Nedd4-2 functionally interacts with ClC-5: Involvement in constitutive albumin endocytosis in proximal tubule cells

Deanne H. Hryciw, Jenny Ekberg, Aven Lee, Ingrid L. Lensink, Sharad Kumar, William B. Guggino, David I. Cook, Carol A. Pollock, Philip Poronnik*

*Corresponding author for this work

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Abstract

Constitutive albumin uptake by the proximal tubule is achieved by a receptor-mediated process in which the Cl- channel, ClC-5, plays an obligate role. Here we investigated the functional interaction between ClC-5 and ubiquitin ligases Nedd4 and Nedd4-2 and their role in albumin uptake in opossum kidney proximal tubule (OK) cells. In vivo immunoprecipitation using an anti-HECT antibody demonstrated that ClC-5 bound to ubiquitin ligases, whereas glutathione S-transferase pull-downs confirmed that the C terminus of ClC-5 bound both Nedd4 and Nedd4-2. Nedd4-2 alone was able to alter ClC-5 currents in Xenopus oocytes by decreasing cell surface expression of ClC-5. In OK cells, a physiological concentration of albumin (10 μg/ml) rapidly increased cell surface expression of ClC-5, which was also accompanied by the ubiquitination of ClC-5. Albumin uptake was reduced by inhibiting either the lysosome or proteasome. Total levels of Nedd4-2 and proteasome activity also increased rapidly in response to albumin. Overexpression of ligase defective Nedd4-2 or knockdown of endogenous Nedd4-2 with small interfering RNA resulted in significant decreases in albumin uptake. In contrast, pathophysiological concentrations of albumin (100 and 1000 μg/ml) reduced the levels of ClC-5 and Nedd4-2 and the activity of the proteasome to the levels seen in the absence of albumin. These data demonstrate that normal constitutive uptake of albumin by the proximal tubule requires Nedd4-2, which may act via ubiquitination to shunt ClC-5 into the endocytic pathway.

Original languageEnglish
Pages (from-to)54996-55007
Number of pages12
JournalJournal of Biological Chemistry
Volume279
Issue number53
DOIs
Publication statusPublished - 31 Dec 2004
Externally publishedYes

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Hryciw, D. H., Ekberg, J., Lee, A., Lensink, I. L., Kumar, S., Guggino, W. B., ... Poronnik, P. (2004). Nedd4-2 functionally interacts with ClC-5: Involvement in constitutive albumin endocytosis in proximal tubule cells. Journal of Biological Chemistry, 279(53), 54996-55007. https://doi.org/10.1074/jbc.M411491200