Department of Medicine, Kidney Center, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, Japan.
Histochem Cell Biol. 2011 Jul;136(1):25-35. doi: 10.1007/s00418-011-0827-x. Epub 2011 Jun 10.
Initial reports claim that WNK4 localization is mainly at intercellular junctions of distal convoluted tubules (DCT) and cortical collecting ducts (CCD) in the kidney. However, we recently clarified the major targets of WNK4 kinase to be the OSR1/SPAK kinases and the Na-Cl co-transporter (NCC), an apical membrane protein in the DCT, thus raising the question of whether the cellular localization of WNK4 is at intercellular junctions. In this study, we re-evaluate the intrarenal and intracellular immunolocalization of WNK4 in the mouse kidney using a newly generated anti-WNK4 antibody. By performing double immunofluorescence of WNK4 with several nephron-segment-specific markers, we have found that WNK4 is present in podocytes in glomeruli, the cortical thick ascending limb of Henle's loop including macula densa, and the medullary collecting ducts (MCD), in addition to the previously identified nephron segments, i.e., DCT and CCD. These results are consistent with the finding that WNK4 constitutes a kinase cascade with OSR1/SPAK and NCC in the DCT, and highlights a novel role for WNK4 in nephron segments newly identified as being WNK4-positive in this study.
最初的报告声称，WNK4 的定位主要在肾脏的远曲小管（DCT）和皮质集合管（CCD）的细胞间连接处。然而，我们最近阐明了 WNK4 激酶的主要靶标是 OSR1/SPAK 激酶和 Na-Cl 共转运体（NCC），这是 DCT 中的一种顶膜蛋白，因此提出了 WNK4 的细胞定位是否在细胞间连接处的问题。在这项研究中，我们使用新生成的抗 WNK4 抗体重新评估了小鼠肾脏中 WNK4 的肾内和细胞内免疫定位。通过将 WNK4 与几个肾单位段特异性标记物进行双重免疫荧光染色，我们发现 WNK4 存在于肾小球中的足细胞、包括致密斑的 Henle 袢皮质升支粗段以及髓质集合管（MCD）中，除了先前鉴定的肾单位段，即 DCT 和 CCD。这些结果与 WNK4 在 DCT 中与 OSR1/SPAK 和 NCC 构成激酶级联反应的发现一致，并突出了 WNK4 在本研究中新鉴定为 WNK4 阳性的肾单位段中的新作用。
