title: Dectin-2 Recognizes Mannosylated O-antigens of Human Opportunistic Pathogens and Augments Lipopolysaccharide Activation of Myeloid Cells.
abstract: LPS consists of a relatively conserved region of lipid A and core oligosaccharide and a highly variable region of O-antigen polysaccharide. Whereas lipid A is known to bind to the Toll-like receptor 4 (TLR4)-myeloid differentiation factor 2 (MD2) complex, the role of the O-antigen remains unclear. Here we report a novel molecular interaction between dendritic cell-associated C-type lectin-2 (Dectin-2) and mannosylated O-antigen found in a human opportunistic pathogen, Hafnia alvei PCM 1223, which has a repeating unit of [-Man-α1,3-Man-α1,2-Man-α1,2-Man-α1,2-Man-α1,3-]. H. alvei LPS induced higher levels of TNFα and IL-10 from mouse bone marrow-derived dendritic cells (BM-DCs), when compared with Salmonella enterica O66 LPS, which has a repeat of [-Gal-α1,6-Gal-α1,4-[Glc-β1,3]GalNAc-α1,3-GalNAc-β1,3-]. In a cell-based reporter assay, Dectin-2 was shown to recognize H. alvei LPS. This binding was inhibited by mannosidase treatment of H. alvei LPS and by mutations in the carbohydrate-binding domain of Dectin-2, demonstrating that H. alvei LPS is a novel glycan ligand of Dectin-2. The enhanced cytokine production by H. alvei LPS was Dectin-2-dependent, because Dectin-2 knock-out BM-DCs failed to do so. This receptor cross-talk between Dectin-2 and TLR4 involved events including spleen tyrosine kinase (Syk) activation and receptor juxtaposition. Furthermore, another mannosylated LPS from Escherichia coli O9a also bound to Dectin-2 and augmented TLR4 activation of BM-DCs. Taken together, these data indicate that mannosylated O-antigens from several Gram-negative bacteria augment TLR4 responses through interaction with Dectin-2.
authors.affiliation: From the Food and Health Institute Strategic Programme, Institute of Food Research, Norwich NR4 7UA, United Kingdom.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Wittmann
authors.affiliation: From the Food and Health Institute Strategic Programme, Institute of Food Research, Norwich NR4 7UA, United Kingdom.
authors.forename: Dimitra
authors.initials: D
authors.lastname: Lamprinaki
authors.affiliation: Norwich Medical School, University of East Anglia, Norwich NR4 7TJ, United Kingdom.
authors.forename: Kristian M
authors.initials: KM
authors.lastname: Bowles
authors.affiliation: the Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Wroclaw 53-114, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Katzenellenbogen
authors.affiliation: the N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 119991, Russia.
authors.forename: Yuriy A
authors.initials: YA
authors.lastname: Knirel
authors.affiliation: the Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Chris
authors.initials: C
authors.lastname: Whitfield
authors.affiliation: the Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Chiba 277-8562, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nishimura
authors.affiliation: the Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Chiba 277-8562, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Matsumoto
authors.affiliation: the Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Chiba 277-8562, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yamamoto
authors.affiliation: the Center for Animal Disease Models, Research Institute for Biomedical Sciences, Tokyo University of Science, Chiba 278-0022, Japan, and.
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Iwakura
authors.affiliation: the Department of Molecular Immunology, Medical Mycology Research Center, Chiba University, Chiba 260-8673, Japan.
authors.forename: Shinobu
authors.initials: S
authors.lastname: Saijo
authors.affiliation: From the Food and Health Institute Strategic Programme, Institute of Food Research, Norwich NR4 7UA, United Kingdom, the Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Chiba 277-8562, Japan, norihito.kawasaki@ifr.ac.uk.
authors.forename: Norihito
authors.initials: N
authors.lastname: Kawasaki
mesh_terms: D000818:Animals; D006090:Gram-Negative Bacteria / Q000276:immunology*; D057809:HEK293 Cells; D006801:Humans; D016753:Interleukin-10 / Q000235:genetics / Q000276:immunology; D037181:Lectins, C-Type / Q000235:genetics / Q000276:immunology*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D022423:Myeloid Cells / Q000276:immunology*; D019081:O Antigens / Q000276:immunology*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000276:immunology
chemical_list: C000593630:CLEC6A protein, human; C508609:IL10 protein, human; C556062:IL10 protein, mouse; D037181:Lectins, C-Type; D019081:O Antigens; C495345:TLR4 protein, human; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; C445340:dectin-2, mouse; D016753:Interleukin-10
keywords: Toll-like receptor 4 (TLR4); immunology; lectin; lipopolysaccharide (LPS); polysaccharide