Tyrosine phosphorylation of Grb2 by Bcr/Abl and epidermal growth factor receptor: a novel regulatory mechanism for tyrosine kinase signaling.

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Animal, Binding-Sites, Blotting-Western, Cell-Line, Cell-Line-Transformed, DNA-Mutational-Analysis, Dose-Response-Relationship-Drug, Down-Regulation, Enzyme-Activation, Fibroblasts, Fusion-Proteins-bcr-abl, Human, K562-Cells, MAP-Kinase-Signaling-System, Mice, Mitogen-Activated-Protein-Kinases, Mutation, Peptide-Mapping, Phosphopeptides, Phosphorylation, Precipitin-Tests, Protein-Binding, Protein-Structure-Tertiary, Proteins, Receptor-Epidermal-Growth-Factor, Signal-Transduction, Son-of-Sevenless-Protein-Drosophila, Spectrum-Analysis-Mass, SUPPORT-NON-U-S-GOVT, SUPPORT-U-S-GOVT-P-H-S, Time-Factors, Transfection, Transformation-Genetic, Tumor-Cells-Cultured, Tyrosine, ras-Proteins, src-Homology-Domains

JAX Source

EMBO J 2001 Dec; 20(23):6793-6804.




Growth factor receptor-binding protein-2 (Grb2) plays a key role in signal transduction initiated by Bcr/Abl oncoproteins and growth factors, functioning as an adaptor protein through its Src homology 2 and 3 (SH2 and SH3) domains. We found that Grb2 was tyrosine-phosphorylated in cells expressing BCR/ABL and in A431 cells stimulated with epidermal growth factor (EGF). Phosphorylation of Grb2 by Bcr/Abl or EGF receptor reduced its SH3-dependent binding to Sos in vivo, but not its SH2-dependent binding to Bcr/Abl. Tyr209 within the C-terminal SH3 domain of Grb2 was identified as one of the tyrosine phosphorylation sites, and phosphorylation of Tyr209 abolished the binding of the SH3 domain to a proline-rich Sos peptide in vitro. In vivo expression of a Grb2 mutant where Tyr209 was changed to phenylalanine enhanced BCR/ABL-induced ERK activation and fibroblast transformation, and potentiated and prolonged Grb2-mediated activation of Ras, mitogen-activated protein kinase and c-Jun N-terminal kinase in response to EGF stimulation. These results suggest that tyrosine phosphorylation of Grb2 is a novel mechanism of down-regulation of tyrosine kinase signaling.