title: Characterization and expression of a novel caspase gene: Evidence of the expansion of caspases in Crassostrea gigas.
abstract: Caspases are a group of cysteine-aspartate proteases involved in apoptosis and a variety of non-apoptotic processes. In this study, a novel caspase gene was cloned and its potential role in apoptosis was investigated. The caspase gene (CgCasp 3/7) has an open reading frame of 1626bp encoding 541 amino acids containing the conserved functional domains and motifs of effector caspases. Its amino acid sequence shows low identity with the other effector caspases of Crassostrea gigas and contains a unique long intersubunit linker (IL). The CgCasp 3/7 mRNA was expressed highly in oocytes and then decreased gradually after fertilization, indicating CgCasp 3/7 could function in oocyte apoptosis. In adult tissues, it is located primarily in the gills and hepatopancreas. We examined the mRNA expression of CgCasp 3/7 in gills of oysters immersed in ambient (17°C) or heated (27°C) seawater. The thermal stress stimulated mRNA expression of CgCasp 3/7 by 2.5- and 4.1-fold at 2h and 6h post-treatment, respectively, indicating CgCasp3/7 was involved in the early response to thermal stress. To examine the function of the IL, CgCasp 3/7 and CgCasp 3/7-T (with a truncated IL) were expressed using an in vitro translation system and their DEVDase activity was measured. Both proteins showed a significantly higher level of DEVDase activity than control, but CgCasp3/7-T had lower DEVDase activity than CgCasp3/7, indicating CgCasp3/7 had DEVDase activity and the IL was required for maximal DEVDase activity. Our study adds to the complexity of caspases in C. gigas.
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Graduate School of the Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Zhongxiao
authors.initials: Z
authors.lastname: Li
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Wang
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Graduate School of the Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Fengjuan
authors.initials: F
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
authors.forename: Pin
authors.initials: P
authors.lastname: Huan
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, 266000 Qingdao, China. Electronic address: bzliu@qdio.ac.cn.
authors.forename: Baozhong
authors.initials: B
authors.lastname: Liu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D020169:Caspases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D049896:Crassostrea / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic; D018869:Heat-Shock Response / Q000235:genetics; D016366:Open Reading Frames / Q000235:genetics; D009928:Organ Specificity; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D020169:Caspases
keywords: Apoptosis; Caspase; Crassostrea gigas; Thermal stress