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Interactions with WNK (with no lysine) family members regulate oxidative stress response 1 and ion co-transporter

Samarpita Sengupta1, Szu-Wei Tu, Kyle Wedin

  • 1Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9041, USA.

The Journal of Biological Chemistry
|September 20, 2012
PubMed

Insights

WNK1 protein kinases regulate ion transport and blood pressure by activating OSR1 and SPAK. These kinases phosphorylate key co-transporters, highlighting WNK1

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Physiology

Background:

  • WNK (with no lysine (K)) protein kinases are implicated in heritable hypertension through ion imbalance.
  • WNK1 activates Ste20 family kinases, OSR1 (oxidative stress-responsive 1) and SPAK (STE20/SPS1-related proline-, alanine-rich kinase).
  • Activated OSR1 and SPAK phosphorylate and stimulate sodium-potassium-chloride co-transporters (NKCC1, NKCC2).

Purpose of the Study:

  • To investigate the interaction and functional relationship between WNK1 and OSR1.
  • To elucidate the role of WNK1 in OSR1 activation and localization.
  • To understand the contribution of WNK1-OSR1 signaling to ion co-transporter regulation.

Main Methods:

  • Cellular co-localization studies using GFP-tagged WNK1.
  • Analysis of WNK1 fragments for localization and OSR1 binding.
  • Photobleaching experiments to assess protein mobility under different conditions.
  • In vitro kinase assays and cellular assays measuring ion co-transporter activity.

Main Results:

  • WNK1 and OSR1 co-localize on cytoplasmic puncta.
  • The C-terminal region of WNK1 is crucial for its localization and interaction with OSR1.
  • WNK1 family members efficiently phosphorylate OSR1's activation loop.
  • WNK1 C-terminal fragments bind OSR1, inhibit its activation, and block OSR1-mediated co-transporter stimulation.
  • OSR1 can phosphorylate WNK1 C-terminal fragments, suggesting feedback regulation.

Conclusions:

  • WNK1 association is essential for OSR1 activation and function in ion transport.
  • WNK1 and OSR1 form a signaling complex regulating ion homeostasis.
  • OSR1-mediated feedback phosphorylation of WNK1 suggests a regulatory loop in the pathway.

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