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lüll WNK4 enhances TRPV5-mediated calcium transport: potential role in hypercalciuria of familial hyperkalemic hypertension caused by gene mutation of WNK4 Jiang Y; Ferguson WB; Peng JBAm J Physiol Renal Physiol 2007[Feb]; 292 (2): F545-54The 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.|Animals[MESH]|Calcium/*metabolism/urine[MESH]|Humans[MESH]|Hypercalciuria/physiopathology[MESH]|Hyperkalemia/*genetics[MESH]|Hypertension/*genetics[MESH]|Patch-Clamp Techniques[MESH]|Protein Serine-Threonine Kinases/genetics/*physiology[MESH]|TRPV Cation Channels/*physiology[MESH]|Xenopus laevis[MESH] |