EGF Triggers a Similar Signalling Cascade in Different Cell Types Overexpressing the EGF Receptor
The mechanism by which growth factors stimulate mitogenesis upon binding to their receptors involves several biochemical events and the generation of intracellular second messengers. EGF1 is regarded as a classical example of a growth factor which acts on a receptor harboring tyrosine kinase activity (Berridge, 1987 a,b; Carpenter, 1987). Recently, several reports have indicated that in certain cell types, EGF stimulates inositol lipid turnover with the formation of Ca2+- mobilizing inositol polyphosphates and 1,2-diacylglycerol activating protein kinase C (Hepler et al, 1987; Pandiella et al., 1987; Johnson and Garrison, 1987; Earp et al., 1988; Takasu et al., 1988; Moscat et al., 1988). However, other studies demonstrated that EGF was unable to trigger phosphoinositide metabolism in 3T3 fibroblasts and in a clone of A431 carcinoma cells (Besterman et al, 1986; Macara, 1986; Wakelam et al., 1986; Pandiella et al, 1987). Therefore, EGFinduced inositol lipid turnover might be considered lineagespecific, or at least cell type-specific (Earp et al., 1988), and the role of phosphoinositide metabolism in EGF-induced mitogenesis remains to be established.
KeywordsEpidermal Growth Factor Arachidonic Acid Inositol Phosphate Phosphoinositide Metabolism Inositol Lipid
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