title: WNK2 kinase is a novel regulator of essential neuronal cation-chloride cotransporters.
abstract: NKCC1 and KCC2, related cation-chloride cotransporters (CCC), regulate cell volume and γ-aminobutyric acid (GABA)-ergic neurotranmission by modulating the intracellular concentration of chloride [Cl(-)]. These CCCs are oppositely regulated by serine-threonine phosphorylation, which activates NKCC1 but inhibits KCC2. The kinase(s) that performs this function in the nervous system are not known with certainty. WNK1 and WNK4, members of the WNK (with no lysine [K]) kinase family, either directly or via the downstream SPAK/OSR1 Ste20-type kinases, regulate the furosemide-sensitive NKCC2 and the thiazide-sensitive NCC, kidney-specific CCCs. What role the novel WNK2 kinase plays in this regulatory cascade, if any, is unknown. Here, we show that WNK2, unlike other WNKs, is not expressed in kidney; rather, it is a neuron-enriched kinase primarily expressed in neocortical pyramidal cells, thalamic relay cells, and cerebellar granule and Purkinje cells in both the developing and adult brain. Bumetanide-sensitive and Cl(-)-dependent (86)Rb(+) uptake assays in Xenopus laevis oocytes revealed that WNK2 promotes Cl(-) accumulation by reciprocally activating NKCC1 and inhibiting KCC2 in a kinase-dependent manner, effectively bypassing normal tonicity requirements for cotransporter regulation. TiO(2) enrichment and tandem mass spectrometry studies demonstrate WNK2 forms a protein complex in the mammalian brain with SPAK, a known phosphoregulator of NKCC1. In this complex, SPAK is phosphorylated at Ser-383, a consensus WNK recognition site. These findings suggest a role for WNK2 in the regulation of CCCs in the mammalian brain, with implications for both cell volume regulation and/or GABAergic signaling.
authors: Department of Genetics, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
authors: Jesse
authors: J
authors: Rinehart
authors: Norma
authors: N
authors: Vázquez
authors: Kristopher T
authors: KT
authors: Kahle
authors: Caleb A
authors: CA
authors: Hodson
authors: Aaron M
authors: AM
authors: Ring
authors: Erol E
authors: EE
authors: Gulcicek
authors: Angeliki
authors: A
authors: Louvi
authors: Norma A
authors: NA
authors: Bobadilla
authors: Gerardo
authors: G
authors: Gamba
authors: Richard P
authors: RP
authors: Lifton
mesh_terms: D000818:Animals; D048429:Cell Size; D006801:Humans; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011689:Purkinje Cells / Q000378:metabolism*; D017966:Pyramidal Cells / Q000378:metabolism*; D028021:Sodium-Potassium-Chloride Symporters / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D046912:Multiprotein Complexes; D009419:Nerve Tissue Proteins; D028021:Sodium-Potassium-Chloride Symporters; C523482:WNK2 protein, human; D017346:Protein Serine-Threonine Kinases