Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA, USA.
Division of Nephrology, Department of Pediatrics, University of Pittsburgh, Pittsburgh, PA, USA.
FASEB J. 2020 Sep;34(9):11714-11728. doi: 10.1096/fj.201902254RR. Epub 2020 Jul 11.
The final steps in the Renin-Angiotensin-Aldosterone signaling System (RAAS) involve binding of the corticosteroid hormone, aldosterone to its mineralocorticoid receptor (MR). The bound MR interacts with response elements to induce or repress the transcription of aldosterone-regulated genes. A well characterized aldosterone-induced gene is the serum and glucocorticoid-induced kinase (SGK1), which acts downstream to increase sodium transport in distal kidney nephron epithelial cells. The role of microRNAs (miRs) induced by extended aldosterone stimulation in regulating MR and SGK1 has not been reported. In these studies, miRs predicted to bind to the 3'-UTR of mouse MR were profiled by qRT-PCR after aldosterone stimulation. The miR-466a/b/c/e family was upregulated in mouse kidney cortical collecting duct epithelial cells. A luciferase reporter assay confirmed miR-466 binding to both MR and SGK1 3'-UTRs. Inhibition of miR-466 increased MR and SGK1 mRNA and protein levels. Inhibiting miR-466b and preventing its upregulation after aldosterone stimulation increased amiloride-sensitive sodium transport and sensitivity to aldosterone stimulation. In vivo upregulation of miR-466 was confirmed in distal nephrons of mice on low Na diets. Repression of MR and SGK1 by aldosterone-induced miRs may represent a negative feedback loop that contributes to a form of aldosterone escape in vivo.
肾素-血管紧张素-醛固酮信号系统（RAAS）的最后步骤涉及皮质类固醇激素醛固酮与其盐皮质激素受体（MR）的结合。结合的 MR 与反应元件相互作用，诱导或抑制醛固酮调节基因的转录。一个特征明确的醛固酮诱导基因是血清和糖皮质激素诱导激酶（SGK1），它作为下游因子增加远端肾单位上皮细胞中的钠转运。醛固酮刺激诱导的 microRNAs（miRs）在调节 MR 和 SGK1 中的作用尚未报道。在这些研究中，在醛固酮刺激后，通过 qRT-PCR 对预测与小鼠 MR 3'-UTR 结合的 miRs 进行了分析。miR-466a/b/c/e 家族在小鼠肾脏皮质集合管上皮细胞中上调。荧光素酶报告基因测定证实 miR-466 结合到 MR 和 SGK1 的 3'-UTR。抑制 miR-466 增加了 MR 和 SGK1 的 mRNA 和蛋白水平。抑制 miR-466b 并阻止其在醛固酮刺激后上调增加了阿米洛利敏感的钠转运和对醛固酮刺激的敏感性。在低钠饮食的小鼠的远曲小管中证实了 miR-466 的体内上调。醛固酮诱导的 miRs 对 MR 和 SGK1 的抑制可能代表一种负反馈回路，有助于体内的醛固酮逃逸形式。
