Discovery Research Laboratories, Shionogi & Co., Ltd., Osaka, Japan.
Nephron Exp Nephrol. 2009;113(3):e89-96. doi: 10.1159/000235245. Epub 2009 Aug 14.
BACKGROUND/AIMS: Morphological change of podocytes is closely correlated with the development of proteinuria. Podocalyxin is a major sialoglycoprotein of the podocytes and is thought to be involved in the maintenance of the foot processes structure. Our aim was to examine the mechanism by which podocalyxin contributes to the morphological change of podocytes.
We searched protein(s) which coprecipitate with podocalyxin using rat glomerular lysate. Localization of podocalyxin and the coprecipitated protein, cortactin, was studied in a model of puromycin aminonucleoside (PAN) nephrosis by immunocytochemistry. Tyrosine phosphorylation of cortactin was examined. Association of the podocalyxin/cortactin complex with the actin cytoskeleton was evaluated by extraction with Triton-X and immunoblotting.
Cortactin was found to be co-immunoprecipitated with podocalyxin. Immunocytochemical analysis revealed that these 2 proteins colocalized in the apical side of podocytes. In PAN nephrosis, localization of cortactin was altered after the onset of proteinuria, with increased tyrosine phosphorylation. Simultaneously, the dissociation of the podocalyxin/cortactin complex from the actin cytoskeleton was induced.
These results indicate that cortactin mediates interaction between podocalyxin and actin filaments in podocytes and that alteration of this interaction may play a role in the process of morphological change of podocytes.
背景/目的：足细胞的形态变化与蛋白尿的发展密切相关。足突蛋白是足细胞的主要唾液酸糖蛋白，被认为参与维持足突结构。我们的目的是研究足突蛋白在足细胞形态变化中的作用机制。
我们使用大鼠肾小球裂解物搜索与足突蛋白共沉淀的蛋白质。通过免疫细胞化学研究嘌呤霉素氨基核苷（PAN）肾病模型中足突蛋白和共沉淀蛋白皮质肌动蛋白的定位。检测皮质肌动蛋白的酪氨酸磷酸化。通过 Triton-X 提取和免疫印迹评估足突蛋白/皮质肌动蛋白复合物与肌动蛋白细胞骨架的结合。
发现皮质肌动蛋白与足突蛋白共免疫沉淀。免疫细胞化学分析显示这 2 种蛋白质在足细胞的顶端侧共定位。在 PAN 肾病中，蛋白尿发病后皮质肌动蛋白的定位发生改变，酪氨酸磷酸化增加。同时，足突蛋白/皮质肌动蛋白复合物从肌动蛋白细胞骨架中解离。
这些结果表明，皮质肌动蛋白介导了足细胞中足突蛋白与肌动蛋白丝之间的相互作用，这种相互作用的改变可能在足细胞形态变化过程中起作用。
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