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Alwan HA, van Leeuwen JE.. UBPY-mediated epidermal growth factor receptor (EGFR) de-ubiquitination promotes EGFR degradation. J Biol Chem 282: 1658-1669

Department of Cell Biology, Institute for Neuroscience, Faculty of Natural Sciences, Mathematics and Informatics, Radboud University Nijmegen, 6525 ED Nijmegen, The Netherlands.
Journal of Biological Chemistry (Impact Factor: 4.57). 02/2007; 282(3):1658-69. DOI: 10.1074/jbc.M604711200
Source: PubMed

ABSTRACT Whereas poly-ubiquitination targets protein substrates for proteasomal degradation, mono-ubiquitination is known to regulate protein trafficking in the endosomal system and to target cargo proteins for lysosomal degradation. The role of the de-ubiquitinating enzymes AMSH and UBPY in endosomal trafficking of cargo proteins such as the epidermal growth factor receptor (EGFR) has only very recently been the subject of study and is already a matter of debate. Although one report (Mizuno, E., Iura, T., Mukai, A., Yoshimori, T., Kitamura, N., and Komada, M. (2005) Mol. Biol. Cell 16, 5163-5174) concludes that UBPY negatively regulates EGFR degradation by de-ubiquitinating the EGFR on endosomes, another report (Row, P. E., Prior, I. A., McCullough, J., Clague, M. J., and Urbe, S. (2006) J. Biol. Chem. 281, 12618-12624) concludes that UBPY-mediated EGFR de-ubiquitination is essential for EGFR degradation. Here, we demonstrate that Usp8/UBPY, the mammalian ortholog of budding yeast Ubp4/Doa4, constitutively co-precipitates in a bivalent manner with the EGFR. Moreover, UBPY is a substrate for Src-family tyrosine kinases that are activated after ligand-induced EGFR activation. Using overexpression of three different recombinant dominant negative UBPY mutants (UBPY C748A mutant, UBPY 1-505, and UBPY 640-1080) in NIH3T3 and HEK293 cells, we demonstrate that UBPY affects both constitutive and ligand-induced (i) EGFR ubiquitination, (ii) EGFR expression levels, and (iii) the appearance of intermediate EGFR degradation products as well as (iv) downstream mitogen-activated protein kinase signal transduction. Our findings provide further evidence in favor of the model that UBPY-mediated EGFR de-ubiquitination promotes EGFR degradation.

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    • "Finally, Devor and co-workers (Balut et al., 2011) chose to pursue USP8 because that DUB had been reported in deubiquitylating proteins targeted to the lysosome for degradation (Alwan and van Leeuwen, 2007). After which, they used USP8 overexpression and knockdown experiments to unequivocally demonstrate that USP8 was imperative for proper deubiquitylation of KCa3.1 and delivery of KCa3.1 to the lysosome for degradation (Balut et al., 2011). "
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    • "Mukai et al found no evidence that Fz ubiquitylation– deubiquitylation is influenced by Wnt ligand. This is different from the situation with EGFR, wherein mono-ubiquitylation is ligand dependent (Mizuno et al, 2005; Alwan and van Leeuwen, 2007; Niendorf et al, 2007; Row et al, 2007). Rather than acting in response to Wnt, Fz recycling is important for setting the level of responsiveness of the receiving cells to the Wnt ligand. "
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    • "Interestingly, these enzymes appear to exert opposing effects on lysosomal degradation of activated RTKs, though their precise involvement remains unclear (Alwan and van Leeuwen, 2007; McCullough et al., 2006). "
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