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Chloride sensing by WNK1 involves inhibition of autophosphorylation

Alexander T Piala1, Thomas M Moon, Radha Akella

  • 11Department of Biophysics, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.

Science Signaling
|May 8, 2014
PubMed

Insights

WNK1 kinase, linked to hypertension, acts as a chloride sensor. Chloride binding stabilizes WNK1 in an inactive state, preventing its activation and controlling ion cotransporter phosphorylation.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Physiology

Background:

  • WNK1 (with no lysine [K]) is a serine-threonine kinase implicated in familial hypertension.
  • WNK1 regulates ion cotransporters like NKCC, NCC, and KCC through phosphorylation.
  • Extracellular chloride levels correlate with cotransporter phosphorylation, suggesting a chloride-sensitive kinase regulator.

Purpose of the Study:

  • To investigate the mechanism by which WNK1 senses extracellular chloride.
  • To elucidate the role of chloride in WNK1 autophosphorylation and kinase activity.
  • To understand how WNK1 regulates downstream cotransporters.

Main Methods:

  • X-ray crystallography to determine the structure of inactive WNK1 with chloride.
  • Site-directed mutagenesis to identify the chloride-binding site.
  • Biochemical assays to assess kinase autophosphorylation and activity.

Main Results:

  • Chloride binding stabilizes an inactive conformation of WNK1, inhibiting autophosphorylation.
  • Crystallographic data show chloride directly binds to the catalytic site of WNK1.
  • Mutagenesis of the chloride-binding site reduces WNK1's sensitivity to chloride-mediated inhibition.

Conclusions:

  • WNK1 functions as a direct chloride sensor by binding chloride in its active site.
  • This direct interaction inhibits WNK1 autophosphorylation and activation.
  • WNK1's role as a chloride sensor provides a molecular basis for its regulation of ion cotransporters and its link to hypertension.

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