Clathrin-mediated endocytosis of the epithelial sodium channel. Role of epsin |
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Authors: | Wang Huamin Traub Linton M Weixel Kelly M Hawryluk Mathew J Shah Nirav Edinger Robert S Perry Clint J Kester Lauren Butterworth Michael B Peters Kathryn W Kleyman Thomas R Frizzell Raymond A Johnson John P |
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Institution: | Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA. |
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Abstract: | 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. |
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