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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Motifs
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Amino Acid Sequence
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Animals
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Base Sequence
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Binding Sites
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COS Cells / metabolism
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Calcium-Binding Proteins / genetics*
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Calcium-Binding Proteins / metabolism*
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Cloning, Molecular
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Dogs
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Endosomal Sorting Complexes Required for Transport
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Epithelial Sodium Channels
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Humans
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Ligases*
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Molecular Sequence Data
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Nedd4 Ubiquitin Protein Ligases
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Oocytes / metabolism
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RNA, Messenger
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Sequence Homology, Amino Acid
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Sodium Channels / metabolism*
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Ubiquitin-Protein Ligases*
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Xenopus
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Xenopus Proteins
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src Homology Domains
Substances
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Calcium-Binding Proteins
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Endosomal Sorting Complexes Required for Transport
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Epithelial Sodium Channels
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RNA, Messenger
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Recombinant Proteins
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Sodium Channels
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Xenopus Proteins
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Nedd4 Ubiquitin Protein Ligases
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Nedd4 protein, Xenopus
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Nedd4 protein, human
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nedd4l protein, Xenopus
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Ubiquitin-Protein Ligases
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Ligases