1
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Moser C, Muhle-Goll C. Cell-free protein production of a gamma secretase homolog. Protein Expr Purif 2024; 215:106407. [PMID: 38000778 DOI: 10.1016/j.pep.2023.106407] [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: 08/16/2023] [Revised: 11/17/2023] [Accepted: 11/19/2023] [Indexed: 11/26/2023]
Abstract
Cleavage of the transmembrane domain (TMD) of amyloid-β precursor protein (APP) by γ-secretase, an intramembrane aspartyl protease, generates Aβ peptides of various lengths that form plaques in the brains of Alzheimer's disease patients. Although the debate has not been finally resolved whether these plaques trigger the onset of Alzheimer's or are side products, disease-related mutations suggest their implication in the etiology of the dementia. These occur both in presenilin, the catalytic subunit of γ-secretase, and in the TMD of APP. Despite two seminal cryo-electron microscopy structures that show the complex of γ-secretase with its substrates APP and Notch, the mechanism of γ-secretase is not yet fully understood. Especially on which basis it selects its substrates is still an enigma. The presenilin homolog PSH from the archaeon Methanoculleus marisnigri JR1 (MCMJR1) is catalytically active without accessory proteins in contrast to γ-secretase making it an excellent model for studies of the basic cleavage process. We here focused on the cell-free expression of PSH screening a range of conditions. Cleavage assays to verify the activity show that not only the yield, but mainly the activity of the protease depends on the careful selection of expression conditions. Optimal results were found for a cell-free expression at relatively low temperature, 20 °C, employing cell lysates prepared from E. coli Rosetta cells. To speed up protein preparation for immediate functional assays, a crude purification protocol was developed. This allows to produce ready-made PSH in a fast and efficient manner in less than two days.
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Affiliation(s)
- Celine Moser
- Institute for Biological Interfaces 4, Karlsruhe Institute of Technology, 76344 Eggenstein- Leopoldshafen, Germany; Institute of Organic Chemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Claudia Muhle-Goll
- Institute for Biological Interfaces 4, Karlsruhe Institute of Technology, 76344 Eggenstein- Leopoldshafen, Germany; Institute of Organic Chemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.
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2
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Höger B, Peifer C, Beitz E. Cell-free production of fluorescent proteins for the discovery of novel ribosome-targeting antibiotics. J Microbiol Methods 2023; 213:106814. [PMID: 37652138 DOI: 10.1016/j.mimet.2023.106814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 08/14/2023] [Accepted: 08/29/2023] [Indexed: 09/02/2023]
Abstract
Various issues including the overuse of antibiotics has led to the development of threatening multidrug-resistant bacterial strains urging development of novel anti-infectives. One quarter of current clinical phase III antibiotic drug candidates address ribosomal protein translation as a target. Here, we describe an effective cell-free in vitro screening system for inhibitors of bacterial ribosome activity with direct fluorescence read-out. Using ribosomal S30 extracts from Escherichia coli, Salmonella enterica, and Pseudomonas putida, the validity of this system is demonstrated by concentration-dependent inhibition of translation by a set of different classes of translation-targeting drugs. The single-compartment cell-free translation reaction is compatible with multi-well formats. Fluorophore formation of green fluorescent protein or monomeric NeonGreen occurs in an hour time frame without the need of adding reagents for secondary enzymatic detection saving handling time, and prohibiting false positives. As label-free readout, the dose response further allows for IC50 determination in the same setup. Together, we show that cell-free production of fluorescent proteins for the discovery of ribosome-targeting antibiotics is feasible and amenable to high-throughput applications.
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Affiliation(s)
- Bastian Höger
- Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel, Gutenbergstraße 76, Kiel, Germany
| | - Christian Peifer
- Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel, Gutenbergstraße 76, Kiel, Germany
| | - Eric Beitz
- Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel, Gutenbergstraße 76, Kiel, Germany.
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3
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Wang J, Li J, Li M, Ma K, Wang D, Su L, Zhang X, Tang BZ. Nanolab in a Cell: Crystallization-Induced In Situ Self-Assembly for Cancer Theranostic Amplification. J Am Chem Soc 2022; 144:14388-14395. [PMID: 35900284 DOI: 10.1021/jacs.2c06111] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Conducting crystallization-assisted self-assembly in living biosystems to obtain large-size nanoparticles and achieve a specific physiological purpose remains an appealing yet significantly challenging task. In this study, we designed Au(I)-disulfide nanosheets containing an aggregation-induced emission photosensitizer, namely, NSs@TTVP, which exhibited pH-responsive crystallization-driven self-assembly capability in lysosomes of cancer cells and tumor tissues of mice. The crystallization process endowed NSs@TTVP with a microscale morphology, stronger fluorescence output, and highly enhanced reactive oxygen species production efficiency. The in vivo results demonstrated that NSs@TTVP shows both long-term retention in tumors and extensive destruction to cancer cells, making it supremely powerful for fluorescence imaging-guided tumor tracking and inhibition.
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Affiliation(s)
- Jianxing Wang
- Center for AIE Research, College of Materials Science and Engineering, Shenzhen University, Shenzhen 518060, China.,School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, China
| | - Jie Li
- Center for AIE Research, College of Materials Science and Engineering, Shenzhen University, Shenzhen 518060, China
| | - Meng Li
- Center for AIE Research, College of Materials Science and Engineering, Shenzhen University, Shenzhen 518060, China
| | - Ke Ma
- Center for AIE Research, College of Materials Science and Engineering, Shenzhen University, Shenzhen 518060, China
| | - Dong Wang
- Center for AIE Research, College of Materials Science and Engineering, Shenzhen University, Shenzhen 518060, China
| | - Lei Su
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, China
| | - Xueji Zhang
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, China
| | - Ben Zhong Tang
- Center for AIE Research, College of Materials Science and Engineering, Shenzhen University, Shenzhen 518060, China.,School of Science and Engineering, Shenzhen Institute of Aggregate Science and Technology, The Chinese University of Hong Kong, Shenzhen 518172, China
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4
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Ferrer-Miralles N, Saccardo P, Corchero JL, Garcia-Fruitós E. Recombinant Protein Production and Purification of Insoluble Proteins. Methods Mol Biol 2022; 2406:1-31. [PMID: 35089548 DOI: 10.1007/978-1-0716-1859-2_1] [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] [Indexed: 06/14/2023]
Abstract
Proteins are synthesized in heterologous systems because of the impossibility to obtain satisfactory yields from natural sources. The efficient production of soluble and functional recombinant proteins is among the main goals in the biotechnological field. In this context, it is important to point out that under stress conditions, protein folding machinery is saturated and this promotes protein misfolding and, consequently, protein aggregation. Thus, the selection of the optimal expression organism and its growth conditions to minimize the formation of insoluble protein aggregates should be done according to the protein characteristics and downstream requirements. Escherichia coli is the most popular recombinant protein expression system despite the great development achieved so far by eukaryotic expression systems. Besides, other prokaryotic expression systems, such as lactic acid bacteria and psychrophilic bacteria, are gaining interest in this field. However, it is worth mentioning that prokaryotic expression system poses, in many cases, severe restrictions for a successful heterologous protein production. Thus, eukaryotic systems such as mammalian cells, insect cells, yeast, filamentous fungus, and microalgae are an interesting alternative for the production of these difficult-to-express proteins.
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Affiliation(s)
- Neus Ferrer-Miralles
- Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain
- CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Cerdanyola del Vallès, Spain
| | - Paolo Saccardo
- Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain
- CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Cerdanyola del Vallès, Spain
| | - José Luis Corchero
- Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain
- CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Cerdanyola del Vallès, Spain
| | - Elena Garcia-Fruitós
- Department of Ruminant Production, Institut de Recerca i Tecnologia Agroalimentàries (IRTA), Caldes de Montbui, Spain.
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Cell-Free Expression of a Plant Membrane Protein BrPT2 From Boesenbergia Rotunda. Mol Biotechnol 2021; 63:316-326. [PMID: 33565047 DOI: 10.1007/s12033-021-00304-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/21/2021] [Indexed: 10/22/2022]
Abstract
Prenylation of aromatic natural products by membrane-bound prenyltransferases (PTs) is an important biosynthesis step of many bioactive compounds. At present, only a few plant flavonoid-related PT genes have been functionally characterized, mainly due to the difficulties of expressing these membrane proteins. Rapid and effective methods to produce functional plant membrane proteins are thus indispensable. Here, we evaluated expression systems through cell-based and cell-free approaches to express Boesenbergia rotunda BrPT2 encoding a membrane-bound prenyltransferase. We attempted to express BrPT2 in Escherichia coli and tobacco plants but failed to detect this protein using the Western-blot technique, whereas an intact single band of 43 kDa was detected when BrPT2 was expressed using a cell-free protein synthesis system (PURE). Under in vitro enzymatic condition, the synthesized BrPT2 successfully catalyzed pinostrobin chalcone to pinostrobin. Molecular docking analysis showed that pinostrobin chalcone interacts with BrPT2 at two cavities: (1) the main binding site at the central cavity and (2) the allosteric binding site located away from the central cavity. Our findings suggest that cell-free protein synthesis could be an alternative for rapid production of valuable difficult-to-express membrane proteins.
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Abstract
Proteins are the main source of drug targets and some of them possess therapeutic potential themselves. Among them, membrane proteins constitute approximately 50% of the major drug targets. In the drug discovery pipeline, rapid methods for producing different classes of proteins in a simple manner with high quality are important for structural and functional analysis. Cell-free systems are emerging as an attractive alternative for the production of proteins due to their flexible nature without any cell membrane constraints. In a bioproduction context, open systems based on cell lysates derived from different sources, and with batch-to-batch consistency, have acted as a catalyst for cell-free synthesis of target proteins. Most importantly, proteins can be processed for downstream applications like purification and functional analysis without the necessity of transfection, selection, and expansion of clones. In the last 5 years, there has been an increased availability of new cell-free lysates derived from multiple organisms, and their use for the synthesis of a diverse range of proteins. Despite this progress, major challenges still exist in terms of scalability, cost effectiveness, protein folding, and functionality. In this review, we present an overview of different cell-free systems derived from diverse sources and their application in the production of a wide spectrum of proteins. Further, this article discusses some recent progress in cell-free systems derived from Chinese hamster ovary and Sf21 lysates containing endogenous translocationally active microsomes for the synthesis of membrane proteins. We particularly highlight the usage of internal ribosomal entry site sequences for more efficient protein production, and also the significance of site-specific incorporation of non-canonical amino acids for labeling applications and creation of antibody drug conjugates using cell-free systems. We also discuss strategies to overcome the major challenges involved in commercializing cell-free platforms from a laboratory level for future drug development.
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Affiliation(s)
- Srujan Kumar Dondapati
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, 14476, Potsdam, Germany
| | - Marlitt Stech
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, 14476, Potsdam, Germany
| | - Anne Zemella
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, 14476, Potsdam, Germany
| | - Stefan Kubick
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, 14476, Potsdam, Germany.
- Faculty of Health Sciences, Joint Faculty of the Brandenburg University of Technology Cottbus-Senftenberg, The Brandenburg Medical School Theodor Fontane and the University of Potsdam, Potsdam, Germany.
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Hajek P, Bader A, Helmstetter F, Henke B, Arnold P, Beitz E. Cell-Free and Yeast-Based Production of the Malarial Lactate Transporter, PfFNT, Delivers Comparable Yield and Protein Quality. Front Pharmacol 2019; 10:375. [PMID: 31024323 PMCID: PMC6467934 DOI: 10.3389/fphar.2019.00375] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 03/26/2019] [Indexed: 11/16/2022] Open
Abstract
Cell-free protein production is an attractive alternative to cell-based expression. Rapid results, small-volume reactions, irrelevance of protein toxicity, flexibility, and openness of the system are strong points in favor of the cell-free system. However, the in vitro situation lacks the cellular quality control machinery comprising e.g., the translocon for inserting membrane proteins into lipid bilayers, and chaperon-assisted protein degradation pathways. Here, we compare yield and protein quality of the lactate transporter, PfFNT, from malaria parasites when produced in Pichia pastoris yeast, or in an Escherichia coli S30-extract-based cell-free system. Besides solubilization and correct folding, PfFNT requires oligomerization into homopentamers. We assessed PfFNT folding/oligomerization and function by transmission electron microscopy imaging, transport assays, and binding of small-molecule inhibitors. For the latter, we used chromatography of the PfFNT-inhibitor complex with dual-wavelength detection, and biolayer interferometry. Our data show, that PfFNT possesses an intrinsic capability for assuming the correct fold, oligomerization pattern, and functionality during in vitro translation. This competence depended on the detergent present in the cell-free reaction. The choice of detergent further affected purification and inhibitor binding. In conclusion, in the presence of a suitable detergent, cell-free systems are very well capable of producing high quality membrane proteins.
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Affiliation(s)
- Philipp Hajek
- Department of Pharmaceutical and Medicinal Chemistry, Pharmaceutical Institute, Christian-Albrechts-University Kiel, Kiel, Germany
| | - Annika Bader
- Department of Pharmaceutical and Medicinal Chemistry, Pharmaceutical Institute, Christian-Albrechts-University Kiel, Kiel, Germany
| | - Folknand Helmstetter
- Department of Pharmaceutical and Medicinal Chemistry, Pharmaceutical Institute, Christian-Albrechts-University Kiel, Kiel, Germany
| | - Björn Henke
- Department of Pharmaceutical and Medicinal Chemistry, Pharmaceutical Institute, Christian-Albrechts-University Kiel, Kiel, Germany
| | - Philipp Arnold
- Anatomical Institute, Christian-Albrechts-University Kiel, Kiel, Germany
| | - Eric Beitz
- Department of Pharmaceutical and Medicinal Chemistry, Pharmaceutical Institute, Christian-Albrechts-University Kiel, Kiel, Germany
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8
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Helmstetter F, Arnold P, Höger B, Petersen LM, Beitz E. Formate-nitrite transporters carrying nonprotonatable amide amino acids instead of a central histidine maintain pH-dependent transport. J Biol Chem 2018; 294:623-631. [PMID: 30455351 DOI: 10.1074/jbc.ra118.006340] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 11/09/2018] [Indexed: 01/25/2023] Open
Abstract
Microbial formate-nitrite transporter-type proteins (FNT) exhibit dual transport functionality. At neutral pH, electrogenic anion currents are detectable, whereas upon acidification transport of the neutral, protonated monoacid predominates. Physiologically, FNT-mediated proton co-transport is vital when monocarboxylic acid products of the energy metabolism, such as l-lactate, are released from the cell. Accordingly, Plasmodium falciparum malaria parasites can be killed by small-molecule inhibitors of PfFNT. Two opposing hypotheses on the site of substrate protonation are plausible. The proton relay mechanism postulates proton transfer from a highly conserved histidine centrally positioned in the transport path. The dielectric slide mechanism assumes decreasing acidity of substrates entering the lipophilic vestibules and protonation via the bulk water. Here, we defined the transport mechanism of the FNT from the amoebiasis parasite Entamoeba histolytica, EhFNT, and also show that BtFdhC from Bacillus thuringiensis is a functional formate transporter. Both FNTs carry a nonprotonatable amide amino acid, asparagine or glutamine, respectively, at the central histidine position. Despite having a nonprotonatable residue, EhFNT displayed the same substrate selectivity for larger monocarboxylates including l-lactate, a low substrate affinity as is typical for FNTs, and, strikingly, proton motive force-dependent transport as observed for PfFNT harboring a central histidine. These results argue against a proton relay mechanism, indicating that substrate protonation must occur outside of the central histidine region, most likely in the vestibules. Furthermore, EhFNT is the sole annotated FNT in the Entamoeba genome suggesting that it could be a putative new drug target with similar utility as that of the malarial PfFNT.
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Affiliation(s)
| | - Philipp Arnold
- the Anatomical Institute, Christian-Albrechts-University of Kiel, 24118 Kiel, Germany
| | - Bastian Höger
- From the Department of Pharmaceutical and Medicinal Chemistry, and
| | | | - Eric Beitz
- From the Department of Pharmaceutical and Medicinal Chemistry, and
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9
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Transmembrane solute transport in the apicomplexan parasite Plasmodium. Emerg Top Life Sci 2017; 1:553-561. [PMID: 33525850 DOI: 10.1042/etls20170097] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2017] [Revised: 11/12/2017] [Accepted: 11/16/2017] [Indexed: 12/22/2022]
Abstract
Apicomplexa are a large group of eukaryotic, single-celled parasites, with complex life cycles that occur within a wide range of different microenvironments. They include important human pathogens such as Plasmodium, the causal agent of malaria, and Toxoplasma, which causes toxoplasmosis most often in immunocompromised individuals. Despite environmental differences in their life cycles, these parasites retain the ability to obtain nutrients, remove waste products, and control ion balances. They achieve this flexibility by relying on proteins that can deliver and remove solutes. This reliance on transport proteins for essential functions makes these pathways excellent potential targets for drug development programmes. Transport proteins are frequently key mediators of drug resistance by their ability to remove drugs from their sites of action. The study of transport processes mediated by integral membrane proteins and, in particular, identification of their physiological functions and localisation, and differentiation from host orthologues has already established new validated drug targets. Our understanding of how apicomplexan parasites have adapted to changing environmental challenges has also increased through the study of their transporters. This brief introduction to membrane transporters of apicomplexans highlights recent discoveries focusing on Plasmodium and emphasises future directions.
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Wiechert M, Erler H, Golldack A, Beitz E. A widened substrate selectivity filter of eukaryotic formate-nitrite transporters enables high-level lactate conductance. FEBS J 2017; 284:2663-2673. [PMID: 28544379 DOI: 10.1111/febs.14117] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Revised: 05/05/2017] [Accepted: 05/18/2017] [Indexed: 12/24/2022]
Abstract
Bacterial formate-nitrite transporters (FNT) regulate the metabolic flow of small weak mono-acids derived from anaerobic mixed-acid fermentation, such as formate, and further transport nitrite and hydrosulfide. The eukaryotic Plasmodium falciparumFNT is vital for the malaria parasite by its ability to release the larger l-lactate substrate as the metabolic end product of anaerobic glycolysis in symport with protons preventing cytosolic acidification. However, the molecular basis for substrate discrimination by FNTs has remained unclear. Here, we identified a size-selective FNT substrate filter region around an invariant lysine at the bottom of the periplasmic/extracellular vestibule. The selectivity filter is reminiscent of the aromatic/arginine constriction of aquaporin water and solute channels regarding composition, location in the protein, and the size-selection principle. Bioinformatics support an adaptation of the eukaryotic FNT selectivity filter to accommodate larger physiologically relevant substrates. Mutations that affect the diameter at the filter site predictably modulated substrate selectivity. The shape of the vestibule immediately above the filter region further affects selectivity. This study indicates that eukaryotic FNTs evolved to transport larger mono-acid substrates, especially l-lactic acid as a product of energy metabolism.
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Affiliation(s)
- Marie Wiechert
- Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel, Germany
| | - Holger Erler
- Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel, Germany
| | - André Golldack
- Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel, Germany
| | - Eric Beitz
- Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel, Germany
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Hapuarachchi SV, Cobbold SA, Shafik SH, Dennis ASM, McConville MJ, Martin RE, Kirk K, Lehane AM. The Malaria Parasite's Lactate Transporter PfFNT Is the Target of Antiplasmodial Compounds Identified in Whole Cell Phenotypic Screens. PLoS Pathog 2017; 13:e1006180. [PMID: 28178359 PMCID: PMC5298231 DOI: 10.1371/journal.ppat.1006180] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 01/11/2017] [Indexed: 11/19/2022] Open
Abstract
In this study the ‘Malaria Box’ chemical library comprising 400 compounds with antiplasmodial activity was screened for compounds that perturb the internal pH of the malaria parasite, Plasmodium falciparum. Fifteen compounds induced an acidification of the parasite cytosol. Two of these did so by inhibiting the parasite’s formate nitrite transporter (PfFNT), which mediates the H+-coupled efflux from the parasite of lactate generated by glycolysis. Both compounds were shown to inhibit lactate transport across the parasite plasma membrane, and the transport of lactate by PfFNT expressed in Xenopus laevis oocytes. PfFNT inhibition caused accumulation of lactate in parasitised erythrocytes, and swelling of both the parasite and parasitised erythrocyte. Long-term exposure of parasites to one of the inhibitors gave rise to resistant parasites with a mutant form of PfFNT that showed reduced inhibitor sensitivity. This study provides the first evidence that PfFNT is a druggable antimalarial target. The emergence and spread of Plasmodium falciparum strains resistant to leading antimalarial drugs has intensified the need to discover and develop drugs that kill the parasite via new mechanisms. Here we screened compounds that are known to inhibit P. falciparum growth for their effects on the pH inside the parasite. We identified fifteen compounds that decrease the pH inside the parasite, and determined the mechanism by which two of these, MMV007839 and MMV000972, disrupt pH and kill the parasite. The two compounds were found to inhibit the P. falciparum formate nitrite transporter (PfFNT), a transport protein that is located on the parasite surface and that serves to remove the waste product lactic acid from the parasite. The compounds inhibited both the H+-coupled transport of lactate across the parasite plasma membrane and the transport of lactate by PfFNT expressed in Xenopus oocytes. In addition to disrupting pH, PfFNT inhibition led to a build-up of lactate in the parasite-infected red blood cell and the swelling of both the parasite and the infected red blood cell. Exposing parasites to MMV007839 over a prolonged time period gave rise to resistant parasites with a mutant form of PfFNT that was less sensitive to the compound. This study validates PfFNT as a novel antimalarial drug target.
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Affiliation(s)
| | - Simon A Cobbold
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, VIC, Australia
| | - Sarah H Shafik
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Adelaide S M Dennis
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Malcolm J McConville
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, VIC, Australia
| | - Rowena E Martin
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Kiaran Kirk
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Adele M Lehane
- Research School of Biology, Australian National University, Canberra, ACT, Australia
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