Abstract
The ligand-mediated down-regulation of the growth factor receptors is preceded by the involvement of various other factors. In particular, a ubiquitin ligase, Cbl, plays a central role in this event. Several candidates that have potential effects on the negative control of the epidermal growth factor (EGF) receptor have now been identified by our recent studies in phospho-proteomics. Among these molecules, we focus on characterizing a novel protein, Ymer, which is a tyrosine-phosphorylated and ubiquitinated protein. Ymer is found to be phosphorylated at tyrosine 145 and 146 upon EGF stimulation, and lysine 129 of Ymer has been identified as a ubiquitination site. Ymer has two motifs interacting with the ubiquitin (MIU) domains that might function as a binding site for the ubiquitinated EGF receptor. Although Ymer and EGF receptors are associated in an EGF-dependent manner, their interaction is required not only for MIU domains but also for the tyrosine phosphorylation of Ymer. Phosphorylated Ymer is mainly located at the plasma membrane with EGF receptor and functions in its endocytosis and degradation. Furthermore, EGF-mediated secondary modifications of an activated-EGF receptor are inhibited by overexpressing Ymer in COS7 cells. Therefore, Ymer may have competitive effects on the activation of the EGF receptor. Our findings suggest that Ymer functions as a novel inhibitor for the down-regulation of the EGF receptor and plays a crucial role for regulating the amount of the EGF receptor on the cell surface membrane.
Highlights
Trometry (MS) to identify novel molecules and posttranslational modifications such as phosphorylation and ubiquitination involved in this epidermal growth factor (EGF) signaling pathway [2]
Based on the results of phospho-proteomics that explores the downstream molecules of the EGF receptor, it is suggested that many proteins related to its internalization are involved in the interactome of Cbl, an E3 ubiquitin ligase that plays a central role in the growth factor receptor down-regulation [9]
We focus on Ymer that has been identified by our original phospho-proteomic experiments using EGFstimulated A431 cells,3 and we demonstrate that the functional analysis in the EGF receptor down-regulation events is dependent upon the multiposttranslational modifications of Ymer
Summary
Trometry (MS) to identify novel molecules and posttranslational modifications such as phosphorylation and ubiquitination involved in this EGF signaling pathway [2]. We focus on Ymer that has been identified by our original phospho-proteomic experiments using EGFstimulated A431 cells,3 and we demonstrate that the functional analysis in the EGF receptor down-regulation events is dependent upon the multiposttranslational modifications of Ymer. By using a similar strategy, we have independently identified more than 150 proteins containing Ymer from the lysate of EGF-stimulated A431 cells.3 the function of Ymer in the EGF signaling pathway is yet to be elucidated.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
