title: WNK3 kinase is a positive regulator of NKCC2 and NCC, renal cation-Cl- cotransporters required for normal blood pressure homeostasis.
abstract: WNK1 and WNK4 [WNK, with no lysine (K)] are serine-threonine kinases that function as molecular switches, eliciting coordinated effects on diverse ion transport pathways to maintain homeostasis during physiological perturbation. Gain-of-function mutations in either of these genes cause an inherited syndrome featuring hypertension and hyperkalemia due to increased renal NaCl reabsorption and decreased K(+) secretion. Here, we reveal unique biochemical and functional properties of WNK3, a related member of the WNK kinase family. Unlike WNK1 and WNK4, WNK3 is expressed throughout the nephron, predominantly at intercellular junctions. Because WNK4 is a potent inhibitor of members of the cation-cotransporter SLC12A family, we used coexpression studies in Xenopus oocytes to investigate the effect of WNK3 on NCC and NKCC2, related kidney-specific transporters that mediate apical NaCl reabsorption in the thick ascending limb and distal convoluted tubule, respectively. In contrast to WNK4's inhibitory activity, kinase-active WNK3 is a potent activator of both NKCC2 and NCC-mediated transport. Conversely, in its kinase-inactive state, WNK3 is a potent inhibitor of NKCC2 and NCC activity. WNK3 regulates the activity of these transporters by altering their expression at the plasma membrane. Wild-type WNK3 increases and kinase-inactive WNK3 decreases NKCC2 phosphorylation at Thr-184 and Thr-189, sites required for the vasopressin-mediated plasmalemmal translocation and activation of NKCC2 in vivo. The effects of WNK3 on these transporters and their coexpression in renal epithelia implicate WNK3 in NaCl, water, and blood pressure homeostasis, perhaps via signaling downstream of vasopressin.
authors.affiliation: Department of Genetics, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA.
authors.forename: Jesse
authors.initials: J
authors.lastname: Rinehart
authors.forename: Kristopher T
authors.initials: KT
authors.lastname: Kahle
authors.forename: Paola
authors.initials: P
authors.lastname: de Los Heros
authors.forename: Norma
authors.initials: N
authors.lastname: Vazquez
authors.forename: Patricia
authors.initials: P
authors.lastname: Meade
authors.forename: Frederick H
authors.initials: FH
authors.lastname: Wilson
authors.forename: Steven C
authors.initials: SC
authors.lastname: Hebert
authors.forename: Ignacio
authors.initials: I
authors.lastname: Gimenez
authors.forename: Gerardo
authors.initials: G
authors.lastname: Gamba
authors.forename: Richard P
authors.initials: RP
authors.lastname: Lifton
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D019556:COS Cells; D002522:Chlorocebus aethiops; D004591:Electrophoresis, Polyacrylamide Gel; D006706:Homeostasis; D007668:Kidney / Q000502:physiology*; D051379:Mice; D008856:Microscopy, Fluorescence; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D028021:Sodium-Potassium-Chloride Symporters / Q000502:physiology*; D064466:Solute Carrier Family 12, Member 1; D027981:Symporters / Q000502:physiology*; D014162:Transfection
chemical_list: C578715:Slc12a1 protein, mouse; D028021:Sodium-Potassium-Chloride Symporters; D064466:Solute Carrier Family 12, Member 1; D027981:Symporters; D017346:Protein Serine-Threonine Kinases; C507511:Wnk3 protein, mouse