Differential roles of WNK4 in regulation of NCC in vivo

Yih Sheng Yang, Jian Xie, Sung Sen Yang, Shih Hua Lin, Chou-Long Huang

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

The Na+-Cl- cotransporter (NCC) in distal convoluted tubule (DCT) plays important roles in renal NaCl reabsorption. The current hypothesis for the mechanism of regulation of NCC focuses on WNK4 and intracellular Cl+ concentration ([Cl-]i). WNK kinases bind Cl+, and Cl- binding decreases the catalytic activity. It is believed that hypokalemia under low K+ intake decreases [Cl-]i to activate WNK4, which thereby phosphorylates and stimulates NCC through activation of SPAK. However, increased NCC activity and apical NaCl entry would mitigate the fall in [Cl-]i. Whether [Cl-]i in DCT under low-K+ diet is sufficiently low to activate WNK4 is unknown. Furthermore, increased luminal NaCl delivery also stimulates NCC and causes upregulation of the transporter. Unlike low K+ intake, increased luminal NaCl delivery would tend to increase [Cl-]i. Thus we investigated the role of WNK4 and [Cl-]i in regulating NCC. We generated Wnk4-knockout mice and examined regulation of NCC by low K+ intake and by increased luminal NaCl delivery in knockout (KO) and wild-type mice. Wnk4-KO mice have marked reduction in the abundance, phosphorylation, and functional activity of NCC vs. wild type. Low K+ intake increases NCC phosphorylation and functional activity in wild-type mice, but not in Wnk4-KO mice. Increased luminal NaCl delivery similarly upregulates NCC, which, contrary to low K+ intake, is not abolished in Wnk4-KO mice. The results reveal that modulation of WNK4 activity by [Cl-]i is not the sole mechanism for regulating NCC. Increased luminal NaCl delivery upregulates NCC via yet unknown mechanism(s) that may override inhibition of WNK4 by high [Cl-]i.

Original languageEnglish (US)
Pages (from-to)F999-F1007
JournalAmerican Journal of Physiology - Renal Physiology
Volume314
Issue number5
DOIs
Publication statusPublished - Jan 1 2018

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Keywords

  • DCT
  • Dietary potassium
  • Intracellular chloride
  • NCC
  • WNK1
  • WNK4

ASJC Scopus subject areas

  • Physiology
  • Urology

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