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Profiling of proteolytic enzymes in the gut of the tick Ixodes ricinus reveals an evolutionarily conserved network of aspartic and cysteine peptidases.

Sojka D, Franta Z, Horn M, Hajdusek O, Caffrey CR, Mares M, Kopácek P - Parasit Vectors (2008)

Bottom Line: Overall, our results demonstrate the presence of a network of cysteine and aspartic peptidases that conceivably operates to digest host blood proteins in a concerted manner.Significantly, the peptidase components of this digestive network are orthologous to those described in other parasites, including nematodes and flatworms.Accordingly, the present data and those available for other tick species support the notion of an evolutionary conservation of a cysteine/aspartic peptidase system for digestion that includes ticks, but differs from that of insects relying on serine peptidases.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Parasitology, Biology Centre, Academy of Sciences of the Czech Republic, Ceské Budejovice, CZ-370 05, The Czech Republic. dsojka@seznam.cz.

ABSTRACT

Background: Ticks are vectors for a variety of viral, bacterial and parasitic diseases in human and domestic animals. To survive and reproduce ticks feed on host blood, yet our understanding of the intestinal proteolytic machinery used to derive absorbable nutrients from the blood meal is poor. Intestinal digestive processes are limiting factors for pathogen transmission since the tick gut presents the primary site of infection. Moreover, digestive enzymes may find practical application as anti-tick vaccine targets.

Results: Using the hard tick, Ixodes ricinus, we performed a functional activity scan of the peptidase complement in gut tissue extracts that demonstrated the presence of five types of peptidases of the cysteine and aspartic classes. We followed up with genetic screens of gut-derived cDNA to identify and clone genes encoding the cysteine peptidases cathepsins B, L and C, an asparaginyl endopeptidase (legumain), and the aspartic peptidase, cathepsin D. By RT-PCR, expression of asparaginyl endopeptidase and cathepsins B and D was restricted to gut tissue and to those developmental stages feeding on blood.

Conclusion: Overall, our results demonstrate the presence of a network of cysteine and aspartic peptidases that conceivably operates to digest host blood proteins in a concerted manner. Significantly, the peptidase components of this digestive network are orthologous to those described in other parasites, including nematodes and flatworms. Accordingly, the present data and those available for other tick species support the notion of an evolutionary conservation of a cysteine/aspartic peptidase system for digestion that includes ticks, but differs from that of insects relying on serine peptidases.

No MeSH data available.


Related in: MedlinePlus

Nucleotide and deduced amino acid sequence of Ixodes ricinus cathepsin B, form 1 (IrCB). The PCR primers used are upperlined and named as in Table 1 and 2. The predicted 17 AA signal peptide is underlined, in italics. Three potential N-glycosylation sites are double underlined and the respective asparagine residues are in bold; Active site residues C113, H282, Q107and N302 are bold and shaded. Occluding loop responsible for cathepsin B exo-peptidase activity is bold, and italics.
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Figure 4: Nucleotide and deduced amino acid sequence of Ixodes ricinus cathepsin B, form 1 (IrCB). The PCR primers used are upperlined and named as in Table 1 and 2. The predicted 17 AA signal peptide is underlined, in italics. Three potential N-glycosylation sites are double underlined and the respective asparagine residues are in bold; Active site residues C113, H282, Q107and N302 are bold and shaded. Occluding loop responsible for cathepsin B exo-peptidase activity is bold, and italics.

Mentions: The nucleotide and the deduced amino acid sequences of IrCB (form 1) enzyme precursor are shown in Fig. 4. The cDNA sequence [GenBank:EF428206] is 1073 bp long and contains one open reading frame encoding a polypeptide of 337 amino acid (AA) residues. Use of the SignalP 3.0 server [20] predicts a signal peptide cleavage between G17 and R18. The pro-enzyme has a theoretical mass of 35.725 Da and an isoelectric point 5.76. The catalytic residues C113, H282 and two other active site residues Q107 and N302 were found in positions typical for the C1 peptidase (papain) family. The protein has three potential N-glycosylation sites predicted by the NetNGlyc 1.0 Server [21]. The occluding loop responsible for the putative exo-peptidase (peptidyl dipeptidase) activity is predictable between C191 and C211. Also, the domain 297YWLVANSWxxDWGD310 accords to a domain previously described as being associated with the hemoglobinase activity of cathepsin B in blood feeding helminths [22].


Profiling of proteolytic enzymes in the gut of the tick Ixodes ricinus reveals an evolutionarily conserved network of aspartic and cysteine peptidases.

Sojka D, Franta Z, Horn M, Hajdusek O, Caffrey CR, Mares M, Kopácek P - Parasit Vectors (2008)

Nucleotide and deduced amino acid sequence of Ixodes ricinus cathepsin B, form 1 (IrCB). The PCR primers used are upperlined and named as in Table 1 and 2. The predicted 17 AA signal peptide is underlined, in italics. Three potential N-glycosylation sites are double underlined and the respective asparagine residues are in bold; Active site residues C113, H282, Q107and N302 are bold and shaded. Occluding loop responsible for cathepsin B exo-peptidase activity is bold, and italics.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2289814&req=5

Figure 4: Nucleotide and deduced amino acid sequence of Ixodes ricinus cathepsin B, form 1 (IrCB). The PCR primers used are upperlined and named as in Table 1 and 2. The predicted 17 AA signal peptide is underlined, in italics. Three potential N-glycosylation sites are double underlined and the respective asparagine residues are in bold; Active site residues C113, H282, Q107and N302 are bold and shaded. Occluding loop responsible for cathepsin B exo-peptidase activity is bold, and italics.
Mentions: The nucleotide and the deduced amino acid sequences of IrCB (form 1) enzyme precursor are shown in Fig. 4. The cDNA sequence [GenBank:EF428206] is 1073 bp long and contains one open reading frame encoding a polypeptide of 337 amino acid (AA) residues. Use of the SignalP 3.0 server [20] predicts a signal peptide cleavage between G17 and R18. The pro-enzyme has a theoretical mass of 35.725 Da and an isoelectric point 5.76. The catalytic residues C113, H282 and two other active site residues Q107 and N302 were found in positions typical for the C1 peptidase (papain) family. The protein has three potential N-glycosylation sites predicted by the NetNGlyc 1.0 Server [21]. The occluding loop responsible for the putative exo-peptidase (peptidyl dipeptidase) activity is predictable between C191 and C211. Also, the domain 297YWLVANSWxxDWGD310 accords to a domain previously described as being associated with the hemoglobinase activity of cathepsin B in blood feeding helminths [22].

Bottom Line: Overall, our results demonstrate the presence of a network of cysteine and aspartic peptidases that conceivably operates to digest host blood proteins in a concerted manner.Significantly, the peptidase components of this digestive network are orthologous to those described in other parasites, including nematodes and flatworms.Accordingly, the present data and those available for other tick species support the notion of an evolutionary conservation of a cysteine/aspartic peptidase system for digestion that includes ticks, but differs from that of insects relying on serine peptidases.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Parasitology, Biology Centre, Academy of Sciences of the Czech Republic, Ceské Budejovice, CZ-370 05, The Czech Republic. dsojka@seznam.cz.

ABSTRACT

Background: Ticks are vectors for a variety of viral, bacterial and parasitic diseases in human and domestic animals. To survive and reproduce ticks feed on host blood, yet our understanding of the intestinal proteolytic machinery used to derive absorbable nutrients from the blood meal is poor. Intestinal digestive processes are limiting factors for pathogen transmission since the tick gut presents the primary site of infection. Moreover, digestive enzymes may find practical application as anti-tick vaccine targets.

Results: Using the hard tick, Ixodes ricinus, we performed a functional activity scan of the peptidase complement in gut tissue extracts that demonstrated the presence of five types of peptidases of the cysteine and aspartic classes. We followed up with genetic screens of gut-derived cDNA to identify and clone genes encoding the cysteine peptidases cathepsins B, L and C, an asparaginyl endopeptidase (legumain), and the aspartic peptidase, cathepsin D. By RT-PCR, expression of asparaginyl endopeptidase and cathepsins B and D was restricted to gut tissue and to those developmental stages feeding on blood.

Conclusion: Overall, our results demonstrate the presence of a network of cysteine and aspartic peptidases that conceivably operates to digest host blood proteins in a concerted manner. Significantly, the peptidase components of this digestive network are orthologous to those described in other parasites, including nematodes and flatworms. Accordingly, the present data and those available for other tick species support the notion of an evolutionary conservation of a cysteine/aspartic peptidase system for digestion that includes ticks, but differs from that of insects relying on serine peptidases.

No MeSH data available.


Related in: MedlinePlus