Hepatitis C virus core protein suppresses NF-kappaB activation and cyclooxygenase-2 expression by direct interaction with IkappaB kinase beta.
In addition to hepatocytes, hepatitis C virus (HCV) infects immune cells, including macrophages. However, little is known concerning the impact of HCV infection on cellular functions of these immune effector cells. Lipopolysaccharide (LPS) activates IkappaB kinase (IKK) signalsome and NF-kappaB, which leads to the expression of cyclooxygenase-2 (COX-2), which catalyzes production of prostaglandins, potent effectors on inflammation and possibly hepatitis. Here, we examined whether expression of HCV core interferes with IKK signalsome activity and COX-2 expression in activated macrophages. In reporter assays, HCV core inhibited NF-kappaB activation in RAW 264.7 and MH-S murine macrophage cell lines treated with bacterial LPS. HCV core inhibited IKK signalsome and IKKbeta kinase activities induced by tumor necrosis factor alpha in HeLa cells and coexpressed IKKgamma in 293 cells, respectively. HCV core was coprecipitated with IKappaKappabeta and prevented nuclear translocation of IKKbeta. NF-kappaB activation by either LPS or overexpression of IKKbeta was sufficient to induce robust expression of COX-2, which was markedly suppressed by ectopic expression of HCV core. Together, these data indicate that HCV core suppresses IKK signalsome activity, which blunts COX-2 expression in macrophages. Additional studies are necessary to determine whether interrupted COX-2 expression by HCV core contributes to HCV pathogenesis.
Joo
Myungsoo
M
Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232-2650, USA. myungsoo.joo@vanderbilt.edu
Hahn
Young S
YS
Kwon
Minjae
M
Sadikot
Ruxana T
RT
Blackwell
Timothy S
TS
Christman
John W
JW
D000818:Animals; D002460:Cell Line; D051546:Cyclooxygenase 2; D006367:HeLa Cells; D016174:Hepacivirus / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D006801:Humans; D051550:I-kappa B Kinase; D008070:Lipopolysaccharides / Q000494:pharmacology; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology / Q000378:metabolism / Q000821:virology; D008565:Membrane Proteins; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014758:Viral Core Proteins / Q000378:metabolism*
D008070:Lipopolysaccharides; D008565:Membrane Proteins; D016328:NF-kappa B; D014758:Viral Core Proteins; C069130:nucleocapsid protein, Hepatitis C virus; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; C496564:Chuk protein, mouse; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse