title: SARS Coronavirus Papain-Like Protease Inhibits the TLR7 Signaling Pathway through Removing Lys63-Linked Polyubiquitination of TRAF3 and TRAF6.
abstract: Severe acute respiratory syndrome coronavirus (SARS-CoV) papain-like protease (PLPro) reportedly inhibits the production of type I interferons (IFNs) and pro-inflammatory cytokines in Toll-like receptor 3 (TLR3) and retinoic acid-inducible gene 1 (RIG-I) pathways. The study investigated the inhibitory effect and its antagonistic mechanism of SARS-CoV PLPro on TLR7-mediated cytokine production. TLR7 agonist (imiquimod (IMQ)) concentration-dependently induced activation of ISRE-, NF-κB- and AP-1-luciferase reporters, as well as the production of IFN-α, IFN-β, TNF-α, IL-6 and IL-8 in human promonocyte cells. However, SARS-CoV PLPro significantly inhibited IMQ-induced cytokine production through suppressing the activation of transcription factors IRF-3, NF-κB and AP-1. Western blot analysis with anti-Lys48 and anti-Lys63 ubiquitin antibodies indicated the SARS-CoV PLPro removed Lys63-linked ubiquitin chains of TRAF3 and TRAF6, but not Lys48-linked ubiquitin chains in un-treated and treated cells. The decrease in the activated state of TRAF3 and TRAF6 correlated with the inactivation of TBK1 in response to IMQ by PLPro. The results revealed that the antagonism of SARS-CoV PLPro on TLR7-mediated innate immunity was associated with the negative regulation of TRAF3/6-TBK1-IRF3/NF-κB/AP1 signals.
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung 404, Taiwan. violet7053@gmail.com.
authors.forename: Shih-Wen
authors.initials: SW
authors.lastname: Li
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung 404, Taiwan. spirit1126@hotmail.com.
authors.forename: Ching-Ying
authors.initials: CY
authors.lastname: Wang
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung 404, Taiwan. alvajou@gmail.com.
authors.forename: Yu-Jen
authors.initials: YJ
authors.lastname: Jou
authors.affiliation: Department of Biotechnology, College of Health Science, Asia University, Wufeng, Taichung 413, Taiwan. shhuang@asia.edu.tw.
authors.forename: Su-Hua
authors.initials: SH
authors.lastname: Huang
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung 404, Taiwan. bonny6789@gmail.com.
authors.forename: Li-Hsin
authors.initials: LH
authors.lastname: Hsiao
authors.affiliation: Department of Medical Genetics and Medical Research, China Medical University Hospital, Taichung 404, Taiwan. lei.joseph@gmail.com.
authors.forename: Lei
authors.initials: L
authors.lastname: Wan
authors.affiliation: Department of Medical Genetics and Medical Research, China Medical University Hospital, Taichung 404, Taiwan. yjlin.kath@gmail.com.
authors.forename: Ying-Ju
authors.initials: YJ
authors.lastname: Lin
authors.affiliation: Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming University, Taipei 112, Taiwan. szkung@ym.edu.tw.
authors.forename: Szu-Hao
authors.initials: SH
authors.lastname: Kung
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung 404, Taiwan. cwlin@mail.cmu.edu.tw.|Department of Biotechnology, College of Health Science, Asia University, Wufeng, Taichung 413, Taiwan. cwlin@mail.cmu.edu.tw.
authors.forename: Cheng-Wen
authors.initials: CW
authors.lastname: Lin
mesh_terms: D000634:Aminoquinolines / Q000494:pharmacology; D002460:Cell Line; D000086782:Coronavirus 3C Proteases; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D016207:Cytokines / Q000378:metabolism; D006801:Humans; D000077271:Imiquimod; D047908:Intracellular Signaling Peptides and Proteins; D009000:Monocytes / Q000378:metabolism; D015398:Signal Transduction; D048008:TNF Receptor-Associated Factor 3 / Q000378:metabolism*; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism*; D051199:Toll-Like Receptor 7 / Q000819:agonists / Q000378:metabolism*; D054875:Ubiquitination; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000634:Aminoquinolines; D016207:Cytokines; D047908:Intracellular Signaling Peptides and Proteins; C495348:TLR7 protein, human; D048008:TNF Receptor-Associated Factor 3; D048029:TNF Receptor-Associated Factor 6; C090656:TRAF3 protein, human; C000604754:Tifab protein, human; D051199:Toll-Like Receptor 7; D014764:Viral Proteins; D003546:Cysteine Endopeptidases; D000086782:Coronavirus 3C Proteases; D000077271:Imiquimod
keywords: Lys63-linked polyubiquitin chains; SARS-CoV; TRAF3; TRAF6; Toll-like receptor 7; imiquimod