title: WNK3-SPAK interaction is required for the modulation of NCC and other members of the SLC12 family.
abstract: The serine/threonine with no lysine kinase 3 (WNK3) modulates the activity of the electroneutral cation-coupled chloride cotransporters (CCC) to promote Cl(-) influx and prevent Cl(-) efflux, thus fitting the profile for a putative "Cl(-)-sensing kinase". The Ste20-type kinases, SPAK/OSR1, become phosphorylated in response to reduction in intracellular chloride concentration and regulate the activity of NKCC1. Several studies have now shown that WNKs function upstream of SPAK/OSR1. This study was designed to analyze the role of WNK3-SPAK interaction in the regulation of CCCs with particular emphasis on NCC. In this study we used the functional expression system of Xenopus laevis oocytes to show that different SPAK binding sites in WNK3 ((241, 872, 1336)RFxV) are required for the kinase to have effects on CCCs. WNK3-F1337A no longer activated NKCC2, but the effects on NCC, NKCC1, and KCC4 were preserved. In contrast, the effects of WNK3 on these cotransporters were prevented in WNK3-F242A. The elimination of F873 had no consequence on WNK3 effects. WNK3 promoted NCC phosphorylation at threonine 58, even in the absence of the unique SPAK binding site of NCC, but this effect was abolished in the mutant WNK3-F242A. Thus, our data support the hypothesis that the effects of WNK3 upon NCC and other CCCs require the interaction and activation of the SPAK kinase. The effect is dependent on one of the three binding sites for SPAK that are present in WNK3, but not on the SPAK binding sites on the CCCs, which suggests that WNK3 is capable of binding both SPAK and CCCs to promote their phosphorylation.
authors.affiliation: Escuela de Medicina, Universidad Panamericana, Mexico City, Mexico.
authors.forename: Diana
authors.initials: D
authors.lastname: Pacheco-Alvarez
authors.forename: Norma
authors.initials: N
authors.lastname: Vázquez
authors.forename: María
authors.initials: M
authors.lastname: Castañeda-Bueno
authors.forename: Paola
authors.initials: P
authors.lastname: de-Los-Heros
authors.forename: César
authors.initials: C
authors.lastname: Cortes-González
authors.forename: Erika
authors.initials: E
authors.lastname: Moreno
authors.forename: Patricia
authors.initials: P
authors.lastname: Meade
authors.forename: Norma A
authors.initials: NA
authors.lastname: Bobadilla
authors.forename: Gerardo
authors.initials: G
authors.lastname: Gamba
mesh_terms: D000818:Animals; D001665:Binding Sites; D057809:HEK293 Cells; D006801:Humans; D009154:Mutation; D009865:Oocytes / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D049992:Sodium Chloride Symporters / Q000378:metabolism*; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism*; D014982:Xenopus laevis / Q000254:growth & development / Q000378:metabolism
chemical_list: D049992:Sodium Chloride Symporters; D028021:Sodium-Potassium-Chloride Symporters; D017346:Protein Serine-Threonine Kinases; C486409:STK39 protein, human; C488586:WNK3 protein, human