Plasmodium falciparum Homologue of the Genes for Plasmodium vivax and Plasmodium yoelii Adhesive Proteins, Which Is Transcribed but Not Translated
Helen TaylorTony TrigliaJenny ThompsonMohammed SajidRuth E. FowlerMark E. WickhamAlan F. CowmanAnthony A. Holder
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ABSTRACT The 235-kDa family of rhoptry proteins in Plasmodium yoelii and the two reticulocyte binding proteins of P. vivax comprise a family of proteins involved in host cell selection and erythrocyte invasion. Here we described a member of the gene family found in P. falciparum ( PfRH3 ) that is transcribed in its entirety, under stage-specific control, with correct splicing of the intron, but appears not to be translated, probably due to two reading frameshifts at the 5′ end of the gene.Keywords:
Plasmodium yoelii
Rhoptry
Plasmodium (life cycle)
Rhoptry
Plasmodium yoelii
genomic DNA
Merozoite surface protein
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To detect the rhoptry and surface proteins of invasive stages of Plasmodium yoelii and P. berghei with monoclonal antibodies.Subcellular localization of antigens was detected by IFA. The antigens of different stages of the two species malaria parasites were analyzed by Western blotting.The antigens of rhoptry are very complicated. There are similar epitopes of the rhoptry proteins detected between the two species of Plasmodium. The similar epitopes were also detected between ookinetes and merozoites of P. yoelii, and ookinete antigens between the two species. But there are different antigens detected between merozoites and ookinetes in P. yoelii. The sporozoite surface antigen of P. yoelii was not detected in the ookinetes and merozoites in the same species.There are similar epitopes in the rhoptry and surface antigens of different stages and different species of rodent malaria parasites. There are also distinct antigens among them.
Rhoptry
Plasmodium yoelii
Plasmodium berghei
Plasmodium (life cycle)
Merozoite surface protein
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Apicomplexa is a protozoan class of obligate intracellular parasites,including Toxoplasma gondii,Cryptosporidium spp.,Plasmodium spp.,Babesia spp.and Eimeria spp.,many of them are important pathogens to human and animal.They have conserved subcellular structures and invasion mechanism.The results of lots of researches demonstrate that the invasion mechanisms are mediated by many invasion-associated factors,including the proteins secreted from micronemes,rhoptries and dense granules.The researches about these proteins make great progress with the development of bioinformatics and biotechnologies.In this paper,we review the latest progress of invasion-associated factor combining with our research results in recent years.
Rhoptry
Obligate
Plasmodium (life cycle)
Theileria
Microneme
Coccidia
Intracellular parasite
Babesia bovis
Propagule pressure
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Plasmodium sporozoites are transmitted by Anopheles mosquitoes and first infect the liver of their mammalian host, where they develop as liver stages before the onset of erythrocytic infection and malaria symptoms. Sporozoite entry into hepatocytes is an attractive target for anti-malarial prophylactic strategies but remains poorly understood at the molecular level. Apicomplexan parasites invade host cells by forming a parasitophorous vacuole that is essential for parasite development, a process that involves secretion of apical organelles called rhoptries. We previously reported that the host membrane protein CD81 is required for infection by Plasmodium falciparum and Plasmodium yoelii sporozoites. CD81 acts at an early stage of infection, possibly at the entry step, but the mechanisms involved are still unknown. To investigate the role of CD81 during sporozoite entry, we generated transgenic P. yoelii parasites expressing fluorescent versions of three known rhoptry proteins, RON2, RON4 and RAP2/3. We observed that RON2 and RON4 are lost following rhoptry discharge during merozoite and sporozoite entry. In contrast, our data indicate that RAP2/3 is secreted into the parasitophorous vacuole during infection. We further show that sporozoite rhoptry discharge occurs only in the presence of CD81, providing the first direct evidence for a role of CD81 during sporozoite productive invasion.
Rhoptry
Plasmodium yoelii
CD81
Plasmodium (life cycle)
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Rhoptry
Dense granule
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Granule (geology)
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Rhoptry
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Obligate
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Brefeldin A
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Plasmodium yoelii
Rhoptry
Plasmodium (life cycle)
Evasion (ethics)
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A 235 kD rhoptry protein produced by the malaria parasite, Plasmodium yoelii is the target of antibodies that protect mice against blood-stage challenge with the virulent YM strain. In the protected animals the parasites are confined to reticulocytes and the course of parasitaemia is reminiscent of an avirulent 17X strain infection. The DNA coding for the rhoptry protein has been identified as a multigene family containing at least four members. Sequence analysis of short DNA clones has identified the C-terminus of the protein; a preliminary analysis of longer clones confirms that the genes are polymorphic. The possible implications of these findings for the biology of the parasite are discussed.
Rhoptry
Plasmodium yoelii
Plasmodium (life cycle)
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The highly virulent rodent malaria parasite, Plasmodium yoelii strain YM is capable of invading both mature erythrocytes and reticulocytes throughout the course of the infection. YM had been reported to have arisen abruptly from the avirulent P. yoelii strain 17X which is reticulocyte-restricted for most of the course of infection. A genetic cross between YM and an avirulent parasite strain derived from 17X indicated that the two parasites differed only at a single genetic locus, which was considered to confer the virulent phenotype. Monoclonal antibodies directed at a complex of 235 kiloDalton (kDa) proteins, present in the rhoptries of the pre-invasive P. yoelii merozoites had been reported to convert a virulent YM infection into an avirulent, reticulocyte-restricted, 17X-like disease. This indicated that the rhoptry protein complex might mediate virulence. DNA clones encoding three different 235kDa rhoptry proteins had been isolated and sequenced. In this thesis electrophoretic karyotypes were produced for P. yoelii strains YM and 17X, and where possible individual chromosomes have been identified as homologues of those of other malaria species by their hybridisation with specific DNA probes. Four chromosomes of strain 17X were shown to migrate at appreciably different rates from their YM homologues, indicating that they differed in size. The genomic location of members of the 235kDa rhoptry protein gene family and the gene copy number have been examined in both strains. A two-dimensional Southern blot technique was used to visualise the restriction fragments containing members of the rhoptry protein gene family derived from resolved chromosomes. These blots permitted the localisation of the cloned rhoptry protein genes within individual chromosomes. In strain YM the gene family was demonstrated to be present on six chromosomes and to have an estimated minimum copy number of forty. On individual chromosomes, the gene family members are organised in tandem arrays which occur almost exclusively in sub-telomeric locations. Two chromosomes have rhoptry protein genes at each end. A series of subclones derived from strain YM, which exhibited different levels of virulence, were also examined. No differences were detected in the distribution of the major loci for the rhoptry protein gene family in these parasite clones but a difference was observed in the rhoptry complex proteins immunoprecipitated from one of the clones using anti-rhoptry protein monoclonal antibodies. The major rhoptry protein gene loci which had been identified in YM were also present in strain 17X, in additional two major loci were also detected in this parasite which do not occur in YM. One of these loci was present on a chromosome (13 or 14) which does not contain rhoptry protein genes in YM. Immunoprecipitation experiments indicated that there was differential expression of the rhoptry protein genes in strains YM and 17X. Hybridisation with rhoptry protein gene probes demonstrated the presence of homologous sequences on at least six chromosomes in another rodent malaria parasite, P. berghei. The extent and the organisation of the gene family appeared to be similar in P. yoelii and P. berghei. Initial experiments appeared to link a single genetic locus of the gene family with reticulocyte-restriction in both species. However analysis of the progeny of a genetic cross between virulent and avirulent parasites indicated that this was not the case. While ail of the data collected supported a very close relationship between P. yoelii strains YM and 17X, the fact that the strains had been demonstrated to differ at more than one genetic locus, and possessed four differently sized chromosomes indicated that YM could not have evolved directly from 17X as the result of an abrupt mutation. No evidence was found to support the hypothesis that the rhoptry protein complex is responsible for the virulent phenotype.
Rhoptry
Plasmodium yoelii
Southern blot
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