Epidermal growth factor induces phosphorylation of extracellular signal-regulated kinase 2 via multiple pathways.
Expression of p21rasAsn-17, a dominant negative mutant of p21ras that blocks p21ras 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 p21rasAsn-17 does not abolish epidermal growth factor (EGF)-induced phosphorylation of ERK2 in fibroblasts. Since EGF activates p21ras in these cells, this indicates that EGF induces a p21ras-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 p21ras-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(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) pretreatment, did not abolish EGF-induced ERK2 phosphorylation. However, a combined inhibition of both p21ras 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 p21ras 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.
Burgering
B M
BM
Laboratory of Physiological Chemistry, Utrecht University, The Netherlands.
de Vries-Smits
A M
AM
Medema
R H
RH
van Weeren
P C
PC
Tertoolen
L G
LG
Bos
J L
JL
D000818:Animals; D002118:Calcium / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002460:Cell Line; D004533:Egtazic Acid / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D010982:Platelet-Derived Growth Factor; D004533:Egtazic Acid; D004815:Epidermal Growth Factor; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D016283:Proto-Oncogene Proteins p21(ras); D013755:Tetradecanoylphorbol Acetate; D002118:Calcium