title: cPLA(2)α gene activation by IL-1β is dependent on an upstream kinase pathway, enzymatic activation and downstream 15-lipoxygenase activity: a positive feedback loop.
abstract: Cytosolic phospholipase A(2)α (cPLA(2)α) is the most widely studied member of the Group IV PLA(2) family. The enzyme is Ca(2+)-dependent with specificity for phospholipid substrates containing arachidonic acid. As the pinnacle of the arachidonic acid pathway, cPLA(2)α has a primary role in the biosynthesis of a diverse family of eicosanoid metabolites, with potent physiological, inflammatory and pathological consequences. cPLA(2)α activity is regulated by pro-inflammatory stimuli through pathways involving increased intracellular Ca(2+) levels, phosphorylation coupled to increased enzymatic activity and de novo gene transcription. This study addresses the signal transduction pathways for protein phosphorylation and gene induction following IL-1β stimulation in human fetal lung fibroblasts. Our results utilizing both inhibitors and kinase-deficient cells demonstrate that cPLA(2)α is phosphorylated within 10min of IL-1β treatment, an event requiring p38 MAPK as well as the upstream kinase, MKK3/MKK6. Inhibition of p38 MAPK also blocks the phosphorylation of a downstream, nuclear kinase, MSK-1. Our results further demonstrate that the activities of both cPLA(2)α and a downstream lipoxygenase (15-LOX2) are required for IL-1β-dependent induction of cPLA(2)α mRNA expression. Overall, these data support an MKK3/MKK6→p38 MAPK→MSK-1→cPLA(2)α→15-LOX2-dependent, positive feedback loop where a protein's enzymatic activity is required to regulate its own gene induction by a pro-inflammatory stimulus.
authors.affiliation: Department of Neuroscience, University of Florida, Gainesville, FL 32610, USA.
authors.forename: Jewell N
authors.initials: JN
authors.lastname: Walters
authors.forename: Justin S
authors.initials: JS
authors.lastname: Bickford
authors.forename: Dawn E
authors.initials: DE
authors.lastname: Beachy
authors.forename: Kimberly J
authors.initials: KJ
authors.lastname: Newsom
authors.forename: John-David H
authors.initials: JD
authors.lastname: Herlihy
authors.forename: Molly V
authors.initials: MV
authors.lastname: Peck
authors.forename: Xiaolei
authors.initials: X
authors.lastname: Qiu
authors.forename: Harry S
authors.initials: HS
authors.lastname: Nick
mesh_terms: D000818:Animals; D001093:Arachidonate 15-Lipoxygenase / Q000378:metabolism*; D002460:Cell Line; D004789:Enzyme Activation; D025461:Feedback, Physiological; D005449:Fluorenes / Q000494:pharmacology; D015870:Gene Expression; D055786:Gene Knockout Techniques; D054513:Group IV Phospholipases A2 / Q000378:metabolism*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D053583:Interleukin-1beta / Q000494:pharmacology / Q000502:physiology*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D047311:Luteolin / Q000494:pharmacology; D048371:MAP Kinase Kinase 3 / Q000235:genetics / Q000378:metabolism; D048669:MAP Kinase Kinase 6 / Q000235:genetics / Q000378:metabolism; D020935:MAP Kinase Signaling System; D009637:Masoprocol / Q000494:pharmacology; D051379:Mice; D010766:Phosphorylation; D011725:Pyridines / Q000494:pharmacology; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism; D015533:Transcriptional Activation; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
chemical_list: C106248:6,11-dihydro-5-thia-11-aza-benzo(a)-fluorene; D005449:Fluorenes; D007093:Imidazoles; D053583:Interleukin-1beta; D007527:Isoenzymes; D016859:Lipoxygenase Inhibitors; D011725:Pyridines; D009637:Masoprocol; D001093:Arachidonate 15-Lipoxygenase; D038744:Ribosomal Protein S6 Kinases, 90-kDa; C116919:mitogen and stress-activated protein kinase 1; D048051:p38 Mitogen-Activated Protein Kinases; D048371:MAP Kinase Kinase 3; D048669:MAP Kinase Kinase 6; C482530:MAP2K3 protein, human; C482566:MAP2K6 protein, human; D054513:Group IV Phospholipases A2; D047311:Luteolin; C093642:SB 203580; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole