Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, Guangdong Provincial Engineering Technology Research Center for Environmentally-Friendly Aquaculture, College of Life Sciences, South China Normal University, Guangdong, 510631, PR China.
Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, Guangdong Provincial Engineering Technology Research Center for Environmentally-Friendly Aquaculture, College of Life Sciences, South China Normal University, Guangdong, 510631, PR China.
Mol Immunol. 2018 Nov;103:21-34. doi: 10.1016/j.molimm.2018.08.012. Epub 2018 Sep 3.
Collectin-K1 (CL-K1), a multifunctional Ca-dependent lectin, is able to bind carbohydrates on pathogens and inhibit infection by direct neutralization, agglutination, opsonization and killing, which plays an important role in innate immunity. In this study, a CL-K1 homolog (OnCL-K1) was identified from Nile tilapia (Oreochromis niloticus) and characterized at expression and agglutination functional levels. The open reading frame of OnCL-K1 is 720 bp of nucleotide sequence encoding a polypeptide of 239 amino acids. The deduced amino acid sequence has two characteristic structures, containing a collagen-like region and a carbohydrate recognition domain. Expression analysis revealed that the OnCL-K1 was highly expressed in the liver, and widely exhibited in other tissues including kidney, intestine and spleen. In addition, the OnCL-K1 expression was significantly up-regulated in spleen and anterior kidney following challenges with a Gram-positive bacterial pathogen (Streptococcus agalactiae) and a Gram-negative bacterial pathogen (Aeromonas hydrophila). The up-regulation of OnCL-K1 expression was also demonstrated in hepatocytes and monocytes/macrophages in vitro stimulation with S. agalactiae and A. hydrophila. Recombinant OnCL-K1 protein was able to agglutinate both S. agalactiae and A. hydrophila in vitro, and participate in the regulation of inflammatory, migration reaction and promote the phagocytosis by monocytes/macrophages. Taken together, the results of this study indicated that OnCL-K1, possessing apparent agglutination, opsonization and killing ability to bacterial pathogens and participating in the regulation mechanisms of the non-specific cellular immune, might be involved in host defense of innate immunity against bacterial infection in Nile tilapia.
收集素-K1（CL-K1）是一种多功能 Ca 依赖性凝集素，能够通过直接中和、凝集、调理和杀伤作用来结合病原体上的碳水化合物，从而抑制感染，在先天免疫中发挥重要作用。本研究从尼罗罗非鱼（Oreochromis niloticus）中鉴定出一种 CL-K1 同源物（OnCL-K1），并在表达和凝集功能水平上进行了表征。OnCL-K1 的开放阅读框为 720 bp 核苷酸序列，编码 239 个氨基酸的多肽。推导的氨基酸序列具有两个特征结构，包含一个胶原样区和一个碳水化合物识别结构域。表达分析显示，OnCL-K1 在肝脏中高度表达，在包括肾脏、肠道和脾脏在内的其他组织中广泛表达。此外，OnCL-K1 在受到革兰氏阳性菌（无乳链球菌）和革兰氏阴性菌（嗜水气单胞菌）病原体挑战后，在脾脏和前肾中的表达显著上调。在体外用无乳链球菌和嗜水气单胞菌刺激肝细胞和单核细胞/巨噬细胞时，也证明了 OnCL-K1 表达的上调。重组 OnCL-K1 蛋白能够在体外凝集无乳链球菌和嗜水气单胞菌，并参与炎症、迁移反应的调节，促进单核细胞/巨噬细胞的吞噬作用。综上所述，本研究结果表明，OnCL-K1 具有明显的凝集、调理和杀伤细菌病原体的能力，并参与非特异性细胞免疫的调节机制，可能参与尼罗罗非鱼对细菌感染的先天免疫防御。
