Niu Shengwen, Yang Linwei, Zuo Hongliang, Zheng Jiefu, Weng Shaoping, He Jianguo, Xu Xiaopeng
MOE Key Laboratory of Aquatic Product Safety / State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, PR China; Institute of Aquatic Economic Animals and Guangdong Province Key Laboratory for Aquatic Economic Animals, Sun Yat-sen University, Guangzhou, PR China.
MOE Key Laboratory of Aquatic Product Safety / State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, PR China; Institute of Aquatic Economic Animals and Guangdong Province Key Laboratory for Aquatic Economic Animals, Sun Yat-sen University, Guangzhou, PR China; South China Sea Resource Exploitation and Protection Collaborative Innovation Center (SCS-REPIC), Guangzhou, PR China.
Dev Comp Immunol. 2018 Aug;85:161-169. doi: 10.1016/j.dci.2018.04.013. Epub 2018 Apr 17.
Chitinases are a group of hydrolytic enzymes that hydrolyze chitin and widely exist in organisms. Studies in mammals have demonstrated that chitinases play important roles in regulation of humoral and cellular immune responses. In arthropods, although it is well known that chitinases are involved in growth, molting and development, the current knowledge on the role of chitinases in immunity, especially in immune regulation, remains largely unknown. In this study, a chitinase (LvChi5) from Litopenaeus vannamei was representatively selected for studying its immune function. The start codon of LvChi5 was corrected by 5'RACE analysis and its protein sequence was reanalyzed. LvChi5 contains a catalytic domain and a chitin binding domain and shows no inhibitory effect on growth of bacteria in vitro. However, in vivo experiments demonstrated that silencing of LvChi5 increased the mortality of shrimp infected with white spot syndrome virus (WSSV) and Vibro parahaemolyticus and significantly upregulated the load of pathogens in tissues. The expression of various immune related genes, including transcription factors, antimicrobial peptides and other functional proteins with antibacterial and antiviral activities, was widely changed in LvChi5 silencing shrimp. Moreover, the recombinant LvChi5 protein could enhance the phagocytic activity of hemocytes against bacteria. These suggested that shrimp chitinase could play a role in regulation of both humoral and cellular immune responses in shrimp.
几丁质酶是一类能水解几丁质的水解酶，广泛存在于生物体中。哺乳动物研究表明，几丁质酶在体液免疫和细胞免疫反应的调节中发挥重要作用。在节肢动物中，虽然已知几丁质酶参与生长、蜕皮和发育，但目前关于几丁质酶在免疫尤其是免疫调节方面作用的认识仍知之甚少。本研究中，从凡纳滨对虾中代表性地选取了一种几丁质酶（LvChi5）来研究其免疫功能。通过5'RACE分析校正了LvChi5的起始密码子，并对其蛋白质序列进行了重新分析。LvChi5含有一个催化结构域和一个几丁质结合结构域，体外对细菌生长无抑制作用。然而，体内实验表明，沉默LvChi5会增加感染白斑综合征病毒（WSSV）和副溶血性弧菌的对虾死亡率，并显著上调组织中病原体的载量。在沉默LvChi5的对虾中，包括转录因子、抗菌肽和其他具有抗菌和抗病毒活性的功能蛋白在内的各种免疫相关基因的表达发生了广泛变化。此外，重组LvChi5蛋白可增强血细胞对细菌的吞噬活性。这些结果表明，对虾几丁质酶可能在对虾体液免疫和细胞免疫反应的调节中发挥作用。
