The Uncoupling of Shc Activation from Distal Intracellular Signalling in a Cell Line Which Expresses a Truncated Human Epidermal Growth Factor Receptor

Abstract We have examined epidermal growth factor (EGF) signalling in a CHO cell line (CHO11) which expresses a human EGF receptor truncated at amino acid 990. Previous studies showed that EGF treatment of these cells failed to increase prostaglandin production or phospholipase A 2 activity. In the current study EGF increased the tyrosine phosphorylation of the intracellular signalling protein Shc in CHO11 cells but did not activate either of the downstream signalling enzymes raf or mitogen activated protein kinase (MAPK). The uncoupling of Shc activation from distal signalling in CHO11 cells contrasts with other cells which express similar mutant EGF receptors. The failure of Shc to activate distal signalling may reflect qualitative differences in the way thatthis protein is activated or could result from the activation of an inhibitory signalling pathway.