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Thompson TA, Chahine Z, Le Roch KG. The role of long noncoding RNAs in malaria parasites. Trends Parasitol 2023; 39:517-531. [PMID: 37121862 DOI: 10.1016/j.pt.2023.03.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 03/16/2023] [Accepted: 03/18/2023] [Indexed: 05/02/2023]
Abstract
The human malaria parasites, including Plasmodium falciparum, persist as a major cause of global morbidity and mortality. The recent stalling of progress toward malaria elimination substantiates a need for novel interventions. Controlled gene expression is central to the parasite's numerous life cycle transformations and adaptation. With few specific transcription factors (TFs) identified, crucial roles for chromatin states and epigenetics in parasite transcription have become evident. Although many chromatin-modifying enzymes are known, less is known about which factors mediate their impacts on transcriptional variation. Like those of higher eukaryotes, long noncoding RNAs (lncRNAs) have recently been shown to have integral roles in parasite gene regulation. This review aims to summarize recent developments and key findings on the role of lncRNAs in P. falciparum.
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Affiliation(s)
- Trevor A Thompson
- Department of Molecular, Cell and Systems Biology, University of California Riverside, CA, USA
| | - Zeinab Chahine
- Department of Molecular, Cell and Systems Biology, University of California Riverside, CA, USA
| | - Karine G Le Roch
- Department of Molecular, Cell and Systems Biology, University of California Riverside, CA, USA.
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2
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Patterns of Heterochromatin Transitions Linked to Changes in the Expression of Plasmodium falciparum Clonally Variant Genes. Microbiol Spectr 2023; 11:e0304922. [PMID: 36515553 PMCID: PMC9927496 DOI: 10.1128/spectrum.03049-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The survival of malaria parasites in the changing human blood environment largely depends on their ability to alter gene expression by epigenetic mechanisms. The active state of Plasmodium falciparum clonally variant genes (CVGs) is associated with euchromatin characterized by the histone mark H3K9ac, whereas the silenced state is characterized by H3K9me3-based heterochromatin. Expression switches are linked to euchromatin-heterochromatin transitions, but these transitions have not been characterized for the majority of CVGs. To define the heterochromatin distribution patterns associated with the alternative transcriptional states of CVGs, we compared H3K9me3 occupancy at a genome-wide level among several parasite subclones of the same genetic background that differed in the transcriptional state of many CVGs. We found that de novo heterochromatin formation or the complete disruption of a heterochromatin domain is a relatively rare event, and for the majority of CVGs, expression switches can be explained by the expansion or retraction of heterochromatin domains. We identified different modalities of heterochromatin changes linked to transcriptional differences, but despite this complexity, heterochromatin distribution patterns generally enable the prediction of the transcriptional state of specific CVGs. We also found that in some subclones, several var genes were simultaneously in an active state. Furthermore, the heterochromatin levels in the putative regulatory region of the gdv1 antisense noncoding RNA, a regulator of sexual commitment, varied between parasite lines with different sexual conversion rates. IMPORTANCE The malaria parasite P. falciparum is responsible for more than half a million deaths every year. P. falciparum clonally variant genes (CVGs) mediate fundamental host-parasite interactions and play a key role in parasite adaptation to fluctuations in the conditions of the human host. The expression of CVGs is regulated at the epigenetic level by changes in the distribution of a type of chromatin called heterochromatin. Here, we describe at a genome-wide level the changes in the heterochromatin distribution associated with the different transcriptional states of CVGs. Our results also reveal a likely role for heterochromatin at a particular locus in determining the parasite investment in transmission to mosquitoes. Additionally, this data set will enable the prediction of the transcriptional state of CVGs from epigenomic data, which is important for the study of parasite adaptation to the conditions of the host in natural malaria infections.
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3
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Real E, Nardella F, Scherf A, Mancio-Silva L. Repurposing of Plasmodium falciparum var genes beyond the blood stage. Curr Opin Microbiol 2022; 70:102207. [PMID: 36183663 DOI: 10.1016/j.mib.2022.102207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 08/26/2022] [Accepted: 09/03/2022] [Indexed: 01/25/2023]
Abstract
A commonly observed survival strategy in protozoan parasites is the sequential expression of clonally variant-surface antigens to avoid elimination by the host's immune response. In malaria-causing P. falciparum, the immunovariant erythrocyte-membrane protein-1 (PfEMP1) adhesin family, encoded by var genes, is responsible for both antigenic variation and cytoadherence of infected erythrocytes to the microvasculature. Until recently, the biological function of these variant genes was believed to be restricted to intraerythrocytic developmental stages. With the advent of new technologies, var gene expression has been confirmed in transmission and pre-erythrocytic stages. Here, we discuss how repurposing of var gene expression beyond chronic blood-stage infection may be critical for successful transmission.
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Affiliation(s)
- Eliana Real
- Institut Pasteur, Université Paris Cité, Inserm U1201, CNRS EMR9195, Unité de Biologie des Interactions Hôte-Parasite, 25 Rue du Dr Roux, F-75015 Paris, France
| | - Flore Nardella
- Institut Pasteur, Université Paris Cité, Inserm U1201, CNRS EMR9195, Unité de Biologie des Interactions Hôte-Parasite, 25 Rue du Dr Roux, F-75015 Paris, France
| | - Artur Scherf
- Institut Pasteur, Université Paris Cité, Inserm U1201, CNRS EMR9195, Unité de Biologie des Interactions Hôte-Parasite, 25 Rue du Dr Roux, F-75015 Paris, France.
| | - Liliana Mancio-Silva
- Institut Pasteur, Université Paris Cité, Inserm U1201, CNRS EMR9195, Unité de Biologie des Interactions Hôte-Parasite, 25 Rue du Dr Roux, F-75015 Paris, France.
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4
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Epigenetic and Epitranscriptomic Gene Regulation in Plasmodium falciparum and How We Can Use It against Malaria. Genes (Basel) 2022; 13:genes13101734. [PMID: 36292619 PMCID: PMC9601349 DOI: 10.3390/genes13101734] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 09/15/2022] [Accepted: 09/21/2022] [Indexed: 11/16/2022] Open
Abstract
Malaria, caused by Plasmodium parasites, is still one of the biggest global health challenges. P. falciparum is the deadliest species to humans. In this review, we discuss how this parasite develops and adapts to the complex and heterogenous environments of its two hosts thanks to varied chromatin-associated and epigenetic mechanisms. First, one small family of transcription factors, the ApiAP2 proteins, functions as master regulators of spatio-temporal patterns of gene expression through the parasite life cycle. In addition, chromatin plasticity determines variable parasite cell phenotypes that link to parasite growth, virulence and transmission, enabling parasite adaptation within host conditions. In recent years, epitranscriptomics is emerging as a new regulatory layer of gene expression. We present evidence of the variety of tRNA and mRNA modifications that are being characterized in Plasmodium spp., and the dynamic changes in their abundance during parasite development and cell fate. We end up outlining that new biological systems, like the mosquito model, to decipher the unknowns about epigenetic mechanisms in vivo; and novel methodologies, to study the function of RNA modifications; are needed to discover the Achilles heel of the parasite. With this new knowledge, future strategies manipulating the epigenetics and epitranscriptomic machinery of the parasite have the potential of providing new weapons against malaria.
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5
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Portugaliza HP, Natama HM, Guetens P, Rovira-Vallbona E, Somé AM, Millogo A, Ouédraogo DF, Valéa I, Sorgho H, Tinto H, van Hong N, Sitoe A, Varo R, Bassat Q, Cortés A, Rosanas-Urgell A. Plasmodium falciparum sexual conversion rates can be affected by artemisinin-based treatment in naturally infected malaria patients. EBioMedicine 2022; 83:104198. [PMID: 35961203 PMCID: PMC9385555 DOI: 10.1016/j.ebiom.2022.104198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 07/05/2022] [Accepted: 07/18/2022] [Indexed: 10/25/2022] Open
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6
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Epigenetics of malaria parasite nutrient uptake, but why? Trends Parasitol 2022; 38:618-628. [PMID: 35641406 PMCID: PMC9283302 DOI: 10.1016/j.pt.2022.05.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Revised: 05/01/2022] [Accepted: 05/10/2022] [Indexed: 11/23/2022]
Abstract
The conserved plasmodial surface anion channel (PSAC) mediates nutrient uptake by bloodstream malaria parasites and is an antimalarial target. This pathogen-associated channel is linked to the clag multigene family, which is variably expanded in Plasmodium spp. Member genes are under complex epigenetic regulation, with the clag3 genes of the human P. falciparum pathogen exhibiting monoallelic transcription and mutually exclusive surface exposure on infected erythrocytes. While other multigene families use monoallelic expression to evade host immunity, the reasons of epigenetic control of clag genes are unclear. I consider existing models and their implications for nutrient acquisition and immune evasion. Understanding the reasons for epigenetic regulation of PSAC-mediated nutrient uptake will help clarify host-pathogen interactions and guide development of therapies resistant to allele switching.
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7
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Tintó-Font E, Cortés A. Malaria parasites do respond to heat. Trends Parasitol 2022; 38:435-449. [PMID: 35301987 DOI: 10.1016/j.pt.2022.02.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 02/17/2022] [Accepted: 02/18/2022] [Indexed: 01/09/2023]
Abstract
The capacity of malaria parasites to respond to changes in their environment at the transcriptional level has been the subject of debate, but recent evidence has unambiguously demonstrated that Plasmodium spp. can produce adaptive transcriptional responses when exposed to some specific types of stress. These include metabolic conditions and febrile temperature. The Plasmodium falciparum protective response to thermal stress is similar to the response in other organisms, but it is regulated by a transcription factor evolutionarily unrelated to the conserved transcription factor that drives the heat shock (HS) response in most eukaryotes. Of the many genes that change expression during HS, only a subset constitutes an authentic response that contributes to parasite survival.
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Affiliation(s)
- Elisabet Tintó-Font
- ISGlobal, Hospital Clínic, Universitat de Barcelona, Barcelona 08036, Catalonia, Spain
| | - Alfred Cortés
- ISGlobal, Hospital Clínic, Universitat de Barcelona, Barcelona 08036, Catalonia, Spain; ICREA, Barcelona 08010, Catalonia, Spain.
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8
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Native structure of the RhopH complex, a key determinant of malaria parasite nutrient acquisition. Proc Natl Acad Sci U S A 2021; 118:2100514118. [PMID: 34446549 PMCID: PMC8536402 DOI: 10.1073/pnas.2100514118] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Malaria parasites invade and replicate within human red blood cells, which lack nuclei and have minimal metabolic activity. To survive, the parasites create new pathways that alter the permeability of the red blood cell membrane, allowing them to import nutrients and export waste. Here, we present the native structure of the three-membered RhopH protein complex, which plays a key role in this process. We determined the structure of this essential complex from a heterogeneous mixture of proteins enriched directly from parasite cell lysate, using a cryo-electron microscopy–enabled endogenous structural proteomics approach. The native structure of the RhopH complex in a soluble, trafficking state helps elucidate the long-standing question of how parasite transmembrane proteins are trafficked to the erythrocyte membrane. The RhopH complex is implicated in malaria parasites’ ability to invade and create new permeability pathways in host erythrocytes, but its mechanisms remain poorly understood. Here, we enrich the endogenous RhopH complex in a native soluble form, comprising RhopH2, CLAG3.1, and RhopH3, directly from parasite cell lysates and determine its atomic structure using cryo–electron microscopy (cryo-EM), mass spectrometry, and the cryoID program. CLAG3.1 is positioned between RhopH2 and RhopH3, which both share substantial binding interfaces with CLAG3.1 but make minimal contacts with each other. The forces stabilizing individual subunits include 13 intramolecular disulfide bonds. Notably, CLAG3.1 residues 1210 to 1223, previously predicted to constitute a transmembrane helix, are embedded within a helical bundle formed by residues 979 to 1289 near the C terminus of CLAG3.1. Buried in the core of the RhopH complex and largely shielded from solvent, insertion of this putative transmembrane helix into the erythrocyte membrane would likely require a large conformational rearrangement. Given the unusually high disulfide content of the complex, it is possible that such a rearrangement could be initiated by the breakage of allosteric disulfide bonds, potentially triggered by interactions at the erythrocyte membrane. This first direct observation of an exported Plasmodium falciparum transmembrane protein—in a soluble, trafficking state and with atomic details of buried putative membrane-insertion helices—offers insights into the assembly and trafficking of RhopH and other parasite-derived complexes to the erythrocyte membrane. Our study demonstrates the potential the endogenous structural proteomics approach holds for elucidating the molecular mechanisms of hard-to-isolate complexes in their native, functional forms.
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9
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Expression Patterns of Plasmodium falciparum Clonally Variant Genes at the Onset of a Blood Infection in Malaria-Naive Humans. mBio 2021; 12:e0163621. [PMID: 34340541 PMCID: PMC8406225 DOI: 10.1128/mbio.01636-21] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clonally variant genes (CVGs) play fundamental roles in the adaptation of Plasmodium falciparum to fluctuating conditions of the human host. However, their expression patterns under the natural conditions of the blood circulation have been characterized in detail for only a few specific gene families. Here, we provide a detailed characterization of the complete P. falciparum transcriptome across the full intraerythrocytic development cycle (IDC) at the onset of a blood infection in malaria-naive human volunteers. We found that the vast majority of transcriptional differences between parasites obtained from the volunteers and the parental parasite line maintained in culture occurred in CVGs. In particular, we observed a major increase in the transcript levels of most genes of the pfmc-2tm and gbp families and of specific genes of other families, such as phist, hyp10, rif, or stevor, in addition to previously reported changes in var and clag3 gene expression. Increased transcript levels of individual pfmc-2tm, rif, and stevor genes involved activation in small subsets of parasites. Large transcriptional differences correlated with changes in the distribution of heterochromatin, confirming their epigenetic nature. Furthermore, the similar expression of several CVGs between parasites collected at different time points along the blood infection suggests that the epigenetic memory for multiple CVG families is lost during transmission stages, resulting in a reset of their transcriptional state. Finally, the CVG expression patterns observed in a volunteer likely infected by a single sporozoite suggest that new epigenetic patterns are established during liver stages.
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10
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Schureck MA, Darling JE, Merk A, Shao J, Daggupati G, Srinivasan P, Olinares PDB, Rout MP, Chait BT, Wollenberg K, Subramaniam S, Desai SA. Malaria parasites use a soluble RhopH complex for erythrocyte invasion and an integral form for nutrient uptake. eLife 2021; 10:e65282. [PMID: 33393463 PMCID: PMC7840181 DOI: 10.7554/elife.65282] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Accepted: 01/04/2021] [Indexed: 12/12/2022] Open
Abstract
Malaria parasites use the RhopH complex for erythrocyte invasion and channel-mediated nutrient uptake. As the member proteins are unique to Plasmodium spp., how they interact and traffic through subcellular sites to serve these essential functions is unknown. We show that RhopH is synthesized as a soluble complex of CLAG3, RhopH2, and RhopH3 with 1:1:1 stoichiometry. After transfer to a new host cell, the complex crosses a vacuolar membrane surrounding the intracellular parasite and becomes integral to the erythrocyte membrane through a PTEX translocon-dependent process. We present a 2.9 Å single-particle cryo-electron microscopy structure of the trafficking complex, revealing that CLAG3 interacts with the other subunits over large surface areas. This soluble complex is tightly assembled with extensive disulfide bonding and predicted transmembrane helices shielded. We propose a large protein complex stabilized for trafficking but poised for host membrane insertion through large-scale rearrangements, paralleling smaller two-state pore-forming proteins in other organisms.
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Affiliation(s)
- Marc A Schureck
- Laboratory of Malaria and Vector Research, NIAID, National Institutes of HealthRockvilleUnited States
| | - Joseph E Darling
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of HealthBethesdaUnited States
| | - Alan Merk
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of HealthBethesdaUnited States
| | - Jinfeng Shao
- Laboratory of Malaria and Vector Research, NIAID, National Institutes of HealthRockvilleUnited States
| | - Geervani Daggupati
- Department of Molecular Microbiology and Immunology, and Johns Hopkins Malaria Institute, Johns Hopkins Bloomberg School of Public HealthBaltimoreUnited States
| | - Prakash Srinivasan
- Department of Molecular Microbiology and Immunology, and Johns Hopkins Malaria Institute, Johns Hopkins Bloomberg School of Public HealthBaltimoreUnited States
| | - Paul Dominic B Olinares
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller UniversityNew YorkUnited States
| | - Michael P Rout
- Laboratory of Cellular and Structural Biology, The Rockefeller UniversityNew YorkUnited States
| | - Brian T Chait
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller UniversityNew YorkUnited States
| | - Kurt Wollenberg
- Office of Cyber Infrastructure & Computational Biology, National Institute of Allergy and Infectious Diseases, National Institutes of HealthBethesdaUnited States
| | - Sriram Subramaniam
- Department of Biochemistry and Molecular Biology, University of British ColumbiaVancouverCanada
| | - Sanjay A Desai
- Laboratory of Malaria and Vector Research, NIAID, National Institutes of HealthRockvilleUnited States
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11
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Transcriptional Analysis of Tightly Synchronized Plasmodium falciparum Intraerythrocytic Stages by RT-qPCR. Methods Mol Biol 2021; 2369:165-185. [PMID: 34313989 DOI: 10.1007/978-1-0716-1681-9_10] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
In Plasmodium falciparum, the parasite responsible for the most severe forms of human malaria, many fundamental processes are controlled at the transcriptional level. Studies on diverse aspects of basic parasite biology as well as molecular epidemiology studies often rely on the ability to accurately measure transcript levels, but this is complicated by the cyclic expression patterns of the majority of malaria parasite genes. Here, we provide a complete workflow to measure transcript levels in P. falciparum intraerythrocytic blood stages, overcoming the confounding factors that are commonly encountered. The method described covers all the steps from synchronization of parasite cultures to reverse transcriptase quantitative PCR (RT-qPCR) analysis.
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12
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Hollin T, Le Roch KG. From Genes to Transcripts, a Tightly Regulated Journey in Plasmodium. Front Cell Infect Microbiol 2020; 10:618454. [PMID: 33425787 PMCID: PMC7793691 DOI: 10.3389/fcimb.2020.618454] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Accepted: 11/19/2020] [Indexed: 12/17/2022] Open
Abstract
Over the past decade, we have witnessed significant progresses in understanding gene regulation in Apicomplexa including the human malaria parasite, Plasmodium falciparum. This parasite possesses the ability to convert in multiple stages in various hosts, cell types, and environments. Recent findings indicate that P. falciparum is talented at using efficient and complementary molecular mechanisms to ensure a tight control of gene expression at each stage of its life cycle. Here, we review the current understanding on the contribution of the epigenome, atypical transcription factors, and chromatin organization to regulate stage conversion in P. falciparum. The adjustment of these regulatory mechanisms occurring during the progression of the life cycle will be extensively discussed.
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Affiliation(s)
- Thomas Hollin
- Department of Molecular, Cell and Systems Biology, University of California Riverside, CA, United States
| | - Karine G Le Roch
- Department of Molecular, Cell and Systems Biology, University of California Riverside, CA, United States
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13
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Portugaliza HP, Miyazaki S, Geurten FJ, Pell C, Rosanas-Urgell A, Janse CJ, Cortés A. Artemisinin exposure at the ring or trophozoite stage impacts Plasmodium falciparum sexual conversion differently. eLife 2020; 9:60058. [PMID: 33084568 PMCID: PMC7577739 DOI: 10.7554/elife.60058] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 10/07/2020] [Indexed: 12/12/2022] Open
Abstract
Malaria transmission is dependent on the formation of gametocytes in the human blood. The sexual conversion rate, the proportion of asexual parasites that convert into gametocytes at each multiplication cycle, is variable and reflects the relative parasite investment between transmission and maintaining the infection. The impact of environmental factors such as drugs on sexual conversion rates is not well understood. We developed a robust assay using gametocyte-reporter parasite lines to accurately measure the impact of drugs on sexual conversion rates, independently from their gametocytocidal activity. We found that exposure to subcurative doses of the frontline antimalarial drug dihydroartemisinin (DHA) at the trophozoite stage resulted in a ~ fourfold increase in sexual conversion. In contrast, no increase was observed when ring stages were exposed or in cultures in which sexual conversion was stimulated by choline depletion. Our results reveal a complex relationship between antimalarial drugs and sexual conversion, with potential public health implications.
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Affiliation(s)
- Harvie P Portugaliza
- ISGlobal, Hospital Clinic - Universitat de Barcelona, Barcelona, Spain.,Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.,Department of Global Health, Amsterdam University Medical Centers, location Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Shinya Miyazaki
- Department of Parasitology, Leiden University Medical Center, Leiden, Netherlands
| | - Fiona Ja Geurten
- Department of Parasitology, Leiden University Medical Center, Leiden, Netherlands
| | - Christopher Pell
- Department of Global Health, Amsterdam University Medical Centers, location Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands.,Amsterdam Institute for Global Health and Development (AIGHD), Amsterdam, Netherlands
| | - Anna Rosanas-Urgell
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Chris J Janse
- Department of Parasitology, Leiden University Medical Center, Leiden, Netherlands
| | - Alfred Cortés
- ISGlobal, Hospital Clinic - Universitat de Barcelona, Barcelona, Spain.,ICREA, Barcelona, Spain
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14
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Llorà-Batlle O, Michel-Todó L, Witmer K, Toda H, Fernández-Becerra C, Baum J, Cortés A. Conditional expression of PfAP2-G for controlled massive sexual conversion in Plasmodium falciparum. SCIENCE ADVANCES 2020; 6:eaaz5057. [PMID: 32577509 PMCID: PMC7286680 DOI: 10.1126/sciadv.aaz5057] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Accepted: 04/15/2020] [Indexed: 05/19/2023]
Abstract
Malaria transmission requires that some asexual parasites convert into sexual forms termed gametocytes. The initial stages of sexual development, including sexually committed schizonts and sexual rings, remain poorly characterized, mainly because they are morphologically identical to their asexual counterparts and only a small subset of parasites undergo sexual development. Here, we describe a system for controlled sexual conversion in the human malaria parasite Plasmodium falciparum, based on conditional expression of the PfAP2-G transcription factor. Using this system, ~90 percent of the parasites converted into sexual forms upon induction, enabling the characterization of committed and early sexual stages without further purification. We characterized sexually committed schizonts and sexual rings at the transcriptomic and phenotypic levels, which revealed down-regulation of genes involved in solute transport upon sexual commitment, among other findings. The new inducible lines will facilitate the study of early sexual stages at additional levels, including multiomic characterization and drug susceptibility assays.
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Affiliation(s)
- Oriol Llorà-Batlle
- ISGlobal, Hospital Clinic–Universitat de Barcelona, Barcelona 08036, Catalonia, Spain
| | - Lucas Michel-Todó
- ISGlobal, Hospital Clinic–Universitat de Barcelona, Barcelona 08036, Catalonia, Spain
| | - Kathrin Witmer
- Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK
| | - Haruka Toda
- ISGlobal, Hospital Clinic–Universitat de Barcelona, Barcelona 08036, Catalonia, Spain
| | - Carmen Fernández-Becerra
- ISGlobal, Hospital Clinic–Universitat de Barcelona, Barcelona 08036, Catalonia, Spain
- IGTP Institut d’Investigació Germans Trias i Pujol, Badalona 08916, Catalonia, Spain
| | - Jake Baum
- Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK
| | - Alfred Cortés
- ISGlobal, Hospital Clinic–Universitat de Barcelona, Barcelona 08036, Catalonia, Spain
- ICREA, Barcelona 08010, Catalonia, Spain
- Corresponding author.
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15
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Ruiz JL, Gómez-Díaz E. The second life of Plasmodium in the mosquito host: gene regulation on the move. Brief Funct Genomics 2020; 18:313-357. [PMID: 31058281 DOI: 10.1093/bfgp/elz007] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 03/08/2019] [Accepted: 03/26/2019] [Indexed: 01/08/2023] Open
Abstract
Malaria parasites face dynamically changing environments and strong selective constraints within human and mosquito hosts. To survive such hostile and shifting conditions, Plasmodium switches transcriptional programs during development and has evolved mechanisms to adjust its phenotype through heterogeneous patterns of gene expression. In vitro studies on culture-adapted isolates have served to set the link between chromatin structure and functional gene expression. Yet, experimental evidence is limited to certain stages of the parasite in the vertebrate, i.e. blood, while the precise mechanisms underlying the dynamic regulatory landscapes during development and in the adaptation to within-host conditions remain poorly understood. In this review, we discuss available data on transcriptional and epigenetic regulation in Plasmodium mosquito stages in the context of sporogonic development and phenotypic variation, including both bet-hedging and environmentally triggered direct transcriptional responses. With this, we advocate the mosquito offers an in vivo biological model to investigate the regulatory networks, transcription factors and chromatin-modifying enzymes and their modes of interaction with regulatory sequences, which might be responsible for the plasticity of the Plasmodium genome that dictates stage- and cell type-specific blueprints of gene expression.
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Affiliation(s)
- José L Ruiz
- Instituto de Parasitología y Biomedicina López-Neyra (IPBLN), Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Elena Gómez-Díaz
- Instituto de Parasitología y Biomedicina López-Neyra (IPBLN), Consejo Superior de Investigaciones Científicas, Granada, Spain
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16
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Llorà-Batlle O, Tintó-Font E, Cortés A. Transcriptional variation in malaria parasites: why and how. Brief Funct Genomics 2020; 18:329-341. [PMID: 31114839 DOI: 10.1093/bfgp/elz009] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 02/04/2019] [Accepted: 04/10/2019] [Indexed: 12/24/2022] Open
Abstract
Transcriptional differences enable the generation of alternative phenotypes from the same genome. In malaria parasites, transcriptional plasticity plays a major role in the process of adaptation to fluctuations in the environment. Multiple studies with culture-adapted parasites and field isolates are starting to unravel the different transcriptional alternatives available to Plasmodium falciparum and the underlying molecular mechanisms. Here we discuss how epigenetic variation, directed transcriptional responses and also genetic changes that affect transcript levels can all contribute to transcriptional variation and, ultimately, parasite survival. Some transcriptional changes are driven by stochastic events. These changes can occur spontaneously, resulting in heterogeneity within parasite populations that provides the grounds for adaptation by dynamic natural selection. However, transcriptional changes can also occur in response to external cues. A better understanding of the mechanisms that the parasite has evolved to alter its transcriptome may ultimately contribute to the design of strategies to combat malaria to which the parasite cannot adapt.
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Affiliation(s)
- Oriol Llorà-Batlle
- ISGlobal, Hospital Clínic - Universitat de Barcelona, 08036 Barcelona, Catalonia, Spain
| | - Elisabet Tintó-Font
- ISGlobal, Hospital Clínic - Universitat de Barcelona, 08036 Barcelona, Catalonia, Spain
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17
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Oli AN, Obialor WO, Ifeanyichukwu MO, Odimegwu DC, Okoyeh JN, Emechebe GO, Adejumo SA, Ibeanu GC. Immunoinformatics and Vaccine Development: An Overview. Immunotargets Ther 2020; 9:13-30. [PMID: 32161726 PMCID: PMC7049754 DOI: 10.2147/itt.s241064] [Citation(s) in RCA: 102] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 01/25/2020] [Indexed: 12/11/2022] Open
Abstract
The use of vaccines have resulted in a remarkable improvement in global health. It has saved several lives, reduced treatment costs and raised the quality of animal and human lives. Current traditional vaccines came empirically with either vague or completely no knowledge of how they modulate our immune system. Even at the face of potential vaccine design advance, immune-related concerns (as seen with specific vulnerable populations, cases of emerging/re-emerging infectious disease, pathogens with complex lifecycle and antigenic variability, need for personalized vaccinations, and concerns for vaccines' immunological safety -specifically vaccine likelihood to trigger non-antigen-specific responses that may cause autoimmunity and vaccine allergy) are being raised. And these concerns have driven immunologists toward research for a better approach to vaccine design that will consider these challenges. Currently, immunoinformatics has paved the way for a better understanding of some infectious disease pathogenesis, diagnosis, immune system response and computational vaccinology. The importance of this immunoinformatics in the study of infectious diseases is diverse in terms of computational approaches used, but is united by common qualities related to host–pathogen relationship. Bioinformatics methods are also used to assign functions to uncharacterized genes which can be targeted as a candidate in vaccine design and can be a better approach toward the inclusion of women that are pregnant into vaccine trials and programs. The essence of this review is to give insight into the need to focus on novel computational, experimental and computation-driven experimental approaches for studying of host–pathogen interactions and thus making a case for its use in vaccine development.
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Affiliation(s)
- Angus Nnamdi Oli
- Department of Pharmaceutical Microbiology and Biotechnology, Faculty of Pharmaceutical Sciences, Nnamdi Azikiwe University, Awka, Nigeria
| | - Wilson Okechukwu Obialor
- Department of Pharmaceutical Microbiology and Biotechnology, Faculty of Pharmaceutical Sciences, Nnamdi Azikiwe University, Awka, Nigeria
| | - Martins Ositadimma Ifeanyichukwu
- Department of Immunology, College of Health Sciences, Faculty of Medicine, Nnamdi Azikiwe University, Anambra, Nigeria.,Department of Medical Laboratory Science,Faculty of Health Science and Technology, College of Health Sciences, Nnamdi Azikiwe University,Nnewi Campus, Nnewi, Nigeria
| | - Damian Chukwu Odimegwu
- Department of Pharmaceutical Microbiology and Biotechnology, Faculty of Pharmaceutical Sciences, University of Nigeria Nsukka, Enugu, Nigeria
| | - Jude Nnaemeka Okoyeh
- Department of Biology and Clinical Laboratory Science, Division of Arts and Sciences, Neumann University, Aston, PA 19014-1298, USA
| | - George Ogonna Emechebe
- Department of Pediatrics, Faculty of Clinical Medicine, Chukwuemeka Odumegwu Ojukwu University, Awka, Nigeria
| | - Samson Adedeji Adejumo
- Department of Pharmaceutical Microbiology and Biotechnology, Faculty of Pharmaceutical Sciences, Nnamdi Azikiwe University, Awka, Nigeria
| | - Gordon C Ibeanu
- Department of Pharmaceutical Science, North Carolina Central University, Durham, NC 27707, USA
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18
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Gupta A, Bokhari AAB, Pillai AD, Crater AK, Gezelle J, Saggu G, Nasamu AS, Ganesan SM, Niles JC, Desai SA. Complex nutrient channel phenotypes despite Mendelian inheritance in a Plasmodium falciparum genetic cross. PLoS Pathog 2020; 16:e1008363. [PMID: 32069335 PMCID: PMC7048409 DOI: 10.1371/journal.ppat.1008363] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 02/28/2020] [Accepted: 01/28/2020] [Indexed: 12/30/2022] Open
Abstract
Malaria parasites activate a broad-selectivity ion channel on their host erythrocyte membrane to obtain essential nutrients from the bloodstream. This conserved channel, known as the plasmodial surface anion channel (PSAC), has been linked to parasite clag3 genes in P. falciparum, but epigenetic switching between the two copies of this gene hinders clear understanding of how the encoded protein determines PSAC activity. Here, we used linkage analysis in a P. falciparum cross where one parent carries a single clag3 gene to overcome the effects of switching and confirm a primary role of the clag3 product with high confidence. Despite Mendelian inheritance, CLAG3 conditional knockdown revealed remarkably preserved nutrient and solute uptake. Even more surprisingly, transport remained sensitive to a CLAG3 isoform-specific inhibitor despite quantitative knockdown, indicating that low doses of the CLAG3 transgene are sufficient to confer block. We then produced a complete CLAG3 knockout line and found it exhibits an incomplete loss of transport activity, in contrast to rhoph2 and rhoph3, two PSAC-associated genes that cannot be disrupted because nutrient uptake is abolished in their absence. Although the CLAG3 knockout did not incur a fitness cost under standard nutrient-rich culture conditions, this parasite could not be propagated in a modified medium that more closely resembles human plasma. These studies implicate oligomerization of CLAG paralogs encoded by various chromosomes in channel formation. They also reveal that CLAG3 is dispensable under standard in vitro conditions but required for propagation under physiological conditions.
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Affiliation(s)
- Ankit Gupta
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Abdullah A. B. Bokhari
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Ajay D. Pillai
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Anna K. Crater
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Jeanine Gezelle
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Gagandeep Saggu
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Armiyaw S. Nasamu
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Suresh M. Ganesan
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Jacquin C. Niles
- Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Sanjay A. Desai
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
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19
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Reporter lines based on the gexp02 promoter enable early quantification of sexual conversion rates in the malaria parasite Plasmodium falciparum. Sci Rep 2019; 9:14595. [PMID: 31601834 PMCID: PMC6787211 DOI: 10.1038/s41598-019-50768-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Accepted: 09/16/2019] [Indexed: 12/19/2022] Open
Abstract
Transmission of malaria parasites from humans to mosquito vectors requires that some asexual parasites differentiate into sexual forms termed gametocytes. The balance between proliferation in the same host and conversion into transmission forms can be altered by the conditions of the environment. The ability to accurately measure the rate of sexual conversion under different conditions is essential for research addressing the mechanisms underlying sexual conversion, and to assess the impact of environmental factors. Here we describe new Plasmodium falciparum transgenic lines with genome-integrated constructs in which a fluorescent reporter is expressed under the control of the promoter of the gexp02 gene. Using these parasite lines, we developed a sexual conversion assay that shortens considerably the time needed for an accurate determination of sexual conversion rates, and dispenses the need to add chemicals to inhibit parasite replication. Furthermore, we demonstrate that gexp02 is expressed specifically in sexual parasites, with expression starting as early as the sexual ring stage, which makes it a candidate marker for circulating sexual rings in epidemiological studies.
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20
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Ruiz JL, Tena JJ, Bancells C, Cortés A, Gómez-Skarmeta JL, Gómez-Díaz E. Characterization of the accessible genome in the human malaria parasite Plasmodium falciparum. Nucleic Acids Res 2019; 46:9414-9431. [PMID: 30016465 PMCID: PMC6182165 DOI: 10.1093/nar/gky643] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2018] [Accepted: 07/10/2018] [Indexed: 12/27/2022] Open
Abstract
Human malaria is a devastating disease and a major cause of poverty in resource-limited countries. To develop and adapt within hosts Plasmodium falciparum undergoes drastic switches in gene expression. To identify regulatory regions in the parasite genome, we performed genome-wide profiling of chromatin accessibility in two culture-adapted isogenic subclones at four developmental stages during the intraerythrocytic cycle by using the Assay for Transposase-Accessible Chromatin by sequencing (ATAC-seq). Tn5 transposase hypersensitivity sites (THSSs) localize preferentially at transcriptional start sites (TSSs). Chromatin accessibility by ATAC-seq is predictive of active transcription and of the levels of histone marks H3K9ac and H3K4me3. Our assay allows the identification of novel regulatory regions including TSS and enhancer-like elements. We show that the dynamics in the accessible chromatin profile matches temporal transcription during development. Motif analysis of stage-specific ATAC-seq sites predicts the in vivo binding sites and function of multiple ApiAP2 transcription factors. At last, the alternative expression states of some clonally variant genes (CVGs), including eba, phist, var and clag genes, associate with a differential ATAC-seq signal at their promoters. Altogether, this study identifies genome-wide regulatory regions likely to play an essential function in the developmental transitions and in CVG expression in P. falciparum.
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Affiliation(s)
- José Luis Ruiz
- Estación Biológica de Doñana (EBD), Consejo Superior de Investigaciones Científicas, Seville 41092, Spain
| | - Juan J Tena
- Centro Andaluz de Biología del Desarrollo (CABD), Consejo Superior de Investigaciones Científicas-Universidad Pablo de Olavide-Junta de Andalucía, Seville 41013, Spain
| | - Cristina Bancells
- ISGlobal, Hospital Clínic - Universitat de Barcelona, Barcelona, Catalonia 08036, Spain
| | - Alfred Cortés
- ISGlobal, Hospital Clínic - Universitat de Barcelona, Barcelona, Catalonia 08036, Spain.,ICREA, Barcelona, Catalonia 08010, Spain
| | - José Luis Gómez-Skarmeta
- Centro Andaluz de Biología del Desarrollo (CABD), Consejo Superior de Investigaciones Científicas-Universidad Pablo de Olavide-Junta de Andalucía, Seville 41013, Spain
| | - Elena Gómez-Díaz
- Estación Biológica de Doñana (EBD), Consejo Superior de Investigaciones Científicas, Seville 41092, Spain.,Instituto de Parasitología y Biomedicina 'López-Neyra' (IPBLN), Consejo Superior de Investigaciones Científicas, Granada 18016, Spain
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21
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Identification of Antimalarial Compounds That Require CLAG3 for Their Uptake by Plasmodium falciparum-Infected Erythrocytes. Antimicrob Agents Chemother 2019; 63:AAC.00052-19. [PMID: 30782998 DOI: 10.1128/aac.00052-19] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 02/01/2019] [Indexed: 01/15/2023] Open
Abstract
During the intraerythrocytic asexual cycle malaria parasites acquire nutrients and other solutes through a broad selectivity channel localized at the membrane of the infected erythrocyte termed the plasmodial surface anion channel (PSAC). The protein product of the Plasmodium falciparum clonally variant clag3.1 and clag3.2 genes determines PSAC activity. Switches in the expression of clag3 genes, which are regulated by epigenetic mechanisms, are associated with changes in PSAC-dependent permeability that can result in resistance to compounds toxic for the parasite, such as blasticidin S. Here, we investigated whether other antimalarial drugs require CLAG3 to reach their intracellular target and consequently are prone to parasite resistance by epigenetic mechanisms. We found that the bis-thiazolium salts T3 (also known as albitiazolium) and T16 require the product of clag3 genes to enter infected erythrocytes. P. falciparum populations can develop resistance to these compounds via the selection of parasites with dramatically reduced expression of both genes. However, other compounds previously demonstrated or predicted to enter infected erythrocytes through transport pathways absent from noninfected erythrocytes, such as fosmidomycin, doxycycline, azithromycin, lumefantrine, or pentamidine, do not require expression of clag3 genes for their antimalarial activity. This suggests that they use alternative CLAG3-independent routes to access parasites. Our results demonstrate that P. falciparum can develop resistance to diverse antimalarial compounds by epigenetic changes in the expression of clag3 genes. This is of concern for drug development efforts because drug resistance by epigenetic mechanisms can arise quickly, even during the course of a single infection.
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22
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Bancells C, Llorà-Batlle O, Poran A, Nötzel C, Rovira-Graells N, Elemento O, Kafsack BFC, Cortés A. Revisiting the initial steps of sexual development in the malaria parasite Plasmodium falciparum. Nat Microbiol 2019; 4:144-154. [PMID: 30478286 PMCID: PMC6294672 DOI: 10.1038/s41564-018-0291-7] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 10/11/2018] [Indexed: 01/01/2023]
Abstract
Human to vector transmission of malaria requires that some blood-stage parasites abandon asexual growth and convert into non-replicating sexual forms called gametocytes. The initial steps of gametocytogenesis remain largely uncharacterized. Here, we study this part of the malaria life cycle in Plasmodium falciparum using PfAP2-G, the master regulator of sexual conversion, as a marker of commitment. We demonstrate the existence of PfAP2-G-positive sexually committed parasite stages that precede the previously known committed schizont stage. We also found that sexual conversion can occur by two different routes: the previously described route in which PfAP2-G-expressing parasites complete a replicative cycle as committed forms before converting into gametocytes upon re-invasion, or a direct route with conversion within the same cycle as initial PfAP2-G expression. The latter route is linked to early PfAP2-G expression in ring stages. Reanalysis of published single-cell RNA-sequencing (RNA-seq) data confirmed the presence of both routes. Consistent with these results, using plaque assays we observed that, in contrast to the prevailing model, many schizonts produced mixed plaques containing both asexual parasites and gametocytes. Altogether, our results reveal unexpected features of the initial steps of sexual development and extend the current view of this part of the malaria life cycle.
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Affiliation(s)
- Cristina Bancells
- ISGlobal, Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
| | | | - Asaf Poran
- Institute for Computational Biomedicine, Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, USA
- Caryl and Israel Englander Institute for Precision Medicine, Weill Cornell Medicine, New York, NY, USA
- Physiology, Biophysics and Systems Biology Graduate Program, Weill Cornell Medicine, New York, NY, USA
| | - Christopher Nötzel
- Biochemistry, Cell & Molecular Biology Graduate Program, Weill Cornell Medicine, New York, NY, USA
- Department of Microbiology & Immunology, Weill Cornell Medicine, New York, NY, USA
| | | | - Olivier Elemento
- Institute for Computational Biomedicine, Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, USA
- Caryl and Israel Englander Institute for Precision Medicine, Weill Cornell Medicine, New York, NY, USA
| | - Björn F C Kafsack
- Department of Microbiology & Immunology, Weill Cornell Medicine, New York, NY, USA
| | - Alfred Cortés
- ISGlobal, Hospital Clínic - Universitat de Barcelona, Barcelona, Spain.
- ICREA, Barcelona, Spain.
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23
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Abstract
Controlled human malaria infection (CHMI) entails deliberate infection with malaria parasites either by mosquito bite or by direct injection of sporozoites or parasitized erythrocytes. When required, the resulting blood-stage infection is curtailed by the administration of antimalarial drugs. Inducing a malaria infection via inoculation with infected blood was first used as a treatment (malariotherapy) for neurosyphilis in Europe and the United States in the early 1900s. More recently, CHMI has been applied to the fields of malaria vaccine and drug development, where it is used to evaluate products in well-controlled early-phase proof-of-concept clinical studies, thus facilitating progression of only the most promising candidates for further evaluation in areas where malaria is endemic. Controlled infections have also been used to immunize against malaria infection. Historically, CHMI studies have been restricted by the need for access to insectaries housing infected mosquitoes or suitable malaria-infected individuals. Evaluation of vaccine and drug candidates has been constrained in these studies by the availability of a limited number of Plasmodium falciparum isolates. Recent advances have included cryopreservation of sporozoites, the manufacture of well-characterized and genetically distinct cultured malaria cell banks for blood-stage infection, and the availability of Plasmodium vivax-specific reagents. These advances will help to accelerate malaria vaccine and drug development by making the reagents for CHMI more widely accessible and also enabling a more rigorous evaluation with multiple parasite strains and species. Here we discuss the different applications of CHMI, recent advances in the use of CHMI, and ongoing challenges for consideration.
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