title: A novel phagocytic receptor (CgNimC) from Pacific oyster Crassostrea gigas with lipopolysaccharide and gram-negative bacteria binding activity.
abstract: Phagocytosis is an evolutionarily conserved process to ingest the invading microbes and apoptotic or necrotic corpses, playing vital roles in defensing invaders and maintenance of normal physiological conditions. In the present study, a new Nimrod family phagocytic receptor with three EGF-like domains was identified in Pacific oyster Crassostrea gigas (designated CgNimC). CgNimC shared homology with other identified multiple EGF-like domain containing proteins. The mRNA transcripts of CgNimC were mainly distributed in mantle and hemocytes. Its relative expression level in hemocytes was significantly (P < 0.01) up-regulated after the injection of bacteria Vibrio anguillarum. Different to the NimC in Drosophila and Anopheles gambiae, the recombinant protein of CgNimC (rCgNimC) could bind directly to two gram-negative bacteria V. anguillarum and Vibrio splendidus, but not to gram-positive bacteria Staphylococci aureus, Micrococcus luteus or fungi Yarrowia lipolytica and Pichia pastoris. The affinity of rCgNimC toward M. luteus and Y. lipolytica was enhanced when the microorganisms were pre-incubated with the cell free hemolymph. rCgNimC exhibited higher affinity to lipopolysaccharide (LPS) and relatively lower affinity to peptidoglycan (PGN), while no affinity to glucan (GLU). After the CgNimC receptor was blocked by anti-rCgNimC antibody in vitro, the phagocytic rate of hemocytes toward two gram-negative bacteria V. anguillarum and V. splendidus was reduced significantly (P < 0.05), but no significant change of phagocytic rate was observed toward M. luteus and Y. lipolytica. All these results implied that CgNimC, with significant binding capability to LPS and gram-negative bacteria, was a novel phagocytic receptor involved in immune response of Pacific oyster. Further, it was speculated that receptors of Nimrod family might function as a phagocytic receptor to recognize PAMPs on the invaders and its recognition could be promoted by opsonization of molecules in hemolymph.
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: Rui
authors.initials: R
authors.lastname: Liu
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: Tao
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Ningbo University, Ningbo 315211, China.
authors.forename: Ran
authors.initials: R
authors.lastname: Zhang
authors.affiliation: SUN YAT-SEN University, Guangzhou 510275, China.
authors.forename: Xuan
authors.initials: X
authors.lastname: Song
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China. Electronic address: wanglingling@ms.qdio.ac.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.
authors.forename: Linsheng
authors.initials: L
authors.lastname: Song
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D049896:Crassostrea / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D006090:Gram-Negative Bacteria / Q000502:physiology; D006094:Gram-Positive Bacteria / Q000502:physiology; D006434:Hemocytes; D008070:Lipopolysaccharides / Q000494:pharmacology; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010587:Phagocytosis; D010843:Pichia / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011897:Random Allocation; D051192:Receptors, Pattern Recognition / Q000737:chemistry / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D008070:Lipopolysaccharides; D012333:RNA, Messenger; D051192:Receptors, Pattern Recognition; D011994:Recombinant Proteins
keywords: Crassostrea gigas; Immune response; Lipopolysaccharide; Nimrod; Phagocytic receptor