title: WNK4 inhibition of ENaC is independent of Nedd4-2-mediated ENaC ubiquitination.
abstract: A serine-threonine protein kinase, WNK4, reduces Na⁺ reabsorption and K⁺ secretion in the distal convoluted tubule by reducing trafficking of the thiazide-sensitive Na-Cl cotransporter to and enhancing renal outer medullary potassium channel retrieval from the apical membrane. Epithelial sodium channels (ENaC) in the distal nephron also play a role in regulating Na⁺ reabsorption and are also regulated by WNK4, but the mechanism is unclear. In A6 distal nephron cells, transepithelial current measurement and single channel recording show that WNK4 inhibits ENaC activity. Analysis of the number of channel per patch shows that WNK4 reduces channel number but has no effect on channel open probability. Western blots of apical and total ENaC provide additional evidence that WNK4 reduces apical as well as total ENaC expression. WNK4 enhances ENaC internalization independent of Nedd4-2-mediated ENaC ubiquitination. WNK4 also reduced the amount of ENaC available for recycling but has no effect on the rate of transepithelial current increase to forskolin. In contrast, Nedd4-2 not only reduced ENaC in the recycling pool but also decreased the rate of increase of current after forskolin. WNK4 associates with wild-type as well as Liddle's mutated ENaC, and WNK4 reduces both wild-type and mutated ENaC expressed in HEK293 cells.
authors.affiliation: Center for Cell and Molecular Signaling, Department of Physiology, Emory University School of Medicine, Atlanta, GA, USA. lyu@njau.edu.cn
authors.forename: Ling
authors.initials: L
authors.lastname: Yu
authors.forename: Hui
authors.initials: H
authors.lastname: Cai
authors.forename: Qian
authors.initials: Q
authors.lastname: Yue
authors.forename: Abdel A
authors.initials: AA
authors.lastname: Alli
authors.forename: DeXuan
authors.initials: D
authors.lastname: Wang
authors.forename: Otor
authors.initials: O
authors.lastname: Al-Khalili
authors.forename: Hui-Fang
authors.initials: HF
authors.lastname: Bao
authors.forename: Douglas C
authors.initials: DC
authors.lastname: Eaton
mesh_terms: D000818:Animals; D015153:Blotting, Western; D005576:Colforsin / Q000494:pharmacology; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics / Q000378:metabolism*; D053503:Epithelial Sodium Channels / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008564:Membrane Potentials; D009154:Mutation; D000075702:Nedd4 Ubiquitin Protein Ligases; D009399:Nephrons / Q000187:drug effects / Q000201:enzymology*; D018408:Patch-Clamp Techniques; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D013997:Time Factors; D014162:Transfection; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination; D029867:Xenopus Proteins / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D056827:Endosomal Sorting Complexes Required for Transport; D053503:Epithelial Sodium Channels; C507045:SCNN1A protein, human; C507048:SCNN1B protein, human; C507052:SCNN1G protein, human; D029867:Xenopus Proteins; D005576:Colforsin; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618482:Nedd4 protein, Xenopus; C000618483:Nedd4 protein, human; C000618485:Nedd4L protein, human; C000618460:nedd4l protein, Xenopus; D044767:Ubiquitin-Protein Ligases; D017346:Protein Serine-Threonine Kinases; C433806:WNK4 protein, human
keywords: ENaC; Nedd4-2; WNK4; ubiquitination