title: 14-3-3 proteins modulate the expression of epithelial Na+ channels by phosphorylation-dependent interaction with Nedd4-2 ubiquitin ligase.
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.
authors.affiliation: Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Hachioji-shi, Tokyo 192-0397, Japan. ichimura@mial.comp.metro-u.ac.jp
authors.forename: Tohru
authors.initials: T
authors.lastname: Ichimura
authors.forename: Hisao
authors.initials: H
authors.lastname: Yamamura
authors.forename: Kaname
authors.initials: K
authors.lastname: Sasamoto
authors.forename: Yuri
authors.initials: Y
authors.lastname: Tominaga
authors.forename: Masato
authors.initials: M
authors.lastname: Taoka
authors.forename: Kazue
authors.initials: K
authors.lastname: Kakiuchi
authors.forename: Takashi
authors.initials: T
authors.lastname: Shinkawa
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Takahashi
authors.forename: Shoichi
authors.initials: S
authors.lastname: Shimada
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Isobe
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D002384:Catalysis; D002417:Cattle; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004594:Electrophysiology; D056827:Endosomal Sorting Complexes Required for Transport; D053503:Epithelial Sodium Channels; D005799:Genes, Dominant; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D017874:Immediate-Early Proteins; D000075702:Nedd4 Ubiquitin Protein Ligases; D009687:Nuclear Proteins / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism; D016716:PC12 Cells; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats; D012694:Serine / Q000737:chemistry; D016622:Silver Staining; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000737:chemistry*; D013997:Time Factors; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D014981:Xenopus; D029867:Xenopus Proteins; D014982:Xenopus laevis; D000099184:Serum-Glucocorticoid Regulated Kinases
chemical_list: D048948:14-3-3 Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D053503:Epithelial Sodium Channels; D005982:Glutathione Transferase; D017874:Immediate-Early Proteins; D000075702:Nedd4 Ubiquitin Protein Ligases; D009687:Nuclear Proteins; D010744:Phosphoric Monoester Hydrolases; D017346:Protein Serine-Threonine Kinases; D012694:Serine; D012964:Sodium; D015222:Sodium Channels; D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases; D029867:Xenopus Proteins; D000099184:Serum-Glucocorticoid Regulated Kinases; C000618479:NEDD4L protein, rat; C000618482:Nedd4 protein, Xenopus; C000618483:Nedd4 protein, human; C000618484:Nedd4 protein, rat; C000618485:Nedd4L protein, human; C000618460:nedd4l protein, Xenopus