Double-stranded RNA signaling by Toll-like receptor 3 requires specific tyrosine residues in its cytoplasmic domain.
Double-stranded (ds) RNA, a common product of viral infection, can induce transcription of many cellular genes, including the 561 gene that encodes P56, a regulator of protein synthesis. Here, we report that induction of the 561 mRNA by exogenous dsRNA is mediated by Toll-like receptor 3 (TLR3), and it requires no new protein synthesis. Because gene induction by dsRNA is blocked by inhibitors of tyrosine kinases, we investigated the potential roles of the five tyrosine residues present in the cytoplasmic domain of TLR3 by their individual and combinatorial mutations. Transfection assays, using a reporter gene driven by the 561 promoter, identified specific tyrosine residues to be essential for TLR3 signaling. This conclusion was further validated in permanent cell lines expressing tyrosine-mutant TLR3 proteins; in some of these cell lines dsRNA failed to induce the 561 mRNA. Our results provide the first demonstration of the importance of TLR3 cytoplasmic tyrosine residues in dsRNA signaling.
Sarkar
Saumendra N
SN
Department of Molecular Biology, The Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Smith
Heather L
HL
Rowe
Theresa M
TM
Sen
Ganes C
GC
D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D029721:Drosophila Proteins; D005786:Gene Expression Regulation; D006801:Humans; D007370:Interferon Type I / Q000235:genetics; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D017434:Protein Structure, Tertiary / Q000235:genetics; D012330:RNA, Double-Stranded / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D051196:Toll-Like Receptor 3; D051193:Toll-Like Receptors; D015533:Transcriptional Activation; D014443:Tyrosine
D029721:Drosophila Proteins; D007370:Interferon Type I; D008562:Membrane Glycoproteins; D012330:RNA, Double-Stranded; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C495344:TLR3 protein, human; D051196:Toll-Like Receptor 3; D051193:Toll-Like Receptors; D014443:Tyrosine