title: Stimulation of DDX3 expression by ginsenoside Rg3 through the Akt/p53 pathway activates the innate immune response via TBK1/IKKε/IRF3 signalling.
abstract: DEAD-box RNA helicase DDX3 is a well-known host factor that inhibits hepatitis B viral proliferation and boosts innate immune responses via TANK-binding kinase 1 (TBK1)/IKKε-mediated and/or interferon (IFN)-β promoter stimulator-1 (IPS-1)-mediated IFN-β induction. Previously, we demonstrated the anti-hepatitis B activity of Rg3 via stimulation of TRAF6/TAK1 degradation and inhibition of JNK/AP-1 signaling. To determine the effects of Rg3 on innate immunity, an IFN-β promoter assay was performed. Rg3 ameliorated IFN-β expression via upregulation of both the TBK1/IKKε pathway and DDX3 expression. In addition, Rg3 induced the phosphorylation of IRF3 and its translocation into nucleus, which is a key molecule to induction of IFN-β expression. To evaluate the molecular mechanism of Rg3 on DDX3 expression, the DDX3 promoter (-1406/+105) was subjected to luciferase assay and ChIP analysis. p53 phosphorylation resulted in upregulation of DDX3 expression, which enhanced DDX3 promoter transactivation activity. Transient transfection with wild-type p53 increased DDX3 promoter activity in Hep3B cells which have null mutant of p53, whereas knockdown p53 by si-p53 reduced DDX3 promoter activity in HepG2.2.15 and HepG2 cells, respectively. Rg3- mediated phosphorylation of p53 resulted in inhibition of Akt phosphorylation, which in turn reduced MDM2-mediated p53 degradation. An Akt inhibitor augmented DDX3 promoter activity and reduced the secretion of hepatitis B surface antigen. Our data indicate that Rg3 enhances innate immunity by inducing IFN-β expression through upregulation of DDX3 promoter activity via p53-mediated transactivation and activation of the TBK1/IKKε/IRF3 pathway.
authors.forename: Yeo-Jin
authors.initials: YJ
authors.lastname: Choi
authors.forename: Li-Jung
authors.initials: LJ
authors.lastname: Kang
authors.affiliation: Department of Biotechnology, Chonnam National University, Gwangju 500-757, Korea. sglee3@chonnam.ac.kr.
authors.forename: Seong-Gene
authors.initials: SG
authors.lastname: Lee
mesh_terms: D053487:DEAD-box RNA Helicases / Q000235:genetics*; D036145:Ginsenosides / Q000494:pharmacology*; D056945:Hep G2 Cells; D006801:Humans; D051550:I-kappa B Kinase / Q000276:immunology*; D007113:Immunity, Innate / Q000187:drug effects; D050838:Interferon Regulatory Factor-3 / Q000276:immunology*; D016899:Interferon-beta / Q000235:genetics; D005894:Panax / Q000737:chemistry; D017346:Protein Serine-Threonine Kinases / Q000276:immunology*; D051057:Proto-Oncogene Proteins c-akt / Q000276:immunology*; D015398:Signal Transduction / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000276:immunology*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D036145:Ginsenosides; C494232:IRF3 protein, human; D050838:Interferon Regulatory Factor-3; D016159:Tumor Suppressor Protein p53; C097367:ginsenoside Rg3; D016899:Interferon-beta; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; C403191:TBK1 protein, human; D051550:I-kappa B Kinase; C119332:DDX3X protein, human; D053487:DEAD-box RNA Helicases