Signal Transduction by Epidermal Growth Factor Receptor

The proliferation of cells in vivo and in culture is tightly regulated by polypeptide growth factors. Like all polypeptide hormones, growth factors initiate their action by binding to specific, high-affinity receptor molecules on the cell surface. Interest in growth factors and their receptors has been dramatically intensified by the discovery that at least some of these molecules were identified as viral oncogene products. For example, the v-s/s oncogene ncodes the platelet-derived growth fac-tor (PDGF)-B molecule, whereas the v-erbB oncogene product is a truncated form of the avian receptor for epidermal growth factor (EGF) (for review, see Schles-singer 1988; Yarden and Ullrich 1988). Inappropriate expression of the cellular counterparts of viral on-cogenes is thought o play a role in the initiation an