The alpha-subunit of the epithelial sodium channel is an aldosterone-induced transcript in mammalian collecting ducts, and this transcriptional response is mediated via distinct cis-elements in the 5'-flanking region of the gene.
The alpha-subunit of the epithelial sodium channel is an aldosterone-induced transcript in mammalian collecting ducts, and this transcriptional response is mediated via distinct cis-elements in the 5'-flanking region of the gene.
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DOI：
10.1210/mend.15.4.0620
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发表时间：
2001-04
影响因子：
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通讯作者：
Verity E. Mick;O. Itani;Randy W. Loftus;R. Husted;Thomas J. Schmidt;Christie P. Thomas
中科院分区：
文献类型：
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作者：
Verity E. Mick;O. Itani;Randy W. Loftus;R. Husted;Thomas J. Schmidt;Christie P. Thomas
醛固酮通过增加上皮钠离子通道（ENaC）的活性来刺激钠离子在集合管中的再吸收。全身给药醛固酮增加了哺乳动物肾脏中α ENaC mRNA的表达，表明α ENaC基因是醛固酮在远端肾元中作用的靶标。为了确定醛固酮是否会增加α ENaC基因的转录，将α ENaC 5'-侧翼区与荧光素酶偶联的一部分转染到MDCK-C7细胞中，MDCK-C7细胞是一种醛固酮刺激Na（+）运输的收集管细胞系。地塞米松和醛固酮均通过糖皮质激素受体（GR）刺激α - ENaC偶联报告基因活性，这种反应与这些激素对内源性α - ENaC表达的影响相关。放线菌素D阻断了醛固酮刺激的α ENaC表达，醛固酮对α ENaC mRNA衰变无影响，证实了其转录作用。在HT-29细胞中，GR/矿糖皮质激素受体（MR）缺陷的结肠细胞系具有组成型α - ENaC表达，共转染GR或MR可恢复醛固酮刺激的α - ENaC基因转录；尽管醛固酮对mr具有功能偏好，但缺失结构的分析证实，在MDCK-C7和HT-29细胞中，一个不完美的糖皮质激素反应元件（GRE）是使醛固酮对α - ENaC基因启动子产生反应的必要和充分条件。这些结果证实了α - ENaC是醛固酮诱导的收集管转录物，并描述了这种作用的分子机制。
Aldosterone stimulates Na(+) reabsorption in the collecting ducts by increasing the activity of the epithelial sodium channel, ENaC. Systemic administration of aldosterone increases alpha ENaC mRNA expression in mammalian kidney, suggesting that the alpha ENaC gene is a target for aldosterone action in the distal nephron. To determine whether aldosterone increases alpha ENaC gene transcription, a portion of the alpha ENaC 5'- flanking region coupled to luciferase was transfected into MDCK-C7 cells, a collecting duct cell line with aldosterone-stimulated Na(+) transport. Both dexamethasone and aldosterone stimulated alpha ENaC-coupled reporter gene activity via the glucocorticoid receptor (GR), and this response correlated with the effect of these hormones on endogenous alpha ENaC expression. The aldosterone-stimulated alpha ENaC expression was blocked by actinomycin D, and aldosterone had no effect on alpha ENaC mRNA decay, confirming a transcriptional effect. In HT-29 cells, a GR/mineralocorticoid receptor (MR)-deficient colonic cell line with constitutive alpha ENaC expression, cotransfection with GR or MR restored aldosterone-stimulated alpha ENaC gene transcription, although aldosterone had a functional preference for MR. Analysis of deletion constructs confirmed that a single imperfect glucocorticoid response element (GRE) is necessary and sufficient to confer the aldosterone responsiveness to the alpha ENaC gene promoter in MDCK-C7 and HT-29 cells. These results confirm that alpha ENaC is an aldosterone-induced transcript in the collecting duct and delineates the molecular mechanism for this effect.