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XB-ART-51535
J Am Soc Nephrol 2015 Aug 01;268:1781-6. doi: 10.1681/ASN.2014050470.
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The Effect of WNK4 on the Na+-Cl- Cotransporter Is Modulated by Intracellular Chloride.

Bazúa-Valenti S , Chávez-Canales M , Rojas-Vega L , González-Rodríguez X , Vázquez N , Rodríguez-Gama A , Argaiz ER , Melo Z , Plata C , Ellison DH , García-Valdés J , Hadchouel J , Gamba G .


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It is widely recognized that the phenotype of familial hyperkalemic hypertension is mainly a consequence of increased activity of the renal Na(+)-Cl(-) cotransporter (NCC) because of altered regulation by with no-lysine-kinase 1 (WNK1) or WNK4. The effect of WNK4 on NCC, however, has been controversial because both inhibition and activation have been reported. It has been recently shown that the long isoform of WNK1 (L-WNK1) is a chloride-sensitive kinase activated by a low Cl(-) concentration. Therefore, we hypothesized that WNK4 effects on NCC could be modulated by intracellular chloride concentration ([Cl(-)]i), and we tested this hypothesis in oocytes injected with NCC cRNA with or without WNK4 cRNA. At baseline in oocytes, [Cl(-)]i was near 50 mM, autophosphorylation of WNK4 was undetectable, and NCC activity was either decreased or unaffected by WNK4. A reduction of [Cl(-)]i, either by low chloride hypotonic stress or coinjection of oocytes with the solute carrier family 26 (anion exchanger)-member 9 (SLC26A9) cRNA, promoted WNK4 autophosphorylation and increased NCC-dependent Na(+) transport in a WNK4-dependent manner. Substitution of the leucine with phenylalanine at residue 322 of WNK4, homologous to the chloride-binding pocket in L-WNK1, converted WNK4 into a constitutively autophosphorylated kinase that activated NCC, even without chloride depletion. Elimination of the catalytic activity (D321A or D321K-K186D) or the autophosphorylation site (S335A) in mutant WNK4-L322F abrogated the positive effect on NCC. These observations suggest that WNK4 can exert differential effects on NCC, depending on the intracellular chloride concentration.

???displayArticle.pubmedLink??? 25542968
???displayArticle.pmcLink??? PMC4520168
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Species referenced: Xenopus laevis
Genes referenced: slc12a3 slc26a9 wnk1 wnk4
GO keywords: chloride channel activity [+]

???displayArticle.disOnts??? pseudohypoaldosteronism
???displayArticle.omims??? PSEUDOHYPOALDOSTERONISM, TYPE IIA; PHA2A
References [+] :
Beck, The distribution of potassium, sodium and chloride across the apical membrane of renal tubular cells: effect of acute metabolic alkalosis. 1988, Pubmed