Epidermal growth factor (EGF) stimulates inositol trisphosphate formation in cells which overexpress the EGF receptor.

EGF is a low molecular weight polypeptide hormone which acts as a regulator of cell growth and differentiation. The A-431 cell line has been used frequently to examine receptor-mediated biochemical effects of EGF, since this cell line has an increased (20-50 fold) level of EGF receptors. We have utilized A-431 cells to examine the influence of EGF on formation of an intracellular second messenger, inositol, 1,4,5-trisphosphate (Ins-1,4,5-P3), and other inositol phosphates. The results show that EGF induces rapid formation of Ins-1,4,5-P3 as well as Ins-1,3,4-P3 and Ins-1,3,4,5-P4. There is a concurrent decrease in the level of the lipid precursor for Ins-1,4,5-P3, phosphatidylinositol 4,5-biphosphate (PIP2). Furthermore, we have examined five other cell lines that overexpress the EGF receptor and find that EGF treatment induces formation of inositol polyphosphates in those cell lines also.