title: Ubiquitin-specific peptidase 8 (USP8) regulates endosomal trafficking of the epithelial Na+ channel.
abstract: Ubiquitination plays a key role in trafficking of the epithelial Na(+) channel (ENaC). Previous work indicated that ubiquitination enhances ENaC endocytosis and sorting to lysosomes for degradation. Moreover, a defect in ubiquitination causes Liddle syndrome, an inherited form of hypertension. In this work, we identified a role for USP8 in the control of ENaC ubiquitination and trafficking. USP8 increased ENaC current in Xenopus oocytes and collecting duct epithelia and enhanced ENaC abundance at the cell surface in HEK 293 cells. This resulted from altered endocytic sorting; USP8 abolished ENaC degradation in the endocytic pathway, but it had no effect on ENaC endocytosis. USP8 interacted with ENaC, as detected by co-immunoprecipitation, and it deubiquitinated ENaC. Consistent with a functional role for deubiquitination, mutation of the cytoplasmic lysines of ENaC reduced the effect of USP8 on ENaC cell surface abundance. In contrast to USP8, USP2-45 increased ENaC surface abundance by reducing endocytosis but not degradation. Thus, USP8 and USP2-45 selectively modulate ENaC trafficking at different steps in the endocytic pathway. Together with previous work, the data indicate that the ubiquitination state of ENaC is critical for the regulation of epithelial Na(+) absorption.
authors.affiliation: Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA.
authors.forename: Ruifeng
authors.initials: R
authors.lastname: Zhou
authors.forename: Vivian R
authors.initials: VR
authors.lastname: Tomkovicz
authors.forename: Phillip L
authors.initials: PL
authors.lastname: Butler
authors.forename: Luis A
authors.initials: LA
authors.lastname: Ochoa
authors.forename: Zerubbabel J
authors.initials: ZJ
authors.lastname: Peterson
authors.forename: Peter M
authors.initials: PM
authors.lastname: Snyder
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D019921:Biotinylation; D002462:Cell Membrane / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004594:Electrophysiology / Q000379:methods; D004705:Endocytosis; D010450:Endopeptidases / Q000502:physiology*; D056827:Endosomal Sorting Complexes Required for Transport / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism*; D053503:Epithelial Sodium Channels / Q000378:metabolism*; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D006973:Hypertension / Q000378:metabolism; D008954:Models, Biological; D009865:Oocytes / Q000378:metabolism; D021381:Protein Transport; D025801:Ubiquitin / Q000378:metabolism; D043222:Ubiquitin Thiolesterase / Q000502:physiology*; D014981:Xenopus
chemical_list: D018076:DNA, Complementary; D056827:Endosomal Sorting Complexes Required for Transport; D053503:Epithelial Sodium Channels; D025801:Ubiquitin; D000584:Amiloride; D010450:Endopeptidases; C541534:USP8 protein, human; D043222:Ubiquitin Thiolesterase