A C1 q domain containing protein from Crassostrea gigas serves as pattern recognition receptor and opsonin with high binding affinity to LPS

• Published in: Fish & Shellfish Immunology
• Main Authors: Jiang, Shuai, Li, Hui, Zhang, Daoxiang, Zhang, Huan, Wang, Lingling, Sun, Jinsheng, Song, Linsheng
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2015
• Subjects: Crassostrea Gigas; Innate Immunity; Liposaccharide; Cgc1qdc-1; Phagocytosis; Crassostrea gigas
• Online Access: http://ir.qdio.ac.cn/handle/337002/49671; https://doi.org/10.1016/j.fsi.2015.05.021

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 CgC1 qDC-1 gene was determined by performing a homologous search of eight tryptic peptides identified by IVIALDI-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 beta strands with a jelly-roll topology structure, which was similar to the structure of human gC1q domain. The mRNA transcripts of CgC1 qDC-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 x 10(-6) M). Moreover, CgC1qDC-1 significantly enhanced the phagocytosis of oyster hemocytes towards Gram-negative bacteria Escherichia con 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. (C) 2015 Elsevier Ltd. All rights reserved.