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Stack C, Dalton JP, Robinson MW. The phylogeny, structure and function of trematode cysteine proteases, with particular emphasis on the Fasciola hepatica cathepsin L family. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 712:116-35. [PMID: 21660662 DOI: 10.1007/978-1-4419-8414-2_8] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Helminth parasites (nematodes, flatworms and cestodes) infect over 1 billion of the world's population causing high morbidity and mortality. The large tissue-dwelling worms express papain-like cysteine peptidases, termed cathepsins that play important roles in virulence including host entry, tissue migration and the suppression of host immune responses. Much of our knowledge of helminth cathepsins comes from studies using flatworms or trematode (fluke) parasites. The developmentally-regulated expression of these proteases correlates with the passage of parasites through host tissues and their encounters with different host macromolecules. Recent phylogenetic, biochemical and structural studies indicate that trematode cathepsins exhibit overlapping but distinct substrate specificities due to divergence within the protease active site. Here we provide an overview of the evolution, biochemistry and structure of these important enzymes and highlight how recent advances in proteomics and gene silencing techniques are allowing researchers to probe their biological functions. We focus mainly on members of the cathepsin L gene family of the animal and human pathogen, Fasciola hepatica, because of our deep understanding of their function, biochemistry and structure.
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El Ridi R, Tallima H, Mahana N, Dalton JP. Innate immunogenicity and in vitro protective potential of Schistosoma mansoni lung schistosomula excretory–secretory candidate vaccine antigens. Microbes Infect 2010; 12:700-9. [DOI: 10.1016/j.micinf.2010.04.012] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2010] [Revised: 04/18/2010] [Accepted: 04/23/2010] [Indexed: 10/19/2022]
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Robinson MW, Hutchinson AT, Dalton JP, Donnelly S. Peroxiredoxin: a central player in immune modulation. Parasite Immunol 2010; 32:305-13. [PMID: 20500659 DOI: 10.1111/j.1365-3024.2010.01201.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Peroxiredoxins (Prx) are a family of anti-oxidants that protect cells from metabolically produced reactive oxygen species (ROS). The presence of these enzymes in the secretomes of many parasitic helminths suggests they provide protection against ROS released by host immune effector cells. However, we recently reported that helminth-secreted Prx also contribute to the development of Th2-responses via a mechanism involving the induction of alternatively activated macrophages. In this review, we discuss the role helminth Prx may play in modulating the immune responses of their hosts.
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Robinson MW, Hutchinson AT, Donnelly S, Dalton JP. Worm secretory molecules are causing alarm. Trends Parasitol 2010; 26:371-2. [PMID: 20542734 DOI: 10.1016/j.pt.2010.05.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2010] [Revised: 05/14/2010] [Accepted: 05/17/2010] [Indexed: 11/17/2022]
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Trenholme KR, Brown CL, Skinner-Adams TS, Stack C, Lowther J, To J, Robinson MW, Donnelly SM, Dalton JP, Gardiner DL. Aminopeptidases of malaria parasites: new targets for chemotherapy. Infect Disord Drug Targets 2010; 10:217-225. [PMID: 20334618 DOI: 10.2174/187152610791163363] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2009] [Accepted: 11/02/2009] [Indexed: 05/29/2023]
Abstract
Novel targets for new drug development are urgently required to combat malaria, a disease that puts half of the world's population at risk. One group of enzymes identified within the genome of the most lethal of the causative agents of malaria, Plasmodium falciparum, that may have the potential to become new targets for antimalarial drug development are the aminopeptidases. These enzymes catalyse the cleavage of the N-terminal amino acids from proteins and peptides. P. falciparum appears to encode for at least nine aminopeptidases, two neutral aminopeptidases, one aspartyl aminopeptidase, one aminopeptidase P, one prolyl aminopeptidase and four methionine aminopeptidases. Recent advances in our understanding of these genes and their protein products are outlined in this review, including their potential for antimalarial drug development.
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Mucha A, Drag M, Dalton JP, Kafarski P. Metallo-aminopeptidase inhibitors. Biochimie 2010; 92:1509-29. [PMID: 20457213 PMCID: PMC7117057 DOI: 10.1016/j.biochi.2010.04.026] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Accepted: 04/29/2010] [Indexed: 01/05/2023]
Abstract
Aminopeptidases are enzymes that selectively hydrolyze an amino acid residue from the N-terminus of proteins and peptides. They are important for the proper functioning of prokaryotic and eukaryotic cells, but very often are central players in the devastating human diseases like cancer, malaria and diabetes. The largest aminopeptidase group include enzymes containing metal ion(s) in their active centers, which often determines the type of inhibitors that are the most suitable for them. Effective ligands mostly bind in a non-covalent mode by forming complexes with the metal ion(s). Here, we present several approaches for the design of inhibitors for metallo-aminopeptidases. The optimized structures should be considered as potential leads in the drug discovery process against endogenous and infectious diseases.
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Gardiner DL, Skinner-Adams TS, Brown CL, Andrews KT, Stack CM, McCarthy JS, Dalton JP, Trenholme KR. Plasmodium falciparum: new molecular targets with potential for antimalarial drug development. Expert Rev Anti Infect Ther 2010; 7:1087-98. [PMID: 19883329 DOI: 10.1586/eri.09.93] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Malaria remains one of the world's most devastating infectious diseases. Drug resistance to all classes of antimalarial agents has now been observed, highlighting the need for new agents that act against novel parasite targets. The complete sequencing of the Plasmodium falciparum genome has allowed the identification of new molecular targets within the parasite that may be amenable to chemotherapeutic intervention. In this review, we investigate four possible targets for the future development of new classes of antimalarial agents. These targets include histone deacetylase, the aspartic proteases or plasmepsins, aminopeptidases and the purine salvage enzyme hypoxanthine-xanthine-guanine phosphoribosyltransferase.
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Mendes RE, Pérez-Ecija RA, Zafra R, Buffoni L, Martínez-Moreno A, Dalton JP, Mulcahy G, Pérez J. Evaluation of hepatic changes and local and systemic immune responses in goats immunized with recombinant Peroxiredoxin (Prx) and challenged with Fasciola hepatica. Vaccine 2010; 28:2832-40. [PMID: 20153792 DOI: 10.1016/j.vaccine.2010.01.055] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Revised: 01/25/2010] [Accepted: 01/28/2010] [Indexed: 10/19/2022]
Abstract
Protection against Fasciola hepatica in goats immunized with Peroxiredoxin (Prx) was assessed. The experimental trial consisted of three groups of seven animals; group 1 were unimmunized and uninfected, group 2 were immunized with adjuvant only and group 3 were immunized with recombinant Prx in adjuvant (immunized and infected). Immunization with Prx in Quil A adjuvant, group 3, induced a reduction in fluke burden of 33.04% when compared to adjuvant control, group 2, although this difference was not significant. The hepatic gross and microscopical morphometric study revealed lower damage in the Prx-immunized compared to group 2 (p<0.05). Furthermore, immunohistochemical studies revealed that the Prx-immunized group exhibited reduced infiltration of CD4(+), CD8(+), IFN-gamma(+) and TCR(+) (p<0.05); and CD2(+) and IL-4(+) (p<0.001) in hepatic lesions. Levels of anti-Prx serum IgG in group 3 showed a significant increase at the 4th week after challenge infection compared with group 2 (p<0.0001). This is the first report of ruminant immunization with recombinant Prx of F. hepatica. The study shows that this vaccine significantly reduces hepatic damage and encourages further studies to improve the vaccine efficacy.
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Sripa J, Laha T, To J, Brindley PJ, Sripa B, Kaewkes S, Dalton JP, Robinson MW. Secreted cysteine proteases of the carcinogenic liver fluke, Opisthorchis viverrini: regulation of cathepsin F activation by autocatalysis and trans-processing by cathepsin B. Cell Microbiol 2010; 12:781-95. [PMID: 20070308 DOI: 10.1111/j.1462-5822.2010.01433.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Opisthorchis viverrini is an important helminth pathogen of humans that is endemic in Thailand and Laos. Adult flukes reside within host bile ducts and feed on epithelial tissue and blood cells. Chronic opisthorchiasis is associated with severe hepatobiliary diseases such as cholangiocarcinoma. Here we report that adult O. viverrini secrete two major cysteine proteases: cathepsin F (Ov-CF-1) and cathepsin B1 (Ov-CB-1). Ov-CF-1 is secreted as an inactive zymogen that autocatalytically processes and activates to a mature enzyme at pH 4.5 via an intermolecular cleavage at the prosegment-mature domain junction. Ov-CB-1 is also secreted as a zymogen but, in contrast to Ov-CF-1, is fully active against peptide and macromolecular substrates despite retaining the N-terminal prosegment. The active Ov-CB-1 zymogen was capable of trans-activating Ov-CF-1 by proteolytic removal of its prosegment at pH 5.5, a pH at which the Ov-CF-1 zymogen cannot autocatalytically activate. Both cathepsins hydrolyse human haemoglobin but their combined action more efficiently degrades haemoglobin to smaller peptides than each enzyme alone. Ov-CF-1 degraded extracellular matrix proteins more effectively than Ov-CB-1 at physiological pH. We propose that Ov-CB-1 regulates Ov-CF-1 activity and that both enzymes work together to degrade host tissue contributing to the development of liver fluke-associated cholangiocarcinoma.
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Moran BW, Anderson FP, Ruth DM, Fágáin CÓ, Dalton JP, Kenny PTM. Fluorobenzoyl dipeptidyl derivatives as inhibitors of the Fasciola hepatica cysteine protease cathepsin L1. J Enzyme Inhib Med Chem 2009; 25:1-12. [DOI: 10.3109/14756360902888184] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Robinson MW, Dalton JP. Zoonotic helminth infections with particular emphasis on fasciolosis and other trematodiases. Philos Trans R Soc Lond B Biol Sci 2009; 364:2763-76. [PMID: 19687044 DOI: 10.1098/rstb.2009.0089] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Zoonotic infections are among the most common on earth and are responsible for >60 per cent of all human infectious diseases. Some of the most important and well-known human zoonoses are caused by worm or helminth parasites, including species of nematodes (trichinellosis), cestodes (cysticercosis, echinococcosis) and trematodes (schistosomiasis). However, along with social, epidemiological and environmental changes, together with improvements in our ability to diagnose helminth infections, several neglected parasite species are now fast-becoming recognized as important zoonotic diseases of humans, e.g. anasakiasis, several fish-borne trematodiasis and fasciolosis. In the present review, we discuss the current disease status of these primary helminth zoonotic infections with particular emphasis on their diagnosis and control. Advances in molecular biology, proteomics and the release of helminth genome-sequencing project data are revolutionizing parasitology research. The use of these powerful experimental approaches, and their potential benefits to helminth biology are also discussed in relation to the future control of helminth infections of animals and humans.
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Donnelly S, O'Neill SM, Stack CM, Robinson MW, Turnbull L, Whitchurch C, Dalton JP. Helminth cysteine proteases inhibit TRIF-dependent activation of macrophages via degradation of TLR3. J Biol Chem 2009; 285:3383-92. [PMID: 19923225 DOI: 10.1074/jbc.m109.060368] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Helminth pathogens prepare a Th2 type immunological environment in their hosts to ensure their longevity. They achieve this by secreting molecules that not only actively drive type 2 responses but also suppress type 1 responses. Here, we show that the major cysteine proteases secreted from the helminth pathogens Fasciola hepatica (FheCL1) and Schistosoma mansoni (SmCB1) protect mice from the lethal effects of lipopolysaccharide by preventing the release of inflammatory mediators, nitric oxide, interleukin-6, tumor necrosis factor alpha, and interleukin-12, from macrophages. The proteases specifically block the MyD88-independent TRIF-dependent signaling pathway of Toll-like receptor (TLR)4 and TLR3. Microscopical and flow cytometric studies, however, show that alteration of macrophage function by cysteine protease is not mediated by cleavage of components of the TLR4 complex on the cell surface but occurs by degradation of TLR3 within the endosome. This is the first study to describe a parasite molecule that degrades this receptor and pinpoints a novel mechanism by which helminth parasites modulate the innate immune responses of their hosts to suppress the development of Th1 responses.
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Skinner-Adams TS, Stack CM, Trenholme KR, Brown CL, Grembecka J, Lowther J, Mucha A, Drag M, Kafarski P, McGowan S, Whisstock JC, Gardiner DL, Dalton JP. Plasmodium falciparum neutral aminopeptidases: new targets for anti-malarials. Trends Biochem Sci 2009; 35:53-61. [PMID: 19796954 DOI: 10.1016/j.tibs.2009.08.004] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Revised: 08/05/2009] [Accepted: 08/05/2009] [Indexed: 11/19/2022]
Abstract
The neutral aminopeptidases M1 alanyl aminopeptidase (PfM1AAP) and M17 leucine aminopeptidase (PfM17LAP) of the human malaria parasite Plasmodium falciparum are targets for the development of novel anti-malarial drugs. Although the functions of these enzymes remain unknown, they are believed to act in the terminal stages of haemoglobin degradation, generating amino acids essential for parasite growth and development. Inhibitors of both enzymes are lethal to P. falciparum in culture and kill the murine malaria P. chabaudi in vivo. Recent biochemical, structural and functional studies provide the substrate specificity and mechanistic binding data needed to guide the development of more potent anti-malarial drugs. Together with biological studies, these data form the rationale for choosing PfM1AAP and PfM17LAP as targets for anti-malarial development.
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Maric S, Donnelly SM, Robinson MW, Skinner-Adams T, Trenholme KR, Gardiner DL, Dalton JP, Stack CM, Lowther J. The M17 leucine aminopeptidase of the malaria parasite Plasmodium falciparum: importance of active site metal ions in the binding of substrates and inhibitors. Biochemistry 2009; 48:5435-9. [PMID: 19408962 DOI: 10.1021/bi9003638] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The M17 leucine aminopeptidase of the intraerythrocytic stages of the malaria parasite Plasmodium falciparum (PfLAP) plays a role in releasing amino acids from host hemoglobin that are used for parasite protein synthesis, growth, and development. This enzyme represents a target at which new antimalarials could be designed since metalloaminopeptidase inhibitors prevent the growth of the parasites in vitro and in vivo. A study on the metal ion binding characteristics of recombinant P. falciparum M17 leucine aminopeptidase (rPfLAP) shows that the active site of this exopeptidase contains two metal-binding sites, a readily exchangeable site (site 1) and a tight binding site (site 2). The enzyme retains activity when the metal ion is removed from site 1, while removal of metal ions from both sites results in an inactive apoenzyme that cannot be reactivated by the addition of divalent metal cations. The metal ion at site 1 is readily exchangeable with several divalent metal ions and displays a preference in the order of preference Zn(2+) > Mn(2+) > Co(2+) > Mg(2+). While it is likely that native PfLAP contains a Zn(2+) in site 2, the metal ion located in site 1 may be dependent on the type and concentration of metal ions in the cytosolic compartment of the parasite. Importantly, the type of metal ion present at site 1 influences not only the catalytic efficiency of the enzyme for peptide substrates but also the mode of binding by bestatin, a metal-chelating inhibitor of M17 aminopeptidases with antimalarial activity.
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Goh F, Irvine KM, Lovelace E, Donnelly S, Jones MK, Brion K, Hume DA, Kotze AC, Dalton JP, Ingham A, Sweet MJ. Selective induction of the Notch ligand Jagged-1 in macrophages by soluble egg antigen from Schistosoma mansoni involves ERK signalling. Immunology 2009; 127:326-37. [PMID: 19019093 PMCID: PMC2712101 DOI: 10.1111/j.1365-2567.2008.02979.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2008] [Revised: 09/18/2008] [Accepted: 09/26/2008] [Indexed: 01/30/2023] Open
Abstract
Soluble egg antigen (SEA) from the helminth Schistosoma mansoni promotes T helper type 2 (Th2) responses by modulating antigen-presenting cell function. The Jagged/Notch pathway has recently been implicated in driving Th2 development. We show here that SEA rapidly up-regulated mRNA and protein expression of the Notch ligand Jagged-1 in both murine bone marrow-derived macrophages (BMMs) and human monocyte-derived macrophages (HMDMs). Another potential Th2-promoting factor, interleukin (IL)-33, was not transcriptionally induced by SEA in BMMs. Up-regulation of Jagged-1 mRNA by SEA was also apparent in conventional dendritic cells (DCs), although the effect was less striking than in BMMs. Conversely, SEA-pulsed DCs, but not BMMs, promoted IL-4 production upon T-cell activation, suggesting that Jagged-1 induction alone is insufficient for instructing Th2 development. A comparison of the responses initiated in BMMs by SEA and the bacterial endotoxin lipopolysaccharide (LPS) revealed common activation of extracellular signal-regulated kinase-1/2 (ERK-1/2) and p38 phosphorylation, as well as induction of Jagged-1 mRNA. However, only LPS triggered IkappaB degradation, phosphorylation of c-Jun N-terminal kinase (Jnk) and signal transducer and activator of transcription 1 (Stat1) Tyr701, and IL-33 and IL-12p40 mRNA up-regulation. Inducible gene expression was modified by the presence of the macrophage growth factor colony-stimulating factor (CSF)-1, which inhibited Jagged-1 induction by SEA and LPS, but enhanced LPS-induced IL-12p40 expression. Unlike LPS, SEA robustly activated signalling in HEK293 cells expressing either Toll-like receptor 2 (TLR2) or TLR4/MD2. Pharmacological inhibition of the ERK-1/2 pathway impaired SEA- and LPS-inducible Jagged-1 expression in BMMs. Taken together, our data suggest that Jagged-1 is an ERK-dependent target of TLR signalling that has a macrophage-specific function in the response to SEA.
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Rinaldi G, Morales ME, Alrefaei YN, Cancela M, Castillo E, Dalton JP, Tort JF, Brindley PJ. RNA interference targeting leucine aminopeptidase blocks hatching of Schistosoma mansoni eggs. Mol Biochem Parasitol 2009; 167:118-26. [PMID: 19463860 DOI: 10.1016/j.molbiopara.2009.05.002] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2009] [Revised: 05/08/2009] [Accepted: 05/11/2009] [Indexed: 10/20/2022]
Abstract
Schistosoma mansoni leucine aminopeptidase (LAP) is thought to play a central role in hatching of the miracidium from the schistosome egg. We identified two discrete LAPs genes in the S. mansoni genome, and their orthologs in S. japonicum. The similarities in sequence and exon/intron structure of the two genes, LAP1 and LAP2, suggest that they arose by gene duplication and that this occurred before separation of the mansoni and japonicum lineages. The SmLAP1 and SmLAP2 genes have different expression patterns in diverse stages of the cycle; whereas both are equally expressed in the blood dwelling stages (schistosomules and adult), SmLAP2 expression was higher in free living larval (miracidia) and in parasitic intra-snail (sporocysts) stages. We investigated the role of each enzyme in hatching of schistosome eggs and the early stages of schistosome development by RNA interference (RNAi). Using RNAi, we observed marked and specific reduction of mRNAs, along with a loss of exopeptidase activity in soluble parasite extracts against the diagnostic substrate l-leucine-7-amido-4-methylcoumarin hydroxide. Strikingly, knockdown of either SmLAP1 or SmLAP2, or both together, was accompanied by >or=80% inhibition of hatching of schistosome eggs showing that both enzymes are important to the escape of miracidia from the egg. The methods employed here refine the utility of RNAi for functional genomics studies in helminth parasites and confirm these can be used to identify potential drug targets, in this case schistosome aminopeptidases.
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Robinson MW, Menon R, Donnelly SM, Dalton JP, Ranganathan S. An integrated transcriptomics and proteomics analysis of the secretome of the helminth pathogen Fasciola hepatica: proteins associated with invasion and infection of the mammalian host. Mol Cell Proteomics 2009; 8:1891-907. [PMID: 19443417 DOI: 10.1074/mcp.m900045-mcp200] [Citation(s) in RCA: 219] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To infect their mammalian hosts, Fasciola hepatica larvae must penetrate and traverse the intestinal wall of the duodenum, move through the peritoneum, and penetrate the liver. After migrating through and feeding on the liver, causing extensive tissue damage, the parasites move to their final niche in the bile ducts where they mature and produce eggs. Here we integrated a transcriptomics and proteomics approach to profile Fasciola secretory proteins that are involved in host-pathogen interactions and to correlate changes in their expression with the migration of the parasite. Prediction of F. hepatica secretory proteins from 14,031 expressed sequence tags (ESTs) available from the Wellcome Trust Sanger Centre using the semiautomated EST2Secretome pipeline showed that the major components of adult parasite secretions are proteolytic enzymes including cathepsin L, cathepsin B, and asparaginyl endopeptidase cysteine proteases as well as novel trypsin-like serine proteases and carboxypeptidases. Proteomics analysis of proteins secreted by infective larvae, immature flukes, and adult F. hepatica showed that these proteases are developmentally regulated and correlate with the passage of the parasite through host tissues and its encounters with different host macromolecules. Proteases such as FhCL3 and cathepsin B have specific functions in larvae activation and intestinal wall penetration, whereas FhCL1, FhCL2, and FhCL5 are required for liver penetration and tissue and blood feeding. Besides proteases, the parasites secrete an array of antioxidants that are also highly regulated according to their migration through host tissues. However, whereas the proteases of F. hepatica are secreted into the parasite gut via a classical endoplasmic reticulum/Golgi pathway, we speculate that the antioxidants, which all lack a signal sequence, are released via a non-classical trans-tegumental pathway.
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Pinlaor P, Kaewpitoon N, Laha T, Sripa B, Kaewkes S, Morales ME, Mann VH, Parriott SK, Suttiprapa S, Robinson MW, To J, Dalton JP, Loukas A, Brindley PJ. Cathepsin F cysteine protease of the human liver fluke, Opisthorchis viverrini. PLoS Negl Trop Dis 2009; 3:e398. [PMID: 19308250 PMCID: PMC2654340 DOI: 10.1371/journal.pntd.0000398] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2008] [Accepted: 02/25/2009] [Indexed: 01/30/2023] Open
Abstract
Background The liver fluke Opisthorchis viverrini is classified as a class I carcinogen due to the association between cholangiocarcinoma and chronic O. viverrini infection. During its feeding activity within the bile duct, the parasite secretes several cathepsin F cysteine proteases that may induce or contribute to the pathologies associated with hepatobiliary abnormalities. Methodology/Principal Findings Here, we describe the cDNA, gene organization, phylogenetic relationships, immunolocalization, and functional characterization of the cathepsin F cysteine protease gene, here termed Ov-cf-1, from O. viverrini. The full length mRNA of 1020 nucleotides (nt) encoded a 326 amino acid zymogen consisting of a predicted signal peptide (18 amino acids, aa), prosegment (95 aa), and mature protease (213 aa). BLAST analysis using the Ov-CF-1 protein as the query revealed that the protease shared identity with cathepsin F-like cysteine proteases of other trematodes, including Clonorchis sinensis (81%), Paragonimus westermani (58%), Schistosoma mansoni and S. japonicum (52%), and with vertebrate cathepsin F (51%). Transcripts encoding the protease were detected in all developmental stages that parasitize the mammalian host. The Ov-cf-1 gene, of ∼3 kb in length, included seven exons interrupted by six introns; the exons ranged from 69 to 267 bp in length, the introns from 43 to 1,060 bp. The six intron/exon boundaries of Ov-cf-1 were conserved with intron/exon boundaries in the human cathepsin F gene, although the gene structure of human cathepsin F is more complex. Unlike Ov-CF-1, human cathepsin F zymogen includes a cystatin domain in the prosegment region. Phylogenetic analysis revealed that the fluke, human, and other cathepsin Fs branched together in a clade discrete from the cathepsin L cysteine proteases. A recombinant Ov-CF-1 zymogen that displayed low-level activity was expressed in the yeast Pichia pastoris. Although the recombinant protease did not autocatalytically process and activate to a mature enzyme, trans-processing by Fasciola hepatica cathepsin L cleaved the prosegment of Ov-CF-1, releasing a mature cathepsin F with activity against the peptide Z-Phe-Arg-NHMec >50 times that of the zymogen. Immunocytochemistry using antibodies raised against the recombinant enzyme showed that Ov-CF-1 is expressed in the gut of the mature hermaphroditic fluke and also in the reproductive structures, including vitelline glands, egg, and testis. Ov-CF-1 was detected in bile duct epithelial cells surrounding the flukes several weeks after infection of hamsters with O. viverrini and, in addition, had accumulated in the secondary (small) bile ducts where flukes cannot reach due to their large size. Conclusions/Significance A cathepsin F cysteine protease of the human liver fluke O. viverrini has been characterized at the gene and protein level. Secretion of this protease may contribute to the hepatobiliary abnormalities, including cholangiocarcinogenesis, observed in individuals infected with this parasite. Opisthorchiasis, oriental liver fluke infection, is a food-borne parasitic disease that afflicts millions of residents in northern Thailand and Laos. Related infections occur in North Asia, including China and Korea. This kind of liver fluke infection is the consequence of eating certain uncooked or undercooked freshwater fish contaminated with the larvae of the parasite Opisthorchis viverrini. Whereas the infection can cause disease in the bile ducts and liver, infection with the oriental fluke can lead to the development of a liver cancer, cholangiocarcinoma (bile duct cancer). Our recent studies have begun to focus on products and metabolites from the parasite that are carcinogenic. Many proteolytic enzymes are known to be secreted by parasites. This report centers on a specific category of protease, termed cathepsin F. We determined here that O. viverrini expresses a cathepsin F in its gut and in other organs. In the liver fluke, cathepsin F likely plays a role in digesting ingested human cells. The gene encoding the parasite enzyme shows evolutionary relatedness to a similar gene in humans. The fluke cathepsin F also is released from the parasite into livers of infected mammals, where it appears to contribute to inflammation surrounding the parasite. In this regard, it may be involved in early events that lead to bile duct cancer.
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Lowther J, Robinson MW, Donnelly SM, Xu W, Stack CM, Matthews JM, Dalton JP. The importance of pH in regulating the function of the Fasciola hepatica cathepsin L1 cysteine protease. PLoS Negl Trop Dis 2009; 3:e369. [PMID: 19172172 PMCID: PMC2621350 DOI: 10.1371/journal.pntd.0000369] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2008] [Accepted: 12/26/2008] [Indexed: 11/23/2022] Open
Abstract
The helminth parasite Fasciola hepatica secretes cathepsin L cysteine proteases to invade its host, migrate through tissues and digest haemoglobin, its main source of amino acids. Here we investigated the importance of pH in regulating the activity and functions of the major cathepsin L protease FheCL1. The slightly acidic pH of the parasite gut facilitates the auto-catalytic activation of FheCL1 from its inactive proFheCL1 zymogen; this process was approximately 40-fold faster at pH 4.5 than at pH 7.0. Active mature FheCL1 is very stable at acidic and neutral conditions (the enzyme retained approximately 45% activity when incubated at 37 degrees C and pH 4.5 for 10 days) and displayed a broad pH range for activity peptide substrates and the protein ovalbumin, peaking between pH 5.5 and pH 7.0. This pH profile likely reflects the need for FheCL1 to function both in the parasite gut and in the host tissues. FheCL1, however, could not cleave its natural substrate Hb in the pH range pH 5.5 and pH 7.0; digestion occurred only at pH=4.5, which coincided with pH-induced dissociation of the Hb tetramer. Our studies indicate that the acidic pH of the parasite relaxes the Hb structure, making it susceptible to proteolysis by FheCL1. This process is enhanced by glutathione (GSH), the main reducing agent contained in red blood cells. Using mass spectrometry, we show that FheCL1 can degrade Hb to small peptides, predominantly of 4-14 residues, but cannot release free amino acids. Therefore, we suggest that Hb degradation is not completed in the gut lumen but that the resulting peptides are absorbed by the gut epithelial cells for further processing by intracellular di- and amino-peptidases to free amino acids that are distributed through the parasite tissue for protein anabolism.
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Kašný M, Mikeš L, Hampl V, Dvořák J, Caffrey CR, Dalton JP, Horák P. Chapter 4 Peptidases of Trematodes. ADVANCES IN PARASITOLOGY 2009; 69:205-97. [DOI: 10.1016/s0065-308x(09)69004-7] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Donnelly S, Stack CM, O'Neill SM, Sayed AA, Williams DL, Dalton JP. Helminth 2-Cys peroxiredoxin drives Th2 responses through a mechanism involving alternatively activated macrophages. FASEB J 2008; 22:4022-32. [PMID: 18708590 DOI: 10.1096/fj.08-106278] [Citation(s) in RCA: 185] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
During helminth infections, alternatively activated macrophages (AAMacs) are key to promoting Th2 responses and suppressing Th1-driven inflammatory pathology. Th2 cytokines IL-4 and/or IL-13 are believed to be important in the induction and activation of AAMacs. Using murine models for the helminth infections caused by Fasciola hepatica (Fh) and Schistosoma mansoni (Sm), we show that a secreted antioxidant, peroxiredoxin (Prx), induces alternative activation of macrophages. These activated, Ym1-expressing macrophages enhanced the secretion of IL-4, IL-5, and IL-13 from naive CD4(+) T cells. Administration of recombinant FhPrx and SmPrx to wild-type and IL-4(-/-) and IL-13(-/-) mice induced the production of AAMacs. In addition, Prx stimulated the expression of markers of AAMacs (particularly, Ym1) in vitro, and therefore can act independently of IL-4/IL-13 signaling. The immunomodulatory property of Prx is not due to its antioxidant activity, as an inactive recombinant variant with active site Cys residues replaced by Gly could also induce AAMacs and Th2 responses. Immunization of mice with recombinant Prx or passive transfer of anti-Prx antibodies prior to infection with Fh not only blocked the induction of AAMacs but also the development of parasite-specific Th2 responses. We propose that Prx activates macrophages as an initial step in the induction of Th2 responses by helminth parasites and is thereby a novel pathogen-associated molecular pattern.
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Robinson MW, Tort JF, Lowther J, Donnelly SM, Wong E, Xu W, Stack CM, Padula M, Herbert B, Dalton JP. Proteomics and Phylogenetic Analysis of the Cathepsin L Protease Family of the Helminth Pathogen Fasciola hepatica. Mol Cell Proteomics 2008; 7:1111-23. [DOI: 10.1074/mcp.m700560-mcp200] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Stack CM, Caffrey CR, Donnelly SM, Seshaadri A, Lowther J, Tort JF, Collins PR, Robinson MW, Xu W, McKerrow JH, Craik CS, Geiger SR, Marion R, Brinen LS, Dalton JP. Structural and functional relationships in the virulence-associated cathepsin L proteases of the parasitic liver fluke, Fasciola hepatica. J Biol Chem 2008; 283:9896-908. [PMID: 18160404 PMCID: PMC3979170 DOI: 10.1074/jbc.m708521200] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2007] [Revised: 11/28/2007] [Indexed: 11/06/2022] Open
Abstract
The helminth parasite Fasciola hepatica secretes cysteine proteases to facilitate tissue invasion, migration, and development within the mammalian host. The major proteases cathepsin L1 (FheCL1) and cathepsin L2 (FheCL2) were recombinantly produced and biochemically characterized. By using site-directed mutagenesis, we show that residues at position 67 and 205, which lie within the S2 pocket of the active site, are critical in determining the substrate and inhibitor specificity. FheCL1 exhibits a broader specificity and a higher substrate turnover rate compared with FheCL2. However, FheCL2 can efficiently cleave substrates with a Pro in the P2 position and degrade collagen within the triple helices at physiological pH, an activity that among cysteine proteases has only been reported for human cathepsin K. The 1.4-A three-dimensional structure of the FheCL1 was determined by x-ray crystallography, and the three-dimensional structure of FheCL2 was constructed via homology-based modeling. Analysis and comparison of these structures and our biochemical data with those of human cathepsins L and K provided an interpretation of the substrate-recognition mechanisms of these major parasite proteases. Furthermore, our studies suggest that a configuration involving residue 67 and the "gatekeeper" residues 157 and 158 situated at the entrance of the active site pocket create a topology that endows FheCL2 with its unusual collagenolytic activity. The emergence of a specialized collagenolytic function in Fasciola likely contributes to the success of this tissue-invasive parasite.
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Flynn RJ, Irwin JA, Olivier M, Sekiya M, Dalton JP, Mulcahy G. Alternative activation of ruminant macrophages by Fasciola hepatica. Vet Immunol Immunopathol 2007; 120:31-40. [PMID: 17719651 DOI: 10.1016/j.vetimm.2007.07.003] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The helminth parasite, Fasciola hepatica, has a worldwide distribution and infects a wide variety of mammalian hosts, including ruminants and man. In response to infection, these hosts mount a type 2 helper (Th2) response that is highly polarized and results in the downregulation of type 1 helper (Th1) mechanisms. In a murine macrophage model F. hepatica induces alternative activation of macrophages. These macrophages differ from classically activated cells in that they preferentially use arginase instead of inducible nitric oxide synthase (iNOS) for metabolism of nitrogen. In this study we sought to characterize macrophage phenotype following stimulation of the ovine cell line MOCL7 with recombinant F. hepatica enzymes and crude parasite extracts. An in vitro model using the MOCL7 cell line was established and arginase levels in cells were used to determine the activation status of cells. Stimulation of this cell-line in vitro with F. hepatica products induces alternative activation. We have also found a chitinase-like protein in supernatants which is capable of differentiating alternatively activated from classically activated macrophages.
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Skinner-Adams TS, Lowther J, Teuscher F, Stack CM, Grembecka J, Mucha A, Kafarski P, Trenholme KR, Dalton JP, Gardiner DL. Identification of Phosphinate Dipeptide Analog Inhibitors Directed against the Plasmodium falciparum M17 Leucine Aminopeptidase as Lead Antimalarial Compounds. J Med Chem 2007; 50:6024-31. [DOI: 10.1021/jm070733v] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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