title: WNK3 modulates transport of Cl- in and out of cells: implications for control of cell volume and neuronal excitability.
abstract: The regulation of Cl(-) transport into and out of cells plays a critical role in the maintenance of intracellular volume and the excitability of GABA responsive neurons. The molecular determinants of these seemingly diverse processes are related ion cotransporters: Cl(-) influx is mediated by the Na-K-2Cl cotransporter NKCC1 and Cl(-) efflux via K-Cl cotransporters, KCC1 or KCC2. A Cl(-)/volume-sensitive kinase has been proposed to coordinately regulate these activities via altered phosphorylation of the transporters; phosphorylation activates NKCC1 while inhibiting KCCs, and dephosphorylation has the opposite effects. We show that WNK3, a member of the WNK family of serine-threonine kinases, colocalizes with NKCC1 and KCC1/2 in diverse Cl(-)-transporting epithelia and in neurons expressing ionotropic GABA(A) receptors in the hippocampus, cerebellum, cerebral cortex, and reticular activating system. By expression studies in Xenopus oocytes, we show that kinase-active WNK3 increases Cl(-) influx via NKCC1, and that it inhibits Cl(-) exit through KCC1 and KCC2; kinase-inactive WNK3 has the opposite effects. WNK3's effects are imparted via altered phosphorylation and surface expression of its downstream targets and bypass the normal requirement of altered tonicity for activation of these transporters. Together, these data indicate that WNK3 can modulate the level of intracellular Cl(-) via opposing actions on entry and exit pathways. They suggest that WNK3 is part of the Cl(-)/volume-sensing mechanism necessary for the maintenance of cell volume during osmotic stress and the dynamic modulation of GABA neurotransmission.
authors.affiliation: Department of Genetics, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA.
authors.forename: Kristopher T
authors.initials: KT
authors.lastname: Kahle
authors.forename: Jesse
authors.initials: J
authors.lastname: Rinehart
authors.forename: Paola
authors.initials: P
authors.lastname: de Los Heros
authors.forename: Angeliki
authors.initials: A
authors.lastname: Louvi
authors.forename: Patricia
authors.initials: P
authors.lastname: Meade
authors.forename: Norma
authors.initials: N
authors.lastname: Vazquez
authors.forename: Steven C
authors.initials: SC
authors.lastname: Hebert
authors.forename: Gerardo
authors.initials: G
authors.lastname: Gamba
authors.forename: Ignacio
authors.initials: I
authors.lastname: Gimenez
authors.forename: Richard P
authors.initials: RP
authors.lastname: Lifton
mesh_terms: D000818:Animals; D048429:Cell Size; D002712:Chlorides / Q000378:metabolism*; D017403:In Situ Hybridization; D017136:Ion Transport / Q000502:physiology*; D051379:Mice; D009474:Neurons / Q000502:physiology*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*
chemical_list: D002712:Chlorides; D017346:Protein Serine-Threonine Kinases; C000592126:WNK3 protein, Xenopus; C507511:Wnk3 protein, mouse