Publications
160 results found
Andrews M, Baum J, Gilson PR, et al., 2023, Bottoms up! Malaria parasite invasion the right way around., Trends Parasitol, Vol: 39, Pages: 1004-1013
A critical part of the malaria parasite's life cycle is invasion of red blood cells (RBCs) by merozoites. Inside RBCs, the parasite forms a schizont, which undergoes segmentation to produce daughter merozoites. These cells are released, establishing cycles of invasion. Traditionally, merozoites are represented as nonmotile, egg-shaped cells that invade RBCs 'narrower end' first and pack within schizonts with this narrower end facing outwards. Here, we discuss recent evidence and re-evaluate previous data which suggest that merozoites are capable of motility and have spherical or elongated-teardrop shapes. Furthermore, merozoites invade RBCs 'wider end' first and pack within schizonts with this wider end facing outwards. We encourage the field to review this revised model and consider its implications for future studies.
Malpartida-Cardenas K, Baum J, Cunnington A, et al., 2023, A dual paper-based nucleic acid extraction method from blood in under ten minutes for point-of-care diagnostics, The Analyst, Vol: 148, Pages: 3036-3044, ISSN: 0003-2654
Nucleic acid extraction (NAE) plays a crucial role for diagnostic testing procedures. For decades, dried blood spots (DBS) have been used for serology, drug monitoring, and molecular studies. However, extracting nucleic acids from DBS remains a significant challenge, especially when attempting to implement these applications to the point-of-care (POC). To address this issue, we have developed a paper-based NAE method using cellulose filter papers (DBSFP) that operates without the need for electricity (at room temperature). Our method allows for NAE in less than 7 min, and it involves grade 3 filter paper pre-treated with 8% (v/v) igepal surfactant, 1 min washing step with 1× PBS, and 5 min incubation at room temperature in 1× TE buffer. The performance of the methodology was assessed with loop-mediated isothermal amplification (LAMP), targeting the human reference gene beta-actin and the kelch 13 gene from P. falciparum. The developed method was evaluated against FTA cards and magnetic bead-based purification, using time-to-positive (min) for comparative analysis. Furthermore, we optimised our approach to take advantage of the dual functionality of the paper-based extraction, allowing for elution (eluted disk) as well as direct placement of the disk in the LAMP reaction (in situ disk). This flexibility extends to eukaryotic cells, bacterial cells, and viral particles. We successfully validated the method for RNA/DNA detection and demonstrated its compatibility with whole blood stored in anticoagulants. Additionally, we studied the compatibility of DBSFP with colorimetric and lateral flow detection, showcasing its potential for POC applications. Across various tested matrices, targets, and experimental conditions, our results were comparable to those obtained using gold standard methods, highlighting the versatility of our methodology. In summary, this manuscript presents a cost-effective solution for NAE from DBS, enabling molecular testing in virtually
Moussaoui D, Robblee JP, Robert-Paganin J, et al., 2023, Mechanism of small molecule inhibition of <i>Plasmodium falciparum</i> myosin A informs antimalarial drug design, NATURE COMMUNICATIONS, Vol: 14
Murdoch J, Baum J, 2023, A sting in the tail-are antibodies against the C-terminus of <i>Plasmodium falciparum</i> circumsporozoite protein protective?, EMBO MOLECULAR MEDICINE, Vol: 15, ISSN: 1757-4676
Ramakrishnan C, Fort C, Marques SR, et al., 2023, Radial spoke protein 9 is necessary for axoneme assembly in Plasmodium but not in trypanosomatid parasites., J Cell Sci, Vol: 136
Flagella are important for eukaryote cell motility, including in sperm, and are vital for life cycle progression of many unicellular eukaryotic pathogens. The '9+2' axoneme in most motile flagella comprises nine outer doublet and two central-pair singlet microtubules. T-shaped radial spokes protrude from the outer doublets towards the central pair and are necessary for effective beating. We asked whether there were radial spoke adaptations associated with parasite lineage-specific properties in apicomplexans and trypanosomatids. Following an orthologue search for experimentally uncharacterised radial spoke proteins (RSPs), we identified and analysed RSP9. Trypanosoma brucei and Leishmania mexicana have an extensive RSP complement, including two divergent RSP9 orthologues, necessary for flagellar beating and swimming. Detailed structural analysis showed that neither orthologue is needed for axoneme assembly in Leishmania. In contrast, Plasmodium has a reduced set of RSPs including a single RSP9 orthologue, deletion of which in Plasmodium berghei leads to failure of axoneme formation, failed male gamete release, greatly reduced fertilisation and inefficient life cycle progression in the mosquito. This indicates contrasting selection pressures on axoneme complexity, likely linked to the different mode of assembly of trypanosomatid versus Plasmodium flagella.
Ramakrishnan C, Fort C, Marques SR, et al., 2023, Radial spoke protein 9 is necessary for axoneme assembly in Plasmodium but not in trypanosomatid parasites, JOURNAL OF CELL SCIENCE, Vol: 136, ISSN: 0021-9533
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Malpartida Cardenas K, Moser N, Ansah F, et al., 2023, Sensitive detection of asymptomatic and symptomatic malaria with seven novel parasite-specific LAMP assays and translation for use at point-of-care, Microbiology Spectrum, Vol: 11, Pages: 1-12, ISSN: 2165-0497
Human malaria is a life-threatening parasitic disease with high impact in the sub-Saharan Africa region, where 95% of global cases occurred in 2021. While most malaria diagnostic tools are focused on Plasmodium falciparum, there is a current lack of testing non-P. falciparum cases, which may be underreported and, if undiagnosed or untreated, may lead to severe consequences. In this work, seven species-specific loop-mediated isothermal amplification (LAMP) assays were designed and evaluated against TaqMan quantitative PCR (qPCR), microscopy, and enzyme-linked immunosorbent assays (ELISAs). Their clinical performance was assessed with a cohort of 164 samples of symptomatic and asymptomatic patients from Ghana. All asymptomatic samples with a parasite load above 80 genomic DNA (gDNA) copies per μL of extracted sample were detected with the Plasmodium falciparum LAMP assay, reporting 95.6% (95% confidence interval [95% CI] of 89.9 to 98.5) sensitivity and 100% (95% CI of 87.2 to 100) specificity. This assay showed higher sensitivity than microscopy and ELISA, which were 52.7% (95% CI of 39.7 to 67%) and 67.3% (95% CI of 53.3 to 79.3%), respectively. Nine samples were positive for P. malariae, indicating coinfections with P. falciparum, which represented 5.5% of the tested population. No samples were detected as positive for P. vivax, P. ovale, P. knowlesi, or P. cynomolgi by any method. Furthermore, translation to the point-of-care was demonstrated with a subcohort of 18 samples tested locally in Ghana using our handheld lab-on-chip platform, Lacewing, showing comparable results to a conventional fluorescence-based instrument. The developed molecular diagnostic test could detect asymptomatic malaria cases, including submicroscopic parasitemia, and it has the potential to be used for point-of-care applications.
Imlay LS, Lawong AK, Gahalawat S, et al., 2023, Fast-Killing Tyrosine Amide ((S)-SW228703) with Blood- and Liver-Stage Antimalarial Activity Associated with the Cyclic Amine Resistance Locus (Pf CARL), ACS INFECTIOUS DISEASES, Vol: 9, Pages: 527-539, ISSN: 2373-8227
Nguyen W, Dans MG, Currie I, et al., 2023, 7-<i>N</i>-Substituted-3-oxadiazole Quinolones with Potent Antimalarial Activity Target the Cytochrome <i>bc</i><sub>1</sub> Complex, ACS INFECTIOUS DISEASES, Vol: 9, Pages: 668-691, ISSN: 2373-8227
Ashton TD, Dans MG, Favuzza P, et al., 2023, Optimization of 2,3-Dihydroquinazolinone-3-carboxamides as Antimalarials Targeting PfATP4, JOURNAL OF MEDICINAL CHEMISTRY, Vol: 66, Pages: 3540-3565, ISSN: 0022-2623
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- Citations: 1
Yahiya S, Saunders CN, Hassan S, et al., 2023, A novel class of sulphonamides potently block malaria transmission by targeting a Plasmodium vacuole membrane protein, Disease Models & Mechanisms, Vol: 16, Pages: 1-20, ISSN: 1754-8403
Phenotypic cell-based screens are critical tools for discovering candidate drugs for development, yet identification of the cellular target and mode of action of a candidate drug is often lacking. Using an imaging-based screen, we recently discovered an N-[(4-hydroxychroman-4-yl)methyl]-sulphonamide (N-4HCS) compound, DDD01035881, that blocks male gamete formation in the malaria parasite life cycle and subsequent transmission of the parasite to the mosquito with nanomolar activity. To identify the target(s) of DDD01035881, and of the N-4HCS class of compounds more broadly, we synthesised a photoactivatable derivative, probe 2. Photoaffinity labelling of probe 2 coupled with mass spectrometry identified the 16 kDa Plasmodium falciparum parasitophorous vacuole membrane protein Pfs16 as a potential parasite target. Complementary methods including cellular thermal shift assays confirmed that the parent molecule DDD01035881 stabilised Pfs16 in lysates from activated mature gametocytes. Combined with high-resolution, fluorescence and electron microscopy data, which demonstrated that parasites inhibited with N-4HCS compounds phenocopy the targeted deletion of Pfs16 in gametocytes, these data implicate Pfs16 as a likely target of DDD01035881. This finding establishes N-4HCS compounds as being flexible and effective starting candidates from which transmission-blocking antimalarials can be developed in the future.
Andradi-Brown C, Wichers-Misterek JS, von Thien H, et al., 2023, A novel computational pipeline for var gene expression augments the discovery of changes in the Plasmodium falciparum transcriptome during transition from in vivo to short-term in vitro culture, eLife, Vol: 12
The pathogenesis of severe Plasmodium falciparum malaria involves cytoadhesive microvascular sequestration of infected erythrocytes, mediated by P. falciparum erythrocyte membrane protein 1 (PfEMP1). PfEMP1 variants are encoded by the highly polymorphic family of var genes, the sequences of which are largely unknown in clinical samples. Previously, we published new approaches for var gene profiling and classification of predicted binding phenotypes in clinical P. falciparum isolates (Wichers et al., 2021), which represented a major technical advance. Building on this, we report here a novel method for var gene assembly and multidimensional quantification from RNA-sequencing that even outperforms the earlier approach of (Wichers et al., 2021) on both laboratory and clinical isolates across a combination of metrics. It is a powerful tool to interrogate the var transcriptome in context with the rest of the transcriptome and can be applied to enhance our understanding of the role of var genes in malaria pathogenesis. We applied this new method to investigate changes in var gene expression through early transition to in vitro culture, using paired sets of ex vivo samples from our previous study, cultured for up to three generations. In parallel, changes in non-polymorphic core gene expression were investigated. Unpredictable var gene switching and convergence towards var2csa were observed in culture, along with differential expression of 19% of the core transcriptome between paired ex vivo and generation 1 samples. Our results cast doubt on the validity of the common practice of using short-term cultured parasites to make inferences about in vivo phenotype and behaviour.
Wilkinson MD, Ferreira JL, Beeby M, et al., 2022, The malaria parasite chaperonin containing TCP-1 (CCT) complex: Data integration with other CCT proteomes, FRONTIERS IN MOLECULAR BIOSCIENCES, Vol: 9
Benns HJ, Storch M, Falco JA, et al., 2022, CRISPR-based oligo recombineering prioritizes apicomplexan cysteines for drug discovery., Nat Microbiol
Nucleophilic amino acids are important in covalent drug development yet underutilized as anti-microbial targets. Chemoproteomic technologies have been developed to mine chemically accessible residues via their intrinsic reactivity towards electrophilic probes but cannot discern which chemically reactive sites contribute to protein function and should therefore be prioritized for drug discovery. To address this, we have developed a CRISPR-based oligo recombineering (CORe) platform to support the rapid identification, functional prioritization and rational targeting of chemically reactive sites in haploid systems. Our approach couples protein sequence and function with biological fitness of live cells. Here we profile the electrophile sensitivity of proteinogenic cysteines in the eukaryotic pathogen Toxoplasma gondii and prioritize functional sites using CORe. Electrophile-sensitive cysteines decorating the ribosome were found to be critical for parasite growth, with target-based screening identifying a parasite-selective anti-malarial lead molecule and validating the apicomplexan translation machinery as a target for ongoing covalent ligand development.
Najer A, Blight J, Ducker CB, et al., 2022, Potent virustatic polymer-lipid nanomimics block viral entry and inhibit malaria parasites in vivo, ACS Central Science, Vol: 8, Pages: 1238-1257, ISSN: 2374-7943
Infectious diseases continue to pose a substantial burden on global populations, requiring innovative broad-spectrum prophylactic and treatment alternatives. Here, we have designed modular synthetic polymer nanoparticles that mimic functional components of host cell membranes, yielding multivalent nanomimics that act by directly binding to varied pathogens. Nanomimic blood circulation time was prolonged by reformulating polymer–lipid hybrids. Femtomolar concentrations of the polymer nanomimics were sufficient to inhibit herpes simplex virus type 2 (HSV-2) entry into epithelial cells, while higher doses were needed against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Given their observed virustatic mode of action, the nanomimics were also tested with malaria parasite blood-stage merozoites, which lose their invasive capacity after a few minutes. Efficient inhibition of merozoite invasion of red blood cells was demonstrated both in vitro and in vivo using a preclinical rodent malaria model. We envision these nanomimics forming an adaptable platform for developing pathogen entry inhibitors and as immunomodulators, wherein nanomimic-inhibited pathogens can be secondarily targeted to sites of immune recognition.
Malpartida-Cardenas K, Baum J, Cunnington A, et al., 2022, Electricity-free nucleic acid extraction method from dried blood spots on filter paper for point-of-care diagnostics
<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>Nucleic acid extraction is a crucial step for molecular biology applications, being a determinant for any diagnostic test procedure. Dried blood spots (DBS) have been used for decades for serology, drug monitoring, environmental investigations, and molecular studies. Nevertheless, nucleic acid extraction from DBS remains one of the main challenges to translate them to the point-of-care (POC).</jats:p></jats:sec><jats:sec><jats:title>Method</jats:title><jats:p>We have developed a fast nucleic acid extraction (NAE) method from DBS which is electricity-free and relies on cellulose filter papers (DBSFP). The performance of NAE was assessed with loop-mediated isothermal amplification (LAMP), targeting the human reference gene beta-actin. The developed method was evaluated against FTA cards and magnetic bead-based purification, using time-to-positive (min) for comparative analysis. We optimised and validated the developed method for elution (<jats:italic>eluted disk</jats:italic>) and disk directly in the reaction (<jats:italic>in-situ disk)</jats:italic>, RNA and DNA detection, and whole blood stored in anticoagulants (K<jats:sub>2</jats:sub>EDTA and lithium heparin). Furthermore, the compatibility of DBSFP with colourimetric detection was studied to show the transferability to the POC.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>The proposed DBSFP is based on grade 3 filter paper pre-treated with 8% (v/v) igepal surfactant, 1 min washing step with PBS 1X and elution in TE 1X buffer after 5 min incubation at room temperature, enabling NAE under 7 min. Obtained results were comparable to gold standard methods across tested matrices, targets and experimental conditions, demonstrating the versatility of the methodology. Las
Tamaki F, Fisher F, Milne R, et al., 2022, High-Throughput Screening Platform To Identify Inhibitors of Protein Synthesis with Potential for the Treatment of Malaria, ANTIMICROBIAL AGENTS AND CHEMOTHERAPY, Vol: 66, ISSN: 0066-4804
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- Citations: 4
Xie SC, Metcalfe RD, Dunn E, et al., 2022, Reaction hijacking of tyrosine tRNA synthetase as a new whole-of-life-cycle antimalarial strategy, SCIENCE, Vol: 376, Pages: 1074-+, ISSN: 0036-8075
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- Citations: 15
Bullen HE, Sanders PR, Dans MG, et al., 2022, The <i>Plasmodium falciparum</i> parasitophorous vacuole protein P113 interacts with the parasite protein export machinery and maintains normal vacuole architecture, MOLECULAR MICROBIOLOGY, Vol: 117, Pages: 1245-1262, ISSN: 0950-382X
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- Citations: 4
de Vries LE, Jansen PAM, Barcelo C, et al., 2022, Preclinical characterization and target validation of the antimalarial pantothenamide MMV693183, NATURE COMMUNICATIONS, Vol: 13
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- Citations: 10
Yahiya S, Jordan S, Smith HX, et al., 2022, Live-cell fluorescence imaging of microgametogenesis in the human malaria parasite <i>Plasmodium falciparum</i>, PLOS PATHOGENS, Vol: 18, ISSN: 1553-7366
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- Citations: 5
Davidson M, Andradi-Brown C, Yahiya S, et al., 2022, Automated detection and staging of malaria parasites from cytological smears using convolutional neural networks, Biological Imaging, Vol: 1, Pages: 1-13, ISSN: 2633-903X
Microscopic examination of blood smears remains the gold standard for laboratory inspection and diagnosis of malaria. Smear inspection is, however, time consuming and dependent on trained microscopists with results varying in accuracy. We sought to develop an automated image analysis method to improve accuracy and standardisation of smear inspection that retains capacity for expert confirmation and image archiving. Here we present a machine-learning method that achieves red blood cell (RBC) detection, differentiation between infected/uninfected cells and parasite life stage categorisation from unprocessed, heterogeneous smear images. Based on a pre-trained Faster Region-Based Convolutional Neural Networks (R-CNN) model for RBC detection, our model performs accurately, with average precision of 0.99 at an intersection-over-union threshold of 0.5. Application of a residual neural network (ResNet)-50 model to infected cells also performs accurately, with an area under the receiver operating characteristic curve of 0.98. Lastly, combining our method with a regression model successfully recapitulates intra-erythrocytic developmental cycle with accurate lifecycle stage categorisation. Combined with a mobile-friendly web-based interface, called PlasmoCount, our method permits rapid navigation through and review of results for quality assurance. By standardising assessment of Giemsa smears, our method markedly improves inspection reproducibility and presents a realistic route to both routine lab but also future field-based automated malaria diagnosis.
Ellis KM, Lucantoni L, Chavchich M, et al., 2021, The Novel bis-1,2,4-Triazine MIPS-0004373 Demonstrates Rapid and Potent Activity against All Blood Stages of the Malaria Parasite, ANTIMICROBIAL AGENTS AND CHEMOTHERAPY, Vol: 65, ISSN: 0066-4804
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- Citations: 4
Xie SC, Metcalfe RD, Mizutani H, et al., 2021, Design of proteasome inhibitors with oral efficacy in vivo against <i>Plasmodium falciparum</i> and selectivity over the human proteasome, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 118, ISSN: 0027-8424
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- Citations: 15
Yahiya S, Jordan S, Smith HX, et al., 2021, 4D live-cell imaging of microgametogenesis in the human malaria parasite <i>Plasmodium falciparum</i>
<jats:title>ABSTRACT</jats:title><jats:p>Formation of gametes in the malaria parasite occurs in the midgut of the mosquito and is critical to onward parasite transmission. Transformation of the male gametocyte into microgametes, called microgametogenesis, is an explosive cellular event and one of the fastest eukaryotic DNA replication events known. The transformation of one microgametocyte into eight flagellated microgametes requires reorganisation of the parasite cytoskeleton, replication of the 22.9 Mb genome, axoneme formation and host erythrocyte egress, all of which occur simultaneously in <20 minutes. Whilst high-resolution imaging has been a powerful tool for defining stages of microgametogenesis, it has largely been limited to fixed parasite samples, given the speed of the process and parasite photosensitivity. Here, we have developed a live-cell fluorescence imaging workflow that captures the explosive dynamics of microgametogenesis in full. Using the most virulent human malaria parasite, <jats:italic>Plasmodium falciparum</jats:italic>, our live-cell approach combines three-dimensional imaging through time (4D imaging) and covers early microgametocyte development through to microgamete release. Combining live-cell stains for DNA, tubulin and the host erythrocyte membrane, 4D imaging enables definition of the positioning of newly replicated and segregated DNA. It also shows the microtubular cytoskeleton, location of newly formed basal bodies and elongation of axonemes, as well as behaviour of the erythrocyte membrane, including its specific perforation prior to microgamete egress. 4D imaging was additionally undertaken in the presence of known transmission-blocking inhibitors and the untested proteasomal inhibitor bortezomib. Here, for the first time we find that bortezomib inhibition results in a clear block of DNA replication, full axoneme nucleation and elongation. These data not only define a framework for understand
Blight J, Sala K, Atcheson E, et al., 2021, Dissection-independent production of a Plasmodium sporozoites from whole mosquitoes, Life Science Alliance, Vol: 4, ISSN: 2575-1077
Progress towards a protective vaccine against malaria remains slow. To date, only limited protection has been routinely achieved following immunisation with either whole-parasite (sporozoite) or subunit-based vaccines. One major roadblock to vaccine progress, and to pre-erythrocytic parasite biology in general, is the continued reliance on manual salivary gland dissection for sporozoite isolation from infected mosquitoes. Here, we report development of a multi-step method, based on batch processing of homogenised whole mosquitoes, slurry, and density-gradient filtration, which combined with free-flow electrophoresis rapidly produces a pure, infective sporozoite inoculum. Human-infective Plasmodium falciparum and rodent-infective Plasmodium berghei sporozoites produced in this way are two- to threefold more infective than salivary gland dissection sporozoites in in vitro hepatocyte infection assays. In an in vivo rodent malaria model, the same P. berghei sporozoites confer sterile protection from mosquito-bite challenge when immunisation is delivered intravenously or 60–70% protection when delivered intramuscularly. By improving purity, infectivity, and immunogenicity, this method represents a key advancement in capacity to produce research-grade sporozoites, which should impact delivery of a whole-parasite based malaria vaccine at scale in the future.
Okaniwa M, Shibata A, Ochida A, et al., 2021, Repositioning and characterization of 1-(Pyridin-4-yl)pyrrolidin-2-one derivatives as plasmodium cytoplasmic prolyl-tRNA synthetase inhibitors, ACS Infectious Diseases, Vol: 7, Pages: 1680-1689, ISSN: 2373-8227
Prolyl-tRNA synthetase (PRS) is a clinically validated antimalarial target. Screening of a set of PRS ATP-site binders, initially designed for human indications, led to identification of 1-(pyridin-4-yl)pyrrolidin-2-one derivatives representing a novel antimalarial scaffold. Evidence designates cytoplasmic PRS as the drug target. The frontrunner 1 and its active enantiomer 1- S exhibited low-double-digit nanomolar activity against resistant Plasmodium falciparum (Pf) laboratory strains and development of liver schizonts. No cross-resistance with strains resistant to other known antimalarials was noted. In addition, a similar level of growth inhibition was observed against clinical field isolates of Pf and P. vivax. The slow killing profile and the relative high propensity to develop resistance in vitro (minimum inoculum resistance of 8 × 105 parasites at a selection pressure of 3 × IC50) constitute unfavorable features for treatment of malaria. However, potent blood stage and antischizontal activity are compelling for causal prophylaxis which does not require fast onset of action. Achieving sufficient on-target selectivity appears to be particularly challenging and should be the primary focus during the next steps of optimization of this chemical series. Encouraging preliminary off-target profile and oral efficacy in a humanized murine model of Pf malaria allowed us to conclude that 1-(pyridin-4-yl)pyrrolidin-2-one derivatives represent a promising starting point for the identification of novel antimalarial prophylactic agents that selectively target Plasmodium PRS.
Real E, Howick VM, Dahalan FA, et al., 2021, A single-cell atlas of <i>Plasmodium falciparum</i> transmission through the mosquito, NATURE COMMUNICATIONS, Vol: 12
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Haase S, miller D, Cherkaoui D, et al., 2021, Identification and characterisation of a phospholipid scramblase in the malaria parasite Plasmodium falciparum, Molecular and Biochemical Parasitology, Vol: 243, Pages: 1-15, ISSN: 0166-6851
Recent studies highlight the emerging role of lipids as important messengers in malaria parasite biology. In an attempt to identify interacting proteins and regulators of these dynamic and versatile molecules, we hypothesised the involvement of phospholipid translocases and their substrates in the infection of the host erythrocyte by the malaria parasite Plasmodium spp. Here, using a data base searching approach of the Plasmodium Genomics Resources (www.plasmodb.org), we have identified a putative phospholipid (PL) scramblase in P. falciparum (PfPLSCR) that is conserved across the genus and in closely related unicellular algae. By reconstituting recombinant PfPLSCR into liposomes, we demonstrate metal ion dependent PL translocase activity and substrate preference, confirming PfPLSCR as a bona fide scramblase. We show that PfPLSCR is expressed during asexual and sexual parasite development, localising to different membranous compartments of the parasite throughout the intra-erythrocytic life cycle. Two different gene knockout approaches, however, suggest that PfPLSCR is not essential for erythrocyte invasion and asexual parasite development, pointing towards a possible role in other stages of the parasite life cycle.
Lawong A, Gahalawat S, Okombo J, et al., 2021, Novel antimalarial tetrazoles and amides active against the hemoglobin degradation pathway in plasmodium falciparum., Journal of Medicinal Chemistry, Vol: 64, Pages: 2739-2761, ISSN: 0022-2623
Malaria control programs continue to be threatened by drug resistance. To identify new antimalarials, we conducted a phenotypic screen and identified a novel tetrazole-based series that shows fast-kill kinetics and a relatively low propensity to develop high-level resistance. Preliminary structure-activity relationships were established including identification of a subseries of related amides with antiplasmodial activity. Assaying parasites with resistance to antimalarials led us to test whether the series had a similar mechanism of action to chloroquine (CQ). Treatment of synchronized Plasmodium falciparum parasites with active analogues revealed a pattern of intracellular inhibition of hemozoin (Hz) formation reminiscent of CQ's action. Drug selections yielded only modest resistance that was associated with amplification of the multidrug resistance gene 1 (pfmdr1). Thus, we have identified a novel chemical series that targets the historically druggable heme polymerization pathway and that can form the basis of future optimization efforts to develop a new malaria treatment.
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