Journal Article

Molecular Pathogenesis of Inherited Hypertension with Hyperkalemia: The Na-Cl Cotransporter Is Inhibited by Wild-Type but Not Mutant WNK4

Rapson, Alicia K., Lalioti, Maria D., Gamba, Gerardo, Hebert, Steven C., Wilson, Frederick H., Hoover, Robert S., Kahle, Kristopher T., Sabath, Ernesto, Lifton, Richard P.

2003

Overview

Mutations in the serine-threonine kinases WNK1 and WNK4 [with no lysine (K) at a key catalytic residue] cause pseudohypoaldosteronism type II (PHAII), a Mendelian disease featuring hypertension, hyperkalemia, hyperchloremia, and metabolic acidosis. Both kinases are expressed in the distal nephron, although the regulators and targets of WNK signaling cascades are unknown. The Cl-dependence of PHAII phenotypes, their sensitivity to thiazide diuretics, and the observation that they constitute a \"mirror image\" of the phenotypes resulting from loss of function mutations in the thiazide-sensitive Na-Cl cotransporter (NCCT) suggest that PHAII may result from increased NCCT activity due to altered WNK signaling. To address this possibility, we measured NCCT-mediated Na+influx and membrane expression in the presence of wild-type and mutant WNK4 by heterologous expression in Xenopus oocytes. Wild-type WNK4 inhibits NCCT-mediated Na-influx by reducing membrane expression of the cotransporter (22Na-influx reduced 50%,$P < 1 \\times 10^{-9}$, surface expression reduced 75%,$P < 1 \\times 10^{-14}$in the presence of WNK4). This inhibition depends on WNK4 kinase activity, because missense mutations that abrogate kinase function prevent this effect. PHAII-causing missense mutations, which are remote from the kinase domain, also prevent inhibition of NCCT activity, providing insight into the pathophysiology of the disorder. The specificity of this effect is indicated by the finding that WNK4 and the carboxyl terminus of NCCT coimmunoprecipitate when expressed in HEK 293T cells. Together, these findings demonstrate that WNK4 negatively regulates surface expression of NCCT and implicate loss of this regulation in the molecular pathogenesis of an inherited form of hypertension.

• Publisher: National Academy of Sciences,National Acad Sciences,The National Academy of Sciences
• Subject: Animals / Antibodies / Base Sequence / Biological Sciences / Complementary RNA / Epitopes / Female / Genetic mutation / Hyperkalemia - genetics / Hypertension / Hypertension - genetics / Ion Transport / Medical research / Mice / Missense mutation / Molecular biology / Molecular Sequence Data / Mutation / Oocytes / Phenotypes / Protein-Serine-Threonine Kinases - pharmacology / Protein-Serine-Threonine Kinases - physiology / Proteins / Secretion / Sodium - metabolism / Sodium Chloride Symporters / Symporters - antagonists & inhibitors / Symporters - physiology / Xenopus laevis / Xenopus Proteins - pharmacology