Urbanová Veronika, Hartmann David, Grunclová Lenka, Šíma Radek, Flemming Tina, Hajdušek Ondřej, Kopáček Petr
Institute of Parasitology, Biology Centre, Academy of Sciences of the Czech Republic, České Budějovice CZ-370 05, Czech Republic.
Faculty of Science, University of South Bohemia, České Budějovice CZ-370 05, Czech Republic.
Dev Comp Immunol. 2014 Oct;46(2):439-47. doi: 10.1016/j.dci.2014.05.016. Epub 2014 Jun 9.
Limulus Clotting Factor C is a multi-domain serine protease that triggers horseshoe crab hemolymph clotting in the presence of trace amounts of bacterial lipopolysaccharides. Here we describe and functionally characterize an homologous molecule, designated as IrFC, from the hard tick Ixodes ricinus. Tick Factor C consists of an N-terminal cysteine-rich domain, four complement control protein (sushi) modules, an LCCL domain, a truncated C-lectin domain and a C-terminal trypsin-type domain. Developmental expression profiling by quantitative real-time PCR revealed that the irfc mRNA is expressed in all stages including eggs. In tissues dissected from adult I. ricinus females, the irfc mRNA is present mainly in tick hemocytes and accordingly, indirect immunofluorescence microscopy localized IrFC intracellularly, in tick hemocytes. Irfc mRNA levels were markedly increased upon injection of sterile saline, or different microbes, demonstrating that the irfc gene transcription occurs in response to injury. This indicates a possible role of IrFC in hemolymph clotting and/or wound healing, although these defense mechanisms have not been yet definitely demonstrated in ticks. RNAi silencing of irfc expression resulted in a significant reduction in phagocytic activity of tick hemocytes against the Gram-negative bacteria Chryseobacterium indologenes and Escherichia coli, but not against the yeast, Candida albicans. This result suggests that IrFC plays a role in the tick primordial complement system and as such possibly mediates transmission of tick-borne pathogens.
鲎凝血因子C是一种多结构域丝氨酸蛋白酶，在痕量细菌脂多糖存在的情况下可触发鲎血淋巴凝结。在此，我们描述并对来自蓖麻硬蜱的一种同源分子（命名为IrFC）进行功能表征。蜱因子C由一个富含半胱氨酸的N端结构域、四个补体控制蛋白（寿司）模块、一个LCCL结构域、一个截短的C型凝集素结构域和一个C端胰蛋白酶型结构域组成。通过定量实时PCR进行的发育表达谱分析显示，irfc mRNA在包括卵在内的所有阶段均有表达。在从成年蓖麻硬蜱雌性个体解剖的组织中，irfc mRNA主要存在于蜱血细胞中，因此，间接免疫荧光显微镜检查将IrFC定位在蜱血细胞的细胞内。注射无菌盐水或不同微生物后，irfc mRNA水平显著升高，表明irfc基因转录是对损伤的反应。这表明IrFC在血淋巴凝结和/或伤口愈合中可能发挥作用，尽管这些防御机制在蜱中尚未得到明确证实。irfc表达的RNAi沉默导致蜱血细胞对革兰氏阴性菌吲哚金黄杆菌和大肠杆菌的吞噬活性显著降低，但对酵母白色念珠菌没有影响。这一结果表明，IrFC在蜱原始补体系统中发挥作用，因此可能介导蜱传病原体的传播。
