Epithelial sodium channel regulated by aldosterone-induced protein sgk
Epithelial sodium channel regulated by aldosterone-induced protein sgk
复制标题
DOI：
10.1073/pnas.96.5.2514
复制
发表时间：
1999-03-02
影响因子：
11.1
通讯作者：
Pearce, D
中科院分区：
文献类型：
--
作者：
Chen, SY;Bhargava, A;Pearce, D
陆生和淡水脊椎动物的钠稳态由皮质类固醇激素控制，主要是醛固酮，其刺激致密上皮细胞中的生电Na+吸收。虽然已知醛固酮通过基因转录的变化增加靶细胞中顶端膜Na+渗透性，但这种作用的机制基础仍然知之甚少。醛固酮的主要早期作用是增加上皮钠通道（ENaC）的活性，尽管ENaC mRNA和蛋白水平最初不改变。相反，开放的概率和/或在顶端膜通道的数量大大增加了未知的调制器。为了鉴定调节ENaC活性的酶刺激的基因产物，从A6细胞（肾远端肾单位来源的稳定细胞系）产生消减cDNA文库，并在共表达测定中测试候选物对ENaC活性的影响。我们在这里报告的鉴定sgk（血清和糖皮质激素调节激酶），丝氨酸-苏氨酸激酶家族的成员作为醛固酮诱导的调节ENaC活性。在A6细胞和大鼠肾脏中，sgk mRNA和蛋白均受到强烈和快速的激素刺激。此外，sgk刺激ENaC活性约7倍，当它们在非洲爪蟾卵母细胞共表达。这些数据表明，sgk在Na+吸收的醛固酮调节中起着重要作用，因此在细胞外液量，血压和钠稳态的控制中起着重要作用。
Sodium homeostasis in terrestrial and freshwater vertebrates is controlled by the corticosteroid hormones, principally aldosterone, which stimulate electrogenic Na+ absorption in tight epithelia. Although aldosterone is known to increase apical membrane Na+ permeability in target cells through changes in gene transcription, the mechanistic basis of this effect remains poorly understood. The predominant early effect of aldosterone is to increase the activity of the epithelial sodium channel (ENaC), although ENaC mRNA and protein levels do not change initially. Rather, the open probability and/or number of channels in the apical membrane are greatly increased by unknown modulators. To identify hormone-stimulated gene products that modulate ENaC activity, a subtracted cDNA library was generated from A6 cells, a stable cell line of renal distal nephron origin, and the effect of candidates on ENaC activity was tested in a coexpression assay. We report here the identification of sgk (serum and glucocorticoid-regulated kinase), a member of the serine-threonine kinase family as an aldosterone-induced regulator of ENaC activity. sgk mRNA and protein were strongly and rapidly hormone stimulated both in A6 cells and in rat kidney. Furthermore, sgk stimulated ENaC activity approximately 7-fold when they were coexpressed in Xenopus laevis oocytes. These data suggest that sgk plays a central role in aldosterone regulation of Na+ absorption and thus in the control of extracellular fluid volume, blood pressure, and sodium homeostasis.