Purchase this article with an account.
Z Wang, VN Bildin, PS Reinach; Epidermal Growth Factor Activation Of Extracellular Signal-Regulated Protein Kinases In Human Corneal Epithelial Cells . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1653.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Activation of extracellular signal-regulated protein kinase (Erk1/2) is essential for corneal epithelial mitogenesis. We investigated in SV40-immortalized human corneal epithelial cells (HCEC) the relative roles of protein kinase C (PKC) stimulation and tyrosine kinase phosphorylation on the ability of EGF to activate cRaf, Erk and stimulate Elk-1 gene transcription factor as well as induce mitogenesis. Methods: After 24 h incubation without serum, HCEC proliferation was stimulated with 10 ng/ml EGF. The contribution of protein tyrosine phosphorylation steps to Erk activation was evaluated with PD153035 (EGF receptor tyrosine kinase inhibitor) and manumycin A (Ras farnesyltransferase inhibitor). EGF-induced PKC activation was inhibited with bisindolylmaleimide. Levels of cRaf, Erk1/2 and Elk-1 activation were determined by Western blotting/ECL assay 30 min after EGF exposure. Cell proliferation was determined based on measurements of 3H-thymidine incorporation after 20 h. Results: PKC inhibition during serum starvation produced up to a 20% increase in proliferation, but it had no significant effect on the mitogenic response to EGF. Surprisingly PKC inhibition in the presence of EGF caused moderate decreases in cRaf and Erk1/2 activity. On the other hand, inhibition of EGF receptor and cytosolic associated tyrosine kinase phosphorylation dramatically (5-10-fold) decreased Erk1/2 and Elk-1 activation and nearly completely inhibited the mitogenic response to EGF. Conclusion: In HCEC, EGF-induced Erk1/2 stimulation and its mitogenic effect are only partially dependent on the activation of PKC by EGF. This is in contrast to the findings in some other cell types in which there is a greater dependency of these EGF associated responses on PKC activation. On the other hand, EGF-induced EGF receptor and cytosolic associated tyrosine kinase phosphorylation is essential for EGF-induced Erk activation and its stimulation of proliferation.
This PDF is available to Subscribers Only