title: Expression and function of RIG-I in oral keratinocytes and fibroblasts.
abstract: BACKGROUND
  Innate immune response by oral mucosal cells may be the first line of host defense against viral infection. Retinoic acid-inducible gene-I (RIG-I) recognizes viral dsRNA in the cytoplasm, and RIG-I-mediated signaling regulates antiviral type I IFN, and inflammatory chemokine production. Here, we tested the hypothesis that oral mucosal cell participation in host defense against viral infection via RIG-I.
  
  
  METHODS
  RIG-I expression was detected in immortalized oral keratinocytes (RT7), oral fibroblasts (GT1) using and RT-PCR and immunohistochemistry. RT7 and GT1 were exposed to dsRNA virus mimic Poly I:C-LMW/LyoVec (PLV). Expression of IFN-β and CXCL10 via RIG-I was examined by Real-time RT-PCR and ELISA. Phosphorylation of IRF3 and STAT1 were detected by western blotting.
  
  
  RESULTS
  RT7 and GT1 constitutively expressed RIG-I in the cytoplasm. Furthermore, PLV increased IFN-β and CXCL10 productions in both RT7 and GT1 via RIG-I concurrent with phosphorylation of IRF3 and STAT1. PLV-induced CXCL10 production was attenuated by neutralization of IFN-β and blocking of IFN-α/β receptor (IFNAR), indicating primal IFN-β production via the RIG-I-IRF3 axis, which eventually induces CXCL10 production via the IFNAR -STAT1 axis.
  
  
  CONCLUSIONS
  We propose that RIG-I in oral keratinocytes and fibroblasts may cumulatively develop host-defense mechanisms against viral infection in oral mucosa.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Division of Cervico-Gnathostmatology, Programs for Applied Biomedicine, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-Ku, Hiroshima, Japan.
authors.forename: Kouji
authors.initials: K
authors.lastname: Ohta
authors.forename: Akiko
authors.initials: A
authors.lastname: Fukui
authors.forename: Hideo
authors.initials: H
authors.lastname: Shigeishi
authors.forename: Yoko
authors.initials: Y
authors.lastname: Ishida
authors.forename: Hiromi
authors.initials: H
authors.lastname: Nishi
authors.forename: Kei
authors.initials: K
authors.lastname: Tobiume
authors.forename: Masaaki
authors.initials: M
authors.lastname: Takechi
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Kamata
mesh_terms: D002460:Cell Line; D054357:Chemokine CXCL10 / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000235:genetics* / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D007113:Immunity, Innate / Q000235:genetics; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism; D016899:Interferon-beta / Q000378:metabolism; D015603:Keratinocytes / Q000378:metabolism*; D009061:Mouth Mucosa / Q000378:metabolism*; D010766:Phosphorylation / Q000235:genetics; D012330:RNA, Double-Stranded / Q000235:genetics; D053633:Receptor, Interferon alpha-beta / Q000378:metabolism; D011971:Receptors, Immunologic; D050794:STAT1 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics
chemical_list: C114753:CXCL10 protein, human; D054357:Chemokine CXCL10; C507964:IFNAR1 protein, human; C494232:IRF3 protein, human; D050838:Interferon Regulatory Factor-3; D012330:RNA, Double-Stranded; D011971:Receptors, Immunologic; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D053633:Receptor, Interferon alpha-beta; D016899:Interferon-beta; C452820:RIGI protein, human; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases