Toll-like receptor 3 associates with c-Src tyrosine kinase on endosomes to initiate antiviral signaling.
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.
Johnsen
Ingvild Bjellmo
IB
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
Nguyen
Thuy Thanh
TT
Ringdal
Monika
M
Tryggestad
Anne Merete
AM
Bakke
Oddmund
O
Lien
Egil
E
Espevik
Terje
T
Anthonsen
Marit W
MW
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
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