Regulation of sodium transport in mammalian collecting duct cells by aldosterone-induced kinase, SGK1:: structure/function studies
Regulation of sodium transport in mammalian collecting duct cells by aldosterone-induced kinase, SGK1:: structure/function studies
复制标题
DOI：
10.1016/j.mce.2003.10.043
复制
发表时间：
2004-03-31
影响因子：
4.1
通讯作者：
Fejes-Tóth, G
中科院分区：
文献类型：
--
作者：
Náray-Fejes-Tóth, A;Helms, MN;Fejes-Tóth, G
血清和糖皮质激素诱导的激酶（SGK）是丝氨酸-苏氨酸激酶家族的成员。首先鉴定的SGK 1亚型被醛固酮快速诱导。在这项研究中，我们确定，最近描述的两个亚型，SGK 2和SGK 3也表达在肾皮质集合管（CCD）细胞，然而，他们的表达是不诱导醛固酮或糖皮质激素。SGK 1增加卵母细胞中上皮钠通道（ENaC）的活性，但其在天然盐皮质激素靶细胞中的细胞靶点及其作用机制仍然未知。我们研究了SGK 1在稳定过表达或下调SGK 1的M-1小鼠CCD细胞系中皮质类固醇调节的钠转运中的作用。在SGK 1表达或活性下调的CCD细胞中，钠转运的基础速率显著低于SGK 1过表达细胞。重要的是，皮质类固醇治疗未能刺激钠转运细胞下调SGK 1，而它显着增加钠运输在父母和SGK 1过表达M-1 celles.To确定如果C-末端PDZ相互作用是重要的SGK的ENaC活性或贩运的影响，我们研究了突变体SGK 1的影响，其中保守的PDZ结合域已被淘汰。然而，这样的突变并没有减少其刺激作用对非洲爪蟾卵母细胞的ENaC电流。荧光共聚焦显微镜显示，全长和PDZ结合突变的SGK 1的细胞内定位是相同的：它们都定位于细胞内囊泡结构。另一方面，N-末端截短的（δ 60）-SGK 1不增加ENaC活性。我们的结论是，SGK 1是一个关键组成部分，在哺乳动物CCD细胞皮质类固醇调节钠转运。我们的数据还表明，N-末端的SGK 1是必要的钠转运的刺激作用，而消除C-末端PDZ结合结构域没有改变其功能。(C)2003爱思唯尔爱尔兰有限公司保留所有权利。
Serum- and glucocorticoid-induced kinases (SGK) are members of the serine-threonine kinase family. SGK1, the isoform identified first, is rapidly induced by aldosterone. In this study, we determined that the two recently described isoforms, SGK2 and SGK3 are also expressed in renal cortical collecting duct (CCD) cells; however, their expression is not induced by aldosterone or glucocorticoids. SGK1 increases the activity of the epithelial sodium channel (ENaC) in oocytes but its cellular targets in native mineralocorticoid target cells and its mechanism of action are still unknown. We studied the role of SGK1 in corticosteroid-regulated Na transport in M-1 mouse CCD cell lines that stably over-express or down-regulate SGK1. Basal rates of transepithelial Na transport were significantly lower in CCD cells in which SGK1 expression or activity was down-regulated than in SGK1 overexpressing cells. Importantly, corticosteroid treatment failed to stimulate Na transport in cells with down-regulated SGK1 while it significantly increased Na transport in parent and SGK1 overexpressing M-1 cells.To determine if C-terminal PDZ interactions are important for SGK's effect on ENaC activity or trafficking, we examined the effects of mutant SGK1 in which the conserved PDZ binding domain has been eliminated. However, such mutations did not decrease its stimulatory effect on ENaC current in Xenopus oocytes. Fluorescence confocal microscopy revealed that the intracellular localization of full-length and PDZ binding mutated SGK1 was identical: they both localize to intracellular vesicular structures. On the other hand, N-terminally truncated (delta 60)-SGK1 did not increase ENaC activity. We conclude that SGK1 is a critical component in corticosteroid-regulated Na transport in mammalian CCD cells. Our data also indicate that the N-terminal of SGK1 is necessary for its stimulatory effect on Na transport while elimination of the C-terminal PDZ binding domain did not change its function. (C) 2003 Elsevier Ireland Ltd. All rights reserved.