title: Phosphorylation of p42/44(MAPK) by various signal transduction pathways activates cytosolic phospholipase A(2) to variable degrees.
abstract: Arachidonic acid has been implicated to play a role in physiological and pathophysiological processes and is selectively released by the 85-kDa cytosolic phospholipase A(2) (cPLA(2)). The activity of cPLA(2) is regulated by calcium, translocating the enzyme to its substrate, and by phosphorylation by a mitogen-activated protein kinase (MAPK) family member and a MAPK-activated protein kinase. In this study, the signal transduction pathways in growth factor-induced phosphorylation of p42/44(MAPK) and cPLA(2) activation were investigated in Her14 fibroblasts. p42/44(MAPK) in response to epidermal growth factor was not only phosphorylated via the Raf-MEK pathway but mainly through protein kinase C (PKC) or a related or unrelated kinase in which the phosphorylated p42/44(MAPK) corresponded with cPLA(2) activity. Serum-induced phosphorylation of p42/44(MAPK) also corresponded with cPLA(2) activity but is predominantly mediated via Raf-MEK and partly through PKC or a related or unrelated kinase. In contrast, activation of PKC by phorbol ester did not result in increased cPLA(2) activity, while p42/44(MAPK) is phosphorylated, mainly via Raf-MEK and through MEK. Moreover, p42/44(MAPK) phosphorylation is present in quiescent and proliferating cells, and p42/44(MAPK) is entirely phosphorylated via Raf-MEK, but it only corresponds to cPLA(2) activity in the former cells. Collectively, these data show that p42/44(MAPK) in proliferating, quiescent, and stimulated cells is phosphorylated by various signal transduction pathways, suggesting the activation of different populations of p42/44(MAPK) and cPLA(2).
authors.affiliation: Department of Molecular Cell Biology, Utrecht University, Utrecht 3584 CH, The Netherlands. G.S.A.T.vanRossum@bio.uu.nl
authors.forename: G S
authors.initials: GS
authors.lastname: van Rossum
authors.forename: R
authors.initials: R
authors.lastname: Klooster
authors.forename: H
authors.initials: H
authors.lastname: van den Bosch
authors.forename: A J
authors.initials: AJ
authors.lastname: Verkleij
authors.forename: J
authors.initials: J
authors.lastname: Boonstra
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000235:genetics / Q000502:physiology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D048728:MAP Kinase Kinase Kinase 1; D020935:MAP Kinase Signaling System / Q000502:physiology; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D010741:Phospholipases A / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection
chemical_list: D002070:Butadienes; D004791:Enzyme Inhibitors; D005419:Flavonoids; D009570:Nitriles; D011994:Recombinant Proteins; C113580:U 0126; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D011493:Protein Kinase C; 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; C482578:Map3k1 protein, mouse; D010741:Phospholipases A; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D002118:Calcium