title: Inhibition of p90 ribosomal S6 kinase-mediated CCAAT/enhancer-binding protein beta activation and cyclooxygenase-2 expression by salicylate.
abstract: We have previously shown that salicylate at a pharmacological concentration suppresses CCAAT/enhancer-binding protein beta (C/EBPbeta) binding, thereby reducing cyclooxygenase-2 (COX-2) and inducible nitric-oxide synthase expression (Saunders, M. A., Sansores-Garcia, L., Gilroy, D. W., and Wu, K. K. (2001) J. Biol. Chem. 276, 18897-18904; Cieslik, K., Zhu, Y., and Wu, K. K. (2002) J. Biol. Chem. 277, 49304-49310). We postulated that salicylate targets a kinase that phosphorylates and activates C/EBPbeta. Here we report the identification of p90 ribosomal S6 kinase (RSK) as a target of salicylate. Salicylate inhibited RSK in vivo and blocked the activity of RSK2 purified from cells stimulated by phorbol 12-myristate 13-acetate (PMA). Mutation of the RSK-phosphorylation site (T266A) of C/EBPbeta abrogated PMA-stimulated C/EBPbeta binding activity. RSK activation was required for PMA-induced COX-2 transcriptional activation. Salicylate also inhibited Ras and extracellular signal-regulated kinase (ERK) activation induced by PMA. We conclude that salicylate inhibits C/EBPbeta-mediated COX-2 transcriptional activation by blocking RSK activity and Ras signaling pathway.
authors.affiliation: Vascular Biology Research Center and Division of Hematology, Brown Foundation Institute of Molecular Medicine and Medical School, The University of Texas Health Science Center and Texas Heart Institute, Houston, Texas 77030-1503, USA.
authors.forename: Katarzyna A
authors.initials: KA
authors.lastname: Cieslik
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhu
authors.forename: Mikhail
authors.initials: M
authors.lastname: Shtivelband
authors.forename: Kenneth K
authors.initials: KK
authors.lastname: Wu
mesh_terms: D022782:CCAAT-Enhancer-Binding Protein-beta / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D051546:Cyclooxygenase 2; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008297:Male; D008565:Membrane Proteins; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000502:physiology*; D012459:Salicylates / Q000494:pharmacology*
chemical_list: D022782:CCAAT-Enhancer-Binding Protein-beta; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D012459:Salicylates; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D038744:Ribosomal Protein S6 Kinases, 90-kDa