title: Gefitinib-sensitive EGFR lacking residues 746-750 exhibits hypophosphorylation at tyrosine residue 1045, hypoubiquitination, and impaired endocytosis.
abstract: Gefitinib-sensitive nonsmall cell lung cancers (NSCLC) are characterized by somatic mutations in the kinase domain of epidermal growth factor receptor (EGFR). The mutant EGFR forms are reported to mediate characteristic signal transduction pathways that are different from those mediated by the wild-type EGFR and are involved in transformation in vivo. We have examined signal transduction pathways initiated from a frequently identified gefitinib-sensitizing mutant EGFR lacking residues 746-750 by employing a mouse fibroblast cell line that is free of endogenous EGFR and transiently transfected COS-7 cells. Upon EGF stimulation, the deletion-mutant EGFR mediated prolonged downstream signals. The analysis of the phosphotyrosine patterns of the receptor revealed that the deletion-mutant EGFR lacked phosphorylation at tyrosine residue 1045, which is the major binding site of Cbl. The EGF-induced endocytosis of the deletion-mutant EGFR was impaired. The ubiquitination and downregulation of the deletion-mutant EGFR were also reduced. On the other hand, another mutant, EGFR, possessing a L858R substitution, exhibited phosphorylation at 1045 and its downstream signalings were not prolonged. These data suggest that the signal transduction pathways initiated from these mutant forms are different, and that impaired endocytosis might be responsible for the prolonged signals mediated by the deletion-mutant EGFR.
authors.affiliation: Department of Respiratory Medicine, Allergy and Rheumatic Diseases, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: Mitsugi
authors.initials: M
authors.lastname: Furukawa
authors.forename: Izumi
authors.initials: I
authors.lastname: Nagatomo
authors.forename: Toru
authors.initials: T
authors.lastname: Kumagai
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Yamadori
authors.forename: Ryo
authors.initials: R
authors.lastname: Takahashi
authors.forename: Mana
authors.initials: M
authors.lastname: Yoshimura
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Yoneda
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Takeda
authors.forename: Sho
authors.initials: S
authors.lastname: Goya
authors.forename: Hiroto
authors.initials: H
authors.lastname: Matsuoka
authors.forename: Takashi
authors.initials: T
authors.lastname: Kijima
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Yoshida
authors.forename: Tadashi
authors.initials: T
authors.lastname: Osaki
authors.forename: Isao
authors.initials: I
authors.lastname: Tachibana
authors.forename: Mark I
authors.initials: MI
authors.lastname: Greene
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kawase
mesh_terms: D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002522:Chlorocebus aethiops; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D004705:Endocytosis / Q000235:genetics*; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D000077156:Gefitinib; D008024:Ligands; D051379:Mice; D009154:Mutation; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000032:analysis; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D050721:Proto-Oncogene Proteins c-cbl / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology; D017384:Sequence Deletion; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*
chemical_list: D008024:Ligands; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D025801:Ubiquitin; D019000:Phosphotyrosine; D014443:Tyrosine; D004815:Epidermal Growth Factor; D050721:Proto-Oncogene Proteins c-cbl; D066246:ErbB Receptors; D000077156:Gefitinib