Wei Xiumei, Liu Xiangquan, Yang Jianmin, Wang Sheng, Sun Guohua, Yang Jialong
Shandong Provincial Key Laboratory of Marine Ecology Restoration, Shandong Marine Resource and Environment Research Institute, Yantai 264006, China.
Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China.
Fish Shellfish Immunol. 2015 Aug;45(2):791-9. doi: 10.1016/j.fsi.2015.05.037. Epub 2015 Jun 4.
C-type lectin is one important pattern recognition receptor (PRR) that plays crucial roles in multiple immune responses. A C-type lectin from sea cucumber Apostichopus japonicus (AjCTL-1) was characterized in the present study. The amino acid sequence of AjCTL-1 shared high similarities with other C-type lectins from invertebrates and vertebrates. The C-type lectin domain (CTLD) of AjCTL-1 contained a Ca(2+)-binding site 2 and four conserved cysteine residues. AjCTL-1 mRNA expression patterns in tissues and after bacterial challenge were then analysed. Quantitative PCR revealed that AjCTL-1 mRNA was widely expressed in the tested tissues of healthy sea cucumber. The highest expression level occurred in gonad followed by body wall, coelomocytes, tentacle, intestinum and longitudinal muscle, and the lowest expression level was in respiratory tree. AjCTL-1 mRNA expression in coelomocytes was significantly induced by gram-negative Listonella anguillarum and gram-positive Micrococcus luteus, with different up-regulation patterns post-challenge. Recombinant AjCTL-1 exhibited the ability to bind peptidoglycan directly, agglutinate M. luteus, Staphylococcus aureus and Escherichia coli, in a Ca(2+)-dependant manner, and enhance the phagocytosis of coelomocytes against E. coli in vitro. The results indicated that AjCTL-1 could act as a PRR in Apostichopus japonicus and had critical roles in non-self recognition and bacterial clearance against invading microbes.
C型凝集素是一种重要的模式识别受体（PRR），在多种免疫反应中发挥关键作用。本研究对来自海参刺参的一种C型凝集素（AjCTL-1）进行了表征。AjCTL-1的氨基酸序列与来自无脊椎动物和脊椎动物的其他C型凝集素具有高度相似性。AjCTL-1的C型凝集素结构域（CTLD）包含一个钙离子结合位点2和四个保守的半胱氨酸残基。随后分析了AjCTL-1在组织中的mRNA表达模式以及细菌攻击后的表达模式。定量PCR显示，AjCTL-1 mRNA在健康海参的受试组织中广泛表达。最高表达水平出现在性腺，其次是体壁、体腔细胞、触手、肠和纵肌，最低表达水平出现在呼吸树。革兰氏阴性的鳗弧菌和革兰氏阳性的藤黄微球菌可显著诱导体腔细胞中AjCTL-1 mRNA的表达，攻击后呈现不同的上调模式。重组AjCTL-1表现出以钙离子依赖的方式直接结合肽聚糖、凝集藤黄微球菌、金黄色葡萄球菌和大肠杆菌的能力，并在体外增强体腔细胞对大肠杆菌的吞噬作用。结果表明，AjCTL-1可作为刺参中的一种PRR，在对入侵微生物的非自我识别和细菌清除中起关键作用。
