ERK1/2, but not ERK5, is necessary and sufficient for phosphorylation and activation of c-Fos.
Growth factor-stimulated expression and activation of c-Fos is regulated by the ERK1/2 pathway. However, recent reports have also suggested a prominent role for the closely related ERK5 pathway in regulating the expression, transcriptional activation and nuclear localization of c-Fos. Here we have compared the role of ERK1/2 and ERK5 in regulating c-Fos using a combination of conditional protein kinases, selective biochemical inhibitors and ERK5 null fibroblasts. We demonstrate that activation of the ERK1/2 pathway, but not ERK5, is sufficient for c-Fos phosphorylation and transcriptional activation. Furthermore, growth factor-dependent expression of c-Fos is blocked by low doses of PD184352 that selectively inhibit the ERK1/2 pathway but proceeds normally in ERK5-/- 3T9 cells; in addition, nuclear localization of c-Fos is normal in ERK5-/- cells. ERK5-/- cells are, however, defective for c-Jun expression but this is reversed by re-expression of ERK5. In addition to ERK5, neither the JNK nor p38 pathways can substitute for ERK1/2 in the regulation of c-Fos transcriptional activity. These results demonstrate that c-Fos transcriptional activity is not regulated by the ERK5 pathway; rather, of all the MAPKs and SAPKs, c-Fos activation appears to be predominantly linked to the ERK1/2 pathway.
Gilley
Rebecca
R
Laboratory of Molecular Signalling, The Babraham Institute, Babraham Research Campus, Cambridge, UK. becky.gilley@bbsrc.ac.uk
March
H Nikki
HN
Cook
Simon J
SJ
D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048054:Mitogen-Activated Protein Kinase 7 / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects; D016760:Proto-Oncogene Proteins c-fos / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects / Q000235:genetics*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D047428:Protein Kinase Inhibitors; D016760:Proto-Oncogene Proteins c-fos; D018808:Transcription Factor AP-1; D004815:Epidermal Growth Factor; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048054:Mitogen-Activated Protein Kinase 7; D048051:p38 Mitogen-Activated Protein Kinases