title: Molecular characterization and expression analysis of a complement component 3 in the sea cucumber (Apostichopus japonicus).
abstract: The complement system has been discovered in invertebrates and vertebrates, and plays a crucial role in the innate defense against common pathogens. As a central component in the complement system, complement component 3 (C3) is an intermediary between innate and adaptive immune system. In this study, a new isoform of C3 in the sea cucumber Apostichopus japonicus, termed AjC3-2 was identified. Its open reading frame (ORF) is 5085 bp and encodes for 1695 amino acids with a putative signal peptide of 20 amino acid residues. The mature protein molecular weight of AjC3-2 was 187.72 kDa. It has a conserved thioester site and a linker R(689)RRR(692) where AjC3-2 is splitted into β and α chain during posttranslational modification. The expression patterns of two distinct sea cucumber C3 genes, AjC3-2 and AjC3, were similar. During the different development stages from unfertilized egg to juvenile of the sea cucumber, the highest expression levels of AjC3-2 and AjC3 genes were both found in late auricularia. In the adult, the highest expression of these two genes was observed in the coelomocytes and followed by the body wall. AjC3-2 and AjC3 genes expression increased significantly at 6 h after the LPS challenge. These results indicated that these two C3 genes play a pivotal role in immune responses to the bacterial infection in sea cucumber.
authors.affiliation: Liaoning Key Lab of Marine Fishery Molecular Biology, Liaoning Ocean and Fisheries Science Research Institute, Dalian, Liaoning 116023, China. zunchunz@hotmail.com
authors.forename: Zunchun
authors.initials: Z
authors.lastname: Zhou
authors.forename: Dapeng
authors.initials: D
authors.lastname: Sun
authors.forename: Aifu
authors.initials: A
authors.lastname: Yang
authors.forename: Ying
authors.initials: Y
authors.lastname: Dong
authors.forename: Zhong
authors.initials: Z
authors.lastname: Chen
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Wang
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Guan
authors.forename: Bei
authors.initials: B
authors.lastname: Jiang
authors.forename: Bai
authors.initials: B
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003176:Complement C3 / Q000235:genetics* / Q000276:immunology; D018076:DNA, Complementary / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000196:embryology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D007113:Immunity, Innate; D008070:Lipopolysaccharides / Q000494:pharmacology; D008969:Molecular Sequence Data; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D047528:Stichopus / Q000737:chemistry / Q000196:embryology / Q000254:growth & development / Q000502:physiology*
chemical_list: D003176:Complement C3; D018076:DNA, Complementary; D008070:Lipopolysaccharides