Transactivation of the EGF receptor mediates IGF-1- stimulated shc phosphorylation and ERK1/2 activation in COS-7 cells.
The receptor for insulin-like growth factor 1 (IGF-1) mediates multiple cellular responses, including stimulation of both proliferative and anti-apoptotic pathways. We have examined the role of cross talk between the IGF-1 receptor (IGF-1R) and the epidermal growth factor receptor (EGFR) in mediating responses to IGF-1. In COS-7 cells, IGF-1 stimulation causes tyrosine phosphorylation of the IGF-1R beta subunit, the EGFR, insulin receptor substrate-1 (IRS-1), and the Shc adapter protein. Shc immunoprecipitates performed after IGF-1 stimulation contain coprecipitated EGFR, suggesting that IGF-1R activation induces the assembly of EGFR.Shc complexes. Tyrphostin AG1478, an inhibitor of the EGFR kinase, markedly attenuates IGF-1- stimulated phosphorylation of EGFR, Shc, and ERK1/2 but has no effect on phosphorylation of IGF-1R, IRS-1, and protein kinase B (Akt). Cross talk between IGF-1 and EGF receptors is mediated through an autocrine mechanism involving matrix metalloprotease-dependent release of heparin- binding EGF (HB-EGF), because IGF-1- mediated ERK activation is inhibited both by [Glu(52)]Diphtheria toxin, a specific inhibitor of HB-EGF, and the metalloprotease inhibitor 1,10-phenanthroline. These data demonstrate that IGF-1 stimulation of the IRS-1/ PI3K/Akt pathway and the EGFR/Shc/ERK1/2 pathway occurs by distinct mechanisms and suggest that IGF-1- mediated "transactivation" of EGFR accounts for the majority of IGF-1- stimulated Shc phosphorylation and subsequent activation of the ERK cascade.[1]References
- Transactivation of the EGF receptor mediates IGF-1-stimulated shc phosphorylation and ERK1/2 activation in COS-7 cells. Roudabush, F.L., Pierce, K.L., Maudsley, S., Khan, K.D., Luttrell, L.M. J. Biol. Chem. (2000) [Pubmed]
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