title: NLRX1 prevents mitochondrial induced apoptosis and enhances macrophage antiviral immunity by interacting with influenza virus PB1-F2 protein.
abstract: To subvert host immunity, influenza A virus (IAV) induces early apoptosis in innate immune cells by disrupting mitochondria membrane potential via its polymerase basic protein 1-frame 2 (PB1-F2) accessory protein. Whether immune cells have mechanisms to counteract PB1-F2-mediated apoptosis is currently unknown. Herein, we define that the host mitochondrial protein nucleotide-binding oligomerization domain-like receptor (NLR)X1 binds to viral protein PB1-F2, preventing IAV-induced macrophage apoptosis and promoting both macrophage survival and type I IFN signaling. We initially observed that Nlrx1-deficient mice infected with IAV exhibited increased pulmonary viral replication, as well as enhanced inflammatory-associated pulmonary dysfunction and morbidity. Analysis of the lungs of IAV-infected mice revealed markedly enhanced leukocyte recruitment but impaired production of type I IFN in Nlrx1(-/-) mice. Impaired type I IFN production and enhanced viral replication was recapitulated in Nlrx1(-/-) macrophages and was associated with increased mitochondrial mediated apoptosis. Through gain- and loss-of-function strategies for protein interaction, we identified that NLRX1 directly bound PB1-F2 in the mitochondria of macrophages. Using a recombinant virus lacking PB1-F2, we confirmed that deletion of PB1-F2 abrogated NLRX1-dependent macrophage type I IFN production and apoptosis. Thus, our results demonstrate that NLRX1 acts as a mitochondrial sentinel protecting macrophages from PB1-F2-induced apoptosis and preserving their antiviral function. We further propose that NLRX1 is critical for macrophage immunity against IAV infection by sensing the extent of viral replication and maintaining a protective balance between antiviral immunity and excessive inflammation within the lungs.
authors.affiliation: Department of Medicine, Department of Microbiology and Immunology, Department of Pathology, McGill University Health Centre, McGill International TB Centre, Meakins-Christie Laboratories, McGill University, Montreal, QC, Canada H2X 2P2;
authors.forename: Joanna
authors.initials: J
authors.lastname: Jaworska
authors.affiliation: Department of Medicine, Department of Microbiology and Immunology, Department of Pathology, McGill University Health Centre, McGill International TB Centre, Meakins-Christie Laboratories, McGill University, Montreal, QC, Canada H2X 2P2;
authors.forename: François
authors.initials: F
authors.lastname: Coulombe
authors.affiliation: Department of Medicine, Department of Microbiology and Immunology, Department of Pathology, McGill University Health Centre, McGill International TB Centre, Meakins-Christie Laboratories, McGill University, Montreal, QC, Canada H2X 2P2;
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Downey
authors.affiliation: Department of Medicine, Department of Microbiology and Immunology, Department of Pathology, McGill University Health Centre, McGill International TB Centre, Meakins-Christie Laboratories, McGill University, Montreal, QC, Canada H2X 2P2;
authors.forename: Fanny
authors.initials: F
authors.lastname: Tzelepis
authors.affiliation: Department of Medicine, Department of Microbiology and Immunology, Department of Pathology, McGill University Health Centre, McGill International TB Centre, Meakins-Christie Laboratories, McGill University, Montreal, QC, Canada H2X 2P2;
authors.forename: Karim
authors.initials: K
authors.lastname: Shalaby
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada M5S 1A8;
authors.forename: Ivan
authors.initials: I
authors.lastname: Tattoli
authors.affiliation: Department of Medicine, Department of Microbiology and Immunology, Department of Pathology, McGill University Health Centre, McGill International TB Centre, Meakins-Christie Laboratories, McGill University, Montreal, QC, Canada H2X 2P2;
authors.forename: Julie
authors.initials: J
authors.lastname: Berube
authors.affiliation: Department of Medicine, Department of Microbiology and Immunology, Department of Pathology, McGill University Health Centre, McGill International TB Centre, Meakins-Christie Laboratories, McGill University, Montreal, QC, Canada H2X 2P2;
authors.forename: Simon
authors.initials: S
authors.lastname: Rousseau
authors.affiliation: Department of Medicine, Department of Microbiology and Immunology, Department of Pathology, McGill University Health Centre, McGill International TB Centre, Meakins-Christie Laboratories, McGill University, Montreal, QC, Canada H2X 2P2;
authors.forename: James G
authors.initials: JG
authors.lastname: Martin
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada M5S 1A8;
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Girardin
authors.affiliation: Department of Pediatrics, University of Tennessee Health Sciences Center, Memphis, TN 38103; andDepartment of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105-2794.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: McCullers
authors.affiliation: Department of Medicine, Department of Microbiology and Immunology, Department of Pathology, McGill University Health Centre, McGill International TB Centre, Meakins-Christie Laboratories, McGill University, Montreal, QC, Canada H2X 2P2; maziar.divangahi@mcgill.ca.
authors.forename: Maziar
authors.initials: M
authors.lastname: Divangahi
mesh_terms: D000818:Animals; D017209:Apoptosis; D045744:Cell Line, Tumor; D006801:Humans; D007249:Inflammation; D009980:Influenza A virus / Q000276:immunology* / Q000502:physiology; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D014764:Viral Proteins / Q000378:metabolism*; D014779:Virus Replication
chemical_list: D024101:Mitochondrial Proteins; C555655:NLRX1 protein, mouse; C442816:PB1-F2 protein, Influenza A virus; D014764:Viral Proteins
keywords: Nod-like receptor; innate immunity