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Scott AF, Deery E, Lawrence AD, Warren MJ. Plasmodium falciparum hydroxymethylbilane synthase does not house any cosynthase activity within the haem biosynthetic pathway. MICROBIOLOGY-SGM 2021; 167. [PMID: 34661520 PMCID: PMC8698207 DOI: 10.1099/mic.0.001095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Uroporphyrinogen III, the universal progenitor of macrocyclic, modified tetrapyrroles, is produced from aminolaevulinic acid (ALA) by a conserved pathway involving three enzymes: porphobilinogen synthase (PBGS), hydroxymethylbilane synthase (HmbS) and uroporphyrinogen III synthase (UroS). The gene encoding uroporphyrinogen III synthase has not yet been identified in Plasmodium falciparum, but it has been suggested that this activity is housed inside a bifunctional hybroxymethylbilane synthase (HmbS). Additionally, an unknown protein encoded by PF3D7_1247600 has also been predicted to possess UroS activity. In this study it is demonstrated that neither of these proteins possess UroS activity and the real UroS remains to be identified. This was demonstrated by the failure of codon-optimized genes to complement a defined Escherichia coli hemD− mutant (SASZ31) deficient in UroS activity. Furthermore, HPLC analysis of the oxidized reaction product from recombinant, purified P. falciparum HmbS showed that only uroporphyrin I could be detected (corresponding to hydroxymethylbilane production). No uroporphyrin III was detected, showing that P. falciparum HmbS does not have UroS activity and can only catalyze the formation of hydroxymethylbilane from porphobilinogen.
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Affiliation(s)
- Alan F. Scott
- School of Biosciences, University of Kent, Canterbury, Kent, CT2 7NJ, UK
- Present address: School of Chemistry, Cardiff University, Cardiff, CF10 3AT, UK
- *Correspondence: Alan F. Scott,
| | - Evelyne Deery
- School of Biosciences, University of Kent, Canterbury, Kent, CT2 7NJ, UK
| | - Andrew D. Lawrence
- School of Biosciences, University of Kent, Canterbury, Kent, CT2 7NJ, UK
| | - Martin J. Warren
- School of Biosciences, University of Kent, Canterbury, Kent, CT2 7NJ, UK
- Quadram Institute Bioscience, Norwich Research Park, Norwich, NR4 7UQ, UK
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2
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Kloehn J, Harding CR, Soldati-Favre D. Supply and demand-heme synthesis, salvage and utilization by Apicomplexa. FEBS J 2020; 288:382-404. [PMID: 32530125 DOI: 10.1111/febs.15445] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Revised: 05/23/2020] [Accepted: 06/05/2020] [Indexed: 01/05/2023]
Abstract
The Apicomplexa phylum groups important human and animal pathogens that cause severe diseases, encompassing malaria, toxoplasmosis, and cryptosporidiosis. In common with most organisms, apicomplexans rely on heme as cofactor for several enzymes, including cytochromes of the electron transport chain. This heme derives from de novo synthesis and/or the development of uptake mechanisms to scavenge heme from their host. Recent studies have revealed that heme synthesis is essential for Toxoplasma gondii tachyzoites, as well as for the mosquito and liver stages of Plasmodium spp. In contrast, the erythrocytic stages of the malaria parasites rely on scavenging heme from the host red blood cell. The unusual heme synthesis pathway in Apicomplexa spans three cellular compartments and comprises enzymes of distinct ancestral origin, providing promising drug targets. Remarkably given the requirement for heme, T. gondii can tolerate the loss of several heme synthesis enzymes at a high fitness cost, while the ferrochelatase is essential for survival. These findings indicate that T. gondii is capable of salvaging heme precursors from its host. Furthermore, heme is implicated in the activation of the key antimalarial drug artemisinin. Recent findings established that a reduction in heme availability corresponds to decreased sensitivity to artemisinin in T. gondii and Plasmodium falciparum, providing insights into the possible development of combination therapies to tackle apicomplexan parasites. This review describes the microeconomics of heme in Apicomplexa, from supply, either from de novo synthesis or scavenging, to demand by metabolic pathways, including the electron transport chain.
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Affiliation(s)
- Joachim Kloehn
- Department of Microbiology and Molecular Medicine, CMU, University of Geneva, Switzerland
| | - Clare R Harding
- Wellcome Centre for Molecular Parasitology, Institute of Infection, Immunity & Inflammation, University of Glasgow, UK
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Bergmann A, Floyd K, Key M, Dameron C, Rees KC, Thornton LB, Whitehead DC, Hamza I, Dou Z. Toxoplasma gondii requires its plant-like heme biosynthesis pathway for infection. PLoS Pathog 2020; 16:e1008499. [PMID: 32407406 PMCID: PMC7252677 DOI: 10.1371/journal.ppat.1008499] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Revised: 05/27/2020] [Accepted: 03/25/2020] [Indexed: 01/21/2023] Open
Abstract
Heme, an iron-containing organic ring, is essential for virtually all living organisms by serving as a prosthetic group in proteins that function in diverse cellular activities ranging from diatomic gas transport and sensing, to mitochondrial respiration, to detoxification. Cellular heme levels in microbial pathogens can be a composite of endogenous de novo synthesis or exogenous uptake of heme or heme synthesis intermediates. Intracellular pathogenic microbes switch routes for heme supply when heme availability fluctuates in their replicative environment throughout infection. Here, we show that Toxoplasma gondii, an obligate intracellular human pathogen, encodes a functional heme biosynthesis pathway. A chloroplast-derived organelle, termed apicoplast, is involved in heme production. Genetic and chemical manipulation revealed that de novo heme production is essential for T. gondii intracellular growth and pathogenesis. Surprisingly, the herbicide oxadiazon significantly impaired Toxoplasma growth, consistent with phylogenetic analyses that show T. gondii protoporphyrinogen oxidase is more closely related to plants than mammals. This inhibition can be enhanced by 15- to 25-fold with two oxadiazon derivatives, lending therapeutic proof that Toxoplasma heme biosynthesis is a druggable target. As T. gondii has been used to model other apicomplexan parasites, our study underscores the utility of targeting heme biosynthesis in other pathogenic apicomplexans, such as Plasmodium spp., Cystoisospora, Eimeria, Neospora, and Sarcocystis.
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Affiliation(s)
- Amy Bergmann
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Katherine Floyd
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Melanie Key
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Carly Dameron
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Kerrick C. Rees
- Department of Chemistry, Clemson University, Clemson, South Carolina, United States of America
| | - L. Brock Thornton
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Daniel C. Whitehead
- Department of Chemistry, Clemson University, Clemson, South Carolina, United States of America
- Eukaryotic Pathogens Innovation Center, Clemson University, Clemson, South Carolina, United States of America
| | - Iqbal Hamza
- Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland, United States of America
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America
| | - Zhicheng Dou
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
- Eukaryotic Pathogens Innovation Center, Clemson University, Clemson, South Carolina, United States of America
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McFadden GI, Yeh E. The apicoplast: now you see it, now you don't. Int J Parasitol 2016; 47:137-144. [PMID: 27773518 DOI: 10.1016/j.ijpara.2016.08.005] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 08/19/2016] [Accepted: 08/25/2016] [Indexed: 10/20/2022]
Abstract
Parasites such as Plasmodium and Toxoplasma possess a vestigial plastid homologous to the chloroplasts of algae and plants. The plastid (known as the apicoplast; for apicomplexan plastid) is non-photosynthetic and very much reduced, but has clear endosymbiotic ancestry including a circular genome that encodes RNAs and proteins and a suite of bacterial biosynthetic pathways. Here we review the initial discovery of the apicoplast, and recount the major new insights into apicoplast origin, biogenesis and function. We conclude by examining how the apicoplast can be removed from malaria parasites in vitro, ultimately completing its reduction by chemical supplementation.
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Affiliation(s)
| | - Ellen Yeh
- Department of Biochemistry, Stanford Medical School, Stanford, CA, USA; Department of Pathology, Stanford Medical School, Stanford, CA, USA
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Posayapisit N, Songsungthong W, Koonyosying P, Falade MO, Uthaipibull C, Yuthavong Y, Shaw PJ, Kamchonwongpaisan S. Cytochrome c and c1 heme lyases are essential in Plasmodium berghei. Mol Biochem Parasitol 2016; 210:32-36. [PMID: 27520480 DOI: 10.1016/j.molbiopara.2016.08.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 08/04/2016] [Accepted: 08/08/2016] [Indexed: 10/21/2022]
Abstract
Malaria parasites possess a de novo heme synthetic pathway. Interestingly, this pathway is dispensable during the blood stages of development in mammalian hosts. The assembly of the two most important hemeproteins, cytochromes c and c1, is mediated by cytochrome heme lyase enzymes. Plasmodium spp. possess two cytochrome heme lyases encoded by separate genes. Given the redundancy of heme synthesis, we sought to determine if heme lyase function also exhibits redundancy. To answer this question, we performed gene knockout experiments. We found that the PBANKA_143950 and PBANKA_0602600 Plasmodium berghei genes encoding cytochrome c (Pbcchl) and cytochrome c1 (Pbcc1hl) heme lyases, respectively, can only be disrupted when a complementary gene is present. In contrast, four genes in the de novo heme synthesis pathway can be disrupted without complementation. This work provides evidence that Pbcchl and Pbcc1hl are both essential and thus may be antimalarial targets.
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Affiliation(s)
- Navaporn Posayapisit
- National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Neung, Amphoe Khlong Luang, Pathum Thani 12120, Thailand
| | - Warangkhana Songsungthong
- National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Neung, Amphoe Khlong Luang, Pathum Thani 12120, Thailand
| | - Pongpisid Koonyosying
- National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Neung, Amphoe Khlong Luang, Pathum Thani 12120, Thailand
| | - Mofolusho O Falade
- National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Neung, Amphoe Khlong Luang, Pathum Thani 12120, Thailand
| | - Chairat Uthaipibull
- National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Neung, Amphoe Khlong Luang, Pathum Thani 12120, Thailand
| | - Yongyuth Yuthavong
- National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Neung, Amphoe Khlong Luang, Pathum Thani 12120, Thailand
| | - Philip J Shaw
- National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Neung, Amphoe Khlong Luang, Pathum Thani 12120, Thailand.
| | - Sumalee Kamchonwongpaisan
- National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Neung, Amphoe Khlong Luang, Pathum Thani 12120, Thailand.
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Lapp SA, Mok S, Zhu L, Wu H, Preiser PR, Bozdech Z, Galinski MR. Plasmodium knowlesi gene expression differs in ex vivo compared to in vitro blood-stage cultures. Malar J 2015; 14:110. [PMID: 25880967 PMCID: PMC4369371 DOI: 10.1186/s12936-015-0612-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 02/12/2015] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Plasmodium knowlesi is one of five Plasmodium species known to cause malaria in humans and can result in severe illness and death. While a zoonosis in humans, this simian malaria parasite species infects macaque monkeys and serves as an experimental model for in vivo, ex vivo and in vitro studies. It has underpinned malaria discoveries relating to host-pathogen interactions, the immune response and immune evasion strategies. This study investigated differences in P. knowlesi gene expression in samples from ex vivo and in vitro cultures. METHODS Gene expression profiles were generated using microarrays to compare the stage-specific transcripts detected for a clone of P. knowlesi propagated in the blood of a rhesus macaque host and then grown in an ex-vivo culture, and the same clone adapted to long-term in vitro culture. Parasite samples covering one blood-stage cycle were analysed at four-hour intervals. cDNA was generated and hybridized to an oligoarray representing the P. knowlesi genome. Two replicate experiments were developed from in vitro cultures. Expression values were filtered, normalized, and analysed using R and Perl language and applied to a sine wave model to determine changes in equilibrium and amplitude. Differentially expressed genes from ex vivo and in vitro time points were detected using limma R/Bioconductor and gene set enrichment analysis (GSEA). RESULTS Major differences were noted between the ex vivo and in vitro time courses in overall gene expression and the length of the cycle (25.5 hours ex vivo; 33.5 hours in vitro). GSEA of genes up-regulated ex vivo showed an enrichment of various genes including SICAvar, ribosomal- associated and histone acetylation pathway genes. In contrast, certain genes involved in metabolism and cell growth, such as porphobilinogen deaminase and tyrosine phosphatase, and one SICAvar gene, were significantly up-regulated in vitro. CONCLUSIONS This study demonstrates how gene expression in P. knowlesi blood-stage parasites can differ dramatically depending on whether the parasites are grown in vivo, with only one cycle of development ex vivo, or as an adapted isolate in long-term in vitro culture. These data bring emphasis to the importance of studying the parasite, its biology and disease manifestations in the context of the host.
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Affiliation(s)
- Stacey A Lapp
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA.
| | - Sachel Mok
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
| | - Lei Zhu
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
| | - Hao Wu
- Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, USA.
| | - Peter R Preiser
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
| | - Zybnek Bozdech
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
| | - Mary R Galinski
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA.
- Department of Medicine, Division of Infectious Diseases, Emory University, Atlanta, GA, USA.
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Ke H, Sigala PA, Miura K, Morrisey JM, Mather MW, Crowley JR, Henderson JP, Goldberg DE, Long CA, Vaidya AB. The heme biosynthesis pathway is essential for Plasmodium falciparum development in mosquito stage but not in blood stages. J Biol Chem 2014; 289:34827-37. [PMID: 25352601 DOI: 10.1074/jbc.m114.615831] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Heme is an essential cofactor for aerobic organisms. Its redox chemistry is central to a variety of biological functions mediated by hemoproteins. In blood stages, malaria parasites consume most of the hemoglobin inside the infected erythrocytes, forming nontoxic hemozoin crystals from large quantities of heme released during digestion. At the same time, the parasites possess a heme de novo biosynthetic pathway. This pathway in the human malaria parasite Plasmodium falciparum has been considered essential and is proposed as a potential drug target. However, we successfully disrupted the first and last genes of the pathway, individually and in combination. These knock-out parasite lines, lacking 5-aminolevulinic acid synthase and/or ferrochelatase (FC), grew normally in blood-stage culture and exhibited no changes in sensitivity to heme-related antimalarial drugs. We developed a sensitive LC-MS/MS assay to monitor stable isotope incorporation into heme from its precursor 5-[(13)C4]aminolevulinic acid, and this assay confirmed that de novo heme synthesis was ablated in FC knock-out parasites. Disrupting the FC gene also caused no defects in gametocyte generation or maturation but resulted in a greater than 70% reduction in male gamete formation and completely prevented oocyst formation in female Anopheles stephensi mosquitoes. Our data demonstrate that the heme biosynthesis pathway is not essential for asexual blood-stage growth of P. falciparum parasites but is required for mosquito transmission. Drug inhibition of pathway activity is therefore unlikely to provide successful antimalarial therapy. These data also suggest the existence of a parasite mechanism for scavenging host heme to meet metabolic needs.
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Affiliation(s)
- Hangjun Ke
- From the Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129
| | - Paul A Sigala
- the Department of Molecular Microbiology and the Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Kazutoyo Miura
- the Laboratory of Malaria and Vector Research, NIAID, National Institutes of Health, Rockville, Maryland 20852, and
| | - Joanne M Morrisey
- From the Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129
| | - Michael W Mather
- From the Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129
| | - Jan R Crowley
- the Center for Women's Infectious Disease Research and
| | - Jeffrey P Henderson
- the Center for Women's Infectious Disease Research and Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Daniel E Goldberg
- the Department of Molecular Microbiology and the Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, Missouri 63110, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Carole A Long
- the Laboratory of Malaria and Vector Research, NIAID, National Institutes of Health, Rockville, Maryland 20852, and
| | - Akhil B Vaidya
- From the Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129,
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Affiliation(s)
- Paul A. Sigala
- Departments of Medicine and Molecular Microbiology and the Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, Missouri 63110; ,
| | - Daniel E. Goldberg
- Departments of Medicine and Molecular Microbiology and the Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, Missouri 63110; ,
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Clark MA, Goheen MM, Cerami C. Influence of host iron status on Plasmodium falciparum infection. Front Pharmacol 2014; 5:84. [PMID: 24834053 PMCID: PMC4018558 DOI: 10.3389/fphar.2014.00084] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 04/04/2014] [Indexed: 01/25/2023] Open
Abstract
Iron deficiency affects one quarter of the world's population and causes significant morbidity, including detrimental effects on immune function and cognitive development. Accordingly, the World Health Organization (WHO) recommends routine iron supplementation in children and adults in areas with a high prevalence of iron deficiency. However, a large body of clinical and epidemiological evidence has accumulated which clearly demonstrates that host iron deficiency is protective against falciparum malaria and that host iron supplementation may increase the risk of malaria. Although many effective antimalarial treatments and preventive measures are available, malaria remains a significant public health problem, in part because the mechanisms of malaria pathogenesis remain obscured by the complexity of the relationships that exist between parasite virulence factors, host susceptibility traits, and the immune responses that modulate disease. Here we review (i) the clinical and epidemiological data that describes the relationship between host iron status and malaria infection and (ii) the current understanding of the biological basis for these clinical and epidemiological observations.
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Affiliation(s)
- Martha A. Clark
- Microbiology and Immunology, University of North CarolinaChapel Hill, NC, USA
| | - Morgan M. Goheen
- Microbiology and Immunology, University of North CarolinaChapel Hill, NC, USA
| | - Carla Cerami
- Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel HillChapel Hill, NC, USA
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Bung N, Pradhan M, Srinivasan H, Bulusu G. Structural insights into E. coli porphobilinogen deaminase during synthesis and exit of 1-hydroxymethylbilane. PLoS Comput Biol 2014; 10:e1003484. [PMID: 24603363 PMCID: PMC3945110 DOI: 10.1371/journal.pcbi.1003484] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 01/08/2014] [Indexed: 11/19/2022] Open
Abstract
Porphobilinogen deaminase (PBGD) catalyzes the formation of 1-hydroxymethylbilane (HMB), a crucial intermediate in tetrapyrrole biosynthesis, through a step-wise polymerization of four molecules of porphobilinogen (PBG), using a unique dipyrromethane (DPM) cofactor. Structural and biochemical studies have suggested residues with catalytic importance, but their specific role in the mechanism and the dynamic behavior of the protein with respect to the growing pyrrole chain remains unknown. Molecular dynamics simulations of the protein through the different stages of pyrrole chain elongation suggested that the compactness of the overall protein decreases progressively with addition of each pyrrole ring. Essential dynamics showed that domains move apart while the cofactor turn region moves towards the second domain, thus creating space for the pyrrole rings added at each stage. Residues of the flexible active site loop play a significant role in its modulation. Steered molecular dynamics was performed to predict the exit mechanism of HMB from PBGD at the end of the catalytic cycle. Based on the force profile and minimal structural changes the proposed path for the exit of HMB is through the space between the domains flanking the active site loop. Residues reported as catalytically important, also play an important role in the exit of HMB. Further, upon removal of HMB, the structure of PBGD gradually relaxes to resemble its initial stage structure, indicating its readiness to resume a new catalytic cycle. Heme is the prosthetic group at the core of the oxygen carrier metalloprotein hemoglobin. Heme consists of a tetrapyrrole called porphyrin bound to an iron ion. It is synthesized by the heme biosynthetic pathway, which is common to all eukaryotes and most prokaryotes. Porphobilinogen deaminase, an enzyme in the heme biosynthetic pathway, catalyzes the formation of a linear tetrapyrrole product, 1-hydroxymethylbilane, from four units of porphobilinogen. In this study we carried out molecular dynamics simulations to understand the structural changes that the enzyme undergoes while catalyzing this reaction. There are three segments to the study: 1) understanding the changes in the enzyme when the porphobilinogen units get attached to the dipyrromethane cofactor, thereby forming a polypyrrole chain; 2) exit of the product from the active site of the enzyme via steered molecular dynamics; and 3) the relaxation of the enzyme to the initial stage to resume its catalytic cycle. Molecular dynamics simulations of the protein through the different stages of pyrrole chain elongation gives insight into the motions of domains, active site loop and role of conserved active site residues in facilitating the accommodation of the polypyrrole chain. In addition to this, we propose a possible exit path for the product and demonstrate the relaxation of the enzyme after the exit of the product to resume the catalytic cycle.
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Affiliation(s)
- Navneet Bung
- TCS Innovation Labs-Hyderabad (Life Sciences Division), Tata Consultancy Services Limited, Hyderabad, India
| | - Meenakshi Pradhan
- TCS Innovation Labs-Hyderabad (Life Sciences Division), Tata Consultancy Services Limited, Hyderabad, India
| | - Harini Srinivasan
- TCS Innovation Labs-Hyderabad (Life Sciences Division), Tata Consultancy Services Limited, Hyderabad, India
| | - Gopalakrishnan Bulusu
- TCS Innovation Labs-Hyderabad (Life Sciences Division), Tata Consultancy Services Limited, Hyderabad, India
- * E-mail:
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11
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Nagaraj VA, Sundaram B, Varadarajan NM, Subramani PA, Kalappa DM, Ghosh SK, Padmanaban G. Malaria parasite-synthesized heme is essential in the mosquito and liver stages and complements host heme in the blood stages of infection. PLoS Pathog 2013; 9:e1003522. [PMID: 23935500 PMCID: PMC3731253 DOI: 10.1371/journal.ppat.1003522] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2013] [Accepted: 06/10/2013] [Indexed: 01/21/2023] Open
Abstract
Heme metabolism is central to malaria parasite biology. The parasite acquires heme from host hemoglobin in the intraerythrocytic stages and stores it as hemozoin to prevent free heme toxicity. The parasite can also synthesize heme de novo, and all the enzymes in the pathway are characterized. To study the role of the dual heme sources in malaria parasite growth and development, we knocked out the first enzyme, δ-aminolevulinate synthase (ALAS), and the last enzyme, ferrochelatase (FC), in the heme-biosynthetic pathway of Plasmodium berghei (Pb). The wild-type and knockout (KO) parasites had similar intraerythrocytic growth patterns in mice. We carried out in vitro radiolabeling of heme in Pb-infected mouse reticulocytes and Plasmodium falciparum-infected human RBCs using [4-14C] aminolevulinic acid (ALA). We found that the parasites incorporated both host hemoglobin-heme and parasite-synthesized heme into hemozoin and mitochondrial cytochromes. The similar fates of the two heme sources suggest that they may serve as backup mechanisms to provide heme in the intraerythrocytic stages. Nevertheless, the de novo pathway is absolutely essential for parasite development in the mosquito and liver stages. PbKO parasites formed drastically reduced oocysts and did not form sporozoites in the salivary glands. Oocyst production in PbALASKO parasites recovered when mosquitoes received an ALA supplement. PbALASKO sporozoites could infect mice only when the mice received an ALA supplement. Our results indicate the potential for new therapeutic interventions targeting the heme-biosynthetic pathway in the parasite during the mosquito and liver stages. We demonstrated about two decades ago that the malaria parasite could make heme on its own, although it imports heme from red blood cell hemoglobin during the blood stages of infection. We investigated the role of parasite-synthesized heme in all stages of parasite growth by knocking out two genes in the heme-biosynthetic pathway of Plasmodium berghei that infects mice. We found that the parasite-synthesized heme complements the function of hemoglobin-heme during the blood stages. The parasite-synthesized heme appears to be a backup mechanism. The parasite incorporates both sources of heme into hemozoin, a detoxification product, and into mitochondrial cytochromes. The parasite-synthesized heme is, however, absolutely essential for parasite growth during the mosquito and liver stages. We restored the sporozoite formation and liver-stage development of the knockout parasites by providing the missing metabolite. Thus, the heme-biosynthetic pathway could be a target for antimalarial therapies in the mosquito and liver stages of infection. The knockout parasite could also be tested for its potential as a genetically attenuated sporozoite vaccine.
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Abstract
INTRODUCTION The relict plastid, or apicoplast, is a characteristic feature of Plasmodium spp. and reflects the unusual evolutionary origins of these parasites. The essential role this organelle plays in the life of the parasite, and its unusual, non-mammalian metabolism, make the apicoplast an excellent drug target. AREAS COVERED This review focuses on the biological role of the apicoplast in the erythrocytic life cycle and what that reveals about existing drug targets. We also discuss the future of the apicoplast in the development of anti-malarials, emphasizing those pathways with greatest potential as a source of novel drug targets and emphasizing the need to understand in vitro drug responses to optimize eventual use of these drugs to treat malaria. EXPERT OPINION More than a decade of research on the apicoplast has confirmed the promise of this organelle as a source of drug targets. It is now possible to rationally assess the value of existing drugs and new drug targets, and to understand the role these drugs can play in the arsenal of anti-malarial treatments.
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Affiliation(s)
- Christopher D Goodman
- University of Melbourne, School of Botany, Professor's Walk, Parkville, Vic, 3010, Australia.
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van Dooren GG, Kennedy AT, McFadden GI. The use and abuse of heme in apicomplexan parasites. Antioxid Redox Signal 2012; 17:634-56. [PMID: 22320355 DOI: 10.1089/ars.2012.4539] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
SIGNIFICANCE Heme is an essential prosthetic group for most life on Earth. It functions in numerous cellular redox reactions, including in antioxidant defenses and at several stages of the electron transport chain in prokaryotes and eukaryotic mitochondria. Heme also functions as a sensor and transport molecule for gases such as oxygen. Heme is a complex organic molecule and can only be synthesized through a multienzyme pathway from simpler precursors. Most free-living organisms synthesize their own heme by a broadly conserved metabolic pathway. Parasites are adept at scavenging molecules from their hosts, and heme is no exception. RECENT ADVANCES In this review we examine recent advances in understanding heme usage and acquisition in Apicomplexa, a group of parasites that include the causative agents of malaria, toxoplasmosis, and several major parasites of livestock. CRITICAL ISSUES Heme is critical to the survival of Apicomplexa, although the functions of heme in these organisms remain poorly understood. Some Apicomplexa likely scavenge heme from their host organisms, while others retain the ability to synthesize heme. Surprisingly, some Apicomplexa may be able to both synthesize and scavenge heme. Several Apicomplexa live in intracellular environments that contain high levels of heme. Since heme is toxic at high concentrations, parasites must carefully regulate intracellular heme levels and develop mechanisms to detoxify excess heme. Indeed, drugs interfering with heme detoxification serve as major antimalarials. FUTURE DIRECTIONS Understanding heme requirements and regulation in apicomplexan parasites promises to reveal multiple targets for much-needed therapeutic intervention against these parasites.
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Affiliation(s)
- Giel G van Dooren
- Research School of Biology, Australian National University, Canberra, ACT, Australia.
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14
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Abstract
Parasites like malaria and Toxoplasma possess a vestigial plastid homologous to the chloroplasts of plants. The plastid (known as the apicoplast) is non-photosynthetic but retains many hallmarks of its ancestry including a circular genome that it synthesises proteins from and a suite of biosynthetic pathways of cyanobacterial origin. In this review, the discovery of the apicoplast and its integration, function and purpose are explored. New insights into the apicoplast fatty acid biosynthesis pathway and some novel roles of the apicoplast in vaccine development are reviewed.
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15
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Harris F, Pierpoint L. Photodynamic therapy based on 5-aminolevulinic acid and its use as an antimicrobial agent. Med Res Rev 2011; 32:1292-327. [PMID: 21793017 DOI: 10.1002/med.20251] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Exogenous 5-aminolevulinic acid (ALA) is taken up directly by bacteria, yeasts, fungi, and some parasites, which then induces the accumulation of protoporphyrin IX (PPIX). Subsequent light irradiation of PPIX leads to the inactivation of these organisms via photodamage to their cellular structures. ALA uptake and light irradiation of PPIX produced by host cells leads to the inactivation of other parasites, along with some viruses, via the induction of an immune response. ALA-mediated PPIX production by host cells and light irradiation result in the inactivation of other viruses via either the induction of a host cell response or direct photodynamic attack on viral particles. This ALA-mediated production of light-activated PPIX has been extensively used as a form of photodynamic therapy (PDT) and has shown varying levels of efficacy in treating conditions that are associated with microbial infection, ranging from acne and verrucae to leishmaniasis and onychomycosis. However, for the treatment of some of these conditions by ALA-based PDT, the role of an antimicrobial effect has been disputed and in general, the mechanisms by which the technique inactivates microbes are not well understood. In this study, we review current understanding of the antimicrobial mechanisms used by ALA-based PDT and its role in the treatment of microbial infections along with its potential medical and nonmedical applications.
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Affiliation(s)
- Frederick Harris
- School of Forensic and Investigative Sciences, University of Central Lancashire, Preston, Lancashire, United Kingdom. fharris1@.ac.uk
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16
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Nagaraj VA, Arumugam R, Prasad D, Rangarajan PN, Padmanaban G. Protoporphyrinogen IX oxidase from Plasmodium falciparum is anaerobic and is localized to the mitochondrion. Mol Biochem Parasitol 2010; 174:44-52. [PMID: 20603160 DOI: 10.1016/j.molbiopara.2010.06.012] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Revised: 05/21/2010] [Accepted: 06/24/2010] [Indexed: 11/19/2022]
Abstract
Earlier studies in this laboratory had shown that the malarial parasite can synthesize heme de novo and inhibition of the pathway leads to death of the parasite. It has been proposed that the pathway for the biosynthesis of heme in Plasmodium falciparum is unique involving three different cellular compartments, namely mitochondrion, apicoplast and cytosol. Experimental evidences are now available for the functionality and localization of all the enzymes of this pathway, except protoporphyrinogen IX oxidase (PfPPO), the penultimate enzyme. In the present study, PfPPO has been cloned, expressed and shown to be localized to the mitochondrion by immunofluorescence microscopy. Interestingly, the enzyme has been found to be active only under anaerobic conditions and is dependent on electron transport chain (ETC) acceptors for its activity. The native enzyme present in the parasite is inhibited by the ETC inhibitors, atovaquone and antimycin. Atovaquone, a well known inhibitor of parasite dihydroorotate dehydrogenase, dependent on the ETC, inhibits synthesis of heme as well in P. falciparum culture. A model is proposed to explain the ETC dependence of both the pyrimidine and heme-biosynthetic pathways in P. falciparum.
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17
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Nagaraj VA, Prasad D, Arumugam R, Rangarajan PN, Padmanaban G. Characterization of coproporphyrinogen III oxidase in Plasmodium falciparum cytosol. Parasitol Int 2010. [DOI: 10.1016/j.parint.2009.12.001 10.1016/j.molbiopara.2009.05.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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18
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Lim L, McFadden GI. The evolution, metabolism and functions of the apicoplast. Philos Trans R Soc Lond B Biol Sci 2010; 365:749-63. [PMID: 20124342 PMCID: PMC2817234 DOI: 10.1098/rstb.2009.0273] [Citation(s) in RCA: 205] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The malaria parasite, Plasmodium falciparum, harbours a relict plastid known as the ‘apicoplast’. The discovery of the apicoplast ushered in an exciting new prospect for drug development against the parasite. The eubacterial ancestry of the organelle offers a wealth of opportunities for the development of therapeutic interventions. Morphological, biochemical and bioinformatic studies of the apicoplast have further reinforced its ‘plant-like’ characteristics and potential as a drug target. However, we are still not sure why the apicoplast is essential for the parasite's survival. This review explores the origins and metabolic functions of the apicoplast. In an attempt to decipher the role of the organelle within the parasite we also take a closer look at the transporters decorating the plastid to better understand the metabolic exchanges between the apicoplast and the rest of the parasite cell.
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Affiliation(s)
- Liting Lim
- School of Botany, University of Melbourne, Parkville, Victoria 3010, Australia
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19
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Seeber F, Soldati-Favre D. Metabolic Pathways in the Apicoplast of Apicomplexa. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 281:161-228. [DOI: 10.1016/s1937-6448(10)81005-6] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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20
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Nagaraj VA, Prasad D, Arumugam R, Rangarajan PN, Padmanaban G. Characterization of coproporphyrinogen III oxidase in Plasmodium falciparum cytosol. Parasitol Int 2009; 59:121-7. [PMID: 20006984 DOI: 10.1016/j.parint.2009.12.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2009] [Revised: 11/28/2009] [Accepted: 12/07/2009] [Indexed: 10/20/2022]
Abstract
A unique hybrid pathway has been proposed for de novo heme biosynthesis in Plasmodium falciparum involving three different compartments of the parasite, namely mitochondrion, apicoplast and cytosol. While parasite mitochondrion and apicoplast have been shown to harbor key enzymes of the pathway, there has been no experimental evidence for the involvement of parasite cytosol in heme biosynthesis. In this study, a recombinant P. falciparum coproporphyrinogen III oxidase (rPfCPO) was produced in E. coli and confirmed to be active under aerobic conditions. rPfCPO behaved as a monomer of 61kDa molecular mass in gel filtration analysis. Immunofluorescence studies using antibodies to rPfCPO suggested that the enzyme was present in the parasite cytosol. These results were confirmed by detection of enzyme activity only in the parasite soluble fraction. Western blot analysis with anti-rPfCPO antibodies also revealed a 58kDa protein only in this fraction and not in the membrane fraction. The cytosolic presence of PfCPO provides evidence for a hybrid heme-biosynthetic pathway in the malarial parasite.
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21
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Affiliation(s)
- Scott Severance
- Department of Animal & Avian Sciences and Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, Maryland 20742, USA
| | - Iqbal Hamza
- Department of Animal & Avian Sciences and Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, Maryland 20742, USA
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22
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Nagaraj VA, Prasad D, Rangarajan PN, Padmanaban G. Mitochondrial localization of functional ferrochelatase from Plasmodium falciparum. Mol Biochem Parasitol 2009; 168:109-12. [PMID: 19523497 DOI: 10.1016/j.molbiopara.2009.05.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2009] [Revised: 05/13/2009] [Accepted: 05/29/2009] [Indexed: 10/20/2022]
Abstract
In the malarial parasite, enzymes of heme-biosynthetic pathway are distributed in different cellular compartments. The site of localization of ferrochelatase in the malarial parasite is crucial, since it will decide the ultimate site of heme synthesis. Earlier results have differed in terms of localization, being the mitochondrion or apicoplast and the functional enzyme has not been cloned, expressed and characterized. The present study reveals that Plasmodium falciparum ferrochelatase (PfFC) gene encodes multiple transcripts of which the one encoding the full length functional protein (PfFC) has been cloned and the recombinant protein over-expressed and purified from E. coli cells. The enzyme shows maximum activity with iron, while zinc is a poor substrate. Immunofluorescence studies with antibodies to functional ferrochelatase reveal that the native enzyme is localized to the mitochondrion of the parasite indicating that this organelle is the ultimate site of heme synthesis.
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23
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Vargas PD, Furuyama K, Sassa S, Shibahara S. Hypoxia decreases the expression of the two enzymes responsible for producing linear and cyclic tetrapyrroles in the heme biosynthetic pathway. FEBS J 2009; 275:5947-59. [PMID: 19021769 DOI: 10.1111/j.1742-4658.2008.06723.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Heme is synthesized in all cell types in aerobic organisms. Hydroxymethylbilane synthase (HMBS) and uroporphyrinogen III synthase (UROS) catalyze two consecutive reactions in the heme biosynthetic pathway, generating the first linear and the first cyclic tetrapyrroles, respectively. Each of the HMBS and UROS genes contains the two separate promoters that generate ubiquitous and erythroid-specific mRNAs. Despite the functional significance of HMBS and UROS, regulation of their gene expression remains to be investigated. Here, we showed that hypoxia (1% O(2)) decreased the expression of ubiquitous mRNAs for HMBS and UROS by three- and twofold, respectively, in human hepatic cells (HepG2 and Hep3B), whereas the expression of ubiquitous and erythroid HMBS and UROS mRNAs remained unchanged in erythroid cells (YN-1 and K562). Unexpectedly, hypoxia did not decrease the half-life of HMBS mRNA (8.4 h under normoxia versus 9.1 h under hypoxia) or UROS mRNA (9.0 versus 10.4 h) in hepatic cells. It is therefore unlikely that a change in mRNA stability is responsible for the hypoxia-mediated decrease in the expression levels of these mRNAs. Furthermore, expression levels of HMBS and UROS mRNAs were decreased under normoxia by treatment with deferoxamine or cobalt chloride in hepatic cells, while hypoxia-inducible factor 1alpha was accumulated. Thus, the decrease in the expression of ubiquitous HMBS and UROS mRNAs is associated with accumulation of hypoxia-inducible factor 1alpha protein. In conclusion, the expression of HMBS and UROS mRNAs may be coordinately regulated, which represents a newly identified mechanism that is important for heme homeostasis.
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Affiliation(s)
- Patrick D Vargas
- Department of Molecular Biology and Applied Physiology, Tohoku University School of Medicine, Miyagi, Japan
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24
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Localisation of Plasmodium falciparum uroporphyrinogen III decarboxylase of the heme-biosynthetic pathway in the apicoplast and characterisation of its catalytic properties. Int J Parasitol 2008; 39:559-68. [PMID: 19041871 DOI: 10.1016/j.ijpara.2008.10.011] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2008] [Revised: 10/06/2008] [Accepted: 10/15/2008] [Indexed: 11/23/2022]
Abstract
Uroporphyrinogen decarboxylase (UROD) is a key enzyme in the heme-biosynthetic pathway and in Plasmodium falciparum it occupies a strategic position in the proposed hybrid pathway for heme biosynthesis involving shuttling of intermediates between different subcellular compartments in the parasite. In the present study, we demonstrate that an N-terminally truncated recombinant P. falciparum UROD (r(Delta)PfUROD) over-expressed and purified from Escherichia coli cells, as well as the native enzyme from the parasite were catalytically less efficient compared with the host enzyme, although they were similar in other enzyme parameters. Molecular modeling of PfUROD based on the known crystal structure of the human enzyme indicated that the protein manifests a distorted triose phosphate isomerase (TIM) barrel fold which is conserved in all the known structures of UROD. The parasite enzyme shares all the conserved or invariant amino acid residues at the active and substrate binding sites, but is rich in lysine residues compared with the host enzyme. Mutation of specific lysine residues corresponding to residues at the dimer interface in human UROD enhanced the catalytic efficiency of the enzyme and dimer stability indicating that the lysine rich nature and weak dimer interface of the wild-type PfUROD could be responsible for its low catalytic efficiency. PfUROD was localised to the apicoplast, indicating the requirement of additional mechanisms for transport of the product coproporphyrinogen to other subcellular sites for its further conversion and ultimate heme formation.
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25
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Seeber F, Limenitakis J, Soldati-Favre D. Apicomplexan mitochondrial metabolism: a story of gains, losses and retentions. Trends Parasitol 2008; 24:468-78. [PMID: 18775675 DOI: 10.1016/j.pt.2008.07.004] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Revised: 07/11/2008] [Accepted: 07/17/2008] [Indexed: 11/15/2022]
Abstract
Apicomplexans form a large group of obligate intracellular parasites that occupy diverse environmental niches. To adapt to their hosts, these parasites have evolved sophisticated strategies to access host-cell nutrients and minimize exposure to the host's defence mechanisms. Concomitantly, they have drastically reshaped their own metabolic functions by retaining, losing or gaining genes for metabolic enzymes. Although several Apicomplexans remain experimentally intractable, bioinformatic analyses of their genomes have generated preliminary metabolic maps. Here, we compare the metabolic pathways of five Apicomplexans, focusing on their different mitochondrial functions, which highlight their adaptation to their individual intracellular habitats.
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Affiliation(s)
- Frank Seeber
- Molecular Parasitology, Institute for Biology, Humboldt University, Philippstr. 13, 10115 Berlin, Germany
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