Limits...
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

Activity profiling of I. ricinus gut peptidases. Peptidolytic activities in the gut tissue extract of partially engorged tick females (the 5-th day of feeding) were demonstrated in vitro with selective peptide substrates (structure of the fluorogenic substrates is indicated). The activity for individual substrates was suppressed in the presence of selective peptidase inhibitors to obtain diagnostic responses indicative of a protease type. Values are expressed as percent inhibition of the control activities. The identified major activities (Target) correspond to papain-type peptidases cathepsin B, L and C (CathB, CathL and CathC, respectively), cathepsin D-like aspartic peptidase (CathD) and asparaginyl endopeptidase (AE). The assay was performed at pH 4.0, an optimum pH for hemoglobin degradation by the gut extract. The activity of AE and CathL was measured in the presence of CA-074 inhibitor to prevent an interference with the activity of CathB. The error bars indicate standard deviations of the mean of triplicates.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2289814&req=5

Figure 2: Activity profiling of I. ricinus gut peptidases. Peptidolytic activities in the gut tissue extract of partially engorged tick females (the 5-th day of feeding) were demonstrated in vitro with selective peptide substrates (structure of the fluorogenic substrates is indicated). The activity for individual substrates was suppressed in the presence of selective peptidase inhibitors to obtain diagnostic responses indicative of a protease type. Values are expressed as percent inhibition of the control activities. The identified major activities (Target) correspond to papain-type peptidases cathepsin B, L and C (CathB, CathL and CathC, respectively), cathepsin D-like aspartic peptidase (CathD) and asparaginyl endopeptidase (AE). The assay was performed at pH 4.0, an optimum pH for hemoglobin degradation by the gut extract. The activity of AE and CathL was measured in the presence of CA-074 inhibitor to prevent an interference with the activity of CathB. The error bars indicate standard deviations of the mean of triplicates.

Mentions: Next, we focused on dissecting the major component peptidases in gut extracts responsible for the acidic degradation of blood meal using peptidase selective substrates and inhibitors (Fig. 2). At pH 4.0, hydrolytic activity cleaving the substrate Z-Arg-Arg-AMC (i.e., suggestive of cathepsin B activity) was inhibited 90% by the cathepsin B inhibitor, CA-074. Likewise, activity against Z-Phe-Arg-AMC was inhibited 90% by Z-Phe-Phe-DMK. Dipeptidyl peptidase activity of cathepsin C was measured with Gly-Arg-AMC and inhibited > 95% by Gly-Phe-DMK. Asparaginyl endopeptidase activity as measured with Z-Ala-Ala-Asn-AMC was inhibited > 95% by the azapeptide, Aza-N-11a. Cathepsin D-like activity measured with Abz-Lys-Pro-Ala-Glu-Phe-Nph-Ala-Leu was effectively inhibited (~98%) by pepstatin.


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)

Activity profiling of I. ricinus gut peptidases. Peptidolytic activities in the gut tissue extract of partially engorged tick females (the 5-th day of feeding) were demonstrated in vitro with selective peptide substrates (structure of the fluorogenic substrates is indicated). The activity for individual substrates was suppressed in the presence of selective peptidase inhibitors to obtain diagnostic responses indicative of a protease type. Values are expressed as percent inhibition of the control activities. The identified major activities (Target) correspond to papain-type peptidases cathepsin B, L and C (CathB, CathL and CathC, respectively), cathepsin D-like aspartic peptidase (CathD) and asparaginyl endopeptidase (AE). The assay was performed at pH 4.0, an optimum pH for hemoglobin degradation by the gut extract. The activity of AE and CathL was measured in the presence of CA-074 inhibitor to prevent an interference with the activity of CathB. The error bars indicate standard deviations of the mean of triplicates.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Activity profiling of I. ricinus gut peptidases. Peptidolytic activities in the gut tissue extract of partially engorged tick females (the 5-th day of feeding) were demonstrated in vitro with selective peptide substrates (structure of the fluorogenic substrates is indicated). The activity for individual substrates was suppressed in the presence of selective peptidase inhibitors to obtain diagnostic responses indicative of a protease type. Values are expressed as percent inhibition of the control activities. The identified major activities (Target) correspond to papain-type peptidases cathepsin B, L and C (CathB, CathL and CathC, respectively), cathepsin D-like aspartic peptidase (CathD) and asparaginyl endopeptidase (AE). The assay was performed at pH 4.0, an optimum pH for hemoglobin degradation by the gut extract. The activity of AE and CathL was measured in the presence of CA-074 inhibitor to prevent an interference with the activity of CathB. The error bars indicate standard deviations of the mean of triplicates.
Mentions: Next, we focused on dissecting the major component peptidases in gut extracts responsible for the acidic degradation of blood meal using peptidase selective substrates and inhibitors (Fig. 2). At pH 4.0, hydrolytic activity cleaving the substrate Z-Arg-Arg-AMC (i.e., suggestive of cathepsin B activity) was inhibited 90% by the cathepsin B inhibitor, CA-074. Likewise, activity against Z-Phe-Arg-AMC was inhibited 90% by Z-Phe-Phe-DMK. Dipeptidyl peptidase activity of cathepsin C was measured with Gly-Arg-AMC and inhibited > 95% by Gly-Phe-DMK. Asparaginyl endopeptidase activity as measured with Z-Ala-Ala-Asn-AMC was inhibited > 95% by the azapeptide, Aza-N-11a. Cathepsin D-like activity measured with Abz-Lys-Pro-Ala-Glu-Phe-Nph-Ala-Leu was effectively inhibited (~98%) by pepstatin.

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