WNK bodies cluster WNK4 and SPAK/OSR1 to promote NCC activation in hypokalemia

Martin N. Thomson, Catherina A. Cuevas, Tim M. Bewarder, Carsten Dittmayer, Lauren N. Miller, Jinge Si, Ryan J. Cornelius, Xiao Tong Su, Chao Ling Yang, James A. McCormick, Juliette Hadchouel, David H. Ellison, Sebastian Bachmann, Kerim Mutig

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

K+ deficiency stimulates renal salt reuptake via the Na+-Cl cotransporter (NCC) of the distal convoluted tubule (DCT), thereby reducing K+ losses in downstream nephron segments while increasing NaCl retention and blood pressure. NCC activation is mediated by a kinase cascade involving with no lysine (WNK) kinases upstream of Ste20-related proline-alanine-rich kinase (SPAK) and oxidative stress-responsive kinase-1 (OSR1). In K+ deficiency, WNKs and SPAK/OSR1 concentrate in spherical cytoplasmic domains in the DCT termed “WNK bodies,” the significance of which is undetermined. By feeding diets of varying salt and K+ content to mice and using genetically engineered mouse lines, we aimed to clarify whether WNK bodies contribute to WNK-SPAK/OSR1-NCC signaling. Phosphorylated SPAK/OSR1 was present both at the apical membrane and in WNK bodies within 12 h of dietary K+ deprivation, and it was promptly suppressed by K+ loading. In WNK4-deficient mice, however, larger WNK bodies formed, containing unphosphorylated WNK1, SPAK, and OSR1. This suggests that WNK4 is the primary active WNK isoform in WNK bodies and catalyzes SPAK/OSR1 phosphorylation therein. We further examined mice carrying a kidney-specific deletion of the basolateral K+ channel-forming protein Kir4.1, which is required for the DCT to sense plasma K+ concentration. These mice displayed remnant mosaic expression of Kir4.1 in the DCT, and upon K+ deprivation, WNK bodies developed only in Kir4.1-expressing cells. We postulate a model of DCT function in which NCC activity is modulated by plasma K+ concentration via WNK4-SPAK/OSR1 interactions within WNK bodies.

Original languageEnglish (US)
Pages (from-to)F216-F228
JournalAmerican Journal of Physiology - Renal Physiology
Volume318
Issue number1
DOIs
StatePublished - Jan 1 2020

Keywords

  • Distal convoluted tubule
  • Kir4.1
  • Na-Cl cotransporter
  • Oxidative stress-responsive kinase-1
  • Ste20-related proline-alanine-rich kinase
  • WNK bodies
  • WNK4

ASJC Scopus subject areas

  • Physiology
  • Urology

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    Thomson, M. N., Cuevas, C. A., Bewarder, T. M., Dittmayer, C., Miller, L. N., Si, J., Cornelius, R. J., Su, X. T., Yang, C. L., McCormick, J. A., Hadchouel, J., Ellison, D. H., Bachmann, S., & Mutig, K. (2020). WNK bodies cluster WNK4 and SPAK/OSR1 to promote NCC activation in hypokalemia. American Journal of Physiology - Renal Physiology, 318(1), F216-F228. https://doi.org/10.1152/ajprenal.00232.2019