J Clin Invest 111(7): 1039-1045

WNK kinases regulate thiazide-sensitive Na-Cl cotransport

^{Division of Nephrology and Hypertension, Department of Medicine, and}^{Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon, USA}^{Portland Veterans Affairs Medical Center, Portland, Oregon, USA}

Address correspondence to: David H. Ellison, Division of Nephrology and Hypertension, Oregon Health and Science University, PP262, 3314 SW US Veterans Hospital Road, Portland, Oregon 97239, USA. Phone: (503) 494-8490; Fax: (503) 494-5330; E-mail: ude.usho@dnosille.

Received 2002 Nov 21; Accepted 2003 Jan 21.

Abstract

Pseudohypoaldosteronism type II (PHAII) is an autosomal dominant disorder of hyperkalemia and hypertension. Mutations in two members of the WNK kinase family, WNK1 and WNK4, cause the disease. WNK1 mutations are believed to increase WNK1 expression; the effect of WNK4 mutations remains unknown. The clinical phenotype of PHAII is opposite to Gitelman syndrome, a disease caused by dysfunction of the thiazide-sensitive Na-Cl cotransporter. We tested the hypothesis that WNK kinases regulate the mammalian thiazide-sensitive Na-Cl cotransporter (NCC). Mouse WNK4 was cloned and expressed in Xenopus oocytes with or without NCC. Coexpression with WNK4 suppressed NCC activity by more than 85%. This effect did not result from defects in NCC synthesis or processing, but was associated with an 85% reduction in NCC abundance at the plasma membrane. Unlike WNK4, WNK1 did not affect NCC activity directly. WNK1, however, completely prevented WNK4 inhibition of NCC. Some WNK4 mutations that cause PHAII retained NCC-inhibiting activity, but the Q562E WNK4 demonstrated diminished activity, suggesting that some PHAII mutations lead to loss of NCC inhibition. Gain-of-function WNK1 mutations would be expected to inhibit WNK4 activity, thereby activating NCC, contributing to the PHAII phenotype. Together, these results identify WNK kinases as a previously unrecognized sodium regulatory pathway of the distal nephron. This pathway likely contributes to normal and pathological blood pressure homeostasis.

Abstract

Acknowledgments

This work was supported by the NIH National Institute of Diabetes & Digestive & Kidney Diseases (grant R01 DK-51496) and by internal funds provided by Oregon Health and Science University. The authors thank David Cohen, David Rosansky, and Arohan Subramanya for helpful discussions and Melanie Cobb for the WNK1 clone.

Acknowledgments

Footnotes

See the related Commentary beginning on page 947.

Portions of this work were presented at the Experimental Biology Meeting, April 20–24, 2002, New Orleans, Louisiana, USA, and at the meeting of the American Society of Nephrology, October 30–November 4, 2002, Philadelphia, Pennsylvania, USA, and appear in abstract form (2002. Late Breaking Abstract Book, Experimental Biology 2002, page 17 #LB76; 2002. J. Am. Soc. Nephrol. 13:75A).

Conflict of interest: The authors have declared that no conflict of interest exists.

Nonstandard abbreviations used: pseudohypoaldosteronism type II (PHAII); Na-Cl cotransporter (NCC); distal convoluted tubule (DCT); serum- and glucocorticoid-induced kinase (SGK).

Footnotes

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