title: Cell-cycle arrest by PD184352 requires inhibition of extracellular signal-regulated kinases (ERK) 1/2 but not ERK5/BMK1.
abstract: Serum and growth factors activate both the canonical extracellular signal-regulated kinase (ERK) 1/2 pathway and the ERK5/big mitogen-activated protein kinase 1 (BMK) 1 pathway. Pharmacological inhibition of the ERK1/2 pathway using PD98059 and U0126 prevents cyclin D1 expression and inhibits cell proliferation, arguing that the ERK1/2 pathway is rate limiting for cell-cycle re-entry. However, both PD98059 and U0126 also inhibit the ERK5/BMK1 pathway, raising the possibility that the anti-proliferative effect of such drugs may be due to inhibition of ERK5 or both pathways. Here we characterize the effect of the novel mitogen-activated protein kinase/ERK kinase (MEK) inhibitor, PD184352, on the ERK1/2 and ERK5 pathways in the Chinese hamster fibroblast cell line CCl39. In quiescent cells, serum-stimulated ERK1 activity was completely inhibited by PD184352 with an IC50 below 1 microM, whereas ERK5 activation was unaffected even at 20 microM. Serum-stimulated DNA synthesis and cyclin D1 expression was inhibited by low doses of PD184352, which abolished ERK1 activity but had no effect on ERK5. Similarly, in cycling cells PD184352 caused a dose-dependent G1 arrest and inhibition of cyclin D1 expression at low doses, which inhibited ERK1 but were without effect on ERK5. These results indicate that the anti-proliferative effect of PD184352 is due to inhibition of the classical ERK1/2 pathway and does not require inhibition of the ERK5 pathway.
authors.affiliation: Signalling Programme, The Babraham Institute, Babraham Hall, Cambridge CB2 4AT, UK.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Squires
authors.forename: Paula M
authors.initials: PM
authors.lastname: Nixon
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Cook
mesh_terms: D000818:Animals; D001549:Benzamides / Q000494:pharmacology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects*; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000096:biosynthesis; D007700:Kinetics; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors*; D048052:Mitogen-Activated Protein Kinase 3; D048054:Mitogen-Activated Protein Kinase 7; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism
chemical_list: C120227:2-(2-chloro-4-iodophenylamino)-N-cyclopropylmethoxy-3,4-difluorobenzamide; D001549:Benzamides; D004247:DNA; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048054:Mitogen-Activated Protein Kinase 7; D020928:Mitogen-Activated Protein Kinases; D013936:Thymidine