Co-regulation of NF-kappaB and inflammasome-mediated inflammatory responses by myxoma virus pyrin domain-containing protein M013.
NF-kappaB and inflammasomes both play central roles in orchestrating anti-pathogen responses by rapidly inducing a variety of early-response cytokines and chemokines following infection. Myxoma virus (MYXV), a pathogenic poxvirus of rabbits, encodes a member of the cellular pyrin domain (PYD) superfamily, called M013. The viral M013 protein was previously shown to bind host ASC-1 protein and inhibit the cellular inflammasome complex that regulates the activation and secretion of caspase 1-regulated cytokines such as IL-1beta and IL-18. Here, we report that human THP-1 monocytic cells infected with a MYXV construct deleted for the M013L gene (vMyxM013-KO), in stark contrast to the parental MYXV, rapidly induce high levels of secreted pro-inflammatory cytokines like TNF, IL-6, and MCP-1, all of which are regulated by NF-kappaB. The induction of these NF-kappaB regulated cytokines following infection with vMyxM013-KO was also confirmed in vivo using THP-1 derived xenografts in NOD-SCID mice. vMyxM013-KO virus infection specifically induced the rapid phosphorylation of IKK and degradation of IkappaBalpha, which was followed by nuclear translocation of NF-kappaB/p65. Even in the absence of virus infection, transiently expressed M013 protein alone inhibited cellular NF-kappaB-mediated reporter gene expression and nuclear translocation of NF-kappaB/p65. Using protein/protein interaction analysis, we show that M013 protein also binds directly with cellular NF-kappaB1, suggesting a direct physical and functional linkage between NF-kappaB1 and ASC-1. We further demonstrate that inhibition of the inflammasome with a caspase-1 inhibitor did not prevent the induction of NF-kappaB regulated cytokines following infection with vMyxM013-KO virus, but did block the activation of IL-1beta. Thus, the poxviral M013 inhibitor exerts a dual immuno-subversive role in the simultaneous co-regulation of both the cellular inflammasome complex and NF-kappaB-mediated pro-inflammatory responses.
Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, Florida, USA.
Masmudur M
MM
Rahman
Mohamed R
MR
Mohamed
Manbok
M
Kim
Sherin
S
Smallwood
Grant
G
McFadden
D000818:Animals; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000235:genetics; D005260:Female; D006367:HeLa Cells; D054884:Host-Pathogen Interactions / Q000235:genetics; D006801:Humans; D007113:Immunity, Innate / Q000187:drug effects / Q000235:genetics; D007249:Inflammation / Q000139:chemically induced / Q000235:genetics* / Q000821:virology; D018836:Inflammation Mediators / Q000494:pharmacology / Q000502:physiology*; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D009233:Myxoma virus / Q000737:chemistry / Q000235:genetics* / Q000472:pathogenicity; D016328:NF-kappa B / Q000494:pharmacology / Q000502:physiology*; D030781:Organisms, Genetically Modified; D017434:Protein Structure, Tertiary / Q000235:genetics; D000071198:Pyrin; D011817:Rabbits; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014764:Viral Proteins / Q000235:genetics*; D023041:Xenograft Model Antitumor Assays
D003598:Cytoskeletal Proteins; D018836:Inflammation Mediators; C000604192:MEFV protein, human; C000604193:Mefv protein, mouse; D016328:NF-kappa B; D000071198:Pyrin; D014764:Viral Proteins