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

Am J Physiol Renal Physiol. 2020 Jan 1;318(1):F216-F228. doi: 10.1152/ajprenal.00232.2019. Epub 2019 Nov 18.


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.

Keywords: Kir4.1; Na+-Cl− cotransporter; Ste20-related proline-alanine-rich kinase; WNK bodies; WNK4; distal convoluted tubule; oxidative stress-responsive kinase-1.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Female
  • Hypokalemia / blood
  • Hypokalemia / metabolism*
  • Kidney / metabolism*
  • Kidney Tubules, Distal / metabolism
  • Male
  • Mice
  • Mice, Knockout
  • Phosphorylation
  • Potassium / blood
  • Potassium Channels, Inwardly Rectifying / genetics
  • Potassium Channels, Inwardly Rectifying / metabolism
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism*
  • Signal Transduction / physiology
  • Solute Carrier Family 12, Member 3 / metabolism


  • Kcnj10 (channel)
  • Potassium Channels, Inwardly Rectifying
  • Slc12a3 protein, mouse
  • Solute Carrier Family 12, Member 3
  • Prkwnk4 protein, mouse
  • Stk39 protein, mouse
  • OXSR1 protein, mouse
  • Protein Serine-Threonine Kinases
  • Potassium