title: Mitochondrial protein mitofusin 2 is required for NLRP3 inflammasome activation after RNA virus infection.
abstract: Nod-like receptor family, pyrin domain-containing 3 (NLRP3), is involved in the early stages of the inflammatory response by sensing cellular damage or distress due to viral or bacterial infection. Activation of NLRP3 triggers its assembly into a multimolecular protein complex, termed "NLRP3 inflammasome." This event leads to the activation of the downstream molecule caspase-1 that cleaves the precursor forms of proinflammatory cytokines, such as interleukin 1 beta (IL-1β) and IL-18, and initiates the immune response. Recent studies indicate that the reactive oxygen species produced by mitochondrial respiration is critical for the activation of the NLRP3 inflammasome by monosodium urate, alum, and ATP. However, the precise mechanism by which RNA viruses activate the NLRP3 inflammasome is not well understood. Here, we show that loss of mitochondrial membrane potential [ΔΨ(m)] dramatically reduced IL-1β secretion after infection with influenza, measles, or encephalomyocarditis virus (EMCV). Reduced IL-1β secretion was also observed following overexpression of the mitochondrial inner membrane protein, uncoupling protein-2, which induces mitochondrial proton leakage and dissipates ΔΨ(m). ΔΨ(m) was required for association between the NLRP3 and mitofusin 2, a mediator of mitochondrial fusion, after infection with influenza virus or EMCV. Importantly, the knockdown of mitofusin 2 significantly reduced the secretion of IL-1β after infection with influenza virus or EMCV. Our results provide insight into the roles of mitochondria in NLRP3 inflammasome activation.
authors.affiliation: Division of Viral Infection, Department of Infectious Disease Control, International Research Center for Infectious Diseases, Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ichinohe
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Yamazaki
authors.forename: Takumi
authors.initials: T
authors.lastname: Koshiba
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Yanagi
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002352:Carrier Proteins / Q000276:immunology*; D020558:GTP Phosphohydrolases / Q000276:immunology*; D058847:Inflammasomes / Q000276:immunology*; D053583:Interleukin-1beta / Q000276:immunology; D007473:Ion Channels / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D024101:Mitochondrial Proteins / Q000378:metabolism; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D012327:RNA Virus Infections / Q000276:immunology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D000071246:Uncoupling Protein 2
chemical_list: D002352:Carrier Proteins; D058847:Inflammasomes; D053583:Interleukin-1beta; D007473:Ion Channels; D024101:Mitochondrial Proteins; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C492716:Nlrp3 protein, mouse; D017382:Reactive Oxygen Species; C000604390:Ucp2 protein, mouse; D000071246:Uncoupling Protein 2; D020558:GTP Phosphohydrolases; C488751:Mfn2 protein, mouse
keywords: innate immunity; mitochondria