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A C1qDC (CgC1qDC-6) with a collagen-like domain mediates hemocyte phagocytosis and migration in oysters
- Huan Li, Ning Kong, Jiejie Sun, Weilin Wang, Meijia Li, Changhao Gong, Miren Dong, Min Wang, Lingling Wang, Linsheng Song
- Developmental and comparative immunology 2019 v.98 pp. 157-165
- Crassostrea gigas, Escherichia coli, Gram-negative bacteria, Gram-positive bacteria, Komagataella pastoris, Micrococcus luteus, Staphylococcus aureus, Vibrio splendidus, amino acids, chemotaxis, collagen, dose response, fungi, hemocytes, hepatopancreas, immune response, mannose, messenger RNA, muscles, oligomerization, oysters, pathogen-associated molecular patterns, pathogens, peptides, phagocytosis, phylogeny, polyinosinic-polycytidylic acid, protein content, signal peptide, tissues, vertebrates
- Most of the bivalve C1q domain containing proteins (C1qDCs) are either only composed of the globular head domain, or contain an N-terminal coiled-coil domain, presumed to cover a role in oligomerization. On the other hand, collagen regions, widespread in vertebrate C1qDCs, are very uncommon in bivalves. In the present study, a C1qDC with a collagen-like domain (designated CgC1qDC-6) was identified from the Pacific oyster Crassostrea gigas and its possible involvement in immune responses was also characterized. The coding sequence of CgC1qDC-6 was of 756 bp, encoding a peptide of 251 amino acids with an N-terminal signal peptide, a central collagen-like domain, and a C-terminal ghC1q domain. CgC1qDC-6 was clustered with the C1qDCs from several mollusks in the phylogenetic tree. CgC1qDC-6 was detected at both mRNA and protein levels in all tested tissues including hepatopancreas, gonad, gill, mantle, adductor muscle, and hemocytes. The recombinant CgC1qDC-6 protein (rCgC1qDC-6) exhibited binding activity to various pathogen-associated molecular patterns (PAMPs) including LPS, PGN, mannose and Poly I:C, and microorganisms including Gram-negative bacteria (Escherichia coli and Vibrio splendidus), Gram-positive bacteria (Micrococcus luteus and Staphylococcus aureus), and fungus (Pichia pastoris). The phagocytic rates of oyster hemocytes towards V. splendidus pre-incubation with rCgC1qDC-6 were significantly enhanced (p < 0.05). In the chemotaxis assay, rCgC1qDC-6 could mediate the migration of oyster hemocytes in a dose-dependent manner, which exhibited a positive chemotactic effect at low concentration (<10 nM). These results collectively indicated that CgC1qDC-6 could serve as a pattern recognition receptor and mediate the hemocyte phagocytosis and migration to eliminate the invading pathogens.