Kidney Week

Abstract: FR-OR058

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

Session Information

• Fluids and Electrolytes: New Insights on Balance
  October 26, 2018 | Location: 8, San Diego Convention Center
  Abstract Time: 04:30 PM - 04:42 PM

Category: Fluid and Electrolytes

• 901 Fluid and Electrolytes: Basic

Authors

• Chen, Jen-Chi, Tri-Service General Hospital, Taipei City, Taiwan

Jen-Chi Chen, RN



Dr. Chih-Jen Cheng is a physician-scientist whose major interest is ion transport in the distal renal tubule. He graduated from National Defense Medical Center in Taiwan in 2000 and earned his Ph.D. degree from UT Southwestern Medical Center at Dallas, mentored by Prof. Chou-Long Huang, in 2012. He is now the attending physician and associate professor in the Division of Nephrology, Tri-Service General Hospital, National Defense Medical Center.

• Lo, Yi-Fen, Tri-Service General Hospital, Taipei City, Taiwan

Yi-Fen Lo,

• Huang, Chou-Long, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States

Chou-Long Huang,

• Lin, Shih-Hua P., Tri-Service General Hospital, Taipei City, Taiwan

Shih-Hua P. Lin,

• Cheng, Chih-Jen, Tri-Service General Hospital, Taipei City, Taiwan

Chih-Jen Cheng,

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.