Clathrin-mediated endocytosis of the epithelial sodium channel. Role of epsin.
Here we present evidence that the epithelial sodium channel (ENaC), a heteromeric membrane protein whose surface expression is regulated by ubiquitination, is present in clathrin-coated vesicles in epithelial cells that natively express ENaC. The channel subunits are ubiquitinated and co-immunoprecipitate with both epsin and clathrin adaptor proteins, and epsin, as expected, co-immunoprecipitates with clathrin adaptor proteins. The functional significance of these interactions was evaluated in a Xenopus oocyte expression system where co-expression of epsin and ENaC resulted in a down-regulation of ENaC activity; conversely, co-expression of epsin sub-domains acted as dominant-negative effectors and stimulated ENaC activity. These results identify epsin as an accessory protein linking ENaC to the clathrin-based endocytic machinery thereby regulating the activity of this ion channel at the cell surface.
Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
Huamin
H
Wang
Linton M
LM
Traub
Kelly M
KM
Weixel
Mathew J
MJ
Hawryluk
Nirav
N
Shah
Robert S
RS
Edinger
Clint J
CJ
Perry
Lauren
L
Kester
Michael B
MB
Butterworth
Kathryn W
KW
Peters
Thomas R
TR
Kleyman
Raymond A
RA
Frizzell
John P
JP
Johnson
D033942:Adaptor Proteins, Vesicular Transport / Q000737:chemistry*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002966:Clathrin / Q000378:metabolism / Q000502:physiology*; D015536:Down-Regulation; D004594:Electrophysiology; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D051379:Mice; D009154:Mutation; D009865:Oocytes / Q000378:metabolism; D017434:Protein Structure, Tertiary; D025801:Ubiquitin / Q000737:chemistry; D014981:Xenopus
D033942:Adaptor Proteins, Vesicular Transport; D002966:Clathrin; D025801:Ubiquitin; C114154:epsin