title: WNK4 enhances TRPV5-mediated calcium transport: potential role in hypercalciuria of familial hyperkalemic hypertension caused by gene mutation of WNK4.
abstract: The epithelial Ca(2+) channel TRPV5 serves as a gatekeeper for active Ca(2+) reabsorption in the distal convoluted tubule and connecting tubule of the kidney. WNK4, a protein serine/threonine kinase with gene mutations that cause familial hyperkalemic hypertension (FHH), including a subtype with hypercalciuria, is also localized in the distal tubule of the nephron. To understand the role of WNK4 in modulation of Ca(2+) reabsorption, we evaluated the effect of WNK4 on TRPV5-mediated Ca(2+) transport in Xenopus laevis oocytes. Coexpression of TRPV5 with WNK4 resulted in a twofold increase in TRPV5-mediated Ca(2+) uptake. The increase in Ca(2+) uptake was due to the increase in surface expression of TRPV5. When the thiazide-sensitive Na(+)-Cl(-) cotransporter NCC was coexpressed, the effect of WNK4 on TRPV5 was weakened by NCC in a dose-dependent manner. Although the WNK4 disease-causing mutants E562K, D564A, Q565E, and R1185C retained their ability to upregulate TRPV5, the blocking effect of NCC was further strengthened when wild-type WNK4 was replaced by the Q565E mutant, which causes FHH with hypercalciuria. We conclude that WNK4 positively regulates TRPV5-mediated Ca(2+) transport and that the inhibitory effect of NCC on this process may be involved in the pathogenesis of hypercalciuria of FHH caused by gene mutation in WNK4.
authors.affiliation: Department of Medicine, Division of Nephrology, University of Alabama at Birmingham, AL 35294-0006, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Jiang
authors.forename: William B
authors.initials: WB
authors.lastname: Ferguson
authors.forename: Ji-Bin
authors.initials: JB
authors.lastname: Peng
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000652:urine; D006801:Humans; D053565:Hypercalciuria / Q000503:physiopathology; D006947:Hyperkalemia / Q000235:genetics*; D006973:Hypertension / Q000235:genetics*; D018408:Patch-Clamp Techniques; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology*; D050916:TRPV Cation Channels / Q000502:physiology*; D014982:Xenopus laevis
chemical_list: D050916:TRPV Cation Channels; C492239:TRPV5 protein, human; D017346:Protein Serine-Threonine Kinases; C433806:WNK4 protein, human; D002118:Calcium