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A Phosphorylated Intermediate in the Activation of WNK Kinases

Radha Akella1, Mateusz A Drozdz1, John M Humphreys1

  • 1Department of Biophysics, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390-8816, United States.

Biochemistry
|April 22, 2020
PubMed

Insights

WNK kinases autoactivate through phosphorylation. Osmotic stress alters their structure and enhances ATPase activity, suggesting a multistage activation process for these kinases.

Area of Science:

  • Biochemistry
  • Structural Biology
  • Molecular Biology

Background:

  • WNK (With No Lysine) kinases are crucial regulators activated by osmotic stress.
  • Autophosphorylation is the primary mechanism for WNK kinase autoactivation.

Purpose of the Study:

  • To elucidate the structural basis of WNK kinase activation by osmotic stress.
  • To investigate the impact of osmolytes on WNK kinase structure and activity.

Main Methods:

  • X-ray crystallography of phosphorylated WNK1 (pWNK1) in the presence of AMP-PNP.
  • Osmotic stress experiments involving crystal soaking with sucrose.
  • In vitro ATPase activity assays using WNK1 and WNK3.

Main Results:

  • The crystal structure of pWNK1 revealed a well-ordered but inactive conformation with unique phosphoserine interactions.
  • Osmotic stress induced structural changes in pWNK1, particularly in the activation loop and helix C.
  • The osmolyte PEG400 significantly enhanced the ATPase activity of pWNK1 and pWNK3.

Conclusions:

  • WNK kinase activation involves multistage processes influenced by osmotic pressure.
  • Structural rearrangements triggered by osmolytes are key to WNK kinase functional modulation.
  • These findings provide insights into the regulatory mechanisms of WNK kinases under cellular stress conditions.

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