title: Phosphoregulation of K+-Cl-cotransporters during cell swelling: Novel insights.
abstract: The K+-Cl-cotransporters (KCCs) belong to the cation-Cl-cotransporter family and consist of four isoforms and many splice variants. Their main role is to promote electroneutral efflux of K+and Cl-ions across the surface of many cell types and, thereby, to regulate intracellular ion concentration, cell volume, and epithelial salt movement. These transport systems are induced by an increase in cell volume and are less active at lower intracellular [Cl-] (Cli), but the mechanisms at play are still ill-defined. In this work, we have exploited the Xenopus laevis expression system to study the role of lysine-deficient protein kinases (WNKs), protein phosphatases 1 (PP1s), and SPS1-related proline/alanine-rich kinase (SPAK) in KCC4 regulation during cell swelling. We have found that WNK4 and PP1 regulate KCC4 activity as part of a common signaling module, but that they do not exert their effects through SPAK or carrier dephosphorylation. We have also found that the phosphatases at play include PP1α and PP1γ1, but that WNK4 acts directly on the PP1s instead of the opposite. Unexpectedly, however, both cell swelling and a T926A substitution in the C-terminus of full-length KCC4 led to higher levels of heterologous K+-Cl-cotransport and overall carrier phosphorylation. These results imply that the response to cell swelling must also involve allosteric-sensitive kinase-dependent phosphoacceptor sites in KCC4. They are thus partially inconsistent with previous models of KCC regulation.
authors.affiliation: Nephrology Research Group, Department of Medicine, Laval University, Québec, Québec, Canada.
authors.forename: Rachelle
authors.initials: R
authors.lastname: Frenette-Cotton
authors.affiliation: Nephrology Research Group, Department of Medicine, Laval University, Québec, Québec, Canada.
authors.forename: Andrée-Anne
authors.initials: AA
authors.lastname: Marcoux
authors.affiliation: Nephrology Research Group, Department of Medicine, Laval University, Québec, Québec, Canada.
authors.forename: Alexandre P
authors.initials: AP
authors.lastname: Garneau
authors.affiliation: Nephrology Research Group, Department of Medicine, Laval University, Québec, Québec, Canada.
authors.forename: Micheline
authors.initials: M
authors.lastname: Noel
authors.affiliation: Nephrology Research Group, Department of Medicine, Laval University, Québec, Québec, Canada.
authors.forename: Paul
authors.identifier: http://orcid.org/0000-0002-4544-2107
authors.initials: P
authors.lastname: Isenring
mesh_terms: D000818:Animals; D048429:Cell Size / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008387:Marine Toxins; D009154:Mutation; D010080:Oxazoles / Q000494:pharmacology; D010766:Phosphorylation; D054645:Protein Phosphatase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D027981:Symporters / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis; D000096922:K Cl- Cotransporters
chemical_list: D004791:Enzyme Inhibitors; D008387:Marine Toxins; D010080:Oxazoles; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases; D027981:Symporters; D000096922:K Cl- Cotransporters; C492282:Slc12a7 protein, mouse; C059041:calyculin A; C499024:Prkwnk4 protein, mouse
keywords: K+-Cl− cotransporters; cation-Cl− cotransporters; lysine-deficient protein kinases; membrane transport; protein phosphatase 1