title: Myxoma virus lacking the pyrin-like protein M013 is sensed in human myeloid cells by both NLRP3 and multiple Toll-like receptors, which independently activate the inflammasome and NF-κB innate response pathways.
abstract: The myxoma virus (MYXV)-encoded pyrin domain-containing protein M013 coregulates inflammatory responses mediated by both the inflammasome and the NF-κB pathways. Infection of human THP-1 monocytic cells with a MYXV construct deleted for the M013 gene (vMyxM013-KO), but not the parental MYXV, activates both the inflammasome and NF-κB pathways and induces a spectrum of proinflammatory cytokines and chemokines, like interleukin-1β (IL-1β), tumor necrosis factor (TNF), IL-6, and monocyte chemoattractant protein 1. Here, we report that vMyxM013-KO virus-mediated activation of inflammasomes and secretion of IL-1β are dependent on the adaptor protein ASC, caspase-1, and NLRP3 receptor. However, vMyxM013-KO virus-mediated activation of NF-κB signaling, which induces TNF secretion, was independent of ASC, caspase-1, and either the NLRP3 or AIM2 inflammasome receptors. We also report that early synthesis of pro-IL-1β in response to vMyxM013-KO infection is dependent upon the components of the inflammasome complex. Activation of the NLRP3 inflammasome and secretion of IL-1β was also dependent on the release of cathepsin B and production of reactive oxygen species (ROS). By using small interfering RNA screening, we further demonstrated that, among the RIG-I-like receptors (RLRs) and Toll-like receptors (TLRs), only TLR2, TLR6, TLR7, and TLR9 contribute to the NF-κB-dependent secretion of TNF and the inflammasome-dependent secretion of IL-1β in response to vMyxM013-KO virus infection. Additionally, we demonstrate that early triggering of the mitogen-activated protein kinase pathway by vMyxM013-KO virus infection of THP-1 cells plays a critical common upstream role in the coordinate induction of both NF-κB and inflammasome pathways. We conclude that an additional cellular sensor(s)/receptor(s) in addition to the known RLRs/TLRs plays a role in the M013 knockout virus-induced activation of NF-κB pathway signaling, but the activation of inflammasomes entirely depends on sensing by the NLRP3 receptor in response to vMyxM013-KO infection of human myeloid cells.
authors.affiliation: Department of Molecular Genetics and Microbiology, University of Florida, 1600 SW Archer Road, Gainesville, FL 32610, USA.
authors.forename: Masmudur M
authors.initials: MM
authors.lastname: Rahman
authors.forename: Grant
authors.initials: G
authors.lastname: McFadden
mesh_terms: D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D020170:Caspase 1 / Q000378:metabolism; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007113:Immunity, Innate; D058847:Inflammasomes / Q000378:metabolism*; D053583:Interleukin-1beta / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009000:Monocytes / Q000378:metabolism; D022423:Myeloid Cells / Q000378:metabolism*; D009233:Myxoma virus / Q000235:genetics* / Q000276:immunology; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D011213:Poxviridae Infections / Q000235:genetics / Q000276:immunology* / Q000821:virology; D017434:Protein Structure, Tertiary; D000071198:Pyrin; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D051193:Toll-Like Receptors / Q000378:metabolism*; D014412:Tumor Virus Infections / Q000235:genetics / Q000276:immunology* / Q000821:virology; D014764:Viral Proteins / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D058847:Inflammasomes; D053583:Interleukin-1beta; D015850:Interleukin-6; C000604192:MEFV protein, human; D016328:NF-kappa B; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C453881:NLRP3 protein, human; D000071198:Pyrin; D017382:Reactive Oxygen Species; D051193:Toll-Like Receptors; D014764:Viral Proteins; D020928:Mitogen-Activated Protein Kinases; D020170:Caspase 1