title: Phosphorylation of initiation factor 4E is resistant to SB203580 in cells expressing a drug-resistant mutant of stress-activated protein kinase 2a/p38.
abstract: Previous work has shown that increased phosphorylation of eukaryotic initiation factor (eIF) 4E at Ser209 in the C-terminal loop of the protein is observed in response to cellular stress. SB203580, a cell permeable inhibitor of stress-activated protein kinase 2a (SAPK2a/p38), suppresses this response in a number of cell types. To validate the in vivo specificity of this inhibitor for the investigation of signalling pathways, which modulate the phosphorylation of eIF4E, we have used 293 cells which inducibly express either a wild-type form (WT-SAPK2a) or a drug-resistant mutant of SAPK2a (DR-SAPK2a). These data show that while the arsenite-induced increase in the phosphorylation of eIF4E and hsp25 was sensitive to SB203580 in cells expressing WT-SAPK2a, these responses to SB203580 were abrogated in cells expressing DR-SAPK2a. In addition, the phosphorylation of the eIF4E kinase, MAP kinase integrating kinase-1 (Mnk1), which is activated in response to growth factors or stress, was insensitive to SB203580 in DR-SAPK2a-expressing cells. However, a cell-permeable, specific inhibitor of Mnk1, CGP57380 and the phosphatidylinositol-3-kinase (PI3-K) inhibitor, LY294002, prevented eIF4E phosphorylation in 293 cells irrespective of SAPK2a expression. Therefore, this study validates the use of SB203580 for investigating signalling pathways modulating the phosphorylation of eIF4E in cultured cells.
authors.affiliation: Biochemistry Laboratory, School of Biological Sciences, University of Sussex, Falmer, BN1 9QG, Brighton, UK. s.j.morley@sussex.ac.uk
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Morley
authors.forename: Susanne
authors.initials: S
authors.lastname: Naegele
mesh_terms: D000814:Aniline Compounds / Q000494:pharmacology; D018053:Arsenites / Q000494:pharmacology; D002460:Cell Line; D002867:Chromones / Q000494:pharmacology; D004351:Drug Resistance / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D039561:Eukaryotic Initiation Factor-4E / Q000187:drug effects* / Q000378:metabolism*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D009154:Mutation / Q000187:drug effects / Q000235:genetics; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011687:Purines / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D013312:Stress, Physiological / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D000814:Aniline Compounds; D018053:Arsenites; D002867:Chromones; D004791:Enzyme Inhibitors; D039561:Eukaryotic Initiation Factor-4E; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D020928:Mitogen-Activated Protein Kinases; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011687:Purines; D011725:Pyridines; D048051:p38 Mitogen-Activated Protein Kinases; C466997:CGP 57380; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C491395:MKNK1 protein, human; C015001:arsenite; C093642:SB 203580