title: Compartmentalization of signaling-competent epidermal growth factor receptors in endosomes.
abstract: In this study, the preparation of detergent-resistant membranes (DRMs) and the immunoisolation of intracellular vesicles enriched in raft markers were used to investigate the effect of physiological doses of epidermal growth factor (EGF) in vivo on the compartmentalization and activation of EGF receptor (EGFR) in rat liver endosomes. Both of these techniques show that after EGF administration, a distinctive population of intracellular EGFR, which was characterized by a high level of tyrosine phosphorylation, accumulated in endosomes. EGFR recruited to early endosomes were more tyrosine phosphorylated than those from late endosomes. However, the level of tyrosine phosphorylation of EGFR in DRMs isolated from early and late endosomes was comparable, suggesting that EGFR in endosomal DRMs are more resistant to tyrosine dephosphorylation. In accordance with the higher level of Tyr phosphorylation, EGF induced an augmented recruitment of Grb2 and Shc to endosomal DRMs compared with whole endosomes. Furthermore, a proteomic analysis identified a selective increase of many alpha-subunits of heterotrimeric G proteins in endosomal DRMs in response to EGF. These observations suggest that a distinctive pool of endocytic EGFR, potentially competent for signaling, is actively trafficking through intracellular compartments with the characteristic of lipid rafts.
authors.affiliation: Polypeptide Hormone Laboratory, Faculty of Medicine, McGill University, 3640 University Street, Montreal, Quebec, Canada.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Balbis
authors.forename: Amanda
authors.initials: A
authors.lastname: Parmar
authors.forename: Ye
authors.initials: Y
authors.lastname: Wang
authors.forename: Gerardo
authors.initials: G
authors.lastname: Baquiran
authors.forename: Barry I
authors.initials: BI
authors.lastname: Posner
mesh_terms: D000818:Animals; D002451:Cell Compartmentation / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D011992:Endosomes / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism* / Q000502:physiology*; D005260:Female; D008099:Liver / Q000737:chemistry; D021962:Membrane Microdomains / Q000378:metabolism; D008954:Models, Biological; D021381:Protein Transport / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D003902:Detergents; D025801:Ubiquitin; D004815:Epidermal Growth Factor; C410467:insulin receptor tyrosine kinase; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases