Li Hui, Zhang Huan, Jiang Shuai, Wang Weilin, Xin Lusheng, Wang Hao, Wang Lingling, Song Linsheng
Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
Fish Shellfish Immunol. 2015 Jun;44(2):566-75. doi: 10.1016/j.fsi.2015.03.011. Epub 2015 Mar 20.
C-type lectins (CTLs), serving as pattern recognition receptors (PRRs), are a superfamily of Ca(2+)-dependent carbohydrate-recognition proteins that participate in nonself-recognition and pathogen elimination. In the present study, a single carbohydrate-recognition domain (CRD) CTL was identified from oyster Crassostrea gigas (designated as CgCLec-2). There was only one CRD within the deduced amino acid sequence of CgCLec-2 consisting of 129 amino acid residues. A conserved EPN (Glu246-Pro247-Asn248) motif was found in Ca(2+)-binding site 2 of CgCLec-2. The CgCLec-2 mRNA could be detected in all the examined tissues at different expression levels in oysters. The mRNA expression of CgCLec-2 in hemocytes was up-regulated significantly at 6 h post Vibrio splendidus challenge. The recombinant CgCLec-2 (rCgCLec-2) could bind various Pathogen-Associated Molecular Patterns (PAMPs), including lipopolysaccharide, mannan and peptidoglycan, and displayed strong binding abilities to Vibrio anguillarum, V. splendidus and Yarrowiali polytica and week binding ability to Staphylococcus aureus. It could also enhance the phagocytic activity of oyster hemocytes to V. splendidus and exhibited growth suppression activity against gram-positive bacteria S. aureus but no effect on gram-negative bacteria V. splendidus. Furthermore, the interaction between rCgCLec-2 and rCgMASPL-1 was confirmed by GST Pull down. The results suggested that CgCLec-2 served as not only a PRR in immune recognition but also a regulatory factor in pathogen elimination, and played a potential role in the activation of complement system.
C型凝集素（CTLs）作为模式识别受体（PRRs），是一类Ca(2+)依赖的碳水化合物识别蛋白超家族，参与非自我识别和病原体清除。在本研究中，从太平洋牡蛎（Crassostrea gigas）中鉴定出一种单碳水化合物识别结构域（CRD）的CTL（命名为CgCLec-2）。CgCLec-2的推导氨基酸序列中只有一个CRD，由129个氨基酸残基组成。在CgCLec-2的Ca(2+)结合位点2中发现了一个保守的EPN（Glu246-Pro247-Asn248）基序。在牡蛎的所有检测组织中均可检测到CgCLec-2 mRNA，但表达水平不同。在灿烂弧菌攻击后6小时，血细胞中CgCLec-2的mRNA表达显著上调。重组CgCLec-2（rCgCLec-2）可以结合多种病原体相关分子模式（PAMPs），包括脂多糖、甘露聚糖和肽聚糖，并且对鳗弧菌、灿烂弧菌和海氏肠球菌具有较强的结合能力，而对金黄色葡萄球菌的结合能力较弱。它还可以增强牡蛎血细胞对灿烂弧菌的吞噬活性，并对革兰氏阳性菌金黄色葡萄球菌表现出生长抑制活性，但对革兰氏阴性菌灿烂弧菌没有影响。此外，通过GST下拉实验证实了rCgCLec-2与rCgMASPL-1之间的相互作用。结果表明，CgCLec-2不仅作为免疫识别中的PRR，而且作为病原体清除中的调节因子，在补体系统的激活中发挥潜在作用。
