COMMD1 downregulates the epithelial sodium channel through Nedd4-2.
The epithelial sodium channel (ENaC) is important for the long-term control of Na(+) homeostasis and blood pressure. Our previous studies demonstrated that Copper Metabolism Murr1 Domain-containing protein 1 (COMMD1; previously known as Murr1), a protein involved in copper metabolism, inhibited amiloride-sensitive current in Xenopus laevis oocytes expressing ENaC (J Biol Chem 279: 5429, 2004). In this study, we report that COMMD1 inhibits amiloride-sensitive current in mammalian epithelial cells expressing ENaC, that the COMM domain of COMMD1 is sufficient for this effect, and that knockdown of COMMD1 increases amiloride-sensitive current. COMMD1 is coexpressed with ENaC in rat kidney medulla cells. COMMD1 increased ubiquitin modification of ENaC and decreased its cell surface expression. COMMD1 abolished insulin-stimulated amiloride-sensitive current and attenuated the stimulation of current by activated serum and glucocorticoid-regulated kinase (SGK1). COMMD1 was found to interact with both SGK1 and Akt1/protein kinase B, and knockdown of COMMD1 enhanced the stimulatory effect of both SGK1 and Akt1 on amiloride-sensitive current. COMMD1's effects were reduced in the presence of ENaC proteins containing PY motif mutations, abolished in the presence of a dominant negative form of Nedd4-2, and knockdown of COMMD1 reduced the inhibitory effect of Nedd4-2 on ENaC, but did not enhance current when Nedd4-2 was knocked down. These data suggest that COMMD1 modulates Na(+) transport in epithelial cells through regulation of ENaC cell surface expression and this effect is likely mediated via Nedd4-2.
Ke
Ying
Y
Department of Physiology, University of Otago, Dunedin, New Zealand.
Butt
A Grant
AG
Swart
Marianne
M
Liu
Yong Feng
YF
McDonald
Fiona J
FJ
D048868:Adaptor Proteins, Signal Transducing; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002522:Chlorocebus aethiops; D015536:Down-Regulation; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism; D007328:Insulin / Q000378:metabolism; D007679:Kidney Medulla / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials; D000075702:Nedd4 Ubiquitin Protein Ligases; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034622:RNA Interference; D051381:Rats; D011916:Rats, Inbred F344; D017208:Rats, Wistar; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D014162:Transfection; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination; D029867:Xenopus Proteins; D000099184:Serum-Glucocorticoid Regulated Kinases
D048868:Adaptor Proteins, Signal Transducing; D000584:Amiloride; D002352:Carrier Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels; D017874:Immediate-Early Proteins; D007328:Insulin; D000075702:Nedd4 Ubiquitin Protein Ligases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D011993:Recombinant Fusion Proteins; D012964:Sodium; D026941:Sodium Channel Blockers; D044767:Ubiquitin-Protein Ligases; D029867:Xenopus Proteins; D000099184:Serum-Glucocorticoid Regulated Kinases; C480519:COMMD1 protein, human; C549962:COMMD1 protein, rat; C440894:Scnn1a protein, rat; C000618479:NEDD4L protein, rat; C000618482:Nedd4 protein, Xenopus; C000618483:Nedd4 protein, human; C000618484:Nedd4 protein, rat; C000618485:Nedd4L protein, human; C000618460:nedd4l protein, Xenopus; C494920:Akt1 protein, rat