title: A C1q domain containing protein from Crassostrea gigas serves as pattern recognition receptor and opsonin with high binding affinity to LPS.
abstract: C1q proteins serve as pattern recognition receptors and involve in the pathogen recognition and complement pathway activation. In the present study, a novel C1q domain containing protein from Crassostrea gigas (designated CgC1qDC-1) was isolated by liposaccharide-Sepharose 6B affinity chromatography. The coding sequence of CgC1qDC-1 gene was determined by performing a homologous search of eight tryptic peptides identified by MALDI-TOF/TOF-MS against the genome of C. gigas. The coding sequence of CgC1qDC-1 was of 387 bp encoding a polypeptide of 128 amino acids containing a typical globular C1q domain. The globular C1q domain possessed eight β strands with a jelly-roll topology structure, which was similar to the structure of human gC1q domain. The mRNA transcripts of CgC1qDC-1 were dominantly expressed in mantle and hemocytes, while low expressed in hepatopancreas, gonad, gill and muscle. The expression level of CgC1qDC-1 increased drastically at 6 h after Vibrio splendidus stimulation, and then gradually fell to the normal level at about 24 h. ELISA assay quantified that CgC1qDC-1 bound to LPS with high binding affinity (Kd = 0.09 × 10(-6) M). Moreover, CgC1qDC-1 significantly enhanced the phagocytosis of oyster hemocytes towards Gram-negative bacteria Escherichia coli and V. splendidus. These results collectively indicated that CgC1qDC-1 could serve as pattern recognition receptor and opsonin in the innate immune response against invading Gram-negative bacteria.
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
authors.forename: Daoxiang
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
authors.forename: Huan
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
authors.forename: Lingling
authors.initials: L
authors.lastname: Wang
authors.affiliation: Tianjin Key Laboratory of Animal and Plant Resistance, Tianjin 300387, China.
authors.forename: Jinsheng
authors.initials: J
authors.lastname: Sun
authors.affiliation: Dalian Ocean University, Dalian 116023, China. Electronic address: lshsong@dlou.edu.cn.
authors.forename: Linsheng
authors.initials: L
authors.lastname: Song
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D049896:Crassostrea / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli; D006434:Hemocytes / Q000382:microbiology / Q000502:physiology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008969:Molecular Sequence Data; D009895:Opsonin Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010587:Phagocytosis; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D051192:Receptors, Pattern Recognition / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014733:Vibrio
chemical_list: D008070:Lipopolysaccharides; D009895:Opsonin Proteins; D012333:RNA, Messenger; D051192:Receptors, Pattern Recognition
keywords: CgC1qDC-1; Crassostrea gigas; Innate immunity; Liposaccharide; Phagocytosis