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Ullah I, Farringer MA, Burkhard AY, Hathaway E, Khushu M, Willett BC, Shin SH, Sharma AI, Martin MC, Shao KL, Dvorin JD, Hartl DL, Volkman SK, Bopp S, Absalon S, Wirth DF. Artemisinin resistance mutations in Pfcoronin impede hemoglobin uptake. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.12.22.572193. [PMID: 38187525 PMCID: PMC10769401 DOI: 10.1101/2023.12.22.572193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
Artemisinin (ART) combination therapies have been critical in reducing malaria morbidity and mortality, but these important drugs are threatened by growing resistance associated with mutations in Pfcoronin and Pfkelch13 . Here, we describe the mechanism of Pfcoronin -mediated ART resistance. Pf Coronin interacts with Pf Actin and localizes to the parasite plasma membrane (PPM), the digestive vacuole (DV) membrane, and membrane of a newly identified preDV compartment-all structures involved in the trafficking of hemoglobin from the RBC for degradation in the DV. Pfcoronin mutations alter Pf Actin homeostasis and impair the development and morphology of the preDV. Ultimately, these changes are associated with decreased uptake of red blood cell cytosolic contents by ring-stage Plasmodium falciparum . Previous work has identified decreased hemoglobin uptake as the mechanism of Pfkelch 13-mediated ART resistance. This work demonstrates that Pf Coronin appears to act via a parallel pathway. For both Pfkelch13 -mediated and Pfcoronin -mediated ART resistance, we hypothesize that the decreased hemoglobin uptake in ring stage parasites results in less heme-based activation of the artemisinin endoperoxide ring and reduced cytocidal activity. This study deepens our understanding of ART resistance, as well as hemoglobin uptake and development of the DV in early-stage parasites.
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Kumatia EK, Zoiku FK, Asase A, Tung NH. In vitro and in silico anti-malarial activity and cytotoxicity of n-hexyl 1-O-rutinoside (a glycoside) isolated from Annickia polycarpa (DC.) Setten and Maas ex I.M. Turner (Annonaceae). JOURNAL OF ETHNOPHARMACOLOGY 2024; 319:117287. [PMID: 37827299 DOI: 10.1016/j.jep.2023.117287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 09/27/2023] [Accepted: 10/04/2023] [Indexed: 10/14/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Annickia polycarpa leaf is an effective anti-malarial agent. However, its chemical constituents have not been isolated and assayed against any pathogen. AIM OF THE STUDY To isolate and characterize anti-malarial compound(s) from the leaf of A. polycarpa. MATERIALS AND METHODS Bioassay-guided fractionation was employed to isolated the compound (AL1) from the chloroform fraction (ALCF) of the basified ethanol extract of A. polycarpa leaf (ALE). AL1 was characterized by LC-MS, 1D and 2D NMR spectroscopic analysis. Anti-malarial activity was evaluated against drug resistance Dd2 and drug sensitive 3D7 Plasmodium falciparum strains using the SYBR green assay. Cytotoxicity and mechanistic studies were determined using tetrazolium-based colorimetric assay and molecular docking respectively. RESULTS AL1 was characterized as n-hexyl 1-O-rutinoside. The IC50 values of ALE and ALCF against 3D7 and Dd2 P. falciparum strains ranges from 3.441 (0.3389) - 4.255 (0.2246) μg/mL. The IC50s obtained for n-hexyl 1-O-rutinoside and Artesunate (standard drug) were 7.71 (0.5473) and 0.001 (0.00008) nM against the 3D7 parasite strain respectively. Also, the efficacy of n-hexyl 1-O-rutinoside increased by 24.40% against the chloroquine resistance Dd2 P. falciparum strain whiles that of Artesunate decreased by 98.96%. Furthermore, ALE, ALCF and n-hexyl 1-O-rutinoside were weakly cytotoxic to human RBCs with high selectivity indices. N-hexyl 1-O-rutinoside inhibits P. falciparum chloroquine resistance transporter (PfCRT) and dihydrofolate reductase-thymidylate synthase (PfDHFR-TS) better than chloroquine and pyrimethamine respectively. But, produced similar inhibition of P. falciparum 2-trans-enoyl -ACP-reductase (PfERN) as triclosan. CONCLUSION These results show that A. polycarpa leaf and n-hexyl 1-O-rutinoside possessed profound anti-malarial activity and are not cytotoxic. N-hexyl 1-O-rutinoside could therefore, be developed into a new anti-malarial medicine. This is the first study to report the anti-malarial activity of n-hexyl 1-O-rutinoside and its isolation from the genus Annickia.
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Affiliation(s)
- Emmanuel Kofi Kumatia
- Department of Phytochemistry, Centre for Plant Medicine Research, Mampong-Akwapim, Ghana; Department of Quality Management, Centre for Plant Medicine Research, Mampong-Akwapim, Ghana.
| | - Felix Kwame Zoiku
- Depaertment of Epidemiology, Nouguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana.
| | - Alex Asase
- Plant Development Department, Centre for Plant Medicine Research, Mampong-Akwapim, Ghana.
| | - Nguyen Huu Tung
- Faculty of Pharmacy, Phenikaa University, Hanoi 12116, Viet Nam.
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Mandal A, Kushwaha R, Mandal AA, Bajpai S, Yadav AK, Banerjee S. Transition Metal Complexes as Antimalarial Agents: A Review. ChemMedChem 2023; 18:e202300326. [PMID: 37436090 DOI: 10.1002/cmdc.202300326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 07/11/2023] [Accepted: 07/11/2023] [Indexed: 07/13/2023]
Abstract
In antimalarial drug development research, overcoming drug resistance has been a major challenge for researchers. Nowadays, several drugs like chloroquine, mefloquine, sulfadoxine, and artemisinin are used to treat malaria. But increment in drug resistance has pushed researchers to find novel drugs to tackle drug resistance problems. The idea of using transition metal complexes with pharmacophores as ligands/ligand pendants to show enhanced antimalarial activity with a novel mechanism of action has gained significant attention recently. The advantages of metal complexes include tunable chemical/physical properties, redox activity, avoiding resistance factors, etc. Several recent reports have successfully demonstrated that the metal complexation of known organic antimalarial drugs can overcome drug resistance by showing enhanced activities than the parent drugs. This review has discussed the fruitful research works done in the past few years falling into this criterion. Based on transition metal series (3d, 4d, or 5d), the antimalarial metal complexes have been divided into three broad categories (3d, 4d, or 5d metal-based), and their activities have been compared with the similar control complexes as well as the parent drugs. Furthermore, we have also commented on the potential issues and their possible solution for translating these metal-based antimalarial complexes into the clinic.
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Affiliation(s)
- Apurba Mandal
- Department of Chemistry, Indian Institute of Technology (BHU), 221005, Varanasi, India
| | - Rajesh Kushwaha
- Department of Chemistry, Indian Institute of Technology (BHU), 221005, Varanasi, India
| | - Arif Ali Mandal
- Department of Chemistry, Indian Institute of Technology (BHU), 221005, Varanasi, India
| | - Sumit Bajpai
- Department of Chemistry, Indian Institute of Technology (BHU), 221005, Varanasi, India
| | - Ashish Kumar Yadav
- Department of Chemistry, Indian Institute of Technology (BHU), 221005, Varanasi, India
| | - Samya Banerjee
- Department of Chemistry, Indian Institute of Technology (BHU), 221005, Varanasi, India
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Edgar RCS, Counihan NA, McGowan S, de Koning-Ward TF. Methods Used to Investigate the Plasmodium falciparum Digestive Vacuole. Front Cell Infect Microbiol 2022; 11:829823. [PMID: 35096663 PMCID: PMC8794586 DOI: 10.3389/fcimb.2021.829823] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 12/22/2021] [Indexed: 11/13/2022] Open
Abstract
Plasmodium falciparum malaria remains a global health problem as parasites continue to develop resistance to all antimalarials in use. Infection causes clinical symptoms during the intra-erythrocytic stage of the lifecycle where the parasite infects and replicates within red blood cells (RBC). During this stage, P. falciparum digests the main constituent of the RBC, hemoglobin, in a specialized acidic compartment termed the digestive vacuole (DV), a process essential for survival. Many therapeutics in use target one or multiple aspects of the DV, with chloroquine and its derivatives, as well as artemisinin, having mechanisms of action within this organelle. In order to better understand how current therapeutics and those under development target DV processes, techniques used to investigate the DV are paramount. This review outlines the involvement of the DV in therapeutics currently in use and focuses on the range of techniques that are currently utilized to study this organelle including microscopy, biochemical analysis, genetic approaches and metabolomic studies. Importantly, continued development and application of these techniques will aid in our understanding of the DV and in the development of new therapeutics or therapeutic partners for the future.
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Affiliation(s)
- Rebecca C. S. Edgar
- School of Medicine, Deakin University, Geelong, VIC, Australia
- The Institute for Mental and Physical Health and Clinical Translation, Deakin University, Geelong, VIC, Australia
| | - Natalie A. Counihan
- School of Medicine, Deakin University, Geelong, VIC, Australia
- The Institute for Mental and Physical Health and Clinical Translation, Deakin University, Geelong, VIC, Australia
| | - Sheena McGowan
- Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, VIC, Australia
- Centre to Impact AMR, Monash University, Monash University, Clayton, VIC, Australia
| | - Tania F. de Koning-Ward
- School of Medicine, Deakin University, Geelong, VIC, Australia
- The Institute for Mental and Physical Health and Clinical Translation, Deakin University, Geelong, VIC, Australia
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5
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de Oliveira LS, Alborghetti MR, Carneiro RG, Bastos IMD, Amino R, Grellier P, Charneau S. Calcium in the Backstage of Malaria Parasite Biology. Front Cell Infect Microbiol 2021; 11:708834. [PMID: 34395314 PMCID: PMC8355824 DOI: 10.3389/fcimb.2021.708834] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Accepted: 07/14/2021] [Indexed: 12/26/2022] Open
Abstract
The calcium ion (Ca2+) is a ubiquitous second messenger involved in key biological processes in prokaryotes and eukaryotes. In Plasmodium species, Ca2+ signaling plays a central role in the parasite life cycle. It has been associated with parasite development, fertilization, locomotion, and host cell infection. Despite the lack of a canonical inositol-1,4,5-triphosphate receptor gene in the Plasmodium genome, pharmacological evidence indicates that inositol-1,4,5-triphosphate triggers Ca2+ mobilization from the endoplasmic reticulum. Other structures such as acidocalcisomes, food vacuole and mitochondria are proposed to act as supplementary intracellular Ca2+ reservoirs. Several Ca2+-binding proteins (CaBPs) trigger downstream signaling. Other proteins with no EF-hand motifs, but apparently involved with CaBPs, are depicted as playing an important role in the erythrocyte invasion and egress. It is also proposed that a cross-talk among kinases, which are not members of the family of Ca2+-dependent protein kinases, such as protein kinases G, A and B, play additional roles mediated indirectly by Ca2+ regulation. This statement may be extended for proteins directly related to invasion or egress, such as SUB1, ERC, IMC1I, IMC1g, GAP45 and EBA175. In this review, we update our understanding of aspects of Ca2+-mediated signaling correlated to the developmental stages of the malaria parasite life cycle.
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Affiliation(s)
- Lucas Silva de Oliveira
- Laboratory of Biochemistry and Protein Chemistry, Department of Cell Biology, Institute of Biology, University of Brasilia, Brasilia, Brazil
- UMR 7245 MCAM, Molécules de Communication et Adaptation des Micro-organismes, Muséum National d’Histoire Naturelle, CNRS, Équipe Parasites et Protistes Libres, Paris, France
| | - Marcos Rodrigo Alborghetti
- Laboratory of Biochemistry and Protein Chemistry, Department of Cell Biology, Institute of Biology, University of Brasilia, Brasilia, Brazil
- Brazilian Biosciences National Laboratory, Brazilian Center for Research in Energy and Materials, Campinas, Brazil
| | - Renata Garcia Carneiro
- Laboratory of Biochemistry and Protein Chemistry, Department of Cell Biology, Institute of Biology, University of Brasilia, Brasilia, Brazil
| | - Izabela Marques Dourado Bastos
- Laboratory of Host-Pathogen Interaction, Department of Cell Biology, Institute of Biology, University of Brasilia, Brasilia, Brazil
| | - Rogerio Amino
- Unité Infection et Immunité Paludéennes, Institut Pasteur, Paris, France
| | - Philippe Grellier
- UMR 7245 MCAM, Molécules de Communication et Adaptation des Micro-organismes, Muséum National d’Histoire Naturelle, CNRS, Équipe Parasites et Protistes Libres, Paris, France
| | - Sébastien Charneau
- Laboratory of Biochemistry and Protein Chemistry, Department of Cell Biology, Institute of Biology, University of Brasilia, Brasilia, Brazil
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Roux AT, Maharaj L, Oyegoke O, Akoniyon OP, Adeleke MA, Maharaj R, Okpeku M. Chloroquine and Sulfadoxine-Pyrimethamine Resistance in Sub-Saharan Africa-A Review. Front Genet 2021; 12:668574. [PMID: 34249090 PMCID: PMC8267899 DOI: 10.3389/fgene.2021.668574] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 04/20/2021] [Indexed: 12/20/2022] Open
Abstract
Malaria is a great concern for global health and accounts for a large amount of morbidity and mortality, particularly in Africa, with sub-Saharan Africa carrying the greatest burden of the disease. Malaria control tools such as insecticide-treated bed nets, indoor residual spraying, and antimalarial drugs have been relatively successful in reducing the burden of malaria; however, sub-Saharan African countries encounter great challenges, the greatest being antimalarial drug resistance. Chloroquine (CQ) was the first-line drug in the 20th century until it was replaced by sulfadoxine-pyrimethamine (SP) as a consequence of resistance. The extensive use of these antimalarials intensified the spread of resistance throughout sub-Saharan Africa, thus resulting in a loss of efficacy for the treatment of malaria. SP was replaced by artemisinin-based combination therapy (ACT) after the emergence of resistance toward SP; however, the use of ACTs is now threatened by the emergence of resistant parasites. The decreased selective pressure on CQ and SP allowed for the reintroduction of sensitivity toward those antimalarials in regions of sub-Saharan Africa where they were not the primary drug for treatment. Therefore, the emergence and spread of antimalarial drug resistance should be tracked to prevent further spread of the resistant parasites, and the re-emergence of sensitivity should be monitored to detect the possible reappearance of sensitivity in sub-Saharan Africa.
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Affiliation(s)
- Alexandra T. Roux
- Discipline of Genetics, School of Life Sciences, University of KwaZulu-Natal, Westville, South Africa
| | - Leah Maharaj
- Discipline of Genetics, School of Life Sciences, University of KwaZulu-Natal, Westville, South Africa
| | - Olukunle Oyegoke
- Discipline of Genetics, School of Life Sciences, University of KwaZulu-Natal, Westville, South Africa
| | - Oluwasegun P. Akoniyon
- Discipline of Genetics, School of Life Sciences, University of KwaZulu-Natal, Westville, South Africa
| | - Matthew Adekunle Adeleke
- Discipline of Genetics, School of Life Sciences, University of KwaZulu-Natal, Westville, South Africa
| | - Rajendra Maharaj
- Office of Malaria Research, South African Medical Research Council, Cape Town, South Africa
| | - Moses Okpeku
- Discipline of Genetics, School of Life Sciences, University of KwaZulu-Natal, Westville, South Africa
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7
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El Chamy Maluf S, Icimoto MY, Melo PMS, Budu A, Coimbra R, Gazarini ML, Carmona AK. Human plasma plasminogen internalization route in Plasmodium falciparum-infected erythrocytes. Malar J 2020; 19:302. [PMID: 32847585 PMCID: PMC7449074 DOI: 10.1186/s12936-020-03377-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 08/14/2020] [Indexed: 02/03/2023] Open
Abstract
Background The intra-erythrocytic development of the malaria parasite Plasmodium falciparum depends on the uptake of a number of essential nutrients from the host cell and blood plasma. It is widely recognized that the parasite imports low molecular weight solutes from the plasma and the consumption of these nutrients by P. falciparum has been extensively analysed. However, although it was already shown that the parasite also imports functional proteins from the vertebrate host, the internalization route through the different infected erythrocyte membranes has not yet been elucidated. In order to further understand the uptake mechanism, the study examined the trafficking of human plasminogen from the extracellular medium into P. falciparum-infected red blood cells. Methods Plasmodium falciparum clone 3D7 was cultured in standard HEPES-buffered RPMI 1640 medium supplemented with 0.5% AlbuMAX. Exogenous human plasminogen was added to the P. falciparum culture and the uptake of this protein by the parasites was analysed by electron microscopy and Western blotting. Immunoprecipitation and mass spectrometry were performed to investigate possible protein interactions that may assist plasminogen import into infected erythrocytes. The effect of pharmacological inhibitors of different cellular physiological processes in plasminogen uptake was also tested. Results It was observed that plasminogen was selectively internalized by P. falciparum-infected erythrocytes, with localization in plasma membrane erythrocyte and parasite’s cytosol. The protein was not detected in parasitic food vacuole and haemoglobin-containing vesicles. Furthermore, in erythrocyte cytoplasm, plasminogen was associated with the parasite-derived membranous structures tubovesicular network (TVN) and Maurer’s clefts. Several proteins were identified in immunoprecipitation assay and may be involved in the delivery of plasminogen across the P. falciparum multiple compartments. Conclusion The findings here reported reveal new features regarding the acquisition of plasma proteins of the host by P. falciparum-infected erythrocytes, a mechanism that involves the exomembrane system, which is distinct from the haemoglobin uptake, clarifying a route that may be potentially targeted for inhibition studies.
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Affiliation(s)
- Sarah El Chamy Maluf
- Departamento de Biofísica, Universidade Federal de São Paulo, Rua Pedro de Toledo 669, 7°andar, Vila Clementino, São Paulo, 04039032, Brazil
| | - Marcelo Yudi Icimoto
- Departamento de Biofísica, Universidade Federal de São Paulo, Rua Pedro de Toledo 669, 7°andar, Vila Clementino, São Paulo, 04039032, Brazil
| | - Pollyana Maria Saud Melo
- Departamento de Biofísica, Universidade Federal de São Paulo, Rua Pedro de Toledo 669, 7°andar, Vila Clementino, São Paulo, 04039032, Brazil
| | - Alexandre Budu
- Departamento de Biofísica, Universidade Federal de São Paulo, Rua Pedro de Toledo 669, 7°andar, Vila Clementino, São Paulo, 04039032, Brazil
| | - Rita Coimbra
- Centro de Microscopia Eletrônica (CEME), Universidade Federal de São Paulo, Rua Botucatu 862, Vila Clementino, São Paulo, Brazil
| | - Marcos Leoni Gazarini
- Departamento de Biociências, Universidade Federal de São Paulo, Rua Silva Jardim 136, Lab. 329, 3°andar, Vila Mathias, Santos, São Paulo, 11015020, Brazil.
| | - Adriana Karaoglanovic Carmona
- Departamento de Biofísica, Universidade Federal de São Paulo, Rua Pedro de Toledo 669, 7°andar, Vila Clementino, São Paulo, 04039032, Brazil.
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8
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Agrawal P, Manjithaya R, Surolia N. Autophagy‐related protein
Pf
ATG18 participates in food vacuole dynamics and autophagy‐like pathway in
Plasmodium falciparum. Mol Microbiol 2019; 113:766-782. [DOI: 10.1111/mmi.14441] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 12/17/2019] [Accepted: 12/17/2019] [Indexed: 12/30/2022]
Affiliation(s)
- Palak Agrawal
- Molecular Biology and Genetics Unit Jawaharlal Nehru Centre for Advanced Scientific Research Bangalore India
| | - Ravi Manjithaya
- Molecular Biology and Genetics Unit Jawaharlal Nehru Centre for Advanced Scientific Research Bangalore India
| | - Namita Surolia
- Molecular Biology and Genetics Unit Jawaharlal Nehru Centre for Advanced Scientific Research Bangalore India
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Mohring F, Hart MN, Rawlinson TA, Henrici R, Charleston JA, Diez Benavente E, Patel A, Hall J, Almond N, Campino S, Clark TG, Sutherland CJ, Baker DA, Draper SJ, Moon RW. Rapid and iterative genome editing in the malaria parasite Plasmodium knowlesi provides new tools for P. vivax research. eLife 2019; 8:45829. [PMID: 31205002 PMCID: PMC6579517 DOI: 10.7554/elife.45829] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Accepted: 05/28/2019] [Indexed: 12/14/2022] Open
Abstract
Tackling relapsing Plasmodium vivax and zoonotic Plasmodium knowlesi infections is critical to reducing malaria incidence and mortality worldwide. Understanding the biology of these important and related parasites was previously constrained by the lack of robust molecular and genetic approaches. Here, we establish CRISPR-Cas9 genome editing in a culture-adapted P. knowlesi strain and define parameters for optimal homology-driven repair. We establish a scalable protocol for the production of repair templates by PCR and demonstrate the flexibility of the system by tagging proteins with distinct cellular localisations. Using iterative rounds of genome-editing we generate a transgenic line expressing P. vivax Duffy binding protein (PvDBP), a lead vaccine candidate. We demonstrate that PvDBP plays no role in reticulocyte restriction but can alter the macaque/human host cell tropism of P. knowlesi. Critically, antibodies raised against the P. vivax antigen potently inhibit proliferation of this strain, providing an invaluable tool to support vaccine development.
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Affiliation(s)
- Franziska Mohring
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Melissa Natalie Hart
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | | | - Ryan Henrici
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - James A Charleston
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Ernest Diez Benavente
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Avnish Patel
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Joanna Hall
- Division of Infectious Disease Diagnostics, National Institute for Biological Standards and Control, Health Protection Agency, Hertfordshire, United Kingdom
| | - Neil Almond
- Division of Infectious Disease Diagnostics, National Institute for Biological Standards and Control, Health Protection Agency, Hertfordshire, United Kingdom
| | - Susana Campino
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Taane G Clark
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Colin J Sutherland
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - David A Baker
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Simon J Draper
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Robert William Moon
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
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Pasupureddy R, Atul, Seshadri S, Pande V, Dixit R, Pandey KC. Current scenario and future strategies to fight artemisinin resistance. Parasitol Res 2018; 118:29-42. [PMID: 30478733 DOI: 10.1007/s00436-018-6126-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Accepted: 10/19/2018] [Indexed: 02/05/2023]
Abstract
Despite several setbacks in the fight against malaria such as insecticide and drug resistance as well as low efficacy of available vaccines, considerable success in reducing malaria burden has been achieved in the past decade. Artemisinins (ARTs and their combination therapies, ACTs), the current frontline drugs against uncomplicated malaria, rapidly kill plasmodial parasites and are non-toxic at short exposures. Though the exact mode of action remains unclear, the endoperoxide bridge, indispensable for ART activity, is thought to react with heme released from hemoglobin hydrolysis and generate free radicals that alkylate multiple protein targets, thereby disrupting proteostasis pathways. However, rapid development of ART resistance in recent years with no potential alternatives on the horizon threaten the elimination efforts. The Greater Mekong Subregion in South-East Asia continues to churn out mutants resistant to multiple ACTs and detected in increasingly expanding geographies. Extensive research on ART-resistant strains have identified a potential candidate Kelch13, crucial for mediating ART resistance. Parasites with mutations in the propeller domains of Plasmodium falciparum Kelch13 protein were shown to have enhanced phosphatidylinositol 3-kinase levels that were concomitant with delayed parasite clearance. Current research focused on understanding the mechanism of Kelch13-mediated ART resistance could provide better insights into Plasmodium resistome. This review covers the current proposed mechanisms of ART activity, resistance strategies adopted by the parasite in response to ACTs and possible future approaches to mitigate the spread of resistance from South-East Asia.
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Affiliation(s)
- Rahul Pasupureddy
- National Institute of Malaria Research, Dwarka Sector 8, New Delhi, 110077, India.,Institute of Science, Nirma University, SG Highway, Ahmedabad, Gujarat, 382481, India
| | - Atul
- National Institute of Malaria Research, Dwarka Sector 8, New Delhi, 110077, India.,Department of Biotechnology, Kumaun University, Nainital, Uttarakhand, 263001, India
| | - Sriram Seshadri
- Institute of Science, Nirma University, SG Highway, Ahmedabad, Gujarat, 382481, India
| | - Veena Pande
- Department of Biotechnology, Kumaun University, Nainital, Uttarakhand, 263001, India
| | - Rajnikant Dixit
- National Institute of Malaria Research, Dwarka Sector 8, New Delhi, 110077, India
| | - Kailash C Pandey
- National Institute of Malaria Research, Dwarka Sector 8, New Delhi, 110077, India. .,Department of Biochemistry, Indian Council of Medical Research, National Institute for Research in Environmental Health, Bhopal, Madhya Pradesh, 462001, India.
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11
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Tools for attenuation of gene expression in malaria parasites. Int J Parasitol 2017; 47:385-398. [PMID: 28153780 DOI: 10.1016/j.ijpara.2016.11.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 09/15/2016] [Accepted: 11/28/2016] [Indexed: 12/30/2022]
Abstract
An understanding of the biology of Plasmodium parasites, which are the causative agents of the disease malaria, requires study of gene function. Various reverse genetic tools have been described for determining gene function. These tools can be broadly grouped as trans- and cis-acting. Trans-acting tools control gene functions through synthetic nucleic acid probe molecules matching the sequence of the gene of interest. Once delivered to the parasite, the probe engages with the mRNA of the target gene and attenuates its function. Cis-acting tools control gene function through elements introduced into the gene of interest by DNA transfection. The expression of the modified gene can be controlled using external agents, typically small molecule ligands. In this review, we discuss the strengths and weaknesses of these tools to guide researchers in selecting the appropriate tool for studies of gene function, and for guiding future refinements of these tools.
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Pulcini S, Staines HM, Lee AH, Shafik SH, Bouyer G, Moore CM, Daley DA, Hoke MJ, Altenhofen LM, Painter HJ, Mu J, Ferguson DJP, Llinás M, Martin RE, Fidock DA, Cooper RA, Krishna S. Mutations in the Plasmodium falciparum chloroquine resistance transporter, PfCRT, enlarge the parasite's food vacuole and alter drug sensitivities. Sci Rep 2015; 5:14552. [PMID: 26420308 PMCID: PMC4588581 DOI: 10.1038/srep14552] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 08/14/2015] [Indexed: 12/30/2022] Open
Abstract
Mutations in the Plasmodium falciparum chloroquine resistance transporter, PfCRT, are the major determinant of chloroquine resistance in this lethal human malaria parasite. Here, we describe P. falciparum lines subjected to selection by amantadine or blasticidin that carry PfCRT mutations (C101F or L272F), causing the development of enlarged food vacuoles. These parasites also have increased sensitivity to chloroquine and some other quinoline antimalarials, but exhibit no or minimal change in sensitivity to artemisinins, when compared with parental strains. A transgenic parasite line expressing the L272F variant of PfCRT confirmed this increased chloroquine sensitivity and enlarged food vacuole phenotype. Furthermore, the introduction of the C101F or L272F mutation into a chloroquine-resistant variant of PfCRT reduced the ability of this protein to transport chloroquine by approximately 93 and 82%, respectively, when expressed in Xenopus oocytes. These data provide, at least in part, a mechanistic explanation for the increased sensitivity of the mutant parasite lines to chloroquine. Taken together, these findings provide new insights into PfCRT function and PfCRT-mediated drug resistance, as well as the food vacuole, which is an important target of many antimalarial drugs.
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Affiliation(s)
- Serena Pulcini
- Institute for Infection and Immunity, St. George's, University of London, London SW17 0RE, UK
| | - Henry M Staines
- Institute for Infection and Immunity, St. George's, University of London, London SW17 0RE, UK
| | - Andrew H Lee
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY 10032, USA
| | - Sarah H Shafik
- Research School of Biology, Australian National University, Canberra, ACT 2601, Australia
| | - Guillaume Bouyer
- Institute for Infection and Immunity, St. George's, University of London, London SW17 0RE, UK.,Sorbonne Universités, UPMC Univ. Paris 06, UMR 8227, Integrative Biology of Marine Models, Comparative Physiology of Erythrocytes, Station Biologique de Roscoff, Roscoff, France.,CNRS, UMR 8227, Integrative Biology of Marine Models, Comparative Physiology of Erythrocytes, Station Biologique de Roscoff, Roscoff, France
| | - Catherine M Moore
- Institute for Infection and Immunity, St. George's, University of London, London SW17 0RE, UK
| | - Daniel A Daley
- Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529, USA
| | - Matthew J Hoke
- Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529, USA
| | - Lindsey M Altenhofen
- Department of Biochemistry and Molecular Biology and Center for Malaria Research, Pennsylvania State University, State College, Pennsylvania 16802, USA
| | - Heather J Painter
- Department of Biochemistry and Molecular Biology and Center for Malaria Research, Pennsylvania State University, State College, Pennsylvania 16802, USA
| | - Jianbing Mu
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville MD 20852, USA
| | - David J P Ferguson
- Nuffield Department of Clinical Laboratory Sciences, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Manuel Llinás
- Department of Biochemistry and Molecular Biology and Center for Malaria Research, Pennsylvania State University, State College, Pennsylvania 16802, USA
| | - Rowena E Martin
- Research School of Biology, Australian National University, Canberra, ACT 2601, Australia
| | - David A Fidock
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY 10032, USA.,Division of Infectious Diseases, Department of Medicine, Columbia University Medical Center, New York, NY 10032, USA
| | - Roland A Cooper
- Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529, USA.,Department of Natural Sciences and Mathematics, Dominican University of California, San Rafael, CA 94901, USA
| | - Sanjeev Krishna
- Institute for Infection and Immunity, St. George's, University of London, London SW17 0RE, UK
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Design and Synthesis of Novel Hybrid Molecules against Malaria. INTERNATIONAL JOURNAL OF MEDICINAL CHEMISTRY 2015; 2015:458319. [PMID: 25734014 PMCID: PMC4334980 DOI: 10.1155/2015/458319] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 12/05/2014] [Accepted: 12/10/2014] [Indexed: 01/26/2023]
Abstract
The effective treatment of malaria can be very complex: Plasmodium parasites develop in multiple stages within a complex life cycle between mosquitoes as vectors and vertebrates as hosts. For the full and effective elimination of parasites, an effective drug should be active against the earliest stages of the Plasmodium infection: liver stages (reduce the progress of the infection), blood stages (cure the clinical symptoms), and gametocytes (inhibit the transmission cycle). Towards this goal, here we report the design, the synthetic methodology, and the characterization of novel hybrid agents with combined activity against Plasmodium liver stages and blood stages and gametocytes. The divergent synthetic approach allows the access to differently linked primaquine-chloroquine hybrid templates in up to eight steps.
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14
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Design and synthesis of novel antileishmanial compounds. INTERNATIONAL JOURNAL OF MEDICINAL CHEMISTRY 2015; 2015:302723. [PMID: 25685554 PMCID: PMC4320803 DOI: 10.1155/2015/302723] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 12/04/2014] [Indexed: 11/18/2022]
Abstract
According to the WHO, infectious diseases, and in particular neglected tropical diseases in poor developing countries, still play a significant role in a vast number of deaths reported worldwide. Among them, leishmaniasis occurs as a complex and clinically diverse illness caused by protozoan Leishmania species which are transmitted through the bite of sandflies. They develop through a complex life cycle, from promastigotes in sandflies to amastigotes in humans. The severity of disease is determined by the type of infecting Leishmania species and also depends strongly on whether the parasite infection leads to a systemic involvement or not. Since the sensitivity towards diverse medicaments highly differs among the Leishmania species, it is advantageous to treat leishmaniasis with species-specific drugs. Towards this goal we report a synthetic methodology and characterization of novel small molecular agents active against both forms of L. major. This synthetic approach allows for rapid access to new active antileishmanial drug templates and their first derivatives in moderate to very good yields. Although the compounds reported here are bioactive, the detailed biological results are part of a more comprehensive study and will be reported separately by our collaborators.
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15
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Goldfless SJ, Wagner JC, Niles JC. Versatile control of Plasmodium falciparum gene expression with an inducible protein-RNA interaction. Nat Commun 2014; 5:5329. [PMID: 25370483 PMCID: PMC4223869 DOI: 10.1038/ncomms6329] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 09/20/2014] [Indexed: 01/06/2023] Open
Abstract
The available tools for conditional gene expression in Plasmodium falciparum are limited. Here, to enable reliable control of target gene expression, we build a system to efficiently modulate translation. We overcame several problems associated with other approaches for regulating gene expression in P. falciparum. Specifically, our system functions predictably across several native and engineered promoter contexts, and affords control over reporter and native parasite proteins irrespective of their subcellular compartmentalization. Induction and repression of gene expression are rapid, homogeneous and stable over prolonged periods. To demonstrate practical application of our system, we used it to reveal direct links between antimalarial drugs and their native parasite molecular target. This is an important outcome given the rapid spread of resistance, and intensified efforts to efficiently discover and optimize new antimalarial drugs. Overall, the studies presented highlight the utility of our system for broadly controlling gene expression and performing functional genetics in P. falciparum.
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Affiliation(s)
- Stephen J Goldfless
- Department of Biological Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - Jeffrey C Wagner
- Department of Biological Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - Jacquin C Niles
- Department of Biological Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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16
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Webster WAJ, McFadden GI. From the genome to the phenome: tools to understand the basic biology of Plasmodium falciparum. J Eukaryot Microbiol 2014; 61:655-71. [PMID: 25227912 DOI: 10.1111/jeu.12176] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Revised: 09/01/2014] [Accepted: 09/02/2014] [Indexed: 11/30/2022]
Abstract
Malaria plagues one out of every 30 humans and contributes to almost a million deaths, and the problem could worsen. Our current therapeutic options are compromised by emerging resistance by the parasite to our front line drugs. It is thus imperative to better understand the basic biology of the parasite and develop novel drugs to stem this disease. The most facile approach to analyse a gene's function is to remove it from the genome or inhibit its activity. Although genetic manipulation of the human malaria parasite Plasmodium falciparum is a relatively standard procedure, there is no optimal method to perturb genes essential to the intraerythrocytic development cycle--the part of the life cycle that produces the clinical manifestation of malaria. This is a severe impediment to progress because the phenotype we wish to study is exactly the one that is so elusive. In the absence of any utilitarian way to conditionally delete essential genes, we are prevented from investigating the parasite's most vulnerable points. This review aims to focus on the development of tools identifying essential genes of P. falciparum and our ability to elicit phenotypic mutation.
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Affiliation(s)
- Wesley A J Webster
- Centre for Regional and Rural Futures, School of Life and Environmental Sciences, Deakin University, Burwood, 3125, Victoria, Australia; Plant Cell Biology Research Centre, School of Botany, University of Melbourne, Melbourne, 3010, Victoria, Australia
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17
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A dual-targeted aminoacyl-tRNA synthetase in Plasmodium falciparum charges cytosolic and apicoplast tRNACys. Biochem J 2014; 458:513-23. [PMID: 24428730 DOI: 10.1042/bj20131451] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Plasmodium parasites possess two endosymbiotic organelles: a mitochondrion and a relict plastid called the apicoplast. To accommodate the translational requirements of these organelles in addition to its cytosolic translation apparatus, the parasite must maintain a supply of charged tRNA molecules in each of these compartments. In the present study we investigate how the parasite manages these translational requirements for charged tRNACys with only a single gene for CysRS (cysteinyl-tRNA synthetase). We demonstrate that the single PfCysRS (Plasmodium falciparum CysRS) transcript is alternatively spliced, and, using a combination of endogenous and heterologous tagging experiments in both P. falciparum and Toxoplasma gondii, we show that CysRS isoforms traffic to the cytosol and apicoplast. PfCysRS can recognize and charge the eukaryotic tRNACys encoded by the Plasmodium nucleus as well as the bacterial-type tRNA encoded by the apicoplast genome, albeit with a preference for the eukaryotic type cytosolic tRNA. The results of the present study indicate that apicomplexan parasites have lost their original plastidic cysteinyl-tRNA synthetase, and have replaced it with a dual-targeted eukaryotic type CysRS that recognizes plastid and nuclear tRNACys. Inhibitors of the Plasmodium dual-targeted CysRS would potentially offer a therapy capable of the desirable immediate effects on parasite growth as well as the irreversibility of inhibitors that disrupt apicoplast inheritance.
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18
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Elbadry MA, Existe A, Victor YS, Memnon G, Fukuda M, Dame JB, Yowell CA, Okech BA. Survey of Plasmodium falciparum multidrug resistance-1 and chloroquine resistance transporter alleles in Haiti. Malar J 2013; 12:426. [PMID: 24252305 PMCID: PMC3879102 DOI: 10.1186/1475-2875-12-426] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2013] [Accepted: 10/25/2013] [Indexed: 12/04/2022] Open
Abstract
Background In Haiti where chloroquine (CQ) is widely used for malaria treatment, reports of resistance are scarce. However, recent identification of CQ resistance genotypes in one site is suggestive of an emerging problem. Additional studies are needed to evaluate genetic mutations associated with CQ resistance, especially in the Plasmodium falciparum multi-drug resistance-1 gene (pfmdr1) while expanding the already available information on P. falciparum CQ transporter gene (pfcrt) in Haiti. Methods Blood samples were collected on Whatman filter cards (FTA) from eight clinics spread across Haiti. Following the confirmation of P. falciparum in the samples, PCR protocols were used to amplify regions of pfmdr1and pfcrt codons of interest, (86, 184, 1034, 1042, and 1246) and (72-76), respectively. Sequencing and site-specific restriction enzyme digestions were used to analyse these DNA fragments for the presence of single nucleotide polymorphisms (SNPs) known to confer resistance to anti-malarial drugs. Results P. falciparum infection was confirmed in160 samples by amplifying a segment of the P. falciparum 18S small subunit ribosomal RNA gene (pfssurrna). The sequence of pfmdr1 in 54 of these samples was determined between codons 86,184 codons 1034, 1042 and 1246. No sequence differences from that of the NF54 clone 3D7 were found among the 54 samples except at codon 184, where a non-silent mutation was found in all samples predicted to alter the amino acid sequence replacing tyrosine with phenylalanine (Y184F). This altered sequence was also confirmed by restriction enzyme digestion. The sequence of pfmdr1 at codons 86, 184, 1034 and 1042 encoded the NFSN haplotype. The sequence of pfcrt codons 72-76 from 79 samples was determined and found to encode CVMNK, consistent with a CQ sensitive genotype. Conclusion The presence of the Y184F mutation in pfmdr1 of P. falciparum parasites in Haiti may have implications for resistance to antimalarial drugs. The absence of mutation in pfcrt at codon 76 among 79 isolates tested suggests that sensitivity to CQ in Haiti remains common. Wide-spread screening of the pfmdr1 and pfcrt especially among patients experiencing treatment failure may be a useful tool in early detection of the emergence of antimalarial drug resistance in Haiti.
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Affiliation(s)
| | | | | | | | | | | | | | - Bernard A Okech
- Department of Environmental and Global Health, University of Florida, Gainesville, FL 32610, USA.
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19
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Trafficked Proteins-Druggable in Plasmodium falciparum? Int J Cell Biol 2013; 2013:435981. [PMID: 23710183 PMCID: PMC3655585 DOI: 10.1155/2013/435981] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2013] [Accepted: 03/12/2013] [Indexed: 01/09/2023] Open
Abstract
Malaria is an infectious disease that results in serious health problems in the countries in which it is endemic. Annually this parasitic disease leads to more than half a million deaths; most of these are children in Africa. An effective vaccine is not available, and the treatment of the disease is solely dependent on chemotherapy. However, drug resistance is spreading, and the identification of new drug targets as well as the development of new antimalarials is urgently required. Attention has been drawn to a variety of essential plasmodial proteins, which are targeted to intra- or extracellular destinations, such as the digestive vacuole, the apicoplast, or into the host cell. Interfering with the action or the transport of these proteins will impede proliferation of the parasite. In this mini review, we will shed light on the present discovery of chemotherapeutics and potential drug targets involved in protein trafficking processes in the malaria parasite.
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20
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PfCRT and its role in antimalarial drug resistance. Trends Parasitol 2012; 28:504-14. [PMID: 23020971 DOI: 10.1016/j.pt.2012.08.002] [Citation(s) in RCA: 185] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Revised: 08/09/2012] [Accepted: 08/13/2012] [Indexed: 12/15/2022]
Abstract
Plasmodium falciparum resistance to chloroquine, the former gold standard antimalarial drug, is mediated primarily by mutant forms of the chloroquine resistance transporter (PfCRT). These mutations impart upon PfCRT the ability to efflux chloroquine from the intracellular digestive vacuole, the site of drug action. Recent studies reveal that PfCRT variants can also affect parasite fitness, protect immature gametocytes against chloroquine action, and alter P. falciparum susceptibility to current first-line therapies. These results highlight the need to be vigilant in screening for the appearance of novel pfcrt alleles that could contribute to new multi-drug resistance phenotypes.
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Sigala PA, Crowley JR, Hsieh S, Henderson JP, Goldberg DE. Direct tests of enzymatic heme degradation by the malaria parasite Plasmodium falciparum. J Biol Chem 2012; 287:37793-807. [PMID: 22992734 PMCID: PMC3488054 DOI: 10.1074/jbc.m112.414078] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Malaria parasites generate vast quantities of heme during blood stage infection via hemoglobin digestion and limited de novo biosynthesis, but it remains unclear if parasites metabolize heme for utilization or disposal. Recent in vitro experiments with a heme oxygenase (HO)-like protein from Plasmodium falciparum suggested that parasites may enzymatically degrade some heme to the canonical HO product, biliverdin (BV), or its downstream metabolite, bilirubin (BR). To directly test for BV and BR production by P. falciparum parasites, we DMSO-extracted equal numbers of infected and uninfected erythrocytes and developed a sensitive LC-MS/MS assay to quantify these tetrapyrroles. We found comparable low levels of BV and BR in both samples, suggesting the absence of HO activity in parasites. We further tested live parasites by targeted expression of a fluorescent BV-binding protein within the parasite cytosol, mitochondrion, and plant-like plastid. This probe could detect exogenously added BV but gave no signal indicative of endogenous BV production within parasites. Finally, we recombinantly expressed and tested the proposed heme degrading activity of the HO-like protein, PfHO. Although PfHO bound heme and protoporphyrin IX with modest affinity, it did not catalyze heme degradation in vivo within bacteria or in vitro in UV absorbance and HPLC assays. These observations are consistent with PfHO's lack of a heme-coordinating His residue and suggest an alternative function within parasites. We conclude that P. falciparum parasites lack a canonical HO pathway for heme degradation and thus rely fully on alternative mechanisms for heme detoxification and iron acquisition during blood stage infection.
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Affiliation(s)
- Paul A Sigala
- Department of Molecular Microbiology and the Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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