title: Porcine Epidemic Diarrhea Virus 3C-Like Protease Regulates Its Interferon Antagonism by Cleaving NEMO.
abstract: Porcine epidemic diarrhea virus (PEDV) is an enteropathogenic coronavirus causing lethal watery diarrhea in piglets. Since 2010, a PEDV variant has spread rapidly in China, and it emerged in the United States in 2013, posing significant economic and public health concerns. The ability to circumvent the interferon (IFN) antiviral response, as suggested for PEDV, promotes viral survival and regulates pathogenesis of PEDV infections, but the underlying mechanisms remain obscure. Here, we show that PEDV-encoded 3C-like protease, nsp5, is an IFN antagonist that proteolytically cleaves the nuclear transcription factor kappa B (NF-κB) essential modulator (NEMO), an essential adaptor bridging interferon-regulatory factor and NF-κB activation. NEMO is cleaved at glutamine 231 (Q231) by PEDV, and this cleavage impaired the ability of NEMO to activate downstream IFN production and to act as a signaling adaptor of the RIG-I/MDA5 pathway. Mutations specifically disrupting the cysteine protease activity of PEDV nsp5 abrogated NEMO cleavage and the inhibition of IFN induction. Structural analysis suggests that several key residues outside the catalytic sites of PEDV nsp5 probably impact NEMO cleavage by modulating potential interactions of nsp5 with their substrates. These data show that PEDV nsp5 disrupts type I IFN signaling by cleaving NEMO. Previously, we and others demonstrated that NEMO is also cleaved by 3C or 3C-like proteinases of picornavirus and artertivirus. Thus, NEMO probably represents a prime target for 3C or 3C-like proteinases of different viruses.
  
  
  OBJECTIVE
  The continued emergence and reemergence of porcine epidemic diarrhea virus (PEDV) underscore the importance of studying how this virus manipulates the immune responses of its hosts. During coevolution with its hosts, PEDV has acquired mechanisms to subvert host innate immune responses for its survival advantage. At least two proteins encoded by PEDV have been identified as interferon (IFN) antagonists, papain-like protease (PLP) and N protein. Here, we report that the PEDV nsp5 gene, which encodes the 3C-like protease of PEDV, is another IFN antagonist. Mechanistically, the cysteine protease activity of PEDV nsp5 mediates proteolysis of NEMO, the key adaptor for IFN synthesis, and NEMO is cleaved at glutamine 231 (Q231). The new molecular details and determinants impacting NEMO scission by PEDV nsp5 delineated in this study are fundamental to our understanding of critical virus-host interactions that determine PEDV pathogenesis.
authors.affiliation: State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China.
authors.forename: Dang
authors.initials: D
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China.
authors.forename: Liurong
authors.initials: L
authors.lastname: Fang
authors.affiliation: State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China.
authors.forename: Yanling
authors.initials: Y
authors.lastname: Shi
authors.affiliation: State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China.
authors.forename: Huan
authors.initials: H
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China.
authors.forename: Li
authors.initials: L
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China.
authors.forename: Guiqing
authors.initials: G
authors.lastname: Peng
authors.affiliation: State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China.
authors.forename: Huanchun
authors.initials: H
authors.lastname: Chen
authors.affiliation: Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center, Memphis, Tennessee, USA.
authors.forename: Kui
authors.initials: K
authors.lastname: Li
authors.affiliation: State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China vet@mail.hzau.edu.cn.
authors.forename: Shaobo
authors.initials: S
authors.lastname: Xiao
mesh_terms: D000086042:3C Viral Proteases; D000818:Animals; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D004252:DNA Mutational Analysis; D054884:Host-Pathogen Interactions; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism*; D057131:Immune Evasion; D007372:Interferons / Q000037:antagonists & inhibitors*; D053485:Porcine epidemic diarrhea virus / Q000201:enzymology* / Q000235:genetics / Q000276:immunology*; D059748:Proteolysis; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D014764:Viral Proteins; D007372:Interferons; D051550:I-kappa B Kinase; D003546:Cysteine Endopeptidases; D000086042:3C Viral Proteases