title: Subcellular localization of Toll-like receptor 3 in human dendritic cells.
abstract: Toll-like receptor (TLR)3 recognizes dsRNA and transduces signals to activate NF-kappaB and IFN-beta promoter. Type I IFNs (IFN-alpha/beta) function as key cytokines in anti-viral host defense. Human fibroblasts express TLR3 on the cell surface, and anti-TLR3 mAb inhibits dsRNA-induced IFN-beta secretion by fibroblasts, suggesting that TLR3 acts on the cell surface to sense viral infection. In this study, we examined the expression and localization of human TLR3 in various DC subsets using anti-TLR3 mAb. In monocyte-derived immature dendritic cells (iDCs), TLR3 predominantly resided inside the cells but not on the cell surface. iDCs produced IL-12p70 and IFN-alpha and -beta in response to poly(I:C). Similar response was observed in iDCs treated with rotavirus-derived dsRNA. These responses could not be blocked by pretreatment of the cells with anti-TLR3 mAb. In CD11c(+) blood DCs, cytoplasmic retention of TLR3 was also observed as in monocyte-derived iDCs, again endorsing a different TLR3 distribution profile from fibroblasts. In precursor DC2, however, TLR3 could not be detected inside or outside the cells. Of note, there was a putative centrosomal protein that shared an epitope with TLR3 in myeloid DCs and precursor DC2, but not peripheral blood monocytes. Immunoelectron microscopic analysis revealed that TLR3, when stably expressed in the murine B cell line Ba/F3, was specifically accumulated in multivesicular bodies, a subcellular compartment situated in endocytic trafficking pathways. Thus, regulation and localization of TLR3 are different in each cell type, which may reflect participation of cell type-specific multiple pathways in antiviral IFN induction via TLR3.
authors.affiliation: Department of Immunology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Higashinari-ku, Osaka, Japan. matumoto.mi@mc.pref.osaka.jp
authors.forename: Misako
authors.initials: M
authors.lastname: Matsumoto
authors.forename: Kenji
authors.initials: K
authors.lastname: Funami
authors.forename: Masako
authors.initials: M
authors.lastname: Tanabe
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Oshiumi
authors.forename: Masashi
authors.initials: M
authors.lastname: Shingai
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Seto
authors.forename: Akitsugu
authors.initials: A
authors.lastname: Yamamoto
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Seya
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry; D002454:Cell Differentiation / Q000276:immunology; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000097:blood / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D016253:Microscopy, Immunoelectron; D009000:Monocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D010950:Plasma Cells / Q000276:immunology / Q000378:metabolism; D011233:Precipitin Tests; D012330:RNA, Double-Stranded / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000096:biosynthesis / Q000097:blood / Q000276:immunology / Q000378:metabolism*; D013347:Subcellular Fractions / Q000276:immunology* / Q000378:metabolism* / Q000648:ultrastructure; D051196:Toll-Like Receptor 3; D051193:Toll-Like Receptors; D014162:Transfection; D022161:Transport Vesicles / Q000378:metabolism / Q000648:ultrastructure; D015854:Up-Regulation / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D016207:Cytokines; D008562:Membrane Glycoproteins; D012330:RNA, Double-Stranded; D011956:Receptors, Cell Surface; C495344:TLR3 protein, human; D051196:Toll-Like Receptor 3; D051193:Toll-Like Receptors