title: Protein phosphatase 1 modulates the inhibitory effect of With-no-Lysine kinase 4 on ROMK channels.
abstract: With-no-Lysine kinase 4 (WNK4) inhibited ROMK (Kir1.1) channels and the inhibitory effect of WNK4 was abolished by serum-glucocorticoid-induced kinase 1 (SGK1) but restored by c-Src. The aim of the present study is to explore the mechanism by which Src-family tyrosine kinase (SFK) modulates the effect of SGK1 on WNK4 and to test the role of SFK-WNK4-SGK1 interaction in regulating ROMK channels in the kidney. Immunoprecipitation demonstrated that protein phosphatase 1 (PP1) binds to WNK4 at amino acid (aa) residues 695-699 (PP1(#1)) and at aa 1211-1215 (PP1(#2)). WNK4(-PP1#1) and WNK4(-PP1#2), in which the PP1(#1) or PP1(#2) binding site was deleted or mutated, inhibited ROMK channels as potently as WNK4. However, c-Src restored the inhibitory effect of WNK4 but not WNK4(-PP1#1) on ROMK channels in the presence of SGK1. Moreover, expression of c-Src inhibited SGK1-induced phosphorylation of WNK4 but not WNK4(-PP1#1) at serine residue 1196 (Ser(1196)). In contrast, coexpression of c-Src restored the inhibitory effect of WNK4(-PP1#2) on ROMK in the presence of SGK1 and diminished SGK1-induced WNK4 phosphorylation at Ser(1196) in cells transfected with WNK4(-PP1#2). This suggests the possibility that c-Src regulates the interaction between WNK4 and SGK1 through activating PP1 binding to aa 695-9 thereby decreasing WNK4 phosphorylation and restoring the inhibitory effect of WNK4. This mechanism plays a role in suppressing ROMK channel activity during the volume depletion because inhibition of SFK or serine/threonine phosphatases increases ROMK channel activity in the cortical collecting duct of rats on a low-Na diet. We conclude that regulation of phosphatase activity by SFK plays a role in determining the effect of aldosterone on ROMK channels and on renal K secretion.
authors.affiliation: Department of Pharmacology, New York Medical College, Valhalla, New York 10595, USA.
authors.forename: Dao-Hong
authors.initials: DH
authors.lastname: Lin
authors.forename: Peng
authors.initials: P
authors.lastname: Yue
authors.forename: Jesse
authors.initials: J
authors.lastname: Rinehart
authors.forename: Peng
authors.initials: P
authors.lastname: Sun
authors.forename: Zhijian
authors.initials: Z
authors.lastname: Wang
authors.forename: Richard
authors.initials: R
authors.lastname: Lifton
authors.forename: Wen-Hui
authors.initials: WH
authors.lastname: Wang
mesh_terms: D000818:Animals; D057809:HEK293 Cells; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism; D007668:Kidney / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000378:metabolism; D008297:Male; D010766:Phosphorylation; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism*; D054645:Protein Phosphatase 1 / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014162:Transfection; D019061:src-Family Kinases / Q000378:metabolism; D000099184:Serum-Glucocorticoid Regulated Kinases
chemical_list: D017874:Immediate-Early Proteins; D024661:Potassium Channels, Inwardly Rectifying; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases; D019061:src-Family Kinases; D000099184:Serum-Glucocorticoid Regulated Kinases; C086989:KCNJ1 protein, human; C571352:ROMK2 protein, human; C433806:WNK4 protein, human