An enzymatic cascade is responsible for the blood digestion in ticks. It contributes to the cleavage of hemoglobin molecules into shorter fragments and individual amino acids. Almost all of these enzymes occur strictly in the digestive cells inside the gut epithelium. Cathepsin L, however, is the only one peptidase which is expressed in other tissues too (Sojka et al., 2008). Apart from the gut, it can be localized also in the salivary glands, ovaries and Malpighian tubules. Although the function of the cathepsin L and its both isoforms (IrCL1, IrCL3) in the gut seems to be obvious, its role in the salivary glands of tick remains unclear. Detailed immuno-localization of this enzyme in the salivary glands during feeding should help us to find out its function. The specific antibodies against these peptidases were prepared by affinity chromatography and used for their detailed immunogold labeling of thawed cryosections according to Tokuyasu (Tokuyasu, 1973). Using transmission electron microscopes, we localized both isoforms of cathepsin L. It has been shown that both isoforms of cathepsin L are presented in type III acini, inside secretion granules of e cells. It has also been measured up that the amount of both isoforms increases during feeding. To further clear up the position of cathepsin L in the tick physiology, concretely in the digestive cascade, it might be appealing to use these and other methods, such as electron tomography or FIB/SEM, for co-localization of other members of the cascade.
References:
Tokuyasu K. T., 1973. A technique for ultracryotomy of cell suspensions and tissues. J. Cell Biol. 57: 551-565.
Sojka D., Franta Z., Horn M., Hajdušek O., Caffrey C. R., Mareš M., Kopáček P., 2008. Profiling of proteolytic enzymes in the gut of the tick Ixodes ricinus reveals an evolutionarily conserved network of aspartic and cysteine peptidases. Parasit. Vectors.,1: 7.
The authors acknowledge funding from the Technology Agency of the Czech Republic, project TE01020118.