title: Role of extracellular subdomains of p185c-neu and the epidermal growth factor receptor in ligand-independent association and transactivation.
abstract: We investigated the assembly and activation of the epidermal growth factor receptor (EGFR)-p185c-neu heterodimer by using a sequential immunoprecipitation methodology. Using this approach we detected heterodimers and also higher-ordered oligomeric complexes. Phosphorylated EGFR-p185c-neu heterodimeric forms were detected in the absence of EGF, but the species became highly phosphorylated after EGF stimulation. To evaluate heterodimer formation and additional transactivation by EGF, we investigated the roles of the four extracellular subdomains of p185c-neu and the EGFR. Subdomains I-IV of the EGFR dimerized with subdomains I-IV of p185c-neu, respectively, in a parallel manner. In addition, subdomains I-IV of the EGFR also associated with p185c-neu subdomains III, IV, I, and II, respectively. A lack of one of the p185c-neu cysteine-rich domains (subdomains II or IV) resulted in a loss of EGF-induced transactivation. These data suggest that two cysteine-rich domains play defining roles in ligand-dependent transactivation and that both of these cysteine-rich extracellular subdomains as well as non-cysteine-rich extracellular subdomains are involved in ligand-independent interactions with the EGFR. Our studies provide biochemical evidence of the role of the cysteine-rich domains of p185c-neu in assembly and transactivation of erbB complexes and also indicate that these subdomains might be useful clinical targets.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
authors.forename: Toru
authors.initials: T
authors.lastname: Kumagai
authors.forename: Makoto
authors.initials: M
authors.lastname: Katsumata
authors.forename: Akihiro
authors.initials: A
authors.lastname: Hasegawa
authors.forename: Keiji
authors.initials: K
authors.lastname: Furuuchi
authors.forename: Toshiki
authors.initials: T
authors.lastname: Funakoshi
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kawase
authors.forename: Mark I
authors.initials: MI
authors.lastname: Greene
mesh_terms: D000818:Animals; D019556:COS Cells; D003545:Cysteine / Q000737:chemistry; D019281:Dimerization; D066246:ErbB Receptors / Q000737:chemistry* / Q000378:metabolism; D005822:Genetic Vectors; D008024:Ligands; D051379:Mice; D008956:Models, Chemical; D017434:Protein Structure, Tertiary; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000737:chemistry* / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection
chemical_list: D003545:Cysteine; D066246:ErbB Receptors; D008024:Ligands; D018719:Erb-b2 Receptor Tyrosine Kinases