title: A novel Ste20-related proline/alanine-rich kinase (SPAK)-independent pathway involving calcium-binding protein 39 (Cab39) and serine threonine kinase with no lysine member 4 (WNK4) in the activation of Na-K-Cl cotransporters.
abstract: Na(+)-dependent chloride cotransporters (NKCC1, NKCC2, and NCC) are activated by phosphorylation to play critical roles in diverse physiological responses, including renal salt balance, hearing, epithelial fluid secretion, and volume regulation. Serine threonine kinase WNK4 (With No K = lysine member 4) and members of the Ste20 kinase family, namely SPAK and OSR1 (Ste20-related proline/alanine-rich kinase, Oxidative stress-responsive kinase) govern phosphorylation. According to present understanding, WNK4 phosphorylates key residues within SPAK/OSR1 leading to kinase activation, allowing SPAK/OSR1 to bind to and phosphorylate NKCC1, NKCC2, and NCC. Recently, the calcium-binding protein 39 (Cab39) has emerged as a binding partner and enhancer of SPAK/OSR1 activity, facilitating kinase autoactivation and promoting phosphorylation of the cotransporters. In the present study, we provide evidence showing that Cab39 differentially interacts with WNK4 and SPAK/OSR1 to switch the classic two kinase cascade into a signal kinase transduction mechanism. We found that WNK4 in association with Cab39 activates NKCC1 in a SPAK/OSR1-independent manner. We discovered that WNK4 possesses a domain that bears close resemblance to the SPAK/OSR1 C-terminal CCT/PF2 domain, which is required for physical interaction between the Ste20 kinases and the Na(+)-driven chloride cotransporters. Modeling, yeast two-hybrid, and functional data reveal that this PF2-like domain located downstream of the catalytic domain in WNK4 promotes the direct interaction between the kinase and NKCC1. We conclude that in addition to SPAK and OSR1, WNK4 is able to anchor itself to the N-terminal domain of NKCC1 and to promote cotransporter activation.
authors.affiliation: From the Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232 and.
authors.forename: Jose
authors.initials: J
authors.lastname: Ponce-Coria
authors.affiliation: From the Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232 and.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Markadieu
authors.affiliation: From the Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232 and.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Austin
authors.affiliation: From the Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232 and.
authors.forename: Lindsey
authors.initials: L
authors.lastname: Flammang
authors.affiliation: From the Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232 and.
authors.forename: Kerri
authors.initials: K
authors.lastname: Rios
authors.affiliation: the Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Welling
authors.affiliation: From the Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232 and eric.delpire@vanderbilt.edu.
authors.forename: Eric
authors.initials: E
authors.lastname: Delpire
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D064506:Solute Carrier Family 12, Member 2 / Q000235:genetics / Q000378:metabolism*
chemical_list: C000622396:Cab39 protein, rat; D002135:Calcium-Binding Proteins; C578878:Slc12a2 protein, mouse; C578879:Slc12a2 protein, rat; D064506:Solute Carrier Family 12, Member 2; D011494:Protein Kinases; C499024:Prkwnk4 protein, mouse; C486407:Stk39 protein, mouse; C499025:Wnk4 protein, rat; C116037:PAS domain kinases; C534421:OXSR1 protein, mouse; C506604:Oxsr1 protein, rat; D017346:Protein Serine-Threonine Kinases
keywords: Adaptor Protein; Chloride Transport; Membrane Transport; Protein Kinase; Sodium Transport