Gefitinib-sensitive EGFR lacking residues 746-750 exhibits hypophosphorylation at tyrosine residue 1045, hypoubiquitination, and impaired endocytosis.
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.
Furukawa
Mitsugi
M
Department of Respiratory Medicine, Allergy and Rheumatic Diseases, Osaka University Graduate School of Medicine, Osaka, Japan.
Nagatomo
Izumi
I
Kumagai
Toru
T
Yamadori
Tadahiro
T
Takahashi
Ryo
R
Yoshimura
Mana
M
Yoneda
Tsutomu
T
Takeda
Yoshito
Y
Goya
Sho
S
Matsuoka
Hiroto
H
Kijima
Takashi
T
Yoshida
Mitsuhiro
M
Osaki
Tadashi
T
Tachibana
Isao
I
Greene
Mark I
MI
Kawase
Ichiro
I
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*
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