title: Regulation of the delta and alpha epithelial sodium channel (ENaC) by ubiquitination and Nedd8.
abstract: The δ epithelial sodium channel (δENaC) is a proton-activated, sodium-selective, amiloride-sensitive ion channel in the ENaC/degenerin family of ion channels involved in blood pressure regulation and mechanosensation. Other ENaC family members are subject to ubiquitin modification leading to internalization from the cell surface, and degradation of the channel. Here, we show that δENaC is also modified by ubiquitin on three intracellular lysine residues. Absence of these lysines abolished ubiquitin modification of δENaC and increased cell surface levels of δENaC. Although the HECT-domain ubiquitin ligase Nedd4-2 reduced amiloride-sensitive current generated by δβγENaC-containing channels, δENaC does not contain a binding site for Nedd4-2; therefore, this effect is probably mediated by the βγENaC subunits. Nedd8, a ubiquitin-like protein that regulates RING-domain E3 ubiquitin ligases, promoted δENaC ubiquitination, decreased both the intracellular and cell surface δENaC populations, and decreased δβγENaC amiloride-sensitive short circuit current (Isc -amiloride) in a mammalian epithelium. Nedd8 also promoted α- and γENaC ubiquitination, decreased the cell surface pools, and decreased αβγENaC Isc -amiloride. Conversely, XIAP, a single subunit RING E3 ligase, decreased ubiquitinated δENaC, increased the δENaC cell surface pool and increased δβγENaC Isc -amiloride. Therefore δ- and α - βγENaC channel function may be influenced by RING-domain E3 ubiquitin ligases.
authors.affiliation: Department of Physiology, University of Otago, Dunedin, New Zealand.
authors.forename: Kevin
authors.initials: K
authors.lastname: L Y
authors.forename: C Joy
authors.initials: CJ
authors.lastname: McIntosh
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Biasio
authors.forename: Yongfeng
authors.initials: Y
authors.lastname: Liu
authors.forename: Ying
authors.initials: Y
authors.lastname: Ke
authors.forename: Diane R
authors.initials: DR
authors.lastname: Olson
authors.forename: John H
authors.initials: JH
authors.lastname: Miller
authors.forename: Rachel
authors.initials: R
authors.lastname: Page
authors.forename: Peter M
authors.initials: PM
authors.lastname: Snyder
authors.forename: Fiona J
authors.initials: FJ
authors.lastname: McDonald
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000378:metabolism; D019556:COS Cells; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002522:Chlorocebus aethiops; D003600:Cytosol / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D053503:Epithelial Sodium Channels / Q000378:metabolism*; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D008239:Lysine / Q000378:metabolism; D050505:Mutant Proteins / Q000378:metabolism; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D021122:Protein Subunits / Q000378:metabolism; D051381:Rats; D015222:Sodium Channels / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*; D054875:Ubiquitination / Q000187:drug effects; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism; D014981:Xenopus
chemical_list: D053503:Epithelial Sodium Channels; D050505:Mutant Proteins; D021122:Protein Subunits; D015222:Sodium Channels; D025801:Ubiquitin; D051636:X-Linked Inhibitor of Apoptosis Protein; D000584:Amiloride; D001120:Arginine; D008239:Lysine