title: Caspase-3 serves as an intracellular immune receptor specific for lipopolysaccharide in oyster Crassostrea gigas.
abstract: Apoptosis is a form of programmed cell death process controlled by a family of cysteine proteases called caspases, which plays a crucial role in the immune system homeostasis. The apoptosis and the detailed regulation mechanism have been well studied in vertebrate, but the information in lower animals, especially invertebrates, is still very limited. In the present study, Caspase-3 in the Pacific oyster Crassostrea gigas (designated CgCaspase-3) was enriched by lipopolysaccharide (LPS) affinity chromatography and further identified by MALDI-TOF/TOF-mass spectrometry. The binding activity of CgCaspase-3 to LPS was confirmed by enzyme-linked immunosorbent assay, and surface plasmon resonance analysis revealed its high binding specificity and moderate binding affinity (KD = 1.08 × 10(-6) M) to LPS. The recombinant CgCaspase-3 exhibited high proteolytic activity to substrate Ac-DEVD-pNA and relatively weak activity to substrate Ac-DMQD-pNA and Ac-VDQQD-pNA. The binding of CgCaspase-3 to LPS significantly inhibited its proteolytic activity toward AC-DEVD-pNA in vitro. The over-expression of CgCaspase-3 leaded to the phosphatidylserine exposure on the external plasma membrane and the cleavage of poly (ADP-ribose) polymerase, which reduced cell viability, and finally induced cell apoptosis. But the cell apoptosis mediated by CgCaspase-3 in vivo was significantly inhibited by the treatment of LPS. These results collectively indicated that CgCaspase-3 could serve as an intracellular LPS receptor, and the interaction of LPS with CgCaspase-3 specifically inhibited the cell apoptosis induced by CgCaspase-3.
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Jiachao
authors.initials: J
authors.lastname: Xu
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Yiqun
authors.initials: Y
authors.lastname: Li
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Meijia
authors.initials: M
authors.lastname: Li
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Dalian Polytechnic University, Dalian 116034, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Cheng
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Dalian Polytechnic University, Dalian 116034, China.
authors.forename: Depeng
authors.initials: D
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Yang
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Zhihao
authors.initials: Z
authors.lastname: Jia
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
authors.forename: Lingling
authors.initials: L
authors.lastname: Wang
authors.affiliation: Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian 116023, China. Electronic address: lshsong@qdio.ac.cn.
authors.forename: Linsheng
authors.initials: L
authors.lastname: Song
mesh_terms: D000813:Anilides / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D049896:Crassostrea / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D007109:Immunity; D042541:Intracellular Space / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000276:immunology; D009842:Oligopeptides / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism; D011485:Protein Binding; D000072417:Protein Domains / Q000235:genetics; D059748:Proteolysis; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D000813:Anilides; D008070:Lipopolysaccharides; D009842:Oligopeptides; D010718:Phosphatidylserines; C430230:acetyl-aspartyl-glutamyl-valyl-aspartic acid p-nitroanilide; D053148:Caspase 3
keywords: Apoptosis; Caspase-3; Crassostrea gigas; Immune response; Intracellular immune receptor; LPS