title: Phosphorylation of raf-1 by kinase suppressor of ras is inhibited by "MEK-specific" inhibitors PD 098059 and U0126 in differentiating HL60 cells.
abstract: Determination of the involvement of MAP kinase cascades in signaling cell growth or differentiation is aided by the use of the inhibitors PD 098059 [2-(2'-amino-3'-methoxyphenyl)oxananphthalen-4-one] and U0126 [1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio)butadiene], believed to be MEK-specific kinase inhibitors. We report here that the activity of kinase suppressor of ras (KSR-1), a kinase upstream of raf-1, is inhibited by both these compounds at concentrations similar to those that inhibit MEK-1. Further, in HL60 cells induced to differentiate with 1,25-dihydroxyvitamin D(3) raf-1 and p90RSK, but not ERK1/2, are coregulated, and their expression as well as monocytic differentiation is inhibited in parallel by PD 098059. Thus, in this system raf-1 is phosphorylated by KSR-1, and PD 098059 as well as U0126 inhibits this phosphorylation. This suggests great caution in the interpretation of experiments that utilize these pharmacological inhibitors of kinase activity as evidence for a role for the MEK--ERK module in ras or raf-1 signaling.
authors.affiliation: Department of Pathology and Laboratory Medicine, UMD-New Jersey Medical School, Newark, New Jersey 07103, USA.
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: G P
authors.initials: GP
authors.lastname: Studzinski
mesh_terms: D002070:Butadienes / Q000494:pharmacology; D002117:Calcitriol / Q000494:pharmacology*; D002454:Cell Differentiation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D018922:HL-60 Cells; D006801:Humans; D048728:MAP Kinase Kinase Kinase 1; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D009000:Monocytes / Q000166:cytology*; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism*; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D002070:Butadienes; D004791:Enzyme Inhibitors; D005419:Flavonoids; D009570:Nitriles; C113580:U 0126; D011494:Protein Kinases; C097199:KSR-1 protein kinase; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D019893:Ribosomal Protein S6 Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human; D002117:Calcitriol; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one