Liu Yong, Li Ning-Qiu, Zhao Xin-Peng, Yue Bin, He Shu-Wen, Gao Zhi-Xin, Zhou Shun, Zhang Min
Marine Science and Engineering College, Qingdao Agricultural University, Qingdao, 266109, China.
Pearl River Fishery Research Institute, Chinese Academy of Fishery Sciences, China.
Fish Shellfish Immunol. 2016 Oct;57:309-317. doi: 10.1016/j.fsi.2016.08.053. Epub 2016 Aug 26.
C-type lectins (CTLs) are important pattern recognition receptors (PRRs) that play vital roles in innate immunity. In teleosts, a number of CTLs have been reported, but their in vivo effects on host defense are still limited. In this study, a CTL homolog (SsLec1) was identified from black rockfish, Sebastes schlegelii, and its structure, expression and biological function was analyzed. The open reading frame of SsLec1 is 633 bp, with a 5'- untranslated region (UTR) of 36 bp and a 3'- UTR of 117 bp. The deduced amino acid sequence of SsLec1 shares the highest overall identity (73.20%) with the CTL of Oplegnathus fasciatus. SsLec1 possesses conserved CTL features, including a carbohydrate-recognition domain, four disulfide bond-forming cysteine residues, the mannose-type carbohydrate-binding motif, the conserved calcium binding sites and a putative signal peptide. The expression of SsLec1 was highest in liver and could be induced by experimental infection with Listonella anguillarum. Recombinant SsLec1 (rSsLec1) purified from E. coli was able to bind and agglutinate the Gram-negative fish pathogens Vibrio ichthyoenteri and Vibrio vulnificus. The agglutinating ability of rSsLec1 was abolished in the presence of mannose or ethylenediaminetetraacetic acid. Further analysis showed that rSsLec1 could enhance phagocytosis by macrophages. In vivo experiments indicated that rSsLec1 could inhibit bacterial infection and promote viral invasion. Taken together, these results suggest that SsLec1 is a novel CTL that possesses apparent immunoregulation property and plays a critical role in host defense against pathogens invasion.
C型凝集素（CTLs）是重要的模式识别受体（PRRs），在先天免疫中发挥着至关重要的作用。在硬骨鱼中，已报道了多种CTLs，但它们在体内对宿主防御的影响仍然有限。在本研究中，从黑鲪（Sebastes schlegelii）中鉴定出一种CTL同源物（SsLec1），并对其结构、表达和生物学功能进行了分析。SsLec1的开放阅读框为633 bp，5'非翻译区（UTR）为36 bp，3'UTR为117 bp。SsLec1推导的氨基酸序列与条石鲷的CTL具有最高的总体一致性（73.20%）。SsLec1具有保守的CTL特征，包括一个碳水化合物识别结构域、四个形成二硫键的半胱氨酸残基、甘露糖型碳水化合物结合基序、保守的钙结合位点和一个推定的信号肽。SsLec1在肝脏中的表达最高，并且可以通过用鳗弧菌进行实验感染来诱导。从大肠杆菌中纯化的重组SsLec1（rSsLec1）能够结合并凝集革兰氏阴性鱼类病原体鱼肠道弧菌和创伤弧菌。在存在甘露糖或乙二胺四乙酸的情况下，rSsLec1的凝集能力被消除。进一步分析表明，rSsLec1可以增强巨噬细胞的吞噬作用。体内实验表明，rSsLec1可以抑制细菌感染并促进病毒入侵。综上所述，这些结果表明SsLec1是一种新型的CTL，具有明显的免疫调节特性，在宿主抵御病原体入侵中起关键作用。
