Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The malaria parasite Plasmodium falciparum replicates within an intraerythrocytic parasitophorous vacuole (PV). Rupture of the host cell allows release (egress) of daughter merozoites, which invade fresh erythrocytes. We previously showed that a subtilisin-like protease called PfSUB1 regulates egress by being discharged into the PV in the final stages of merozoite development to proteolytically modify the SERA family of papain-like proteins. Here, we report that PfSUB1 has a further role in 'priming' the merozoite prior to invasion. The major protein complex on the merozoite surface comprises three proteins called merozoite surface protein 1 (MSP1), MSP6 and MSP7. We show that just before egress, all undergo proteolytic maturation by PfSUB1. Inhibition of PfSUB1 activity results in the accumulation of unprocessed MSPs on the merozoite surface, and erythrocyte invasion is significantly reduced. We propose that PfSUB1 is a multifunctional processing protease with an essential role in both egress of the malaria merozoite and remodelling of its surface in preparation for erythrocyte invasion.
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PMID:A multifunctional serine protease primes the malaria parasite for red blood cell invasion. 1921 90

The protozoan pathogen responsible for the most severe form of human malaria, Plasmodium falciparum, replicates asexually in erythrocytes within a membrane-bound parasitophorous vacuole (PV). Following each round of intracellular growth, the PV membrane (PVM) and host cell membrane rupture to release infectious merozoites in a protease-dependent process called egress. Previous work has shown that, just prior to egress, an essential, subtilisin-like parasite protease called PfSUB1 is discharged into the PV lumen, where it directly cleaves a number of important merozoite surface and PV proteins. These include the essential merozoite surface protein complex MSP1/6/7 and members of a family of papain-like putative proteases called SERA (serine-rich antigen) that are implicated in egress. To determine whether PfSUB1 has additional, previously unrecognized substrates, we have performed a bioinformatic and proteomic analysis of the entire late asexual blood stage proteome of the parasite. Our results demonstrate that PfSUB1 is responsible for the proteolytic processing of a range of merozoite, PV, and PVM proteins, including the rhoptry protein RAP1 (rhoptry-associated protein 1) and the merozoite surface protein MSRP2 (MSP7-related protein-2). Our findings imply multiple roles for PfSUB1 in the parasite life cycle, further supporting the case for considering the protease as a potential new antimalarial drug target.
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PMID:Global identification of multiple substrates for Plasmodium falciparum SUB1, an essential malarial processing protease. 2122 Apr 81

The burden of Plasmodium vivax malaria is huge in India, affecting a large population annually. Recent reports of P. vivax contributing to severe illness and death, makes vaccine research on P. vivax malaria, a high priority. Extent of sequence variation in antigen coding genes is known to be a major hurdle in vaccine initiatives against malaria. Serine repeat antigens of Plasmodium are promising asexual blood stage vaccine candidates against malaria and have been implicated to have a key role in merozoite invasion and egress. Among the P. vivax SERA proteins, SERA4 and SERA5 are the major transcribed members in erythrocytic stages, making them encouraging candidates to be explored for their polymorphism and vaccine potential. Earlier reports suggest that diversity in these PvSERA antigens is localized to the C-terminal region of the proteins. Hence, genetic diversity study of this region seems prudent. Moreover, as there are no reports available from India, the present study aims to investigate the polymorphism in the C-terminal region of two highly transcribed members PvSERA4 and PvSERA5 in Indian field isolates. Our result of PvSERA5 demonstrates extensive genetic diversity, with major deletions, insertions and SNPs and signifies the gene to be under positive selection. On the other hand, high sequence conservation was seen in the PvSERA4 C-terminal region in Indian field isolates which was contrasting to earlier report from Thailand where they have shown diversity. Research data showcased in this study will greatly aid in gaining better understanding of antigenic variations, immune mediated selection mechanisms and the functional significance of these two vivax proteins. This study also makes a striking contribution towards understanding the antigenic repertoire of PvSERA genes in Indian isolates.
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PMID:Plasmodium vivax: C-terminal diversity in the blood stage SERA genes from Indian field isolates. 2348 60

Egress of the malaria parasite Plasmodium falciparum from its host red blood cell is a rapid, highly regulated event that is essential for maintenance and completion of the parasite life cycle. Egress is protease-dependent and is temporally associated with extensive proteolytic modification of parasite proteins, including a family of papain-like proteins called SERA that are expressed in the parasite parasitophorous vacuole. Previous work has shown that the most abundant SERA, SERA5, plays an important but non-enzymatic role in asexual blood stages. SERA5 is extensively proteolytically processed by a parasite serine protease called SUB1 as well as an unidentified cysteine protease just prior to egress. However, neither the function of SERA5 nor the role of its processing is known. Here we show that conditional disruption of the SERA5 gene, or of both the SERA5 and related SERA4 genes simultaneously, results in a dramatic egress and replication defect characterised by premature host cell rupture and the failure of daughter merozoites to efficiently disseminate, instead being transiently retained within residual bounding membranes. SERA5 is not required for poration (permeabilization) or vesiculation of the host cell membrane at egress, but the premature rupture phenotype requires the activity of a parasite or host cell cysteine protease. Complementation of SERA5 null parasites by ectopic expression of wild-type SERA5 reversed the egress defect, whereas expression of a SERA5 mutant refractory to processing failed to rescue the phenotype. Our findings implicate SERA5 as an important regulator of the kinetics and efficiency of egress and suggest that proteolytic modification is required for SERA5 function. In addition, our study reveals that efficient egress requires tight control of the timing of membrane rupture.
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PMID:The Plasmodium falciparum pseudoprotease SERA5 regulates the kinetics and efficiency of malaria parasite egress from host erythrocytes. 2868 42


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