title: A new non-phagocytic TLR6 with broad recognition ligands from Pacific oyster Crassostrea gigas.
abstract: Toll like receptors (TLRs) are evolutionarily prevalent recognition molecules in the Animalia and Plantae kingdom, which play vital roles in immune defense and homeostasis maintenance. Recently, the expansion of TLRs has been reported in invertebrate genomes, but the characters and immune functions of these expanded TLRs were still not well known. In the present study, a new member of TLR family with five LRR domains was identified in Crassostrea gigas (designated CgTLR6). It shared homology with TLRs from other organisms with the closest phylogenic relationship with molluscan TLRs. The recombinant protein of CgTLR6 (rCgTLR6) displayed direct bind activity to gram-negative bacteria Vibrio anguillarum and Vibrio splendidus, gram-positive bacteria Staphylococci aureus and Micrococcus luteus, and fungi Pichia pastoris, but not to fungi Yarrowia lipolytica. It also exhibited affinity to lipopolysaccharide (LPS) and peptidoglycan (PGN), while no affinity to mannan (MAN). The mRNA of CgTLR6 was mainly detected in hemocytes and hepatopancreas, and was significantly induced (p < 0.01) in hemocytes after the oyster was stimulated with LPS, PGN or bacteria V. splendidus. Immunofluorescence analysis indicated that CgTLR6 was mainly located at the membrane of hemocytes. The blockage of CgTLR6 by anti-rCgTLR6 antibody did not significantly inhibit the phagocytic rates of hemocytes toward recognized gram-negative bacteria V. anguillarum and V. splendidus, and unrecognized fungi Y. lipolytica. These results collectively implied that CgTLR6 was a novel non-phagocytic receptor of C. gigas to mediate humoral immune response by recognizing pathogen-associated molecular patterns on the invaders.
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Weilin
authors.initials: W
authors.lastname: Wang
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian 116023, China. Electronic address: wanglingling@dlou.edu.cn.
authors.forename: Lingling
authors.initials: L
authors.lastname: Wang
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Jiachao
authors.initials: J
authors.lastname: Xu
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Meijia
authors.initials: M
authors.lastname: Li
authors.affiliation: Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian 116023, China.
authors.forename: Anguo
authors.initials: A
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
authors.forename: Limei
authors.initials: L
authors.lastname: Qiu
authors.affiliation: Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian 116023, China.
authors.forename: Linsheng
authors.initials: L
authors.lastname: Song
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D049896:Crassostrea / Q000276:immunology*; D006434:Hemocytes / Q000502:physiology*; D056724:Immunity, Humoral; D009181:Mycoses / Q000276:immunology*; D000069452:Pathogen-Associated Molecular Pattern Molecules / Q000276:immunology / Q000378:metabolism; D010587:Phagocytosis; D010802:Phylogeny; D010843:Pichia / Q000276:immunology*; D051192:Receptors, Pattern Recognition / Q000235:genetics / Q000378:metabolism*; D013203:Staphylococcal Infections / Q000276:immunology*; D051216:Toll-Like Receptor 6 / Q000235:genetics / Q000378:metabolism*; D014735:Vibrio Infections / Q000276:immunology*; D025062:Yarrowia / Q000276:immunology*
chemical_list: D000069452:Pathogen-Associated Molecular Pattern Molecules; D051192:Receptors, Pattern Recognition; D051216:Toll-Like Receptor 6
keywords: CgTLR6; Crassostrea gigas; Immune response; Non-phagocytic receptor; Recognition spectrum