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BioRxiv : the Preprint Server For... Jun 2024malaria parasites invade and multiply inside red blood cells (RBCs), the most iron-rich compartment in humans. Like all cells, requires nutritional iron to support...
malaria parasites invade and multiply inside red blood cells (RBCs), the most iron-rich compartment in humans. Like all cells, requires nutritional iron to support essential metabolic pathways, but the critical mechanisms of iron acquisition and trafficking during RBC infection have remained obscure. Parasites internalize and liberate massive amounts of heme during large-scale digestion of RBC hemoglobin within an acidic food vacuole (FV) but lack a heme oxygenase to release porphyrin-bound iron. Although most FV heme is sequestered into inert hemozoin crystals, prior studies indicate that trace heme escapes biomineralization and is susceptible to non-enzymatic degradation within the oxidizing FV environment to release labile iron. Parasites retain a homolog of divalent metal transporter 1 (DMT1), a known mammalian iron transporter, but its role in iron acquisition has not been tested. Our phylogenetic studies indicate that DMT1 (PfDMT1) retains conserved molecular features critical for metal transport. We localized this protein to the FV membrane and defined its orientation in an export-competent topology. Conditional knockdown of PfDMT1 expression is lethal to parasites, which display broad cellular defects in iron-dependent functions, including impaired apicoplast biogenesis and mitochondrial polarization. Parasites are selectively rescued from partial PfDMT1 knockdown by supplementation with exogenous iron, but not other metals. These results support a cellular paradigm whereby PfDMT1 is the molecular gatekeeper to essential iron acquisition by blood-stage malaria parasites and suggest that therapeutic targeting of PfDMT1 may be a potent antimalarial strategy.
PubMed: 38798484
DOI: 10.1101/2024.05.10.587216 -
BioRxiv : the Preprint Server For... May 2024Malaria parasites have evolved unusual metabolic adaptations that specialize them for growth within heme-rich human erythrocytes. During blood-stage infection,...
Malaria parasites have evolved unusual metabolic adaptations that specialize them for growth within heme-rich human erythrocytes. During blood-stage infection, parasites internalize and digest abundant host hemoglobin within the digestive vacuole. This massive catabolic process generates copious free heme, most of which is biomineralized into inert hemozoin. Parasites also express a divergent heme oxygenase (HO)-like protein (PfHO) that lacks key active-site residues and has lost canonical HO activity. The cellular role of this unusual protein that underpins its retention by parasites has been unknown. To unravel PfHO function, we first determined a 2.8 Å-resolution X-ray structure that revealed a highly α-helical fold indicative of distant HO homology. Localization studies unveiled PfHO targeting to the apicoplast organelle, where it is imported and undergoes N-terminal processing but retains most of the electropositive transit peptide. We observed that conditional knockdown of PfHO was lethal to parasites, which died from defective apicoplast biogenesis and impaired isoprenoid-precursor synthesis. Complementation and molecular-interaction studies revealed an essential role for the electropositive N-terminus of PfHO, which selectively associates with the apicoplast genome and enzymes involved in nucleic acid metabolism and gene expression. PfHO knockdown resulted in a specific deficiency in levels of apicoplast-encoded RNA but not DNA. These studies reveal an essential function for PfHO in apicoplast maintenance and suggest that repurposed the conserved HO scaffold from its canonical heme-degrading function in the ancestral chloroplast to fulfill a critical adaptive role in organelle gene expression.
PubMed: 38853871
DOI: 10.1101/2024.05.30.596652 -
Methods in Molecular Biology (Clifton,... 2024Apicomplexan parasites are unicellular eukaryotes responsible for major human diseases such as malaria and toxoplasmosis, which cause massive social and economic burden....
Apicomplexan parasites are unicellular eukaryotes responsible for major human diseases such as malaria and toxoplasmosis, which cause massive social and economic burden. Toxoplasmosis, caused by Toxoplasma gondii, is a global chronic infectious disease affecting ~1/3 of the world population and is a major threat for any immunocompromised patient. To date, there is no efficient vaccine against these parasites and existing treatments are threatened by rapid emergence of parasite resistance. Throughout their life cycle, Apicomplexa require large amount of nutrients, especially lipids for propagation and survival. Understanding lipid acquisition is key to decipher host-parasite metabolic interactions. Parasite membrane biogenesis relies on a combination of (a) host lipid scavenging, (b) de novo lipid synthesis in the parasite, and (c) fluxes of lipids between host and parasite and within. We recently uncovered that parasite need to store the host-scavenged lipids to avoid their toxic accumulation and to mobilize them for division. How can parasites orchestrate the many lipids fluxes essential for survival? Here, we developed metabolomics approaches coupled to stable isotope labelling to track, monitor, and quantify fatty acid and lipids fluxes between the parasite, its human host cell, and its extracellular environment to unravel the complex lipid fluxes in any physiological environment the parasite could meet.
Topics: Animals; Humans; Parasites; Plastids; Fatty Acids; Toxoplasma; Toxoplasmosis; Protozoan Proteins
PubMed: 38502506
DOI: 10.1007/978-1-0716-3726-5_12 -
Biology Mar 2024DNA polymerases replicate cellular genomes and/or participate in the maintenance of genome integrity. DNA polymerases sharing high sequence homology with DNA polymerase... (Review)
Review
DNA polymerases replicate cellular genomes and/or participate in the maintenance of genome integrity. DNA polymerases sharing high sequence homology with DNA polymerase I (pol I) have been grouped in Family A. Pol I participates in Okazaki fragment maturation and in bacterial genome repair. Since its discovery in 1956, pol I has been extensively studied, primarily to gain deeper insights into the mechanism of DNA replication. As research on DNA polymerases advances, many novel functions of this group of polymerases are being uncovered. For example, human DNA polymerase θ (a Family A DNA pol) has been shown to synthesize DNA using RNA as a template, a function typically attributed to retroviral reverse transcriptase. Increased interest in drug discovery against pol θ has emerged due to its roles in cancer. Likewise, Pol I family enzymes also appear attractive as drug-development targets against microbial infections. Development of antimalarial compounds targeting apicoplast apPOL, an ortholog of Pol I, further extends the targeting of this family of enzymes. Here, we summarize reported drug-development efforts against Family A polymerases and future perspective regarding these enzymes as antibiotic targets. Recently developed techniques, such as artificial intelligence, can be used to facilitate the development of new drugs.
PubMed: 38666816
DOI: 10.3390/biology13040204 -
Experimental Parasitology Apr 2024Toxoplasmosis is a zoonosis that is a worldwide health problem, commonly affecting fetal development and immunodeficient patients. Treatment is carried out with a...
Toxoplasmosis is a zoonosis that is a worldwide health problem, commonly affecting fetal development and immunodeficient patients. Treatment is carried out with a combination of pyrimethamine and sulfadiazine, which can cause cytopenia and intolerance and does not lead to a parasitological cure of the infection. Lysine deacetylases (KDACs), which remove an acetyl group from lysine residues in histone and non-histone proteins are found in the Toxoplasma gondii genome. Previous work showed the hydroxamate-type KDAC inhibitors Tubastatin A (TST) and Vorinostat (Suberoylanilide Hydroxamic Acid, SAHA) were effective against T. gondii. In the present study, the effects of three hydroxamates (KV-24, KV-30, KV-46), which were originally designed to inhibit human KDAC6, showed different effects against T. gondii. These compounds contain a heterocyclic cap group and a benzyl linker bearing the hydroxamic acid group in para-position. All compounds showed selective activity against T. gondii proliferation, inhibiting tachyzoite proliferation with IC values in a nanomolar range after 48h treatment. Microscopy analyses showed that after treatment, tachyzoites presented mislocalization of the apicoplast, disorganization of the inner membrane complex, and arrest in the completion of new daughter cells. The number of dividing cells with incomplete endodyogeny increased significantly after treatment, indicating the compounds can interfere in the late steps of cell division. The results obtained in this work that these new hydroxamates should be considered for future in vivo tests and the development of new compounds for treating toxoplasmosis.
Topics: Humans; Toxoplasma; Lysine; Toxoplasmosis; Pyrimethamine; Hydroxamic Acids; Vorinostat
PubMed: 38431113
DOI: 10.1016/j.exppara.2024.108727 -
BioRxiv : the Preprint Server For... Jan 2024Morphological modifications and shifts in organelle relationships are hallmarks of dormancy in eukaryotic cells. Communications between altered mitochondria and nuclei...
Morphological modifications and shifts in organelle relationships are hallmarks of dormancy in eukaryotic cells. Communications between altered mitochondria and nuclei are associated with metabolic quiescence of cancer cells that can survive chemotherapy. In plants, changes in the pathways between nuclei, mitochondria, and chloroplasts are associated with cold stress and bud dormancy. parasites, the deadliest agent of malaria in humans, contain a chloroplast-like organelle (apicoplast) derived from an ancient photosynthetic symbiont. Antimalarial treatments can fail because a small fraction of the blood stage parasites enter dormancy and recrudesce after drug exposure. Altered mitochondrial-nuclear interactions in these persisters have been described for , but interactions of the apicoplast remained to be characterized. In the present study, we examined the apicoplasts of dormant persisters obtained after exposure to dihydroartemisinin (a first-line antimalarial drug) followed by sorbitol treatment, or after exposure to sorbitol treatment alone. As previously observed, the mitochondrion of persisters was consistently enlarged and in close association with the nucleus. In contrast, the apicoplast varied from compact and oblate, like those of active ring stage parasites, to enlarged and irregularly shaped. Enlarged apicoplasts became more prevalent later in dormancy, but regular size apicoplasts subsequently predominated when actively replicating parasites recrudesced. All three organelles, nucleus, mitochondrion, and apicoplast, became closer during dormancy. Understanding their relationships in erythrocytic-stage persisters may lead to new strategies to prevent recrudescences and protect the future of malaria chemotherapy.
PubMed: 38410435
DOI: 10.1101/2024.01.03.574077 -
Molecular Biology of the Cell Apr 2024Intracellular cargo transport is a ubiquitous cellular process in all eukaryotes. In many cell types, membrane bound cargo is associated with molecular motors which...
Intracellular cargo transport is a ubiquitous cellular process in all eukaryotes. In many cell types, membrane bound cargo is associated with molecular motors which transport cargo along microtubule and actin tracks. In (), an obligate intracellular parasite in the phylum Apicomplexa, organization of the endomembrane pathway depends on actin and an unconventional myosin motor, myosin F (MyoF). Loss of MyoF and actin disrupts vesicle transport, organelle positioning, and division of the apicoplast, a nonphotosynthetic plastid organelle. How this actomyosin system contributes to these cellular functions is still unclear. Using live-cell imaging, we observed that MyoF-EmeraldFP (MyoF-EmFP) displayed a dynamic and filamentous-like organization in the parasite cytosol, reminiscent of cytosolic actin filament dynamics. MyoF was not associated with the Golgi, apicoplast or dense granule surfaces, suggesting that it does not function using the canonical cargo transport mechanism. Instead, we found that loss of MyoF resulted in a dramatic rearrangement of the actin cytoskeleton in interphase parasites accompanied by significantly reduced actin dynamics. However, actin organization during parasite replication and motility was unaffected by the loss of MyoF. These findings revealed that MyoF is an actin organizing protein in and facilitates cargo movement using an unconventional transport mechanism.
Topics: Animals; Actins; Toxoplasma; Myosins; Cytoskeleton; Actin Cytoskeleton; Parasites
PubMed: 38416592
DOI: 10.1091/mbc.E23-12-0510 -
Tropical Biomedicine Sep 2023Malaria, caused by the unicellular Apicomplexan protozoa of the genus Plasmodium, is an infectious disease transmitted via female Anopheles mosquitoes. The sexual stage...
Malaria, caused by the unicellular Apicomplexan protozoa of the genus Plasmodium, is an infectious disease transmitted via female Anopheles mosquitoes. The sexual stage (gametocytes) of malaria parasites is the key to the transmission of parasites from vertebrate hosts to mosquitoes, representing critical bottleneck of the parasite life cycle. This study has established a systematic computational pipeline to achieve the genome-wide in silico analysis and find 708 novels potentially indispensable genes for gametocyte development, consisting of 644 protein coding genes, 56 ncRNA genes and 8 pseudogenes, with a total of 191 genes in the transmembrane, 29 protein coding genes to be exported proteins, and 58 genes in apicoplast regions. Furthermore, Gene Ontology analysis showed that the largest cluster was cellular processes with nucleus and cytosol highest, followed by molecular function with binding and oxidoreductase activities abundant. Meanwhile, when a text searched, using PlasmoDB, there were 300 genes with annotations of "putative", and 196 genes with annotations of "unknown function". These data would be helpful to provide potential targets for effective malaria transmission-blocking strategies.
Topics: Animals; Female; Plasmodium falciparum; Malaria, Falciparum; Malaria; Plasmodium; Anopheles
PubMed: 37897169
DOI: 10.47665/tb.40.3.012 -
Methods in Molecular Biology (Clifton,... 2024Chloroplasts are essential organelles that are responsible for photosynthesis in a wide range of organisms that have colonized all biotopes on Earth such as plants and...
Chloroplasts are essential organelles that are responsible for photosynthesis in a wide range of organisms that have colonized all biotopes on Earth such as plants and unicellular algae. Interestingly, a secondary endosymbiotic event of a red algal ancestor gave rise to a group of organisms that have adopted an obligate parasitic lifestyle named Apicomplexa parasites. Apicomplexa parasites are some of the most widespread and poorly controlled pathogens in the world. These infectious agents are responsible for major human diseases such as toxoplasmosis, caused by Toxoplasma gondii, and malaria, caused by Plasmodium spp. Most of these parasites harbor this relict plastid named the apicoplast, which is essential for parasite survival. The apicoplast has lost photosynthetic capacities but is metabolically similar to plant and algal chloroplasts. The apicoplast is considered a novel and important drug target against Apicomplexa parasites. This chapter focuses on the apicoplast of apicomplexa parasites, its maintenance, and its metabolic pathways.
Topics: Animals; Humans; Apicoplasts; Parasites; Symbiosis; Plasmodium; Toxoplasma
PubMed: 38502497
DOI: 10.1007/978-1-0716-3726-5_3 -
Veterinary Sciences Feb 2024Apicomplexan and nematodes are food-borne parasites whose life cycle is carried-out in various wildlife and domestic animals. The gray wolf () is an apex predator...
Apicomplexan and nematodes are food-borne parasites whose life cycle is carried-out in various wildlife and domestic animals. The gray wolf () is an apex predator acting as an ecosystem engineer. This study aimed to identify the species of and found in the muscles of gray wolves in Lithuania. During the 2017-2022 period, diaphragm, heart, and hind leg samples of 15 animals were examined. Microscopical analysis showed the presence of two types of parasites in 26.7% of the analyzed muscle samples. Based on the sequencing of five loci, nuclear rDNA, rDNA, , mitochondrial , and apicoplast , , and were identified. The current work presents the first report of in gray wolf. Phylogenetically, clustered together with , infecting various carnivorans, and was most closely related to from domestic cats. spp. were found in 12 gray wolves (80%). For the first time, species were molecularly identified in gray wolves from Lithuania. was confirmed in all of the isolated larvae using a multiplex PCR. Gray wolves in Lithuania may serve as a major source of zoonotic pathogens due to the presence of these parasites.
PubMed: 38393103
DOI: 10.3390/vetsci11020085