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.

Faculty of Science University of South Bohemia České Budějovice CZ 370 05 Czech Republic

Institute of Parasitology Biology Centre Academy of Sciences of the Czech Republic České Budějovice CZ 370 05 Czech Republic

References provided by Crossref.org

Activation of the tick Toll pathway to control infection of Ixodes ricinus by the apicomplexan parasite Babesia microti

Mialostatin, a Novel Midgut Cystatin from Ixodes ricinus Ticks: Crystal Structure and Regulation of Host Blood Digestion

Tick Immune System: What Is Known, the Interconnections, the Gaps, and the Challenges

Characterization of Ixodes ricinus Fibrinogen-Related Proteins (Ixoderins) Discloses Their Function in the Tick Innate Immunity

Tick Thioester-Containing Proteins and Phagocytosis Do Not Affect Transmission of Borrelia afzelii from the Competent Vector Ixodes ricinus

Substrate prediction of Ixodes ricinus salivary lipocalins differentially expressed during Borrelia afzelii infection

Acquisition of exogenous haem is essential for tick reproduction

Deep Sequencing Analysis of the Ixodes ricinus Haemocytome

See more in PubMed

GENBANK
KJ150729