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Abstract: FR-OR058

Chloride-Insensitive WNK4 Mice Reveal Differential NCC Regulations by Dietary Potassium

Session Information

Category: Fluid and Electrolytes

  • 901 Fluid and Electrolytes: Basic

Authors

  • Chen, Jen-Chi, Tri-Service General Hospital, Taipei City, Taiwan
  • Lo, Yi-Fen, Tri-Service General Hospital, Taipei City, Taiwan
  • Huang, Chou-Long, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States
  • Lin, Shih-Hua P., Tri-Service General Hospital, Taipei City, Taiwan
  • Cheng, Chih-Jen, Tri-Service General Hospital, Taipei City, Taiwan
Background

With-no-lysine (WNK) kinases critically regulate sodium chloride cotransporter (NCC) in the distal nephron. Earlier works reveal that intracellular chloride ion ([Cl-]i) binds to a hydrophobic pocket of WNKs and inhibits autophosphorylation and activity of WNKs in non-transporting in vitro condition. Substitution of two leucine residues (L319, L321) surrounding the hydrophobic pocket with phenylalanine makes WNK4 less sensitive to [Cl-]i. The Cl--sensing character of WNK4 hasn’t been validated in vivo.

Methods

We generated the Cl--insensitive L319F/L321F WNK4 mice using CRISPR/Cas9.

Results

The Cl--insensitive L319F/L321F WNK4 mice displayed hypertension, hyperkalemia, and metabolic acidosis along with hyperactive NCC and impaired urinary potassium excretion, mimicking pseudohypoaldosteronism type II. To test the Cl--sensing character of WNK4 in response to dietary potassium, we fed L319F/L321F WNK4 mice diets with various potassium contents. Potassium deprivation failed to further enhance NCC in L319F/L321F WNK4 mice. Chronic potassium-rich diet still dephosphorylated NCC in L319F/L321F WNK4 mice. These results suggest that Cl--insensitive WNK4 is an NCC stimulator, and the physiological [Cl-]i in the distal nephron suppresses WNK4 activity. Potassium deprivation enhances NCC through ameliorating Cl--mediated inhibition on WNK4. In chronic potassium adaptation, other mechanism(s) overrides the constitutively active WNK4 to suppress NCC.

Conclusion

In sum, this study provides compelling evidence supporting that WNK4 is a bona fide NCC stimulator and Cl- sensor in the distal convoluted tubule. The Cl--sensing mechanism of WNK4 play an important role in potassium deprivation.

Funding

  • Government Support - Non-U.S.