大菱鲆CD55负调控补体激活及其广谱细菌结合能力

Turbot Scophthalmus maximus CD55 negatively regulates complement activation and binds a variety of bacteria

CD55蛋白在哺乳动物中是一种补体调控因子,但其在鱼类中的功能未知。本研究探索了大菱鲆(Scophthalmus maximus)CD55(SmCD55)蛋白的功能。结果表明,SmCD55蛋白由344个氨基酸残基构成,含有一个N端信号肽和3个补体调控蛋白(CCP)功能域。SmCD55基因在大菱鲆多种组织中均有表达,其中,在肌肉中表达量最低,在脑组织的表达量最高。通过原核表达获得了重组的SmCD55(rSmCD55)蛋白,发现rSmCD55蛋白能够抑制大菱鲆血清的溶血活性和杀菌活性,表明其负调控补体系统的激活。此外,本研究还发现rSmCD55蛋白可以结合包括重要水产病原菌迟缓爱德华氏菌(Edwardsiella tarda)、荧光假单胞杆菌(Pseudomonas fluorescens)、鳗弧菌(Vibrio anguillarum)、哈维氏弧菌(Vibrio harveyi)和海豚链球菌(Streptococcus iniae)在内的多种细菌,其中与哈维氏弧菌的结合能力最强。以上这些研究结果丰富了鱼类补体系统的理论知识,加深了对鱼类补体激活调控的了解。

Turbot(Scophthalmus maximus)is an important commercial fish species in China.CD55 protein is known to be a complement regulator in mammals,but its function in fish is unknown.In this study,we examined the function of turbot CD55(SmCD55)protein.The results showed that SmCD55 protein consisted of 344 amino acid residues and contained an N-terminal signal peptide and three complement control protein domains.SmCD55 gene was expressed in several tissues of turbot,with the lowest expression level in muscle and the highest expression level in brain.A recombinant SmCD55(rSmCD55)protein was obtained from a prokaryotic expression system.rSmCD55 protein significantly inhibited the hemolytic and bactericidal activities of turbot serum,suggesting that rSmCD55 negatively regulates complement activation.In addition,rSmCD55 protein is bound to a variety of bacteria,including the aquaculture pathogens Edwardsiella tarda,Pseudomonas fluorescens,Vibrio anguillarum,Vibrio harveyi,and Streptococcus iniae.Of these bacteria,V.harveyi exhibited the strongest binding ability to rSmCD55 protein.These results add new insight into the complement system in fish and promote our understanding of complement activation and regulation in fish.