Apoptosis signal-regulating kinase 1 in peptidoglycan-induced COX-2 expression in macrophages.
In this study, we investigated the role of ASK1 in PGN-induced C/EBPbeta activation and COX-2 expression in RAW 264.7 macrophages. The PGN-induced COX-2 expression was attenuated by the DNs of ASK1, JNK1, JNK2, a JNK inhibitor (SP600125), and an AP-1 inhibitor (curcumin). PGN caused ASK1 dephosphorylation time-dependently at Ser967, dissociation from the ASK1-14-3-3 complex, and subsequent ASK1 activation. In addition, PGN activated PP2A and suppression of PP2A by okadaic acid markedly inhibited PGN-induced ASK1 Ser967 dephosphorylation and COX-2 expression. PGN induced the activation of the JNK-AP-1 signaling cascade downstream of ASK1. PGN-increased C/EBPbeta expression and DNA-binding activity were inhibited by the ASK1-JNK-AP-1 signaling blockade. COX-2 promoter luciferase activity induced by PGN was attenuated in cells transfected with the COX-2 reporter construct possessing the C/EBP-binding site mutation. In addition, the ASK1-JNK-AP-1-C/EBPbeta cascade was activated in human peripheral mononuclear cells exposure to PGN. The TLR2 agonist Pam(3)CSK(4) was also shown to induce ASK1 Ser967 dephosphorylation, JNK and c-jun phosphorylation, C/EBPbeta activation, and COX-2 expression in RAW 264.7 macrophages. PGN-induced COX-2 promoter luciferase activity was prevented by selective inhibition of TLR2 and c-Jun in RAW 264.7 macrophages. Our data demonstrate that PGN might activate the TLR2-mediated PP2A-ASK1-JNK-AP-1-C/EBPbeta cascade and subsequent COX-2 expression in RAW 264.7 macrophages.
Hsu
Ming-Jen
MJ
Graduate Institute of Medical Sciences, Department of Pharmacology, College of Medicine, Taipei Medical University, 250 Wu-Hsing Street, Taipei 110, Taiwan.
Chang
Chia-Kai
CK
Chen
Mei-Chieh
MC
Chen
Bing-Chang
BC
Ma
Hon-Ping
HP
Hong
Chuang-Ye
CY
Lin
Chien-Huang
CH
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D048848:MAP Kinase Kinase Kinase 5 / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D010457:Peptidoglycan / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D054648:Protein Phosphatase 2 / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D015398:Signal Transduction; D051195:Toll-Like Receptor 2 / Q000819:agonists / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism
D022782:CCAAT-Enhancer-Binding Protein-beta; C545013:Cebpb protein, mouse; D010457:Peptidoglycan; D016755:Proto-Oncogene Proteins c-jun; D051195:Toll-Like Receptor 2; D018808:Transcription Factor AP-1; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2; D048031:JNK Mitogen-Activated Protein Kinases; D048848:MAP Kinase Kinase Kinase 5; C482859:Map3k5 protein, mouse; D054648:Protein Phosphatase 2