Biomedical subjects

Jude M Przyborski

Publications and source records attributed to Jude M Przyborski.

7 recordsLinked to original sources

PubMed2017

Hydrogen peroxide dynamics in subcellular compartments of malaria parasites using genetically encoded redox probes.

Redox balance is essential for the survival, growth and multiplication of malaria parasites and oxidative stress is involved in the mechanism of action of many antimalarial drugs. Hydrogen peroxide (H2O2) plays an important role in redox signalling and pathogen-host cell interactions. For monitoring intra- and subcellular redox events, highly sensitive and specific probes are required. Here, we stably expressed the ratiometric H2O2 redox sensor roGFP2-Orp1 in the cytosol and the mitochondria of Plasmodium falciparum (P. falciparum) NF54-attB blood-stage parasites and evaluated its sensitivity towards oxidative stress, selected antimalarial drugs, and novel lead compounds. In both compartments, the sensor showed reproducible sensitivity towards H2O2 in the low micromolar range and towards antimalarial compounds at pharmacologically relevant concentrations. Upon short-term exposure (4 h), artemisinin derivatives, quinine and mefloquine impacted H2O2 levels in mitochondria, whereas chloroquine and a glucose-6-phosphate dehydrogenase (G6PD) inhibitor affected the cytosol; 24 h exposure to arylmethylamino steroids and G6PD inhibitors revealed oxidation of mitochondria and cytosol, respectively. Genomic integration of an H2O2 sensor expressed in subcellular compartments of P. falciparum provides the basis for studying complex parasite-host cell interactions or drug effects with spatio-temporal resolution while preserving cell integrity, and sets the stage for high-throughput approaches to identify antimalarial agents perturbing redox equilibrium.

Antimalarials↗

PubMed2006

The long and winding road: protein trafficking mechanisms in the Plasmodium falciparum infected erythrocyte.

Mature human erythrocytes infected with the human malarial parasite Plasmodium falciparum are extensively modified to provide a more comfortable "home" for their intracellular guests. This process is mediated by parasite-encoded factors that are exported into, and through the host erythrocyte. This intra- yet simultaneously extra-cellular protein trafficking and sorting system has, in the past decades received much attention, also due to its unusual nature. Recent reports have highlighted the importance of a short peptide sequence, referred to individually as Plasmodium export element (PEXEL), vacuolar translocation signal (VTS) or generally as host cell targeting signal (HCT) in the export of both soluble and membrane bound proteins, allowing the partial definition of the parasite's "exportome". Mechanistically however, the discovery of this sequence raises as many questions as it answers. In this article, we comment on current models of protein transport to the host cell, discuss the mechanistic problems highlighted by these signals, and suggest what might be the next important steps in studying the protein export mechanisms of an obligate intracellular parasite that chooses to inhabit a de-nucleated host cell.

Animals↗

PubMed2005

Trafficking of STEVOR to the Maurer's clefts in Plasmodium falciparum-infected erythrocytes.

The human malarial parasite Plasmodium falciparum exports proteins to destinations within its host erythrocyte, including cytosol, surface and membranous profiles of parasite origin termed Maurer's clefts. Although several of these exported proteins are determinants of pathology and virulence, the mechanisms and trafficking signals underpinning protein export are largely uncharacterized-particularly for exported transmembrane proteins. Here, we have investigated the signals mediating trafficking of STEVOR, a family of transmembrane proteins located at the Maurer's clefts and believed to play a role in antigenic variation. Our data show that, apart from a signal sequence, a minimum of two addition signals are required. This includes a host cell targeting signal for export to the host erythrocyte and a transmembrane domain for final sorting to Maurer's clefts. Biochemical studies indicate that STEVOR traverses the secretory pathway as an integral membrane protein. Our data suggest general principles for transport of transmembrane proteins to the Maurer's clefts and provide new insights into protein sorting and trafficking processes in P. falciparum.

Amino Acid Sequence↗

PubMed2005

Willingness to pay for hypothetical malaria vaccines in rural Burkina Faso.

AIMS: This study aims to set priorities for anti-disease malaria vaccines by determining community preference in a hyperendemic area. METHODS: A bidding game technique was used to elucidate willingness to pay in rural Burkina Faso and 2,326 adults were interviewed. RESULTS: It is shown that there are significant differences between community preference for an anti-disease vaccine aimed at reducing pathology in pregnant women, and for a vaccine directed against childhood malaria. While the target population was willing to pay CFAfr 2101 for a vaccine against maternal malaria, its members were prepared to pay only CFAfr 1433 for a vaccine against childhood malaria. CONCLUSIONS: Whilst it is increasingly likely that anti-disease malaria vaccines will become available in the foreseeable future, lessons from the past suggest that a lack of acceptance and support from the intended recipients may lead to less than optimal compliance, and hence efficacy. For the planning of vaccine development and application strategies, it is therefore highly important to take community views into account. Here it is argued that such information could help researchers and funding agencies to set priorities for future vaccine research.

Adult↗

PubMed2003

The histone H4 gene of Plasmodium falciparum is developmentally transcribed in asexual parasites.

Histones are abundant nuclear core proteins that are present in all eukararyotes and are responsible for linking chromosomes and packaging them into tight chromatin aggregates. The histone H2A, H2B, and H3 genes and a partial sequence of the histone H4 gene from Plasmodium falciparum have been previously identified and share a high level of nucleotide sequence identity. In this study, we compare the histone H4 sequence of the human malaria P. falciparum with the sequences of two mouse malarias, Plasmodium berghei and Plasmodium yoelii, revealing at least 91% identity at the nucleotide level and 100% conservation at the amino acid level. Furthermore, we show the P. falciparum histone H4 is developmentally transcribed in late stage asexual parasites, completing the transcription profile for the genes comprising the histone octamer of P. falciparum and adding support to suggestions that a novel histone mRNA control mechanism exists in this parasite.

Animals↗

PubMed2003

Maurer's clefts--a novel secretory organelle?

During intra-erythrocytic development, the human malarial parasite Plasmodium falciparum extensively remodels its adopted cellular home by exporting proteins beyond the confines of its own plasma membrane, but is, however, faced with a major problem: the lack of an endogenous protein trafficking machinery within the host erythrocyte. Thus, in order to export proteins the parasite has to install its own protein export system within the host erythrocyte. A growing body of evidence suggests that Maurer's clefts, parasite-derived membranous structures in the cytosol of the host cell, are a crucial component of this protein sorting and trafficking machinery. In this review we summarize our current understanding of the ultra-structure of Maurer's clefts and their role in protein transport process.

Animals↗

PubMed2003

Recovery of adhesion to chondroitin-4-sulphate in Plasmodium falciparum varCSA disruption mutants by antigenically similar PfEMP1 variants.

Protection against maternal malaria has been associated with the acquisition of a specific antibody response that prevents adhesion of Plasmodium falciparum-infected erythrocytes to the glycosaminoglycan chondroitin-4-sulphate (CSA), which is present in the placental intervillous space. These antibodies are directed against variant forms of the P. falciparum erythrocyte membrane protein 1 (PfEMP1) that mediate binding to CSA. We have generated insertional disruption mutants of the gene encoding the CSA-binding phenotype in the P. falciparum clone FCR3 (varCSA) to test the hypothesis that strategies targeting the parasite's determinant for this adhesive phenotype may prevent sequestration of infected erythrocytes in the placenta and hence the development of maternal malaria. The varCSA-disruption mutants were initially unable to adhere to CSA; however, they could recover the phenotype after repeated selection over CSA. We show that recovery of CSA binding is varCSA independent and mediated by the activation of a novel var variant. Importantly, the corresponding PfEMP1 protein reacts with a monoclonal antibody recognizing the DBL3 gamma domain of the varCSA gene product, indicating that the DBL3 gamma CSA-binding domains are conserved between these PfEMP1-binding variants. Our data support strategies exploring these conserved epitopes as vaccine candidates against maternal malaria.

Animals↗