Toll-like receptors that sense viral infection |
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Authors: | Seya Tsukasa Shingai Masashi Matsumoto Misako |
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Affiliation: | Department of Immunology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Higashinari-ku, Osaka, 537-8511, Japan. seya-tu@med.hokudai.ac.jp |
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Abstract: | Anti-viral host defense harbors a variety of strategies to coup with viral infection. Recent findings suggested that Toll-like receptors (TLRs) and their signaling pathways involve type I IFN induction in response to virus-specific molecular patterns. TLR 3 and TLR 4 in myeloid dendritic cells (mDCs) recognize viral dsRNA and putative viral products, respectively, to induce IFN-beta via IRF-3 activation. On the other hand, TLR 7 and TLR 9 in plasmacytoid DCs (pDCs) induce IFN-alpha in response to their ligands, U/G-rich ssRNA and non-methylated CpG DNA. We identified TICAM-1 which is recruited to the cytoplasmic domain (designated TIR) of TLR 3 and allows to select the pathway to activation of IRF-3. We also identified TICAM-2 which binds TLR 4 and together with TICAM-1 activates IRF-3. TICAM-1 knockdown by RNAi supported the key role of TICAM-1 in IFN-beta induction. Hence, the IFN-beta induction in mDCs appears in part due to the function of TICAM-1. Viruses are known to activate kinases that directly activate IRF-3 inside the cells, and this pathway may merge with the TLR 3-TICAM-1 pathway. Here we review the relationship between the TLR 3-TICAM-1 pathway and viral infection. |
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