title: The first molluscan acute phase serum amyloid A (A-SAA) identified from oyster Crassostrea hongkongensis: molecular cloning and functional characterization.
abstract: Serum amyloid A (SAA), a major evolutionarily conserved acute-phase protein, participates in many biological processes in eukaryotic cells, including innate immunity. However, little information regarding the relationship between SAA and innate immunity in mollusks is currently available. In this report, the first bivalve SAA (referred to as ChSAA) gene was identified and characterized from the Hong Kong oyster Crassostrea hongkongensis. Its full-length cDNA is 623 bp, including a 5'-UTR of 147 bp, a 3'-UTR of 56 bp containing a poly(A) tail and an open reading frame (ORF) of 420 bp that encodes a polypeptide of 139 amino acids. The predicted amino acid sequence of ChSAA comprises characteristic motifs of the SAA family, including a typical signal peptide and a conserved SAA domain. Comparison and phylogenetic analyses suggested that ChSAA shares a high identity to known acute-phase SAA proteins (A-SAAs). In addition, quantitative real-time PCR analysis revealed that ChSAA is constitutively expressed in all tissues examined, with the highest expression level in the mantle, and that its expression was acutely and significantly up-regulated in hemocytes following challenge by Vibrio alginolyticus (G(-)), Staphylococcus haemolyticus (G(+)) or Saccharomyces cerevisiae (fungus). Furthermore, over-expression of ChSAA via transfection with a ChSAA expression vector led to significantly increased NF-κB activity in HEK293T cells. These results suggest that ChSAA is likely to constitute a member of the A-SAA family involved in anti-pathogen responses in C. hongkongensis.
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China; Graduate School of the Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China.
authors.forename: Fufa
authors.initials: F
authors.lastname: Qu
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China.
authors.forename: Zhiming
authors.initials: Z
authors.lastname: Xiang
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China. Electronic address: carlzyu@scsio.ac.cn.
authors.forename: Ziniu
authors.initials: Z
authors.lastname: Yu
mesh_terms: D000209:Acute-Phase Proteins / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D049896:Crassostrea / Q000276:immunology* / Q000382:microbiology; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000276:immunology*; D057809:HEK293 Cells; D006801:Humans; D007113:Immunity, Innate / Q000235:genetics*; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism; D016366:Open Reading Frames / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D000685:Serum Amyloid A Protein / Q000235:genetics*
chemical_list: D000209:Acute-Phase Proteins; D017931:DNA Primers; D018076:DNA, Complementary; D016328:NF-kappa B; D012333:RNA, Messenger; D000685:Serum Amyloid A Protein
keywords: Acute phase serum amyloid A (A-SAA); Crassostrea hongkongensis; Innate immunity; NF-κB