A MicroRNA Cluster miR-23-24-27 Is Upregulated by Aldosterone in the Distal Kidney Nephron Where it Alters Sodium Transport.

The epithelial sodium channel (ENaC) is expressed in the epithelial cells of the distal convoluted tubules, connecting tubules, and cortical collecting duct (CCD) in the kidney nephron. Under the regulation of the steroid hormone aldosterone, ENaC is a major determinant of sodium (Na+ ) and water balance. The ability of aldosterone to regulate microRNAs (miRs) in the kidney has recently been realized, but the role of miRs in Na+ regulation has not been well established. Here we demonstrate that expression of a miR cluster mmu-miR-23-24-27, is upregulated in the CCD by aldosterone stimulation both in vitro and in vivo. Increasing the expression of these miRs increased Na+ transport in the absence of aldosterone stimulation. Potential miR targets were evaluated and miR-27a/b was verified to bind to the 3'-untranslated region of intersectin-2, a multi-domain protein expressed in the distal kidney nephron and involved in the regulation of membrane trafficking. Expression of Itsn2 mRNA and protein was decreased after aldosterone stimulation. Depletion of Itsn2 expression, mimicking aldosterone regulation, increased ENaC-mediated Na+ transport, while Itsn2 overexpression reduced ENaC's function. These findings reinforce a role for miRs in aldosterone regulation of Na+ transport, and implicate miR-27 in aldosterone's action via a novel target. J. Cell. Physiol. 232: 1306-1317, 2017.