title: Toll-like receptor 3 associates with c-Src tyrosine kinase on endosomes to initiate antiviral signaling.
abstract: Double-stranded RNA (dsRNA) is produced during the replication cycle of most viruses and triggers antiviral immune responses through Toll-like receptor 3 (TLR3). However, the molecular mechanisms and subcellular compartments associated with dsRNA-TLR3-mediated signaling are largely unknown. Here we show that c-Src tyrosine kinase is activated by dsRNA in human monocyte-derived dendritic cells, and is recruited to TLR3 in a dsRNA-dependent manner. DsRNA-induced activation of interferon-regulatory factor 3 and signal transducer and activator of transcription 1 was abolished in Src kinase-deficient cells, and restored by adding back c-Src, suggesting a central role of c-Src in antiviral immunity. We also provide evidence that TLR3 is localized in the endoplasmic reticulum of unstimulated cells, moves to dsRNA-containing endosomes in response to dsRNA, and colocalizes with c-Src on endosomes containing dsRNA in the lumen. These results provide novel insight into the molecular mechanisms of TLR3-mediated signaling, which may contribute to the understanding of innate immune responses during viral infections.
authors.affiliation: Department of Laboratory Medicine, Children's and Women's Health, Institute of Laboratory Medicine, Children's and Women's Health, Norwegian University of Science and Technology, Trondheim, Norway. ingvild.Johnsen@ntnu.no
authors.forename: Ingvild Bjellmo
authors.initials: IB
authors.lastname: Johnsen
authors.forename: Thuy Thanh
authors.initials: TT
authors.lastname: Nguyen
authors.forename: Monika
authors.initials: M
authors.lastname: Ringdal
authors.forename: Anne Merete
authors.initials: AM
authors.lastname: Tryggestad
authors.forename: Oddmund
authors.initials: O
authors.lastname: Bakke
authors.forename: Egil
authors.initials: E
authors.lastname: Lien
authors.forename: Terje
authors.initials: T
authors.lastname: Espevik
authors.forename: Marit W
authors.initials: MW
authors.lastname: Anthonsen
mesh_terms: D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D002478:Cells, Cultured; D003713:Dendritic Cells; D011992:Endosomes / Q000201:enzymology* / Q000502:physiology / Q000821:virology*; D004789:Enzyme Activation / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D011505:Protein-Tyrosine Kinases / Q000378:metabolism / Q000502:physiology*; D012330:RNA, Double-Stranded / Q000037:antagonists & inhibitors* / Q000502:physiology; D012229:Rhinovirus / Q000235:genetics / Q000502:physiology*; D050794:STAT1 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D051196:Toll-Like Receptor 3 / Q000378:metabolism / Q000502:physiology*; D019061:src-Family Kinases
chemical_list: D050838:Interferon Regulatory Factor-3; D012330:RNA, Double-Stranded; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; C495344:TLR3 protein, human; D051196:Toll-Like Receptor 3; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human