title: Regulation of TLR3 Activation by S100A9.
abstract: Recognition of viral dsRNA by endosomal TLR3 activates innate immune response during virus infection. Trafficking of TLR3 to the endolysosomal compartment arising from fusion of late endosome (LE) with lysosome is required for recognition and detection of pathogen associated molecular patterns, which results in activation of the TLR3-dependent signaling cascade. Existing knowledge about the mechanism(s) and cellular factor(s) governing TLR3 trafficking is limited. In the current study, we identified intracellular S100A9 protein as a critical regulator of TLR3 trafficking. S100A9 was required for maturation of TLR3 containing early endosome (EE) into LE, the compartment that fuses with lysosome to form the endolysosomal compartment. A drastic reduction in cytokine production was observed in S100A9-knockout (KO) primary macrophages following RNA virus infection and treatment of cells with polyinosinic-polycytidylic acid (polyIC; a dsRNA mimetic that acts as a TLR3 agonist). Mechanistic studies revealed colocalization and interaction of S100A9 with TLR3 following polyIC treatment. S100A9-TLR3 interaction was critical for maturation of TLR3 containing EE into LE because TLR3 could not be detected in the LE of polyIC-treated S100A9-KO macrophages. Subsequently, TLR3 failed to colocalize with its agonist (i.e., biotin-labeled polyIC) in S100A9-deficient macrophages. The in vivo physiological role of S100A9 was evident from loss of cytokine production in polyIC-treated S100A9-KO mice. Thus, we identified intracellular S100A9 as a regulator of TLR3 signaling and demonstrated that S100A9 functions during pre-TLR3 activation stages by facilitating maturation of TLR3 containing EE into LE.
authors.affiliation: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164; Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229;
authors.forename: Su-Yu
authors.initials: SY
authors.lastname: Tsai
authors.affiliation: Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229;
authors.forename: Jesus A
authors.initials: JA
authors.lastname: Segovia
authors.affiliation: Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229;
authors.forename: Te-Hung
authors.initials: TH
authors.lastname: Chang
authors.affiliation: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164;
authors.forename: Niraj K
authors.initials: NK
authors.lastname: Shil
authors.affiliation: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164;
authors.forename: Swechha M
authors.initials: SM
authors.lastname: Pokharel
authors.affiliation: Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229;
authors.forename: T R
authors.initials: TR
authors.lastname: Kannan
authors.affiliation: Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229;
authors.forename: Joel B
authors.initials: JB
authors.lastname: Baseman
authors.affiliation: Axe Maladies Infectieuses et Immunitaires, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Faculté de Médecine, Université Laval, Quebec, Quebec G1V 4G2, Canada; and.
authors.forename: Joan
authors.initials: J
authors.lastname: Defrêne
authors.affiliation: Axe Maladies Infectieuses et Immunitaires, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Faculté de Médecine, Université Laval, Quebec, Quebec G1V 4G2, Canada; and.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Pagé
authors.affiliation: Axe Maladies Infectieuses et Immunitaires, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Faculté de Médecine, Université Laval, Quebec, Quebec G1V 4G2, Canada; and Collegium Sciences et Techniques, Université d'Orléans, 45100 Orléans, France.
authors.forename: Annabelle
authors.initials: A
authors.lastname: Cesaro
authors.affiliation: Axe Maladies Infectieuses et Immunitaires, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Faculté de Médecine, Université Laval, Quebec, Quebec G1V 4G2, Canada; and.
authors.forename: Philippe A
authors.initials: PA
authors.lastname: Tessier
authors.affiliation: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164; sbose@vetmed.wsu.edu.
authors.forename: Santanu
authors.initials: S
authors.lastname: Bose
mesh_terms: D000818:Animals; D015153:Blotting, Western; D040502:Calgranulin B / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D005260:Female; D057809:HEK293 Cells; D054884:Host-Pathogen Interactions / Q000276:immunology; D006801:Humans; D016899:Interferon-beta / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism / Q000821:virology; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D011070:Poly I-C / Q000276:immunology / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects / Q000276:immunology; D034622:RNA Interference; D012328:RNA Viruses / Q000276:immunology* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000276:immunology; D051196:Toll-Like Receptor 3 / Q000276:immunology* / Q000378:metabolism
chemical_list: D040502:Calgranulin B; C576329:S100A9 protein, mouse; D051196:Toll-Like Receptor 3; D016899:Interferon-beta; D011070:Poly I-C