title: First molluscan TNFR homologue in Zhikong scallop: molecular characterization and expression analysis.
abstract: Tumor necrosis factor receptors (TNFRs) are a superfamily of proteins characterized by the unique cysteine-rich domain (CRD) and their important roles in diverse physiological and pathological events such as inflammation, apoptosis, autoimmunity and organogenesis. The first member of the molluscan TNFR family, designated as CfTNFR, was identified from Zhikong scallop Chlamys farreri by expressed sequence tag (EST) and rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of CfTNFR was of 1334 bp, consisting of a 5' UTR of 17 bp, a 3' UTR of 69 bp with a poly (A) tail, and an open reading frame (ORF) of 1248 bp encoding a polypeptide of 415 amino acids with a theoretical isoelectric point of 8.33 and predicted molecular weight of 47.07 kDa. There were a signal peptide, a CRD, a transmembrane region and a death domain in the deduced amino acid sequence of CfTNFR, suggesting that it was a typical type I membrane protein. The high identities (22-40%) of CfTNFR with other TNFR superfamily members indicated that CfTNFR should be a member of TNFR superfamily, and moreover, it should be the first death domain-containing TNFR found in invertebrates. Phylogenetic analysis revealed that CfTNFR was closely related to TNFR-like proteins from Strongylocentrotus purpuratus, Drosophila melanogaster and Ciona intestinalis, and they formed a separate branch apart from vertebrate TNFRs. The spatial expression of CfTNFR transcripts in healthy and bacteria challenged scallops was examined by quantitative real-time PCR. CfTNFR transcripts could be detected in all tested tissues, including haemocytes, gonad, gill, mantle and hepatopancreas, and significantly up-regulated in the tissues of gonad, gill, mantle and hepatopancreas after Listonella anguillarum challenge, indicating that CfTNFR was constitutive and inducible acute-phase protein involved in immune defence. The present results suggested the existence of the TNFR-like molecules and TNF-TNFR system in low invertebrates, and provided new insights into the role of CfTNFR in scallop innate immune responses to invading microorganisms.
authors.affiliation: The Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Rd, Qingdao 266071, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Li
authors.forename: Limei
authors.initials: L
authors.lastname: Qiu
authors.forename: Linsheng
authors.initials: L
authors.lastname: Song
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Song
authors.forename: Jianmin
authors.initials: J
authors.lastname: Zhao
authors.forename: Lingling
authors.initials: L
authors.lastname: Wang
authors.forename: Changkao
authors.initials: C
authors.lastname: Mu
authors.forename: Huan
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D020224:Expressed Sequence Tags; D008969:Molecular Sequence Data; D049897:Pectinidae / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D019105:Random Amplified Polymorphic DNA Technique; D018124:Receptors, Tumor Necrosis Factor / Q000096:biosynthesis* / Q000235:genetics; D016415:Sequence Alignment
chemical_list: D012333:RNA, Messenger; D018124:Receptors, Tumor Necrosis Factor