Plasmodium falciparum: Chymotryptic-like proteolysis associated with a 101-kDa acidic-basic repeat antigen

Nwagwu, Mark; Haynes, J. David; Orlandi, Palmer A.; Chulay, Jeffrey D.

doi:10.1016/0014-4894(92)90253-7

Cited by 29 publications

(19 citation statements)

References 39 publications

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“…There are a number of malaria proteins that exist in the PV for which functions are unclear, however, others such as GAPDH are known housekeeping enzymes (22). The putative serine protease ABRA (29) and the SERA/SERPH family of serine protease-like molecules have been shown to localize to the parasitophorous vacuole (30) and have been postulated to play a part in parasite egress but their exact role remains to be determined (31).…”

Section: Discussionmentioning

confidence: 99%

The M18 Aspartyl Aminopeptidase of the Human Malaria Parasite Plasmodium falciparum

Teuscher

Lowther

Skinner‐Adams

et al. 2007

Journal of Biological Chemistry

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A member of the M18 family of aspartyl aminopeptidases is expressed by all intra-erythrocytic stages of the human malaria parasite Plasmodium falciparum (PfM18AAP), with highest expression levels in rings. Functionally active recombinant enzyme, rPfM18AAP, and native enzyme in cytosolic extracts of malaria parasites are 560-kDa octomers that exhibit optimal activity at neutral pH and require the presence of metal ions to maintain enzymatic activity and stability. Like the human aspartyl aminopeptidase, the exopeptidase activity of PfM18AAP is exclusive to N-terminal acidic amino acids, glutamate and aspartate, making this enzyme of particular interest and suggesting that it may function alongside the malaria cytosolic neutral aminopeptidases in the release of amino acids from host hemoglobin-derived peptides. Whereas immunocytochemical studies using transgenic P. falciparum parasites show that PfM18AAP is expressed in the cytosol, immunoblotting experiments revealed that the enzyme is also trafficked out of the parasite into the surrounding parasitophorous vacuole. Antisensemediated knockdown of PfM18AAP results in a lethal phenotype as a result of significant intracellular damage and validates this enzyme as a target at which novel antimalarial drugs could be directed. Novel phosphinic derivatives of aspartate and glutamate showed modest inhibition of rPfM18AAP but did not inhibit malaria growth in culture. However, we were able to draw valuable observations concerning the structureactivity relationship of these inhibitors that can be employed in future inhibitor optimization studies.It is estimated that 3.2 billion people currently live in areas where there is a risk of malaria transmission. Three to five hundred million of these individuals become infected each year and over two million die (1). The groups most affected by malaria are children under five years of age and pregnant women in sub-Saharan Africa. Parasite resistance to most of the currently used antimalarial drugs is now widespread and resistance to new drugs is developing (2). With an effective vaccine at least 15 years away there is an urgent need for new malaria treatments.During the intraerythrocytic phase of development the parasite digests 65-75% of the host cell hemoglobin. A proportion of this digested hemoglobin (16%) is used for protein synthesis (3). Hemoglobin degradation is also important in reducing the colloid-osmotic pressure within the infected erythrocyte, which prevents premature cell lysis during parasite growth and establishes a concentration gradient by which rare amino acids enter the malaria-infected erythrocyte from host serum (4, 5, 6). The degradation of hemoglobin to peptide fragments occurs within a specialized acidic digestive vacuole (DV) 9 by the action of aspartic, cysteine, and metalloendoproteases and by dipeptidases. However, small peptide fragments are transported from * This work was supported by Australian Research Council Discovery ProjectGrant DPO666128. The costs of publication of this article were defra...

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Section: Discussionmentioning

confidence: 99%

The M18 Aspartyl Aminopeptidase of the Human Malaria Parasite Plasmodium falciparum

Teuscher

Lowther

Skinner‐Adams

et al. 2007

Journal of Biological Chemistry

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“…The inhibitor-sensitive proteases identified so far that may be involved in erythrocyte plasma membrane rupture are the aspartic protease plasmepsin II, which cleaves erythrocyte spectrin, actin, and protein 4.1 (31); the cysteine protease falcipain-2, which cleaves erythrocyte ankyrin and protein 4.1 (8,32); the putative serine protease ABRA (33); and the SERA/ SERPH family of serine protease-like molecules. These molecules have been shown to localize to the parasitophorous vacuole; some, such as ABRA and the SERA/SERPH family, have been shown to be weakly associated with the merozoite surface (34).…”

Section: Discussionmentioning

confidence: 99%

Selective Inhibition of a Two-step Egress of Malaria Parasites from the Host Erythrocyte

Wickham

Culvenor

Cowman

2003

Journal of Biological Chemistry

146

144

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Escape from the host erythrocyte by the invasive stage of the malaria parasite Plasmodium falciparum is a fundamental step in the pathogenesis of malaria of which little is known. Upon merozoite invasion of the host cell, the parasite becomes enclosed within a parasitophorous vacuole, the compartment in which the parasite undergoes growth followed by asexual division to produce 16 -32 daughter merozoites. These daughter cells are released upon parasitophorous vacuole and erythrocyte membrane rupture. To examine the process of merozoite release, we used P. falciparum lines expressing green fluorescent protein-chimeric proteins targeted to the compartments from which merozoites must exit: the parasitophorous vacuole and the host erythrocyte cytosol. This allowed visualization of merozoite release in live parasites. Herein we provide the first evidence in live, untreated cells that merozoite release involves a primary rupture of the parasitophorous vacuole membrane followed by a secondary rupture of the erythrocyte plasma membrane. We have confirmed, with the use of immunoelectron microscopy, that parasitophorous vacuole membrane rupture occurs before erythrocyte plasma membrane rupture in untransfected wild-type parasites. We have also demonstrated selective inhibition of each step in this two-step process of exit using different protease inhibitors, implicating the involvement of distinct proteases in each of these steps. This will facilitate the identification of the parasite and host molecules involved in merozoite release.During the erythrocytic phase of the Plasmodium falciparum life cycle, the merozoites released initially from infected hepatocytes attach to and invade human erythrocytes in the bloodstream. Upon invasion of the host cell, the parasites become enclosed in a parasitophorous vacuole in which, as ring and trophozoite stages, they undergo growth followed by asexual division (schizogony) to produce 16 -32 daughter merozoites. Newly formed merozoites in the schizont must escape from both this vacuole and the host erythrocyte.Although little is known about the molecules that mediate this process, proteases have been implicated in both parasite exit from the erythrocyte and the subsequent invasion into erythrocytes through the use of protease inhibitors that halt these processes (1-3). After the demonstration that P. knowlesi schizonts incubated in the presence of the protease inhibitors chymostatin and leupeptin show decreased reinvasion caused by inhibition of schizont maturation (3, 4), Lyon and Haynes (2) demonstrated that P. falciparum schizonts cultured in the presence of the inhibitors chymostatin, leupeptin, antipain, and pepstatin also fail to rupture properly. Recently, it has been demonstrated that the protease inhibitors E-64 and E-64d inhibit schizont maturation (5, 6). The role of the proteases involved in schizont rupture is presumably to degrade both the parasitophorous vacuole and the erythrocyte membrane skeleton, thereby facilitating release. However, the proteases involved have no...

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“…Such a polypurine stretch coding for acidic and basic amino acids is also found in the ABRA protein of P. falciparum (14,16). The function of this charged domain (which is not polymorphic) and of ABRA itself is not clear; although ABRA has a pro- tease domain and exhibits chymotrypsin-like activity (22). Another antigen, FIRA, of P. falciparum (33) has some similarity with Ehssp1.…”

Section: Discussionmentioning

confidence: 99%

Stress-Dependent Expression of a Polymorphic, Charged Antigen in the Protozoan Parasite Entamoeba histolytica

Satish

Bakre²,

Bhattacharya³

et al. 2003

Infect Immun

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We have identified a novel stress inducible gene, Ehssp1 in Entamoeba histolytica, the causative agent of amebiasis. Ehssp1 belongs to a polymorphic, multigene family and is present on multiple chromosomes. No homologue of this gene was found in the NCBI database. Sequence alignment of the multiple copies, and genomic PCR data restricted the polymorphism to the central region of the gene. This region contains a polypurine stretch that encodes a domain rich in acidic and basic amino acids. Under normal culture conditions only one copy of this multigene family is expressed, as observed by Northern blot and RT-PCR analysis. The size of this copy of the gene is 1,077 nucleotides, encoding a protein of 359 amino acids. The polymorphic domain in this copy is 64 nucleotides long. However, on exposure of cells to stress conditions such as heat shock or oxidative stress, multiple polymorphic copies of the gene are expressed, suggesting a possible role of this gene in adaptation of cells to stress conditions. The gene copy expressed under normal conditions, and the expression profile of cells under heat stress was identical in two different strains of E. histolytica tested. Interestingly, the extent of polymorphism in this gene was very less in E. dispar, a nonpathogenic sibling species of E. histolytica. Ehssp1 was found to be antigenic in invasive amebiasis patients.

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Plasmodium falciparum: Chymotryptic-like proteolysis associated with a 101-kDa acidic-basic repeat antigen

Cited by 29 publications

References 39 publications

The M18 Aspartyl Aminopeptidase of the Human Malaria Parasite Plasmodium falciparum

The M18 Aspartyl Aminopeptidase of the Human Malaria Parasite Plasmodium falciparum

Selective Inhibition of a Two-step Egress of Malaria Parasites from the Host Erythrocyte

Stress-Dependent Expression of a Polymorphic, Charged Antigen in the Protozoan Parasite Entamoeba histolytica

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