title: Human Nedd4 interacts with the human epithelial Na+ channel: WW3 but not WW1 binds to Na+-channel subunits.
abstract: The epithelial Na(+) channel (ENaC) regulates Na(+) absorption in epithelial tissues including the lung, colon and sweat gland, and in the distal nephrons of the kidney. When Na(+)-channel function is disrupted, salt and water homoeostasis is affected. The cytoplasmic regions of the Na(+)-channel subunits provide binding sites for other proteins to interact with and potentially regulate Na(+)-channel activity. Previously we showed that a proline-rich region of the alpha subunit of the Na(+) channel bound to a protein of 116 kDa from human lung cells. Here we report the identification of this protein as human Nedd4, a ubiquitin-protein ligase that binds to the Na(+)-channel subunits via its WW domains. Further, we show that WW domains 2, 3 and 4 of human Nedd4 bind to the alpha, beta and gamma Na(+)-channel subunits but not to a mutated beta subunit. In addition, when co-expressed in Xenopus oocytes, human Nedd4 down-regulates Na(+)-channel activity.
authors.affiliation: School of Biological Sciences, Victoria University, P.O. Box 600, Wellington 6004, New Zealand.
authors.forename: T J
authors.initials: TJ
authors.lastname: Farr
authors.forename: S J
authors.initials: SJ
authors.lastname: Coddington-Lawson
authors.forename: P M
authors.initials: PM
authors.lastname: Snyder
authors.forename: F J
authors.initials: FJ
authors.lastname: McDonald
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D019556:COS Cells / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D004285:Dogs; D056827:Endosomal Sorting Complexes Required for Transport; D053503:Epithelial Sodium Channels; D006801:Humans; D008025:Ligases; D008969:Molecular Sequence Data; D000075702:Nedd4 Ubiquitin Protein Ligases; D009865:Oocytes / Q000378:metabolism; D012333:RNA, Messenger; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015222:Sodium Channels / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases; D014981:Xenopus; D029867:Xenopus Proteins; D018909:src Homology Domains
chemical_list: D002135:Calcium-Binding Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D053503:Epithelial Sodium Channels; D012333:RNA, Messenger; D011994:Recombinant Proteins; D015222:Sodium Channels; D029867:Xenopus Proteins; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618482:Nedd4 protein, Xenopus; C000618483:Nedd4 protein, human; C000618460:nedd4l protein, Xenopus; D044767:Ubiquitin-Protein Ligases; D008025:Ligases