Identification of Murr1 as a Regulator of the Human δ Epithelial Sodium Channel

• Published in: The Journal of biological chemistry 2004-02, Vol.279 (7), p.5429-5434
• Main Authors: Biasio, Wolfgang, Chang, Tina, McIntosh, C. Joy, McDonald, Fiona J.
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing; Amiloride - pharmacology; Amino Acid Sequence; Animals; Blotting, Western; Brain - metabolism; Carrier Proteins; Copper - chemistry; COS Cells; DNA, Complementary - metabolism; Dose-Response Relationship, Drug; Epithelial Sodium Channels; Gene Deletion; Gene Library; Glutathione Transferase - metabolism; Humans; Models, Genetic; Molecular Sequence Data; Oocytes - metabolism; Patch-Clamp Techniques; Plasmids - metabolism; Precipitin Tests; Protein Structure, Tertiary; Proteins - metabolism; Proteins - physiology; Sequence Homology, Amino Acid; Sodium - chemistry; Sodium Channels - chemistry; Transfection; Two-Hybrid System Techniques; Xenopus
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M311155200

The human δ epithelial sodium channel (δENaC) subunit is related to the α-, β-, and γENaC subunits that control salt homeostasis. δENaC forms an amiloride-sensitive Na+ channel with the β and γ subunits. However, the in vivo function of δENaC is not known. To gain insight into the function of δENaC, a yeast two-hybrid screen of a human brain cDNA library was carried out using the C- and N-terminal domains of δENaC. A novel δENaC-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 δENaC was confirmed by glutathione S-transferase pulldown assay and coimmunoprecipitation. To test the functional significance of the interaction, Murr1 was coexpressed with δβγENaC in Xenopus oocytes. Murr1 inhibited amiloride-sensitive sodium current in a dose-dependent manner. In addition, deletion of the last 59 amino acids of δENaC abolished the inhibition. Murr1 also bound to the β- and γENaC subunits and inhibited αβγENaC sodium current. Therefore, these results suggest that Murr1 is a novel regulator of ENaC.