Expression of the kidney anion exchanger 1 affects WNK4 and SPAK phosphorylation and results in claudin-4 phosphorylation
Rawad Lashhab,
Grace Essuman,
Maria Chavez-Canales,
R. Todd Alexander,
Emmanuelle Cordat
Affiliations
Rawad Lashhab
Department of Physiology and Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
Grace Essuman
Department of Physiology and Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
Maria Chavez-Canales
Unidad de Investigación UNAM-INCICh, Instituto Nacional de Cardiología Ignacio Chávez and Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Tlalpan, Mexico City, 14080, Mexico
R. Todd Alexander
Department of Physiology and Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada; Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
Emmanuelle Cordat
Department of Physiology and Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada; Corresponding author. Department of Physiology, Membrane Protein Research Group, Room 7-34, Medical Sciences Building, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada.
In the renal collecting ducts, chloride reabsorption occurs through both transcellular and paracellular pathways. Recent literature highlights a functional interplay between both pathways. We recently showed that in polarized inner medullary collecting duct cells, expression of the basolateral kidney anion exchanger 1 (kAE1) results in a decreased transepithelial electrical resistance (TEER), in a claudin-4 dependent pathway. Claudin-4 is a paracellular sodium blocker and chloride pore. Here, we show that kAE1 expression in mouse inner medullary collecting duct cells triggers WNK4, SPAK and claudin-4 phosphorylation. Expression of a functionally dead kAE1 E681Q mutant has no effect on phosphorylation of these proteins. Expression of a catalytically inactive WNK4 D321A or chloride-insensitive WNK4 L319F mutant abolishes kAE1 effect on TEER, supporting a contribution of WNK4 to the process. We propose that variations of the cytosolic pH and chloride concentration upon kAE1 expression alter WNK4 kinase activity and tight junction properties.
