Cysteine proteases in protozoan parasites

Siqueira-Neto, Jair L.; Debnath, Anjan; McCall, Laura-Isobel; Bernatchez, Jean A.; Ndao, Momar; Reed, Sharon L.; Rosenthal, Philip J.

doi:10.1371/journal.pntd.0006512

“…The endolysosomal pathway is a vital system in eukaryotic organisms. Proteases associated with these systems are of particular interest due to their role in various biological processes, including catabolism and enzyme activation (2,4,5). The lysosomal cysteine proteases cathepsins L and B are ubiquitously expressed in eukaryotic cells and together are integral for proteolytic activity within lysosomes (6).…”

mentioning

confidence: 99%

“…Lysosomal cathepsin proteases are expressed in multicopy families in some pathogenic protozoa, such as Plasmodium falciparum. P. falciparum is one of the causative agents of malaria and, like many other protozoan parasites, relies on proteases for various aspects of its pathogenesis (2). Plasmodium obtains host hemoglobin and digests it in a specialized organelle, known as the food vacuole (FV), to procure necessary nutrients (12,13).…”

mentioning

confidence: 99%

Toxoplasma Cathepsin Protease B and Aspartyl Protease 1 Are Dispensable for Endolysosomal Protein Digestion

McDonald

¹

,

Smith

²

,

Cristina

³

et al. 2020

mSphere

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The lysosome-like vacuolar compartment (VAC) is a major site of proteolysis in the intracellular parasite Toxoplasma gondii. Previous studies have shown that genetic ablation of a VAC-residing cysteine protease, cathepsin protease L (CPL), resulted in the accumulation of undigested protein in the VAC and loss of parasite viability during the chronic stage of infection. However, since the maturation of another VAC localizing protease, cathepsin protease B (CPB), is dependent on CPL, it remained unknown whether these defects result directly from ablation of CPL or indirectly from a lack of CPB maturation. Likewise, although a previously described cathepsin D-like aspartyl protease 1 (ASP1) could also play a role in proteolysis, its definitive residence and function in the Toxoplasma endolysosomal system were not well defined. Here, we demonstrate that CPB is not necessary for protein turnover in the VAC and that CPB-deficient parasites have normal growth and viability in both the acute and chronic stages of infection. We also show that ASP1 depends on CPL for correct maturation, and it resides in the T. gondii VAC, where, similar to CPB, it plays a dispensable role in protein digestion. Taken together with previous work, our findings suggest that CPL is the dominant protease in a hierarchy of proteolytic enzymes within the VAC. This unusual lack of redundancy for CPL in T. gondii makes it a single exploitable target for disrupting chronic toxoplasmosis. IMPORTANCE Roughly one-third of the human population is chronically infected with the intracellular single-celled parasite Toxoplasma gondii, but little is known about how this organism persists inside people. Previous research suggested that a parasite proteolytic enzyme, termed cathepsin protease L, is important for Toxoplasma persistence; however, it remained possible that other associated proteolytic enzymes could also be involved in the long-term survival of the parasite during infection. Here, we show that two proteolytic enzymes associated with cathepsin protease L play dispensable roles and are dependent on cathepsin L to reach maturity, which differs from the corresponding enzymes in humans. These findings establish a divergent hierarchy of proteases and help focus attention principally on cathepsin protease L as a potential target for interrupting Toxoplasma chronic infection.

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“…Recently, Siqueira-Neto et al, [6] reviewed the proposed functions of the most characterized 29 CPs only in seven protozoa; E. histolytica (six), Leishmania spp. (six), Plasmodium spp.…”

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confidence: 99%

Expression of cysteine proteinases and cystatins in parasites and use of cysteine proteinase inhibitors in parasitic diseases. Part III: Protozoa (1)

Abaza

¹

2019

Parasitologists United Journal

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Cysteine proteinases (CPs) Being essential for parasite survival, CPs are investigated for development of vaccine candidates and/or novel drugs in protozoal diseases with high mortality and morbidity rates such as malignant malaria, African sleeping sickness and Chagas' disease, as well as neglected tropical diseases such as visceral leishmaniasis, toxoplasmosis, extraintestinal amoebiasis and cryptosporidiosis. Caffrey and Steverding [1] , in their review, introduced a unified nomenclature for kinetoplastid cathepsins (CATHs) and discussed their expressions in different developmental stages, essential functions, as well as genomic organization. They also discussed the feasibility of application of these CPs in development of vaccine candidates. Recent evolution in molecular technology and bioinformatics enable researchers to localize and analyze the biologic cellular functions of several expressed CPs. In addition, CPs abundance in parasites compared to their mammalian hosts attract scientists to search for specific CP inhibitors for development of safe chemotherapeutic agents without host adverse side effects. In this regard, Caffrey et al., [2] reviewed CPs of clan CA, family C1 in kinetoplastids and discussed their biochemical and genetic diversity as well as their genomics in relation to stage-specificity and expression control. The reviewers aimed at utilizing literature date as first step to achieve development of novel drugs and/or vaccine candidates to control visceral leishmaniasis, African sleeping sickness and Chagas' disease. On the other hand, complete genome sequences of three human pathogenic trypanosomatids, T. brucei, T. cruzi and Leishmania spp. followed by in silico analyses allowed the researchers to identify and assign 23, 40 and 33 genes involved in calpains (CALPs) expression in different stages of T. brucei, T. cruzi and L. braziliensis, respectively. In a review article published two years later, the reviewers discussed the biochemical and biological aspects of CALPs expressed in these trypanosomatids. They focused on the fact that knowing the genome sequences in drug-resistant and-sensitive strains will allow the investigators to investigate the inhibitory efficiency of several CALP inhibitors [3]. Furthermore, CPs were utilized as diagnostic markers. In 2005, Brazilian investigators described SDS-PAGE for in situ detection of CP activity using its specific CP inhibitor to differentiate between flagellates isolated from insects and plants [4]. In the same year, a group of scientists from UK employed genomic analysis to identify genes encoding CALPs in three human kinetoplastids; L. major, T. cruzi, and T. brucei.

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“…The apicomplexan parasite Toxoplasma gondii is an obligate intracellular protozoan that chronically infects ~2 billion people worldwide (1). Toxoplasmosis can be fatal for those who are immunocompromised, such as AIDS or organ transplant patients (1,2). In pregnant women, Toxoplasma can overcome barriers at the maternal-fetal interface and parasitize the developing fetus, which can cause a spontaneous abortion or neurological pathologies in the surviving offspring (3).…”

mentioning

confidence: 99%

“…Lysosomal cathepsin proteases are expressed in multicopy families in some pathogenic protozoa such as Plasmodium falciparum. P. falciparum is one of the causative agents of malaria and, like many other protozoan parasites, relies on proteases for various aspects of its pathogenesis (2). Plasmodium obtains host haemoglobin and digests it in a specialized organelle known as the food vacuole (FV) to procure necessary nutrients (12,13).…”

mentioning

confidence: 99%

Toxoplasma Cathepsin Protease B and Aspartyl Protease 1 play recessive roles in endolysosomal protein digestion during infection

McDonald

¹

,

Smith

²

,

M

³

et al. 2019

Preprint

0

View full text Add to dashboard Cite

The lysosome-like vacuolar compartment (VAC) is a major site of proteolysis in the intracellular parasite Toxoplasma gondii. Previous studies have shown that genetic ablation of a VAC-residing cysteine protease, cathepsin protease L (CPL), resulted in accumulation of undigested protein in the VAC and loss of parasite viability during the chronic stage of infection. However, since the maturation of another VAC localizing protease, cathepsin protease B (CPB), is dependent on CPL, it remained unknown whether these defects result directly from ablation of CPL or indirectly from a lack of CPB maturation. Likewise, although a previously described cathepsin D-like aspartyl protease 1 (ASP1) could also play a role in proteolysis, its definitive residence and function in the Toxoplasma endolysosomal system was not well defined. Here we demonstrate that CPB is not necessary for protein turnover in the VAC and that CPB deficient parasites have normal growth and viability in both the acute and chronic stages of infection. We also show that ASP1 depends on CPL for correct maturation and it resides in the T. gondii VAC where, similar to CPB, it plays a dispensable role in protein digestion. Taken together with previous work, our findings suggest that CPL is the dominant protease in a hierarchy of proteolytic enzymes within the VAC. This unusual lack of redundancy for CPL in T. gondii makes it a single exploitable target for disrupting chronic toxoplasmosis.

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Cysteine proteases in protozoan parasites

Cited by 137 publications

References 162 publications

Toxoplasma Cathepsin Protease B and Aspartyl Protease 1 Are Dispensable for Endolysosomal Protein Digestion

Toxoplasma Cathepsin Protease B and Aspartyl Protease 1 Are Dispensable for Endolysosomal Protein Digestion

Expression of cysteine proteinases and cystatins in parasites and use of cysteine proteinase inhibitors in parasitic diseases. Part III: Protozoa (1)

Toxoplasma Cathepsin Protease B and Aspartyl Protease 1 play recessive roles in endolysosomal protein digestion during infection

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