Department of Pharmacology, New York Medical College, BSB 538, Valhalla, NY 10595, USA.
J Am Soc Nephrol. 2011 Jun;22(6):1087-98. doi: 10.1681/ASN.2010090927. Epub 2011 May 12.
Dietary potassium stimulates the surface expression of ROMK channels in the aldosterone-sensitive distal nephron, but the mechanism by which this occurs is incompletely understood. Here, a high-potassium diet increased the transcription of microRNA (miR) 802 in the cortical collecting duct in mice. In addition, high-potassium intake decreased the expression of caveolin-1, whose 3' untranslated region contains the seed sequence of miR-802. In vitro, expression of miR-802 suppressed the expression of caveolin-1, and conversely, downregulation of endogenous miR-802 increased the expression of caveolin-1. Sucrose-gradient centrifugation suggested that caveolin-1 closely associated with ROMK channels, and immunoprecipitation showed that caveolin-1 interacted with the N terminus of ROMK. Expression of caveolin-1 varied inversely with the expression of ROMK1 in the plasma membrane, and caveolin-1 inhibited ROMK1 channel activity. Removal of the clathrin-dependent endocytosis motif from ROMK1 failed to abolish the effect of caveolin-1 on ROMK1 channel activity. Last, expression of miR-802 increased ROMK1 channel activity, an effect blocked by coexpression of caveolin-1. Taken together, miR-802 mediates the stimulatory effect of a high-potassium diet on ROMK channel activity by suppressing caveolin-1 expression, which leads to increased surface expression of ROMK channels in the distal nephron.
饮食钾刺激醛固酮敏感的远端肾单位中 ROMK 通道的表面表达，但这一过程的机制尚不完全清楚。在这里，高钾饮食增加了小鼠皮质集合管中 microRNA (miR) 802 的转录。此外，高钾摄入降低了 caveolin-1 的表达，其 3'非翻译区包含 miR-802 的种子序列。在体外，miR-802 的表达抑制了 caveolin-1 的表达，反之，内源性 miR-802 的下调增加了 caveolin-1 的表达。蔗糖梯度离心表明 caveolin-1 与 ROMK 通道密切相关，免疫沉淀表明 caveolin-1 与 ROMK 的 N 端相互作用。caveolin-1 的表达与质膜中 ROMK1 的表达呈负相关，caveolin-1 抑制 ROMK1 通道活性。从 ROMK1 上除去网格蛋白依赖性内吞作用的motif 并没有消除 caveolin-1 对 ROMK1 通道活性的影响。最后，miR-802 增加了 ROMK1 通道活性，这种作用被 caveolin-1 的共表达所阻断。总之，miR-802 通过抑制 caveolin-1 的表达来介导高钾饮食对 ROMK 通道活性的刺激作用，从而导致远端肾单位中 ROMK 通道的表面表达增加。
