Biology subjects

Kaur, S.

Publications and source records attributed to Kaur, S..

At least 73 records · Page 4Linked to original sources

bioRxiv2023

Investigating the ATP binding pocket of CX3CL1 binding protein 2 using in silico approach

Plasmodium falciparum (Pf) causes the most fatal form of malaria owing to its ability to cytoadhere in the microvasculature of various organs in the body. In addition to the Pf erythrocyte membrane protein 1 (PfEMP1) family that binds diverse host receptors, CX3CL1 binding proteins 1 and 2 (CBP1 and 2) also bind the endothelial chemokine CX3CL1 to effect cytoadhesion of parasite infected erthrocytes. CBP2 is a multifaceted protein that binds nucleic acids, Pf skeleton binding protein (PfSBP1) and ATP. ATP binding to the cytoplasmic domain of CBP2 (cCBP2) induces structural changes in the protein, and hints at its role in cell signaling. In this study, we have attempted to identify the ATP binding pocket of CBP2 using an in silico approach. We have also delineated the type of interactions and amino acid residues that are likely to bind ATP. As CX3CL1 binding proteins are central to parasite biology, the obtained information is likely to form the basis for inhibitor and drug design against this molecule.

bioinformatics↗

bioRxiv2023

Understanding the molecular basis for enhanced glutenase activity of actinidin

Management of gluten intolerance is currently possible only by consumption of gluten free diet(GFD) for a lifetime. The scientific community has been searching for alternatives to GFD, like inclusion of natural proteases with meals or pre-treatment of gluten containing foods with glutenases. Actinidin from kiwifruit has shown considerable promise in digesting immunogenic gliadin peptides as compared to other plant derived cysteine proteases. Through this article, we have attempted to understand the structural basis for elevated protease action of actinidin against gliadin peptides by using an in silico approach. Docking experiments reveal key differences between the binding of gliadin peptide to actinidin and papain, which may be responsible for their differential digestive action. Sequence comparison of different plant cysteine proteases highlights amino acid residues surrounding the active site pocket of actinidin that are unique to this molecule and hence likely to contribute to its digestive properties. Graphical summary O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=64 SRC="FIGDIR/small/542047v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@4fcd61org.highwire.dtl.DTLVardef@134c371org.highwire.dtl.DTLVardef@10b5d78org.highwire.dtl.DTLVardef@1257d19_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioinformatics↗

bioRxiv2023

Win-paired cues modulate the effect of dopamine neuron sensitization on decision making and cocaine self-administration: divergent effects across sex

Psychostimulant use and engagement with probabilistic schedules of reward both sensitize the mesocorticolimbic dopamine system. Such behaviours may act synergistically to explain the high comorbidity between stimulant use and gambling disorder. The salient audiovisual stimuli of modern electronic gambling may exacerbate the situation. To probe these interactions, we sensitized ventral tegmental area (VTA) dopamine neurons via chronic chemogenetic stimulation while rats learned the rat gambling task in the presence or absence of casino-like cues. The same rats then learned to self-administer cocaine. In a separate cohort, we confirmed that our chemogenetic methods sensitized the locomotor response to cocaine, and potentiated phasic excitability of VTA dopamine neurons through in vivo electrophysiological recordings. In the absence of cues, sensitization promoted risk-taking in both sexes. When rewards were cued, sensitization expedited the development of a risk-preferring phenotype in males, while attenuating cue-induced risk-taking in females. While these results provide further confirmation that VTA dopamine neurons critically modulate risky decision making, they also reveal stark sex differences in the decisional impact which dopaminergic signals exert when winning outcomes are cued. As previously observed, risky decision-making on the cued rGT increased as both males and females learned to self-administer cocaine. The combination of dopamine sensitization and win-paired cues while gambling lead to significantly greater cocaine-taking, but these rats did not show any increase in risky choice as a result. Cocaine and heavily-cued gambles may therefore partially substitute for each other once the dopamine system is rendered labile through sensitization, compounding addiction risk across modalities.

animal behavior and cognition↗

bioRxiv2023

Complete genome sequences of the species type strains Sinorhizobium garamanticum LMG 24692T and Sinorhizobium numidicum LMG 27395T and CIP 109850T

The genus Sinorhizobium comprises rhizobia that fix nitrogen in symbiosis with legumes. To support taxonomic studies of this genus and of rhizobia more broadly, we report complete genome sequences and annotations for the species type strains Sinorhizobium garamanticum LMG 24692T and Sinorhizobium numidicum LMG 27395T and CIP 109850T. Average nucleotide identity and core-genome phylogenetic analyses confirm that S. garamanticum and S. numidicum represent distinct species.

microbiology↗

bioRxiv2023

Genomic epidemiology and multilevel genome typing of Bordetella pertussis

Bordetella pertussis is responsible for the respiratory infectious disease pertussis (or whooping cough), which causes one of the most severe diseases in infants, although it can be prevented by whole cell and acellular vaccines. The recent resurgence of pertussis is partially due to pathogen adaptation to vaccines as well as resistance to antimicrobials. Surveillance of current circulating and emerging strains is therefore vital to understand the risks they pose to public health. Although there is increased genomics based typing, a genomic nomenclature for this pathogen has not been well established. Here, we implemented the Multilevel Genome Typing (MGT) system for B. pertussis with five levels of resolution, which provide targeted typing of relevant lineages as well as discrimination of closely related strains at the finest scale. The low resolution levels can describe the distribution of alleles of major vaccine antigen genes such as ptxP, fim3, fhaB and prn as well as temporal and spatial trends within the B. pertussis global population. Mid-resolution levels enables typing of antibiotic resistant lineages and Prn deficient lineages within the ptxP3 clade. High resolution levels can capture small-scale epidemiology such as local transmission events and has comparable resolution to existing genomic methods of strain relatedness assessment. The scheme offers stable MGT type assignments aiding harmonisation of typing and communication between laboratories. The scheme is available at www.mgtdb.unsw.edu.au/pertussis/ is regularly updated from global data repositories and accepts public data submissions. The MGT scheme provides a comprehensive, robust, and scalable system for global surveillance of B. pertussis.

microbiology↗

bioRxiv2023

SaLTy: a novel Staphylococcus aureus Lineage Typer

Staphylococcus aureus asymptomatically colonises 30% of humans and in 2017 was associated with 20,000 deaths in the USA alone. Dividing S. aureus into smaller sub-groups can reveal the emergence of distinct sub-populations with varying potential to cause infections. Despite multiple molecular typing methods categorising such sub-groups, they do not take full advantage of S. aureus WGS when describing the fundamental population structure of the species. In this study, we developed Staphylococcus aureus Lineage Typing (SaLTy), which rapidly divides the species into 61 phylogenetically congruent lineages. Alleles of three core genes were identified that uniquely define the 61 lineages and were used for SaLTy typing. SaLTy was validated on 5,000 genomes and 99.12% (4,956/5,000) of isolates were assigned the correct lineage. We compared SaLTy lineages to previously calculated clonal complexes (CCs) from BIGSdb (n=21,173). SALTy improves on CCs by grouping isolates congruently with phylogenetic structure. SaLTy lineages were further used to describe the carriage of Staphylococcal chromosomal cassette containing mecA (SCCmec) which is carried by methicillin-resistant S. aureus (MRSA). Most lineages had isolates lacking SCCmec and the four largest lineages varied in SCCmec over time. Classifying isolates into SaLTy lineages, which were further SCCmec typed, allowed SaLTy to describe high-level MRSA epidemiology We provide SALTy as a simple typing method that defines phylogenetic lineages (https://github.com/LanLab/SaLTy). SALTy is highly accurate and can quickly analyse large amounts of S. aureus WGS. SALTy will aid the characterisation of S. aureus populations and the ongoing surveillance of sub-groups that threaten human health.

microbiology↗

bioRxiv2022

Whole genome assemblies of Zophobas morio and Tenebrio molitor

Zophobas morio (=Zophobas atratus) and Tenebrio molitor are darkling beetles with industrial importance due to their use as feeder insects, their potential for use in aquafeed and human food products, and their apparent ability to biodegrade various plastic polymers. We report draft genome assemblies for Z. morio and T. molitor generated from Nanopore and Illumina data. Following scaffolding against published genomes, haploid assemblies of 462 Mb (scaffold N90 of 16.8 Mb) and 258 Mb (scaffold N90 of 5.9 Mb) were produced for Z. morio and T. molitor, respectively. Gene prediction led to the prediction of 28,544 and 19,830 genes for Z. morio and T. molitor, respectively. BUSCO analyses suggested both assemblies have a high level of completeness; 91.5% and 89.0% of the BUSCO endopterygota marker genes were complete in the Z. morio assembly and proteome, respectively, while 99.1% and 92.8% were complete in the T. molitor assembly and proteome, respectively. Phylogenomic analyses of four genera from the family Tenebrionidae yielded phylogenies consistent with those previously constructed based on mitochondrial genomes. Synteny analyses revealed large stretches of macrosynteny across the family Tenebrionidae, as well as numerous within-chromosome rearrangements. Finally, orthogroup analysis identified [~]28,000 gene families across the family Tenebrionidae, of which 8,185 were identified in all five of the analyzed species, and 10,837 were conserved between Z. morio and T. molitor. We expect that the availability of multiple whole genome sequences for Z. morio and T. molitor will facilitate population genetics studies to identify genetic variation associated with industrially relevant phenotypes.

genomics↗

bioRxiv2022

Characterisation of the functional and transcriptomic effects of pro-inflammatory cytokines on human EndoC- βH5 beta cells

ObjectiveEndoC-{beta}H5 is a newly established human beta-cell model which may be superior to previous models of native human beta cells. Exposure of beta cells to proinflammatory cytokines is a widely used in vitro model of immune-mediated beta-cell failure in type 1 diabetes and we therefore performed an in-depth characterisation of the effects of cytokines on EndoC-{beta}H5 cells. MethodsThe sensitivity profile of EndoC-{beta}H5 cells to the toxic effects of the pro-inflammatory cytokines interleukin-1{beta} (IL-1{beta}), interferon {gamma} (IFN{gamma}) and tumour necrosis factor- (TNF) was examined in titration and time-course experiments. Cell death was evaluated by caspase 3/7 activity, cytotoxicity, viability, TUNEL assay and immunoblotting. Mitochondrial function was evaluated by extracellular flux technology. Activation of signalling pathways and major histocompatibility complex (MHC) class I expression were examined by immunoblotting, immunofluorescence, and real-time quantitative PCR (qPCR). Glucose-stimulated insulin secretion (GSIS) and cytokine-induced chemokine secretion were measured by ELISA and Meso Scale Discovery multiplexing electrochemiluminescence, respectively. Global gene expression was characterised by stranded RNA sequencing. ResultsCytokines increased caspase activity and cytotoxicity in EndoC-{beta}H5 cells in a time- and dose-dependent manner. The proapoptotic effect of cytokines was primarily driven by IFN{gamma}. Cytokine exposure caused impaired mitochondrial function, diminished GSIS, and induced secretion of chemokines. At the signalling level, cytokines increased the phosphorylation of signal transducer and activator of transcription 1 (STAT1) but not c-jun N-terminal kinase (JNK) and did not cause degradation of nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor (I{kappa}B). MHC class I was induced by cytokines. Cytokine exposure caused significant changes to the EndoC-{beta}H5 transcriptome including upregulation of HLA genes, endoplasmic reticulum stress markers, and non-coding RNAs. Among the differentially expressed genes were several type 1 diabetes risk genes. ConclusionsOur study provides detailed insight into the functional and transcriptomic effects of cytokines on EndoC-{beta}H5 cells. This knowledge will be helpful for future investigations studying cytokine effects in this cell model.

cell biology↗

bioRxiv2022

Identification of leaf rust resistance loci in a geographically diverse panel of wheat using genome-wide association analysis

Leaf rust, caused by Puccinia triticina (Pt) is among the most devastating diseases posing a significant threat to global wheat production. The continuously evolving virulent Pt races in North America calls for exploring new sources of leaf rust resistance. A diversity panel of 365 bread wheat accessions selected from a worldwide population of landraces and cultivars was evaluated at the seedling stage against four Pt races (TDBJQ, TBBGS, MNPSD and, TNBJS). A wide distribution of seedling responses against the four Pt races was observed. Majority of the genotypes displayed a susceptible response with only 28 (9.8%), 59 (13.5%), 45 (12.5%), and 29 (8.1%) wheat accessions exhibiting a highly resistant response to TDBJQ, TBBGS, MNPSD and, TNBJS, respectively. Further, we conducted a high-resolution multi-locus genome-wide association study (GWAS) using a set of 302,524 high-quality single nucleotide polymorphisms (SNPs). The GWAS analysis identified 27 marker-trait associations (MTAs) for leaf rust resistance on different wheat chromosomes of which 20 MTAs were found in the vicinity of known Lr genes, MTAs, or quantitative traits loci (QTLs) identified in previous studies. The remaining seven significant MTAs identified represent genomic regions that harbor potentially novel genes for leaf rust resistance. Furthermore, the candidate gene analysis for the significant MTAs identified various genes of interest that may be involved in disease resistance. The identified resistant lines and SNPs linked to the QTLs in this study will serve as valuable resources in wheat rust resistance breeding programs.

plant biology↗

bioRxiv2022

Endothelial cells release microvesicles that harbor multivesicular bodies and secrete exosomes

Extracellular vesicles (EVs) released by resting endothelial cells support vascular homeostasis. To better understand endothelial cell EV biogenesis, we examined cultured human umbilical vein endothelial cells (HUVECs) prepared by rapid freezing, freeze-substitution, and serial thin section electron microscopy. Thin sections of HUVECs revealed clusters of membrane protrusions on the otherwise smooth cell surface. The protrusions contained membrane-bound organelles, including multivesicular bodies (MVBs), and appeared to be on the verge of pinching off to form microvesicles. Beyond cell peripheries, membrane-bound vesicles with internal MVBs were observed, and serial sections confirmed that they were not connected to cells. These observations are consistent with the notion that these multi-compartmented microvesicles (MCMVs) pinch-off from protrusions. Remarkably, omega figures formed by fusion of MVBs with the MCMV limiting membrane were directly observed, apparently caught in the act of releasing exosomes from the MCMV. In summary, MCMVs are a novel form of EV that bud from membrane protrusions on the HUVEC surface, contain MVBs and release exosomes. These observations suggest that exosomes can be harbored within and released from transiting microvesicles after departure from the parent cell, constituting a new site of exosome biogenesis occurring from endothelial and potentially additional cell types.

cell biology↗

bioRxiv2022

The giant diploid faba genome unlocks variation in a global protein crop

Increasing the proportion of locally produced plant protein in currently meat-rich diets could substantially reduce greenhouse gas emission and loss of biodiversity. However, plant protein production is hampered by the lack of a cool-season legume equivalent to soybean in agronomic value. Faba bean (Vicia faba L.) has a high yield potential and is well-suited for cultivation in temperate regions, but genomic resources are scarce. Here, we report a high-quality chromosome-scale assembly of the faba bean genome and show that it has grown to a massive 13 Gb in size through an imbalance between the rates of amplification and elimination of retrotransposons and satellite repeats. Genes and recombination events are evenly dispersed across chromosomes and the gene space is remarkably compact considering the genome size, though with significant copy number variation driven by tandem duplication. Demonstrating practical application of the genome sequence, we develop a targeted genotyping assay and use high-resolution genome-wide association (GWA) analysis to dissect the genetic basis of hilum colour. The resources presented constitute a genomics-based breeding platform for faba bean, enabling breeders and geneticists to accelerate improvement of sustainable protein production across Mediterranean, subtropical, and northern temperate agro-ecological zones.

plant biology↗

bioRxiv2022

MGTdb: A web service and database for studying the global and local genomic epidemiology of bacterial pathogens

Multilevel genome typing (MGT) enables the genomic characterization of bacterial isolates and the relationships among them. The MGT system describes an isolate using multiple multilocus sequence typing (MLST) schemes, referred to as levels. Thus, for a new isolate, sequence types (STs) assigned at multiple precisely defined levels can be used to type isolates at multiple resolutions. The MGT designation for isolates is stable, and assignment is faster than existing approaches. MGTs utility has been demonstrated in multiple species. This paper presents a publicly accessible web service called MGTdb, which enables the assignment of MGT sequence types to isolates, along with their storage, retrieval and analysis. The MGTdb web service enables upload of genome data as sequence reads or alleles, which are processed and assigned MGT identifiers. Additionally, any newly sequenced isolates deposited in NCBI Sequence Read Archive are also regularly retrieved (currently daily), processed, assigned MGT and made publicly available in MGTdb. Interactive visualisation tools are presented to assist analysis, along with capabilities to download publicly available isolates and assignments for use with external software. MGTdb is currently available for Salmonella enterica serovars Typhimurium and Enteritidis, and Vibrio cholerae. We demonstrate the usability of MGTdb through three case studies to study the long-term national surveillance of S. Typhimurium, and the local epidemiology and outbreaks of S. Typhimurium, and the global epidemiology of V. cholerae. Thus, MGTdb enables epidemiological and microbiological investigations at multiple levels of resolution for all publicly available isolates of these pathogens. Database URLhttps://mgtdb.unsw.edu.au

bioinformatics↗

bioRxiv2022

Transcriptional signature pattern in black, blue and purple wheat and impact on seed pigmentation and other associated features: Comparative transcriptomics, genomics and metabolite profiling

Anthocyanin biosynthesis in plants is complex, especially in a polyploid monocot wheat plant. Using whole-genome sequencing, transcriptomics, and LC-MS/MS, we investigated anthocyanin production in pigmented (black, blue, and purple) wheat seeds. According to differential gene expression profiling, 2AS-MYC, 7DL-MYB, WD40 regulatory genes controls purple pericarp coloration, 4DL-MYC, 2AS-MYC, 7DL-MYB, WD40 controls blue aleurone coloration, and 4DL-MYC, 7DL-MYB, WD40 controls black aleurone colour. We believe that at least one MYC and MYB isoform is sufficient to regulate the anthocyanin synthesis in pericarp or aleurone. Based upon the reduced expressions of the genes belonging to the 4D, SSR molecular marker mapping, variant calling using genome sequencing and IGV browser gene structure visualization, it was inferred that the advanced black and blue wheat lines were substitution lines (4E{4D}), with very small recombinations. Pericarp anthocyanin profiling is controlled by a mutation in chromosome 2AS of purple wheat, and environmental variations more influence pigmented pericarp trait. The expression patterns of anthocyanin structural and other genes varied in different colored wheat, corroborating differences in agronomical metrics.

plant biology↗

bioRxiv2022

Genomic epidemiology and multilevel genome typing of Australian Salmonella enterica serovar Enteritidis

Salmonella enterica serovar Enteritidis is one of the leading causes of salmonellosis in Australia. However, the majority of S. Enteritidis cases in Australia are travel-related with a small proportion being locally acquired. This study aimed to characterise the genomic features of Australian S. Enteritidis and compare them with international strains using multilevel genome typing (MGT). A total of 568 S. Enteritidis isolates from two Australian states across two consecutive years were analysed using the S. Enteritidis MGT scheme and database (MGTdb) - which contained 40,390 publicly available genomes from 99 countries. The Australian S. Enteritidis strains were divided into three phylogenetic clades (A, B and C). Clades A and C represented 16.4% and 3.5% of the total isolates, respectively, and were of local origin. Clade B accounted for 80.1% of the isolates which belonged to seven previously defined lineages but was dominated by the global epidemic lineage (MGT4-CC1). At MGT5 level, three out of five top sequence types (STs) in Australia were also top STs in Asia, suggesting that a fair proportion of Australian S. Enteritidis cases may be epidemiologically linked with Asian strains. In 2018, a large egg-associated local outbreak was caused by a recently defined clade B lineage prevalent in Europe and was closely related, but not directly linked, to three isolates from Europe. Additionally, antimicrobial-resistance genes were only found in Australian clade B isolates, with a predicted multidrug resistance (MDR) rate of 11.7%. Over half (54.8%) of the MDR isolates belonged to 10 MDR-associated MGT-STs, which were also frequent in Asian S. Enteritidis. IncX1 plasmids were frequently present in the Australian MDR isolates. Overall, this study investigated the genomic epidemiology of S. Enteritidis in Australia, including the first large local outbreak, using MGT. The open MGT platform enables a standardised and sharable nomenclature that can be effectively applied to public health for unified surveillance of S. Enteritidis nationally and globally. ImportanceSalmonella enterica serovar Enteritidis is a leading cause of foodborne infections. We previously developed a genomic typing database - MGTdb for S. Enteritidis to facilitate global surveillance of this pathogen. In this study we examined the genomic features of Australian S. Enteritidis using the MGTdb and found that Australian S. Enteritidis is mainly epidemiologically linked with Asian strains (especially strains carrying antimicrobial resistance genes) followed by European strains. The first large-scale egg-associated local outbreak in Australia was caused by a recently defined lineage prevalent in Europe, and three European isolates in the MGTdb were closely related but not directly linked to this outbreak. In summary, the S. Enteritidis MGTdb open platform is shown to be a potential powerful tool for national and global public health surveillance of this pathogen.

genomics↗

bioRxiv2022

A CXCL12 morphogen gradient uncovers lung endothelial heterogeneity and promotes distal vascular growth

In adults, there is a growing amount of data uncovering the cellular diversity of the pulmonary circulation and mechanisms governing vascular repair after injury, however, molecular and cellular mechanisms contributing to the morphogenesis and growth of the pulmonary vasculature during embryonic development are less clear. Importantly, deficits in vascular development lead to a large number of lung diseases in children, indicating a need to uncover fetal programs that promote pulmonary vascular growth. To address this, we used a transgenic mouse reporter for expression of Cxcl12, an arterial hallmark gene, and performed single-cell RNA sequencing on isolated Cxcl12-DsRed+ endothelium to assess cellular heterogeneity within pulmonary endothelium. Combining cell annotation, gene ontology analysis, and spatial transcriptomics allowed us to segregate the developing artery into spatially and functionally distinct novel subpopulations. In addition, expression of Cxcl12 suggests a morphogen gradient from arteries to capillaries, suggesting directed cell migration for pulmonary vascular development. Disruption of this gradient led to abnormal branching and pulmonary vascular hypoplasia. These data provide evidence for arterial endothelial functional heterogeneity and reveal conserved signaling mechanisms essential for pulmonary vascular development.

developmental biology↗

bioRxiv2022

Dietary αKG inhibits SARS CoV-2 infection and rescues inflamed lungs to restore normal O2 saturation in animals

Our recent works described the rescue effect of -ketoglutarate (KG, a metabolite of Krebs cycle) on thrombosis and inflammation in animals. KG augments activity of prolyl hydroxylase 2 (PHD2), which in turn degrades proline residues of substrates like phosphorylated Akt (pAkt) and hypoxia inducible factor (HIF). Here we describe the inhibitory effect of octyl KG on pAkt as well as on HIF1/HIF2, and in turn decreasing SARS CoV-2 replication in Vero E6 cells. KG failed to inhibit the viral replication and Akt phosphorylation in PHD2-knockdown U937 cells transiently expressing ACE2. Contrastingly, triciribine (TCN, an Akt-inhibitor) inhibited viral replication alongside a downmodulation of pAkt in PHD2-KD cells. Dietary KG significantly inhibited viral infection and rescued hamsters from thrombus formation and inflammation in lungs, the known causes of acute respiratory distress syndrome (ARDS) in COVID-19. KG supplementation also reduced the apoptotic death of lung tissues in infected animals, alongside a downmodulation of pAkt and HIF2. KG supplementation neither affected IgG levels against SARS CoV-2 RBD protein nor altered the neutralization antibody response against SARS CoV-2. It did not interfere with the percentage of interferon-{gamma} positive (IFN{gamma}+) CD4+ and IFN{gamma}+CD8+ T cells in infected animals. The extended work in balb/c mice transiently expressing ACE2 showed a similar effect of KG in reducing accumulation of inflammatory immune cells and cytokines, including IL6, IL1{beta} and TNF, in lungs as well as in circulation of infected animals. Pro-thrombotic markers like platelet microparticles and platelet-leukocyte aggregates were reduced significantly in infected mice after KG supplementation. Importantly, KG supplementation restored the O2 saturation (SpO2) in circulation of SARS CoV-2 infected hamsters and mice, suggesting a potential therapeutic role of this metabolite in COVID-19 treatment.

pathology↗

bioRxiv2022

Promising Antimalarials targeting Apicoplast DNA Polymerase from Plasmodium falciparum

Malaria is caused by the parasite Plasmodium falciparum, which contains an essential non-photosynthetic plastid called the apicoplast. A single DNA polymerase, apPOL, is targeted to the apicoplast, where it replicates and repairs the genome. apPOL has no direct orthologs in mammals and is considered a promising drug target for the treatment and/or prevention of malaria. We previously reported screening the Malaria Box to identify MMV666123 as an inhibitor of apPOL. Herein we extend our studies and report structure-activity relationships for MMV666123 and identify key structural motifs necessary for inhibition. Although attempts to crystallize apPOL with the inhibitor were not fruitful, kinetic analysis and crystal structure determinations of WT and mutant apo-enzymes, facilitated model building and provided insights into the putative inhibitor binding site. Our results validate apPOL as an antimalarial target and provide an avenue for the design of high potency, specific inhibitors of apPOL and other A-family DNA polymerases.

biochemistry↗

bioRxiv2022

Discovery of small molecule inhibitors of Plasmodium falciparum apicoplast DNA polymerase

Malaria is caused by infection with protozoan parasites of the Plasmodium genus, which is part of the phylum Apicomplexa. Most organisms in this phylum contain a relic plastid called the apicoplast. The apicoplast genome is replicated by a single DNA polymerase (apPOL), which is an attractive target for anti-malarial drugs. We screened small-molecule libraries (206,504 compounds) using a fluorescence-based high-throughput DNA polymerase assay. Dose/response analysis and counter-screening identified 186 specific apPOL inhibitors. Toxicity screening against human HepaRG human cells removed 84 compounds and the remaining were subjected to parasite killing assays using chloroquine resistant P. falciparum parasites. Nine compounds were potent inhibitors of parasite growth and may serve as lead compounds in efforts to discover novel malaria drugs.

biochemistry↗