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Link to original content: https://pubmed.ncbi.nlm.nih.gov/18498246
Regulation of Nedd4-2 self-ubiquitination and stability by a PY motif located within its HECT-domain - PubMed Skip to main page content
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. 2008 Oct 1;415(1):155-63.
doi: 10.1042/BJ20071708.

Regulation of Nedd4-2 self-ubiquitination and stability by a PY motif located within its HECT-domain

M Christine Bruce  1 , Voula Kanelis, Fatemeh Fouladkou, Anne Debonneville, Olivier Staub, Daniela Rotin
Affiliations

Regulation of Nedd4-2 self-ubiquitination and stability by a PY motif located within its HECT-domain

M Christine Bruce et al. Biochem J. .

Abstract

Ubiquitin ligases play a pivotal role in substrate recognition and ubiquitin transfer, yet little is known about the regulation of their catalytic activity. Nedd4 (neural-precursor-cell-expressed, developmentally down-regulated 4)-2 is an E3 ubiquitin ligase composed of a C2 domain, four WW domains (protein-protein interaction domains containing two conserved tryptophan residues) that bind PY motifs (L/PPXY) and a ubiquitin ligase HECT (homologous with E6-associated protein C-terminus) domain. In the present paper we show that the WW domains of Nedd4-2 bind (weakly) to a PY motif (LPXY) located within its own HECT domain and inhibit auto-ubiquitination. Pulse-chase experiments demonstrated that mutation of the HECT PY-motif decreases the stability of Nedd4-2, suggesting that it is involved in stabilization of this E3 ligase. Interestingly, the HECT PY-motif mutation does not affect ubiquitination or down-regulation of a known Nedd4-2 substrate, ENaC (epithelial sodium channel). ENaC ubiquitination, in turn, appears to promote Nedd4-2 self-ubiquitination. These results support a model in which the inter- or intra-molecular WW-domain-HECT PY-motif interaction stabilizes Nedd4-2 by preventing self-ubiquitination. Substrate binding disrupts this interaction, allowing self-ubiquitination of Nedd4-2 and subsequent degradation, resulting in down-regulation of Nedd4-2 once it has ubiquitinated its target. These findings also point to a novel mechanism employed by a ubiquitin ligase to regulate itself differentially compared with substrate ubiquitination and stability.

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