title: Identification of Murr1 as a regulator of the human delta epithelial sodium channel.
abstract: The human delta epithelial sodium channel (deltaENaC) subunit is related to the alpha-, beta-, and gammaENaC subunits that control salt homeostasis. DeltaENaC forms an amiloride-sensitive Na+ channel with the beta and gamma subunits. However, the in vivo function of deltaENaC is not known. To gain insight into the function of deltaENaC, a yeast two-hybrid screen of a human brain cDNA library was carried out using the C- and N-terminal domains of deltaENaC. A novel deltaENaC-interacting protein called Murr1 (mouse U2af1-rs1 region) was isolated in the C-terminal domain screen. Murr1 is a 21-kDa protein mutated in Bedlington terriers suffering from copper toxicosis. The interaction of Murr1 and deltaENaC was confirmed by glutathione S-transferase pulldown assay and coimmunoprecipitation. To test the functional significance of the interaction, Murr1 was coexpressed with deltabetagammaENaC in Xenopus oocytes. Murr1 inhibited amiloride-sensitive sodium current in a dose-dependent manner. In addition, deletion of the last 59 amino acids of deltaENaC abolished the inhibition. Murr1 also bound to the beta- and gammaENaC subunits and inhibited alphabetagammaENaC sodium current. Therefore, these results suggest that Murr1 is a novel regulator of ENaC.
authors.affiliation: Department of Physiology, University of Otago, Dunedin 9001, New Zealand.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Biasio
authors.forename: Tina
authors.initials: T
authors.lastname: Chang
authors.forename: C Joy
authors.initials: CJ
authors.lastname: McIntosh
authors.forename: Fiona J
authors.initials: FJ
authors.lastname: McDonald
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000584:Amiloride / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D019556:COS Cells; D002352:Carrier Proteins; D003300:Copper / Q000737:chemistry; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D053503:Epithelial Sodium Channels; D017353:Gene Deletion; D015723:Gene Library; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D012964:Sodium / Q000737:chemistry; D015222:Sodium Channels / Q000737:chemistry*; D014162:Transfection; D020798:Two-Hybrid System Techniques; D014981:Xenopus
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C480519:COMMD1 protein, human; D002352:Carrier Proteins; D018076:DNA, Complementary; D053503:Epithelial Sodium Channels; D011506:Proteins; D015222:Sodium Channels; D003300:Copper; D000584:Amiloride; D012964:Sodium; D005982:Glutathione Transferase