Involvement of ErbB2 in the signaling pathway leading to cell cycle progression from a truncated epidermal growth factor receptor lacking the C-terminal autophosphorylation sites.
To investigate the mechanisms underlying the enhanced mitogenic activity of the truncated epidermal growth factor receptor (EGFR) lacking the C-terminal autophosphorylation sites (Delta973-EGFR), we studied the intracellular signaling pathways in NR6 cells expressing human wild type EGFR and Delta973-EGFR. Microinjection of dominant/negative p21ras(N17) completely inhibited EGF-induced DNA synthesis in both cell types. EGF stimulated Shc phosphorylation as well as the formation of wild type EGFR.Shc complexes. In contrast, EGF stimulated Shc phosphorylation without formation of Delta973-EGFR.Shc complexes. Tyrosine-phosphorylated Shc formed complexes with Grb2.Sos, and microinjection of anti-Shc antibody and Shc-SH2 GST fusion protein inhibited EGF stimulation of DNA synthesis in both cell lines. EGF markedly increased ErbB2 tyrosine phosphorylation in wild type EGFR cells. In Delta973-EGFR cells, ErbB2 was tyrosine phosphorylated in the basal state and EGFR stimulated further phosphorylation of ErbB2. In addition to ErbB2, additional proteins were tyrosine phosphorylated in Delta973-EGFR cells, mostly in the molecular mass range of 120 170 kDa. Taken together with our findings indicating coupling of ErbB2 to Shc, these data suggest the importance of an alternative signaling pathway in Delta973-EGFR cells mediated by the formation of heterodimeric structures between the truncated EGFR and ErbB2, followed by coupling through Shc to Grb2.Sos and the p21ras pathway, ultimately leading to mitogenesis.
Sasaoka
T
T
First Department of Medicine, Toyama Medical and Pharmaceutical University, Toyama, 930-01, Japan.
Langlois
W J
WJ
Bai
F
F
Rose
D W
DW
Leitner
J W
JW
Decker
S J
SJ
Saltiel
A
A
Gill
G N
GN
Kobayashi
M
M
Draznin
B
B
Olefsky
J M
JM
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D002453:Cell Cycle; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000502:physiology; D066246:ErbB Receptors / Q000502:physiology*; D051380:GRB2 Adaptor Protein; D020662:Guanine Nucleotide Exchange Factors; D006153:Guanosine Diphosphate / Q000378:metabolism; D006801:Humans; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000502:physiology; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000502:physiology*; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction; D020664:Son of Sevenless Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D013329:Structure-Activity Relationship; D020663:ras Guanine Nucleotide Exchange Factors
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D051380:GRB2 Adaptor Protein; D020662:Guanine Nucleotide Exchange Factors; D006153:Guanosine Diphosphate; D046911:Macromolecular Substances; D008565:Membrane Proteins; D019000:Phosphotyrosine; D011506:Proteins; D016283:Proto-Oncogene Proteins p21(ras); D018719:Erb-b2 Receptor Tyrosine Kinases; D055765:Shc Signaling Adaptor Proteins; D020664:Son of Sevenless Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D020663:ras Guanine Nucleotide Exchange Factors; C495948:GRB2 protein, human; C495949:Grb2 protein, mouse; C528024:SHC1 protein, human; C528034:Shc1 protein, mouse; C501009:HRAS protein, human