Biology subjects

Razook, Z.

Publications and source records attributed to Razook, Z..

8 recordsLinked to original sources

bioRxiv2026

MMV687794 blocks Plasmodium falciparum invasion of red blood cells by targeting a Surface-associated Lipid-Interacting Rhoptry Protein, PfSLIRP

Invasion of red blood cells (RBCs) by the human malaria parasite, Plasmodium falciparum, drives disease. During invasion, the parasite pushes its way into the RBC while wrapping the RBC membrane around itself to establish the parasitophorous vacuole, a stable niche within the RBC where the parasite grows. To better understand invasion, we investigated the mechanism of action of an invasion-inhibitory compound, MMV687794 (MMV794). Lattice light-sheet microscopy revealed that MMV794 blocks parasite entry by preventing parasitophorous vacuole formation. In vitro drug resistance selection of parasites with MMV794 found mutations to the /{beta} hydrolase, PF3D7_0403800, and engineering one of these mutations (C36W) into parasites by CRISPR/Cas9 recapitulated the resistance phenotype. Expansion microscopy demonstrated that this protein is expressed in schizonts, localising to the surface of rhoptries, which are specialised apical secretory organelles that function during invasion. Lipidomics and proteomics analyses of C36W parasites uncovered widespread changes to lipid composition/homeostasis and altered abundance of proteins involved in invasion, indicating a role for PF3D7_0403800 in invasion-associated lipid metabolism. Finally, we used solvent-induced proteome profiling and reactivity assays to confirm drug-target engagement. Together, our findings identify a novel Surface-associated Lipid-Interacting Rhoptry Protein (PfSLIRP) that coordinates lipid metabolism at the rhoptries to enable RBC invasion.

microbiology↗

bioRxiv2025

Deconvolution of the on-target activity of plasmepsin V peptidomimetics in P. falciparum parasites

Plasmepsin V (PMV), an essential aspartyl protease, plays a critical role during the asexual blood stage of infection of Plasmodium by enabling the export of parasite proteins into the host red blood cell. This export is vital for parasite survival and pathogenesis, making PMV an attractive target for antimalarial drug development. Peptidomimetic inhibitors designed to mimic the natural substrate of PMV have demonstrated potent parasite-killing activity by blocking protein export. While these compounds have been instrumental in validating PMV as a bona fide antimalarial target, inconsistencies between their biochemical potency and cellular activity have raised questions regarding their precise mechanism of action. In this study, we employed chemoproteomic approaches, including solvent induced protein precipitation (SIP) and intact-cell thermal PISA profiling, to demonstrate PMV target engagement by the peptidomimetics. To further support these findings, we generated parasite lines exhibiting reduced sensitivity to peptidomimetics. Through whole-genome sequencing of these parasite lines, a single nucleotide variant (SNV) within the pmv gene was revealed. This mutation was later validated using reverse genetics, confirming its role in mediating resistance. Together, these data provide strong evidence that the peptidomimetics exert their antimalarial activity by directly targeting PMV. These findings further support the potential of PMV as a validated and promising target for future antimalarial drug development.

cell biology↗

bioRxiv2025

Aryl N-acetamide compounds exert antimalarial activity by acting as agonists of rhomboid protease PfROM8 and cation channel PfCSC1.

With resistance to current frontline antimalarials spreading globally, new drug candidates need to be discovered to populate the antimalarial drug development pipeline. We previously screened the Medicines for Malaria Venture Pathogen Box for compounds that prevent Plasmodium falciparum parasites from exiting and invading human erythrocytes, steps essential for the proliferation of parasites in the blood, which causes disease. Compound MMV020512 (M-512) was identified in this screen and live cell imaging here established that it does not specifically inhibit invasion but likely inhibits intraerythrocytic parasite growth. M-512 resistance selection in parasites led to the identification of mutations in the membrane protease PfROM8 and the cation ion channel PfCSC1. PfROM8 was validated as a target of M-512 when a L562R putative resistance mutation was engineered into wildtype parasites reproducing the resistance phenotype. Knockdown of wildtype PfROM8, the L562R mutant and CSC1 reduced parasite growth, indicating the proteins are functionally important. Counterintuitively, the PfROM8 and PfCSC1 knockdown parasites became more resistant to M-512 suggesting that the compound is an agonist of both proteins which may form a functional complex and that dysregulation of this complex is deleterious to parasite growth.

microbiology↗

bioRxiv2023

Aryl amino acetamides prevent the development of Plasmodium falciparum rings via inhibition of the lipid transfer protein PfSTART1

With resistance to most antimalarials increasing, it is imperative that new antimalarial drugs are developed to replace or complement front-line artemisinin therapies. We previously identified an aryl acetamide compound, MMV006833 (M-833), that inhibited ring development of newly invaded merozoites. Here, we selected parasites resistant to M-833 and identified independent mutations arising in the START lipid transfer protein (PF3D7_0104200, PfSTART1). Introduction of the identified PfSTART1 mutations into wildtype parasites reproduced resistance to both M-833 and highly potent analogues, confirming PfSTART1 mutations were sufficient to confer resistance. The analogues bound to recombinant PfSTART1 with nanomolar affinity. We also demonstrated selective PfSTART1 engagement by the analogues using organic solvent-based Proteome Integral Solubility Alteration (Solvent PISA) assay for the first time in Plasmodium. Imaging of newly invaded merozoites showed the inhibitors prevented the conversion into larger amoeboid ring-stage parasites potentially through the inhibition of phospholipid transfer from the parasite to the encasing parasitophorous vacuole membrane (PVM) and/or within the parasite. We show that these PfSTART1 inhibitors also block transmission. With multiple stages of the parasites lifecycle being targeted by PfSTART1 inhibitors, this protein therefore represents a novel drug target with a new mechanism of action.

cell biology↗

bioRxiv2023

A pyridyl-furan series developed from Open Global Health Library blocks red blood cell invasion and protein trafficking in Plasmodium falciparum through potential inhibition of the parasites PI4KIIIb enzyme.

With resistance increasing to current antimalarial medicines, there is an urgent need to discover new drug targets and to develop new medicines against these targets. We therefore screened the Open Global Health Library of Merck KGaA, Darmstadt, Germany of 250 compounds against the asexual blood stage of the deadliest malarial parasite Plasmodium falciparum, from which eight inhibitors with low micromolar potency were found. Due to its combined potencies against parasite growth and inhibition of red blood cell invasion, the pyridyl-furan compound OGHL250, was prioritised for further optimisation. The potency of the series lead compound (WEHI-518) was improved 250-fold to low nanomolar levels against parasite blood-stage growth. Parasites selected for resistance to a related compound MMV396797, were also resistant to WEHI-518 as well as KDU731, an inhibitor of the phosphatidylinositol kinase PfPI4KIIIB, suggesting this kinase is the target of the pyridyl-furan series. Inhibition of PfPI4KIIIB blocks multiple stages of the parasites life cycle and other potent inhibitors are currently under preclinical development. MMV396797-resistant parasites possess an E1316D mutation in PfPKI4IIIB which clusters with known resistance mutations of other inhibitors of the kinase. Building upon earlier studies which showed that PfPI4KIIIB inhibitors block the development of the invasive merozoite parasite stage, we show that members of the pyridyl-furan series also block invasion and/or the conversion of merozoites into ring-stage intracellular parasites through inhibition of protein secretion and export into red blood cells.

microbiology↗

bioRxiv2022

The sulfonylpiperazine MMV020291 prevents red blood cell invasion by the malaria parasite Plasmodium falciparum through interference with actin-1/profilin dynamics

With emerging resistance to frontline treatments, it is vital that new antimalarial drugs are identified to target Plasmodium falciparum. We have recently described a compound, MMV020291, as a specific inhibitor of red blood cell invasion, and have generated analogues with improved potency. Here, we identify actin and profilin as putative targets of the MMV020291 series through resistance selection and whole genome sequencing of three MMV020291 resistant populations. This revealed three non-synonymous single nucleotide polymorphisms in two genes; two in profilin (N154Y, K124N) and a third one in actin-1 (M356L). Using CRISPR-Cas9, we engineered these mutations into wildtype parasites which rendered them resistant to MMV020291. We demonstrate that MMV020291 reduces actin polymerisation that is required by the merozoite stage parasites to invade red blood cells. Additionally, the series inhibits the actin-1 dependent process of apicoplast segregation, leading to a delayed death phenotype. In vitro co-sedimentation experiments using recombinant P. falciparum actin-1 and profilin proteins indicate that potent MMV020291 analogues amplify the actin-monomer sequestering effect of profilin, thereby reducing the formation of filamentous actin. Altogether, this study identifies the first compound series targeting the actin-1/profilin interaction in P. falciparum and paves the way for future antimalarial development against the highly dynamic process of actin polymerisation.

molecular biology↗

bioRxiv2020

Real time, field-deployable whole genome sequencing of malaria parasites using nanopore technology

Malaria parasite genomes have been generated predominantly using short read sequencing technology which can be slow, requires advanced laboratory training and does not adequately interrogate complex genomic regions that harbour important malaria virulence determinants. The portable Oxford Nanopore Technologies MinION platform generates long reads in real time and may overcome these limitations. We present compelling evidence that Nanopore sequencing delivers valuable additional information for malaria parasites with comparable data fidelity for single nucleotide variant (SNV) calls, compared to standard Illumina whole genome sequencing. We demonstrate this through sequencing of pure Plasmodium falciparum DNA, mock infections and natural isolates. Nanopore has low error rates for haploid SNV genotyping and identifies structural variants (SVs) not detected with short reads. Nanopore genomes are directly comparable to publically available genomes and produce high quality end to end chromosome assemblies. Nanopore sequencing will expedite genomic surveillance of malaria and provide new insights into parasite genome biology.

genomics↗

bioRxiv2019

Monitoring Plasmodium falciparum and Plasmodium vivax using microsatellite markers indicates limited changes in population structure after substantial transmission decline in Papua New Guinea

Monitoring the genetic structure of malaria parasite populations has been proposed as a novel and sensitive approach to quantify the impact of malaria control and elimination efforts. Here we describe the first population genetic analysis of sympatric Plasmodium falciparum (Pf) and Plasmodium vivax (Pv) populations following nationwide distribution of long-lasting insecticide treated nets (LLIN) in Papua New Guinea (PNG). Parasite isolates from serial cross-sectional studies pre-(2005-6) and post-LLIN (2010-2014) were genotyped using microsatellite markers. Despite parasite prevalence declining substantially in these communities (East Sepik: Pf=54.9-8.5%, Pv=35.7-5.6%, Madang: Pf=38.0-9.0%, Pv: 31.8-19.7%), genetically diverse and intermixing parasite populations remained. P. falciparum diversity declined modestly post-LLIN relative to pre-LLIN (East Sepik: Rs = 7.1-6.4, He = 0.77-0.71; Madang: Rs= 8.2-6.1, He = 0.79-0.71). Unexpectedly, population structure present in pre-LLIN populations was lost post-LLIN, suggesting that more frequent human movement between provinces may have contributed to higher gene flow between provinces. P. vivax prevalence initially declined but increased again in one province, yet diversity remained high throughout the study period (East Sepik: Rs=11.4-9.3, He=0.83-0.80; Madang: Rs=12.2-14.5, He=0.85-0.88). Although genetic differentiation values increased between provinces over time, no significant population structure was observed at any time point. For both species, the emergence of clonal transmission and significant multilocus linkage disequilibrium (mLD) due to increased focal inbreeding post-LLIN was a strong indicator of impact on the parasite population using these markers. After eight years of intensive malaria control in PNG and substantial prevalence decline the impact on parasite population diversity and structure detectable by microsatellite genotyping was limited.

microbiology↗