteins. Hence, these findings may elucidate a mechanism by which the backbone proteins are maintained.