Huang, F., Kirkpatrick, D., Jiang, X., Gygi, S. & Sorkin, A. Differential regulation of EGF receptor internalization and degradation by multiubiquitination within the kinase domain. Mol. Cell 21, 737-748

Department of Molecular and Cell Biology, Harvard University, Cambridge, Massachusetts, United States
Molecular Cell (Impact Factor: 14.02). 04/2006; 21(6):737-48. DOI: 10.1016/j.molcel.2006.02.018
Source: PubMed


Ubiquitination of the EGF receptor (EGFR) is believed to play a critical role in regulating both its localization and its stability. To elucidate the role of EGFR ubiquitination, tandem mass spectrometry was used to identify six distinct lysine residues within the kinase domain of the EGFR, which can be conjugated to ubiquitin following growth factor stimulation. Substitution of these lysine residues with arginines resulted in a dramatic decrease in overall ubiquitination but preserved normal tyrosine phosphorylation of EGFR. Ubiquitination-deficient EGFR mutants displayed a severe defect in their turnover rates but were internalized at rates comparable to those of wild-type receptors. Finally, quantitative mass spectrometry demonstrated that more than 50% of all EGFR bound ubiquitin was in the form of polyubiquitin chains, primarily linked through Lys63. Taken together, these data provide direct evidence for the role of EGFR ubiquitination in receptor targeting to the lysosome and implicate Lys63-linked polyubiquitin chains in this sorting process.

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    • "Ubiquitinylation is a dynamic process and protein eventual protein destination depends on the lysine to which it is attached and whether it is monoubiquitinylated, homopolyubiquitinylated , or hetero-polyubiquitinylated [58, 59]. The UBE2v2 preferentially ubiquitinylates Lys63, which is reported to participate in chaperoning proteins for DNA repair, lysosomal degradation of epidermal growth factor receptors, and NF-κB activation by degradation of class I major histocompatibility complex molecules [60] [61] [62] [63]. Here, protein levels of UBE2v2 were increased in the intermediate age group, while phosphorylation levels were decreased in the intermediate and oldest age groups. "
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    • "The alternative mechanism involves the tyrosine residues Tyr 1068 and Tyr 1086 of the activated receptor, which indirectly recruits Cbl through its interaction with the SH3 domain of Grb2 [8]. With Cbl serving as an adaptor to bridge Ubc4/5 E2 ubiquitin-conjugating enzyme interaction with EGFR, ubiquitin is transferred directly from the E2 to distinct lysine residues within the kinase domain of EGFR, including six major ubiquitin conjugation sites (Lys692, Lys713, Lys, 730, Lys843, Lys905, and Lys946) [9], [10]. Although sufficient but not essential for EGFR internalization [11]–[13], EGFR ubiquitination is indeed required for its sorting onto intraluminal vesicles of multivesicular endosomes/bodies and subsequent lysosomes for efficient degradation [12], [14]. "
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    • "ILV formation and cargo sorting are mediated by the endosomal sorting complex required for transport (ESCRT) machinery (Raiborg and Stenmark, 2009). Previous studies indicate that K63-linked polyubiquitylation of cargo proteins specifically functions as an ESCRT-dependent sorting signal to ILVs rather than as an internalization signal (Huang et al., 2006; Barriere et al., 2007; Lauwers et al., 2010; Erpapazoglou et al., 2012), although other reports suggest that multiple or even single monoubiquitylation is sufficient for MVB sorting (Stringer and Piper, 2011). Thus, the exact role of K63- linked ubiquitylation in endocytic processes remains controversial. "
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