title: Cathepsins are required for Toll-like receptor 9 responses.
abstract: Toll-like receptors (TLR) recognize a variety of microbial products and activate defense responses. Pathogen sensing by TLR2/4 requires accessory molecules, whereas little is known about a molecule required for DNA recognition by TLR9. After endocytosis of microbes, microbial DNA is exposed and recognized by TLR9 in lysosomes. We here show that cathepsins, lysosomal cysteine proteases, are required for TLR9 responses. A cell line Ba/F3 was found to be defective in TLR9 responses despite enforced TLR9 expression. Functional cloning with Ba/F3 identified cathepsin B/L as a molecule required for TLR9 responses. The protease activity was essential for the complementing effect. TLR9 responses were also conferred by cathepsin S or F, but not by cathepsin H. TLR9-dependent B cell proliferation and CD86 upregulation were apparently downregulated by cathepsin B/L inhibitors. Cathepsin B inhibitor downregulated interaction of CpG-B with TLR9 in 293T cells. These results suggest roles for cathepsins in DNA recognition by TLR9.
authors.affiliation: Division of Infectious Genetics, The Institute of Medical Science, Department of Microbiology and Immunology, The University of Tokyo, 4-6-1 Shirokanedai, Minatoku, Tokyo 108-8639, Japan.
authors.forename: Fumi
authors.initials: F
authors.lastname: Matsumoto
authors.forename: Shin-Ichiroh
authors.initials: S
authors.lastname: Saitoh
authors.forename: Ryutaroh
authors.initials: R
authors.lastname: Fukui
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Natsuko
authors.initials: N
authors.lastname: Tanimura
authors.forename: Kazunori
authors.initials: K
authors.lastname: Konno
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kusumoto
authors.forename: Sachiko
authors.initials: S
authors.lastname: Akashi-Takamura
authors.forename: Kensuke
authors.initials: K
authors.lastname: Miyake
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology; D002403:Cathepsins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D018899:CpG Islands / Q000276:immunology; D004269:DNA, Bacterial / Q000276:immunology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018014:Gene Transfer Techniques; D006801:Humans; D007113:Immunity, Innate / Q000187:drug effects / Q000502:physiology; D008024:Ligands; D008264:Macrophages / Q000187:drug effects / Q000276:immunology; D051379:Mice; D016297:Mutagenesis, Site-Directed; D016328:NF-kappa B / Q000378:metabolism; D009838:Oligodeoxyribonucleotides / Q000276:immunology / Q000493:pharmacokinetics; D012333:RNA, Messenger / Q000378:metabolism; D013154:Spleen / Q000166:cytology; D051217:Toll-Like Receptor 9 / Q000235:genetics / Q000378:metabolism*
chemical_list: C513201:CpG-B 2006; D004269:DNA, Bacterial; D004791:Enzyme Inhibitors; D008024:Ligands; D016328:NF-kappa B; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; C495370:Tlr9 protein, mouse; D051217:Toll-Like Receptor 9; D002403:Cathepsins