Abstract
The ubiquitin E3 protein ligase Nedd4-2 is a physiological regulator of the epithelial sodium channel ENaC, which is essential for transepithelial Na+ transport and is linked to Liddle's syndrome, an autosomal dominant disorder of human salt-sensitive hypertension. Nedd4-2 function is negatively regulated by phosphorylation via a serum- and glucocorticoid-inducible protein kinase (Sgk1), which serves as a mechanism to inhibit the ubiquitination-dependent degradation of ENaC. We report here that 14-3-3 proteins participate in this regulatory process through a direct interaction with a phosphorylated form of human Nedd4-2 (a human gene product of KIAA0439, termed hNedd4-2). The interaction is dependent on Sgk1-catalyzed phosphorylation of hNedd4-2 at Ser-468. We found that this interaction preserved the activity of the Sgk1-stimulated ENaC-dependent Na+ current while disrupting the interaction decreased ENaC density on the Xenopus laevis oocytes surface possibly by enhancing Nedd4-2-mediated ubiquitination that leads to ENaC degradation. Our findings suggest that 14-3-3 proteins modulate the cell surface density of ENaC cooperatively with Sgk1 kinase by maintaining hNedd4-2 in an inactive phosphorylated state.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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14-3-3 Proteins / metabolism
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14-3-3 Proteins / physiology*
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Animals
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Catalysis
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Cattle
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Cell Line
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Cell Membrane / metabolism
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Electrophoresis, Polyacrylamide Gel
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Electrophysiology
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Endosomal Sorting Complexes Required for Transport
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Epithelial Sodium Channels
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Genes, Dominant
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Glutathione Transferase / metabolism
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Humans
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Immediate-Early Proteins
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Nedd4 Ubiquitin Protein Ligases
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Nuclear Proteins / metabolism
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Oocytes / metabolism
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PC12 Cells
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Phosphoric Monoester Hydrolases / metabolism
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Phosphorylation
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Plasmids / metabolism
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Protein Binding
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Protein Serine-Threonine Kinases / metabolism
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Rats
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Serine / chemistry
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Silver Staining
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Sodium / metabolism
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Sodium Channels / chemistry*
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Time Factors
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Ubiquitin / metabolism
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Ubiquitin-Protein Ligases / metabolism*
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Xenopus
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Xenopus Proteins
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Xenopus laevis
Substances
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14-3-3 Proteins
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Endosomal Sorting Complexes Required for Transport
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Epithelial Sodium Channels
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Immediate-Early Proteins
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Nuclear Proteins
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Sodium Channels
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Ubiquitin
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Xenopus Proteins
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Serine
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Sodium
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NEDD4L protein, rat
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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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Nedd4 protein, rat
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Nedd4L protein, human
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nedd4l protein, Xenopus
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Ubiquitin-Protein Ligases
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Glutathione Transferase
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Protein Serine-Threonine Kinases
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serum-glucocorticoid regulated kinase
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Phosphoric Monoester Hydrolases