c-Src-mediated Phosphorylation of the Epidermal Growth Factor Receptor on Tyr845 and Tyr1101 Is Associated with Modulation of Receptor Function

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作者：

JS Biscardi，MC Maa，DA Tice，ME Cox，TH Leu，SJ Parsons

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摘要：

Accumulating evidence indicates that interactions between the epidermal growth factor receptor (EGFR) and the nonreceptor tyrosine kinase c-Src may contribute to an aggressive phenotype in multiple human tumors. Previous work from our laboratory demonstrated that murine fibroblasts which overexpress both these tyrosine kinases display synergistic increases in DNA synthesis, soft agar growth, and tumor formation in nude mice, and increased phosphorylation of the receptor substrates Shc and phospholipase γ as compared with single overexpressors. These parameters correlated with the ability of c-Src and EGFR to form an EGF-dependent heterocomplex . Here we provide evidence that association between c-Src and EGFR can occur directly, as shown by receptor overlay experiments, and that it results in the appearance of two novel tyrosine phosphorylations on the receptor that are seen both and following EGF stimulation. Edman degradation analyses and co-migration of synthetic peptides with EGFR-derived tryptic phosphopeptides identify these sites as Tyrand Tyr. Tyrlies within the carboxyl-terminal region of the EGFR among sites of receptor autophosphorylation, while Tyrresides in the catalytic domain, in a position analogous to Tyrof c-Src. Phosphorylation of Tyrand homologous residues in other tyrosine kinase receptors has been shown to be required for or to increase catalytic activity, suggesting that c-Src can influence EGFR activity by mediating phosphorylation of Tyr. Indeed, EGF-induced phosphorylation of Tyrwas increased in MDA468 human breast cancer cells engineered to overexpress c-Src as compared with parental MDA 468 cells. Furthermore, transient expression of a Y845F variant EGFR in murine fibroblasts resulted in an ablation of EGF-induced DNA synthesis to nonstimulated levels. Together, these data support the hypothesis that c-Src-mediated phosphorylation of EGFR Tyris involved in regulation of receptor function, as well as in tumor progression.

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关键词：

Animals Mice, Inbred C3H Humans Mice Cell Line Tumor Cells, Cultured Tyrosine Receptor, Epidermal Growth Factor Peptide Mapping src Homology Domains