The activity of the epithelial sodium channels is regulated by caveolin-1 via a Nedd4-2-dependent mechanism.
It has recently been shown that the epithelial Na(+) channel (ENaC) is compartmentalized in caveolin-rich lipid rafts and that pharmacological depletion of membrane cholesterol, which disrupts lipid raft formation, decreases the activity of ENaC. Here we show, for the first time, that a signature protein of caveolae, caveolin-1 (Cav-1), down-regulates the activity and membrane surface expression of ENaC. Physical interaction between ENaC and Cav-1 was also confirmed in a coimmunoprecipitation assay. We found that the effect of Cav-1 on ENaC requires the activity of Nedd4-2, a ubiquitin protein ligase of the Nedd4 family, which is known to induce ubiquitination and internalization of ENaC. The effect of Cav-1 on ENaC requires the proline-rich motifs at the C termini of the beta- and gamma-subunits of ENaC, the binding motifs that mediate interaction with Nedd4-2. Taken together, our data suggest that Cav-1 inhibits the activity of ENaC by decreasing expression of ENaC at the cell membrane via a mechanism that involves the promotion of Nedd4-2-dependent internalization of the channel.
Lee
Il-Ha
IH
Discipline of Physiology, The Bosch Institute, Faculty of Medicine, University of Sydney, New South Wales, Australia.
Campbell
Craig R
CR
Song
Sung-Hee
SH
Day
Margot L
ML
Kumar
Sharad
S
Cook
David I
DI
Dinudom
Anuwat
A
D000818:Animals; D051242:Caveolin 1 / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D015536:Down-Regulation; D056827:Endosomal Sorting Complexes Required for Transport; D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels / Q000378:metabolism*; D015151:Immunoblotting; D047468:Immunoprecipitation; D007685:Kidney Tubules, Collecting / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D000075702:Nedd4 Ubiquitin Protein Ligases; D051381:Rats; D011916:Rats, Inbred F344; D013961:Thyroid Gland / Q000187:drug effects* / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
D051242:Caveolin 1; D056827:Endosomal Sorting Complexes Required for Transport; D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels; C000618479:NEDD4L protein, rat; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618484:Nedd4 protein, rat; C000618461:Nedd4l protein, mouse; D044767:Ubiquitin-Protein Ligases