Epidermal Growth Factor Induces Phosphorylation of Extracellular Signal-Regulated Kinase 2 via Multiple Pathways

• Published in: Molecular and cellular biology Vol. 13; no. 12; pp. 7248 - 7256
• Main Authors: Burgering, Boudewijn M. T., de Vries-Smits, Alida M. M., Medema, René H., van Weeren, Pascale C., Tertoolen, Leon G.J., Bos, Johannes L.
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 01.12.1993
• ISSN: 1098-5549; 1098-5549
• DOI: 10.1128/mcb.13.12.7248-7256.1993

Expression of p21 rasAsn-17 , a dominant negative mutant of p21 ras that blocks p21 ras activation by growth factors, inhibits activation of extracellular signal-regulated kinase 2 (ERK2) by insulin and platelet-derived growth factor in rat-1 cells [A. M. M. de Vries-Smits, B. M. T. Burgering, S. J. Leevers, C. J. Marshall, and J. L. Bos, Nature (London) 357:602-604, 1992]. Here we report that expression of p21 rasAsn-17 does not abolish epidermal growth factor (EGF)-induced phosphorylation of ERK2 in fibroblasts. Since EGF activates p21 ras in these cells, this indicates that EGF induces a p21 ras -independent pathway for the phosphorylation of ERK2 as well. We investigated whether activation of protein kinase C (PKC) or increase in intracellular calcium could be involved in p21 ras -independent signaling. In rat-1 cells, inhibition of either PKC, by prolonged 12-O-tetradecanoylphorbol-13-acetate (TPA) pretreatment, or calcium influx, by ethylene glycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA) pretreatment, did not abolish EGF-induced ERK2 phosphorylation. However, a combined inhibition of both p21 ras and calcium influx, but not PKC, resulted in a complete inhibition of EGF-induced ERK2 phosphorylation. In contrast, in Swiss 3T3 cells, inhibition of both p21 ras activation and TPA-sensitive PKC, but not calcium influx, inhibited EGF-induced ERK2 phosphorylation. These results demonstrate that in fibroblasts, EGF induces alternative pathways of ERK2 phosphorylation in a cell-type-specific manner.