Identification and functional characterization of complement regulatory protein CD59 in golden pompano (Trachinotus ovatus).

CD59, one of the essential inhibitors of the complement membrane attack complex (MAC), plays a crucial role in regulation of complement activation. In this study, we cloned and identified the CD59 gene (named ToCD59) of golden pompano (Trachinotus ovatus). The ORF sequence of ToCD59 is 357 bp long encoding 118 amino acids with a molecular weight of 13.09 kDa. Prediction of protein domains showed that ToCD59 contained an Lu domain and a C-terminal glycosylphosphatidylinositol (GPI) partial anchor. Homology comparisons indicated that ToCD59 shared the high sequence similarity with other fish CD59. RT-qPCR analysis showed that ToCD59 was expressed in all tested healthy tissues of golden pompano, with the highest level of expression in the brain. After stimulation with bacteria, ToCD59 expression levels were significantly up-regulated in head kidney, liver, gill and brain, but down-regulated in spleen. Subcellular localization results showed that ToCD59 localized to the cytoplasm of A549 cells. The hemolytic activity analysis showed that rToCD59 might have complement inhibitory activity through the alternative complement pathway. In addition, antibacterial test showed that rToCD59 had antibacterial ability against S. agalactiae and V. alginolyticus in vitro. These results suggest that ToCD59 might play an important role in the immune response against pathogens, which would provide basic information for elucidating the functional evolutionary history of complement system in teleost. • The ORF sequence of CD59 from golden pompano (ToCD59) was cloned and identified. • ToCD59 was ubiquitously expressed in healthy golden pompano and rapidly up-regulated after bacteria stimulation. • ToCD59 was localized in the cytoplasm of A549 cells. • In vitro, the recombinant protein ToCD59 could inhibit erythrocyte lysis. • The rToCD59 had inhibitory effects on S. agalactiae and V. alginolyticus. [ABSTRACT FROM AUTHOR]