1
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Nguyen JDM, da Hora GCA, Swanson JMJ. Mycolactone A vs. B: Multiscale Simulations Reveal the Roles of Localization and Association in Isomer-Specific Toxicity. Toxins (Basel) 2023; 15:486. [PMID: 37624243 PMCID: PMC10467071 DOI: 10.3390/toxins15080486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 07/22/2023] [Accepted: 07/24/2023] [Indexed: 08/26/2023] Open
Abstract
Mycolactone is an exotoxin produced by Mycobacterium ulcerans that causes the neglected tropical skin disease Buruli ulcer. This toxin inhibits the Sec61 translocon in the endoplasmic reticulum (ER), preventing the host cell from producing several secretory and transmembrane proteins, resulting in cytotoxic and immunomodulatory effects. Interestingly, only one of the two dominant isoforms of mycolactone is cytotoxic. Here, we investigate the origin of this specificity by performing extensive molecular dynamics (MD) simulations with enhanced free energy sampling to query the association trends of the two isoforms with both the Sec61 translocon, using two distinct cryo-electron microscopy (cryo-EM) models as references, and the ER membrane, which serves as a toxin reservoir prior to association. Our results suggest that mycolactone B (the cytotoxic isoform) has a stronger association with the ER membrane than mycolactone A due to more favorable interactions with membrane lipids and water molecules. This could increase the reservoir of toxin proximal to the Sec61 translocon. In one model of Sec61 inhibited by mycolactone, we find that isomer B interacts more closely with residues thought to play a key role in signal peptide recognition and, thus, are essential for subsequent protein translocation. In the other model, we find that isomer B interacts more closely with the lumenal and lateral gates of the translocon, the dynamics of which are essential for protein translocation. These interactions induce a more closed conformation, which has been suggested to block signal peptide insertion and subsequent protein translocation. Collectively, these findings suggest that isomer B's unique cytotoxicity is a consequence of both increased localization to the ER membrane and channel-locking association with the Sec61 translocon, facets that could be targeted in the development of Buruli Ulcer diagnostics and Sec61-targeted therapeutics.
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Affiliation(s)
| | | | - Jessica M. J. Swanson
- Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA; (J.D.M.N.); (G.C.A.d.H.)
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2
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Huang R, Li C, Zhao SG, Liu QT, Liu Y, Xue ZL. Enantioconvergent hydrolysis of racemic 1,2-epoxypentane and 1,2-epoxyhexane by an engineered Escherichia coli strain overexpressing a novel Streptomyces fradiae epoxide hydrolase. Enzyme Microb Technol 2023; 166:110228. [PMID: 36940599 DOI: 10.1016/j.enzmictec.2023.110228] [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: 01/05/2023] [Revised: 03/13/2023] [Accepted: 03/15/2023] [Indexed: 03/19/2023]
Abstract
In order to excavate microbial epoxide hydrolases (EHs) with desired catalytic properties, a novel EH, SfEH1, was identified based on the genome annotation of Streptomyces fradiae and sequence alignment analysis with local protein library. The SfEH1-encoding gene, sfeh1, was then cloned and over-expressed in soluble form in Escherichia coli/BL21(DE3). The optimal temperature and pH of recombinant SfEH1 (reSfEH1) and reSfEH1-expressing E. coli (E. coli/sfeh1) were both determined as 30 ℃ and 7.0, also indicating that the influences of temperature and pH on reSfEH1's activities were more obvious than those of E. coli/sfeh1 whole cells. Subsequently, using E. coli/sfeh1 as catalyst, its catalytic properties towards thirteen common mono-substituted epoxides were tested, in which E. coli/sfeh1 had the highest activity of 28.5 U/g dry cells for rac-1,2-epoxyoctane (rac-6a), and (R)-1,2-pentanediol ((R)-3b) (or (R)-1,2-hexanediol ((R)-4b)) with up to 92.5% (or 94.1%) eep was obtained at almost 100% conversion ratio. Regioselectivity coefficients (αS and βR) displayed in the enantioconvergent hydrolysis of rac-3a (or rac-4a) were calculated to be 98.7% and 93.8% (or 95.2% and 98.9%). Finally, the reason of the high and complementary regioselectivity was confirmed by both kinetic parameter analysis and molecular docking simulations.
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Affiliation(s)
- Rui Huang
- College of Biological and Food Engineering, Anhui Polytechnic University, Wuhu 241000, China
| | - Chuang Li
- College of Biological and Food Engineering, Anhui Polytechnic University, Wuhu 241000, China.
| | - Shi-Guang Zhao
- College of Biological and Food Engineering, Anhui Polytechnic University, Wuhu 241000, China; Anhui Engineering Laboratory for Industrial Microbiology Molecular Breeding, Anhui Polytechnic University, Wuhu 241000, China
| | - Qing-Tao Liu
- College of Biological and Food Engineering, Anhui Polytechnic University, Wuhu 241000, China
| | - Yan Liu
- College of Biological and Food Engineering, Anhui Polytechnic University, Wuhu 241000, China; Anhui Engineering Laboratory for Industrial Microbiology Molecular Breeding, Anhui Polytechnic University, Wuhu 241000, China
| | - Zheng-Lian Xue
- College of Biological and Food Engineering, Anhui Polytechnic University, Wuhu 241000, China; Anhui Engineering Laboratory for Industrial Microbiology Molecular Breeding, Anhui Polytechnic University, Wuhu 241000, China.
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3
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Mycolactone enhances the Ca2+ leak from endoplasmic reticulum by trapping Sec61 translocons in a Ca2+ permeable state. Biochem J 2021; 478:4005-4024. [PMID: 34726690 PMCID: PMC8650850 DOI: 10.1042/bcj20210345] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 10/19/2021] [Accepted: 11/02/2021] [Indexed: 01/17/2023]
Abstract
The Mycobacterium ulcerans exotoxin, mycolactone, is an inhibitor of co-translational translocation via the Sec61 complex. Mycolactone has previously been shown to bind to, and alter the structure of the major translocon subunit Sec61α, and change its interaction with ribosome nascent chain complexes. In addition to its function in protein translocation into the ER, Sec61 also plays a key role in cellular Ca2+ homeostasis, acting as a leak channel between the endoplasmic reticulum (ER) and cytosol. Here, we have analysed the effect of mycolactone on cytosolic and ER Ca2+ levels using compartment-specific sensors. We also used molecular docking analysis to explore potential interaction sites for mycolactone on translocons in various states. These results show that mycolactone enhances the leak of Ca2+ ions via the Sec61 translocon, resulting in a slow but substantial depletion of ER Ca2+. This leak was dependent on mycolactone binding to Sec61α because resistance mutations in this protein completely ablated the increase. Molecular docking supports the existence of a mycolactone-binding transient inhibited state preceding translocation and suggests mycolactone may also bind Sec61α in its idle state. We propose that delayed ribosomal release after translation termination and/or translocon ‘breathing' during rapid transitions between the idle and intermediate-inhibited states allow for transient Ca2+ leak, and mycolactone's stabilisation of the latter underpins the phenotype observed.
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4
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Conditions for Handling and Optimal Storage of Mycolactone. Methods Mol Biol 2021. [PMID: 34643907 DOI: 10.1007/978-1-0716-1779-3_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
The successful isolation of mycolactone in a laboratory or from a clinical sample relies on proper handling and storage of the toxin. Mycolactone is a light-sensitive and an amphiphilic toxin produced by Mycobacterium ulcerans. The biochemistry of the toxin makes it unstable in aqueous matrices such as blood, which causes it to self-aggregate or present in complex with carrier molecules. This biochemistry also impacts the use of the toxin in vitro, in that it tends to aggregate and stick to substrates in an aqueous environment, which alters its physiological presentation and limits its availability in a sample. Glass materials (i.e., tubes, vials, syringes, plates) should be used when possible to avoid loss of mycolactone sticking to plastic surfaces. Dark containers such as amber vials or aluminum-foil wrapped tubes should be used to avoid photodegradation of the toxin upon exposure to light. Sample storage in organic solvents is ideal for mycolactone stability and recovery; however, this is not always amenable as multiple diagnostic assays might be performed on a single sample (such as PCR or ELISA). In these cases, samples can be stored in an aqueous solution containing a small amount of detergent to enhance recovery of the toxin, and in order to avoid aggregation. Therefore, the downstream manipulations should be carefully considered prior to sample collection and storage. Here we present considerations for the optimal handling and storage of mycolactone in order to obtain quality yield of the toxin for various research and diagnostic applications.
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5
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Beemelmanns C, Roman D, Sauer M. Applications of the Horner–Wadsworth–Emmons Olefination in Modern Natural Product Synthesis. SYNTHESIS-STUTTGART 2021. [DOI: 10.1055/a-1493-6331] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
AbstractThe Horner–Wadsworth–Emmons (HWE) reaction is one of the most reliable olefination reaction and can be broadly applied in organic chemistry and natural product synthesis with excellent selectivity. Within the last few years HWE reaction conditions have been optimized and new reagents developed to overcome challenges in the total syntheses of natural products. This review highlights the application of HWE olefinations in total syntheses of structurally different natural products covering 2015 to 2020. Applied HWE reagents and reactions conditions are highlighted to support future synthetic approaches and serve as guideline to find the best HWE conditions for the most complicated natural products.1 Introduction and Historical Background2 Applications of HWE2.1 Cyclization by HWE Reactions2.2.1 Formation of Medium- to Larger-Sized Rings2.2.2 Formation of Small- to Medium-Sized Rings2.3 Synthesis of α,β-Unsaturated Carbonyl Groups2.4 Synthesis of Substituted C=C Bonds2.5 Late-Stage Modifications by HWE Reactions2.6 HWE Reactions on Solid Supports2.7 Synthesis of Poly-Conjugated C=C Bonds2.8 HWE-Mediated Coupling of Larger Building Blocks2.9 Miscellaneous3 Summary and Outlook
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6
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Colucci-Guyon E, Rifflet A, Saint-Auret S, da Costa A, Boucontet L, Laval T, Prehaud C, Blanchard N, Levraud JP, Boneca IG, Demangel C, Guenin-Macé L. Spatiotemporal analysis of mycolactone distribution in vivo reveals partial diffusion in the central nervous system. PLoS Negl Trop Dis 2020; 14:e0008878. [PMID: 33264290 PMCID: PMC7710047 DOI: 10.1371/journal.pntd.0008878] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 10/13/2020] [Indexed: 01/26/2023] Open
Abstract
Mycobacterium ulcerans, the causative agent of Buruli ulcer (BU) disease, is unique amongst human pathogens in its capacity to produce a lipid toxin called mycolactone. While previous studies have demonstrated that bacterially-released mycolactone diffuses beyond infection foci, the spatiotemporal distribution of mycolactone remained largely unknown. Here, we used the zebrafish model to provide the first global kinetic analysis of mycolactone's diffusion in vivo, and multicellular co-culture systems to address the critical question of the toxin's access to the brain. Zebrafish larvae were injected with a fluorescent-derivative of mycolactone to visualize the in vivo diffusion of the toxin from the peripheral circulation. A rapid, body-wide distribution of mycolactone was observed, with selective accumulation in tissues near the injection site and brain, together with an important excretion through the gastro-intestinal tract. Our conclusion that mycolactone reached the central nervous system was reinforced by an in cellulo model of human blood brain barrier and a mouse model of M. ulcerans-infection. Here we show that mycolactone has a broad but heterogenous profile of distribution in vivo. Our investigations in vitro and in vivo support the view that a fraction of bacterially-produced mycolactone gains access to the central nervous system. The relative persistence of mycolactone in the bloodstream suggests that assays of circulating mycolactone are relevant for BU disease monitoring and treatment optimization.
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Affiliation(s)
- Emma Colucci-Guyon
- Macrophages and Development of Immunity, Institut Pasteur, CNRS UMR 3738, Paris, France
| | - Aline Rifflet
- Institut Pasteur, Unité Biologie et génétique de la paroi bactérienne, Paris 75724, France; CNRS, UMR 2001 “Microbiologie intégrative et moléculaire”, Paris 75015, France; INSERM, groupe Avenir, Paris, France
| | - Sarah Saint-Auret
- Université de Haute-Alsace, Université de Strasbourg, CNRS, LIMA, UMR 7042, Mulhouse, France
| | | | - Laurent Boucontet
- Macrophages and Development of Immunity, Institut Pasteur, CNRS UMR 3738, Paris, France
| | - Thomas Laval
- Immunobiology of Infection Unit, Institut Pasteur, INSERM U1221, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | | | - Nicolas Blanchard
- Université de Haute-Alsace, Université de Strasbourg, CNRS, LIMA, UMR 7042, Mulhouse, France
| | - Jean-Pierre Levraud
- Macrophages and Development of Immunity, Institut Pasteur, CNRS UMR 3738, Paris, France
| | - Ivo G. Boneca
- Institut Pasteur, Unité Biologie et génétique de la paroi bactérienne, Paris 75724, France; CNRS, UMR 2001 “Microbiologie intégrative et moléculaire”, Paris 75015, France; INSERM, groupe Avenir, Paris, France
| | - Caroline Demangel
- Immunobiology of Infection Unit, Institut Pasteur, INSERM U1221, Paris, France
| | - Laure Guenin-Macé
- Immunobiology of Infection Unit, Institut Pasteur, INSERM U1221, Paris, France
- * E-mail:
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7
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Wang Y, Chen B, He X, Gui J. Development of Biomimetic Synthesis of Propindilactone G
†. CHINESE J CHEM 2020. [DOI: 10.1002/cjoc.202000293] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Yu Wang
- CAS Key Laboratory of Synthetic Chemistry of Natural Substances, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences Shanghai 200032 China
| | - Bo Chen
- CAS Key Laboratory of Synthetic Chemistry of Natural Substances, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences Shanghai 200032 China
| | - Xubiao He
- CAS Key Laboratory of Synthetic Chemistry of Natural Substances, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences Shanghai 200032 China
| | - Jinghan Gui
- CAS Key Laboratory of Synthetic Chemistry of Natural Substances, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences Shanghai 200032 China
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8
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Larsen MH, Lacourciere K, Parker TM, Kraigsley A, Achkar JM, Adams LB, Dupnik KM, Hall-Stoodley L, Hartman T, Kanipe C, Kurtz SL, Miller MA, Salvador LCM, Spencer JS, Robinson RT. The Many Hosts of Mycobacteria 8 (MHM8): A conference report. Tuberculosis (Edinb) 2020; 121:101914. [PMID: 32279870 PMCID: PMC7428850 DOI: 10.1016/j.tube.2020.101914] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 02/07/2020] [Accepted: 02/09/2020] [Indexed: 12/18/2022]
Abstract
Mycobacteria are important causes of disease in human and animal hosts. Diseases caused by mycobacteria include leprosy, tuberculosis (TB), nontuberculous mycobacteria (NTM) infections and Buruli Ulcer. To better understand and treat mycobacterial disease, clinicians, veterinarians and scientists use a range of discipline-specific approaches to conduct basic and applied research, including conducting epidemiological surveys, patient studies, wildlife sampling, animal models, genetic studies and computational simulations. To foster the exchange of knowledge and collaboration across disciplines, the Many Hosts of Mycobacteria (MHM) conference series brings together clinical, veterinary and basic scientists who are dedicated to advancing mycobacterial disease research. Started in 2007, the MHM series recently held its 8th conference at the Albert Einstein College of Medicine (Bronx, NY). Here, we review the diseases discussed at MHM8 and summarize the presentations on research advances in leprosy, NTM and Buruli Ulcer, human and animal TB, mycobacterial disease comorbidities, mycobacterial genetics and 'omics, and animal models. A mouse models workshop, which was held immediately after MHM8, is also summarized. In addition to being a resource for those who were unable to attend MHM8, we anticipate this review will provide a benchmark to gauge the progress of future research concerning mycobacteria and their many hosts.
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Affiliation(s)
- Michelle H Larsen
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Karen Lacourciere
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20892, USA
| | - Tina M Parker
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20892, USA
| | - Alison Kraigsley
- Center for Infectious Disease Research and Policy, University of Minnesota, Minneapolis, MN, USA
| | - Jacqueline M Achkar
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, USA; Department of Medicine, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Linda B Adams
- Department of Health and Human Services, Health Resources and Services Administration, Healthcare Systems Bureau, National Hansen's Disease Programs, Baton Rouge, LA, USA
| | - Kathryn M Dupnik
- Center for Global Health, Department of Medicine, Weill Cornell Medicine, New York, NY, USA
| | - Luanne Hall-Stoodley
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH, USA
| | - Travis Hartman
- Center for Global Health, Department of Medicine, Weill Cornell Medicine, New York, NY, USA
| | - Carly Kanipe
- Department of Immunobiology, Iowa State University, Ames, IA, USA; Oak Ridge Institute for Science and Education, Oak Ridge, TN, USA; Bacterial Diseases of Livestock Research Unit, National Animal Disease Center, Agricultural Research Service, United States Department of Agriculture, Ames, IA, USA
| | - Sherry L Kurtz
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Washington, DC, USA
| | - Michele A Miller
- DST-NRF Centre of Excellence for Biomedical Tuberculosis Research, South African Medical Research Council Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
| | - Liliana C M Salvador
- Department of Infectious Diseases, University of Georgia, Athens, GA, USA; Institute of Bioinformatics, University of Georgia, Athens, GA, USA; Center for the Ecology of Infectious Diseases, University of Georgia, Athens, GA, USA
| | - John S Spencer
- Department of Microbiology, Immunology, and Pathology, Mycobacteria Research Laboratories, Colorado State University, Fort Collins, CO, USA
| | - Richard T Robinson
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH, USA.
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9
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Gehringer M, Mäder P, Gersbach P, Pfeiffer B, Scherr N, Dangy JP, Pluschke G, Altmann KH. Configurationally Stabilized Analogs of M. ulcerans Exotoxins Mycolactones A and B Reveal the Importance of Side Chain Geometry for Mycolactone Virulence. Org Lett 2019; 21:5853-5857. [PMID: 31295000 DOI: 10.1021/acs.orglett.9b01947] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Mycolactones A/B (1a/b) are exotoxins of Mycobacterium ulcerans that are the molecular cause of Buruli ulcer. 1a/b represent a rapidly equilibrating mixture of Z/E isomers about the C4'═C5' double bond of the C5-side chain. Here, we describe the syntheses of mycolactone analogs with configurationally stable C5-side chains (2a, E mimetic; 2b/c, Z mimetics). Based on the cytotoxicity of 2a-c, the Δ4',5'-trans isomer of mycolactones A/B (1b) appears to be the major virulence factor.
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Affiliation(s)
- Matthias Gehringer
- Swiss Federal Institute of Technology (ETH) Zürich , Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences , Vladimir-Prelog-Weg 4 , 8093 Zürich , Switzerland
| | - Patrick Mäder
- Swiss Federal Institute of Technology (ETH) Zürich , Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences , Vladimir-Prelog-Weg 4 , 8093 Zürich , Switzerland
| | - Philipp Gersbach
- Swiss Federal Institute of Technology (ETH) Zürich , Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences , Vladimir-Prelog-Weg 4 , 8093 Zürich , Switzerland
| | - Bernhard Pfeiffer
- Swiss Federal Institute of Technology (ETH) Zürich , Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences , Vladimir-Prelog-Weg 4 , 8093 Zürich , Switzerland
| | - Nicole Scherr
- Swiss Tropical and Public Health Institute , Socinstrasse 57 , 4002 Basel , Switzerland
| | - Jean-Pierre Dangy
- Swiss Tropical and Public Health Institute , Socinstrasse 57 , 4002 Basel , Switzerland
| | - Gerd Pluschke
- Swiss Tropical and Public Health Institute , Socinstrasse 57 , 4002 Basel , Switzerland
| | - Karl-Heinz Altmann
- Swiss Federal Institute of Technology (ETH) Zürich , Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences , Vladimir-Prelog-Weg 4 , 8093 Zürich , Switzerland
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10
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Recombinant Antibodies against Mycolactone. Toxins (Basel) 2019; 11:toxins11060346. [PMID: 31212961 PMCID: PMC6628451 DOI: 10.3390/toxins11060346] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 06/10/2019] [Accepted: 06/13/2019] [Indexed: 12/21/2022] Open
Abstract
In the past, it has proved challenging to generate antibodies against mycolactone, the primary lipidic toxin A of Mycobacterium ulcerans causing Buruli ulcer, due to its immunosuppressive properties. Here we show that in vitro display, comprising both phage and yeast display, can be used to select antibodies recognizing mycolactone from a large human naïve phage antibody library. Ten different antibodies were isolated, and hundreds more identified by next generation sequencing. These results indicate the value of in vitro display methods to generate antibodies against difficult antigenic targets such as toxins, which cannot be used for immunization unless inactivated by structural modification. The possibility to easily generate anti-mycolactone antibodies is an exciting prospect for the development of rapid and simple diagnostic/detection methods.
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11
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Zong G, Hu Z, O’Keefe S, Tranter D, Iannotti MJ, Baron L, Hall B, Corfield K, Paatero AO, Henderson MJ, Roboti P, Zhou J, Sun X, Govindarajan M, Rohde JM, Blanchard N, Simmonds R, Inglese J, Du Y, Demangel C, High S, Paavilainen VO, Shi WQ. Ipomoeassin F Binds Sec61α to Inhibit Protein Translocation. J Am Chem Soc 2019; 141:8450-8461. [PMID: 31059257 PMCID: PMC6627486 DOI: 10.1021/jacs.8b13506] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Ipomoeassin F is a potent natural cytotoxin that inhibits growth of many tumor cell lines with single-digit nanomolar potency. However, its biological and pharmacological properties have remained largely unexplored. Building upon our earlier achievements in total synthesis and medicinal chemistry, we used chemical proteomics to identify Sec61α (protein transport protein Sec61 subunit alpha isoform 1), the pore-forming subunit of the Sec61 protein translocon, as a direct binding partner of ipomoeassin F in living cells. The interaction is specific and strong enough to survive lysis conditions, enabling a biotin analogue of ipomoeassin F to pull down Sec61α from live cells, yet it is also reversible, as judged by several experiments including fluorescent streptavidin staining, delayed competition in affinity pulldown, and inhibition of TNF biogenesis after washout. Sec61α forms the central subunit of the ER protein translocation complex, and the binding of ipomoeassin F results in a substantial, yet selective, inhibition of protein translocation in vitro and a broad ranging inhibition of protein secretion in live cells. Lastly, the unique resistance profile demonstrated by specific amino acid single-point mutations in Sec61α provides compelling evidence that Sec61α is the primary molecular target of ipomoeassin F and strongly suggests that the binding of this natural product to Sec61α is distinctive. Therefore, ipomoeassin F represents the first plant-derived, carbohydrate-based member of a novel structural class that offers new opportunities to explore Sec61α function and to further investigate its potential as a therapeutic target for drug discovery.
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Affiliation(s)
- Guanghui Zong
- †Department
of Chemistry and Biochemistry and ⬡Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, United States,Department
of Chemistry and Biochemistry, University
of Maryland, College Park, Maryland 20742, United States
| | - Zhijian Hu
- †Department
of Chemistry and Biochemistry and ⬡Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Sarah O’Keefe
- School
of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, United Kingdom
| | - Dale Tranter
- University
of Helsinki, HiLIFE, Helsinki, Finland,Institute
of Biotechnology, Helsinki, Finland
| | - Michael J. Iannotti
- National
Center for Advancing Translational Sciences, National
Institutes of Health, Rockville, Maryland 20850, United States
| | - Ludivine Baron
- Immunobiology
of Infection Unit, Institut Pasteur, 75015 Paris, France,INSERM, U1221, 75005 Paris, France
| | - Belinda Hall
- Department
of Microbial Sciences, School of Biosciences and Medicine, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom
| | - Katherine Corfield
- Department
of Microbial Sciences, School of Biosciences and Medicine, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom
| | - Anja O. Paatero
- University
of Helsinki, HiLIFE, Helsinki, Finland,Institute
of Biotechnology, Helsinki, Finland
| | - Mark J. Henderson
- National
Center for Advancing Translational Sciences, National
Institutes of Health, Rockville, Maryland 20850, United States
| | - Peristera Roboti
- School
of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, United Kingdom
| | - Jianhong Zhou
- †Department
of Chemistry and Biochemistry and ⬡Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Xianwei Sun
- †Department
of Chemistry and Biochemistry and ⬡Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, United States,Department
of Radiology, Baylor College of Medicine, Houston, Texas 77030, United States
| | - Mugunthan Govindarajan
- †Department
of Chemistry and Biochemistry and ⬡Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, United States,Emory
Institute for Drug Development, Emory University, 954 Gatewood Road, Atlanta, Georgia 30329, United States
| | - Jason M. Rohde
- National
Center for Advancing Translational Sciences, National
Institutes of Health, Rockville, Maryland 20850, United States
| | - Nicolas Blanchard
- Université
de Haute-Alsace, Université de Strasbourg, CNRS, LIMA, UMR 7042, 68000 Mulhouse, France
| | - Rachel Simmonds
- Department
of Microbial Sciences, School of Biosciences and Medicine, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom,
| | - James Inglese
- National
Center for Advancing Translational Sciences, National
Institutes of Health, Rockville, Maryland 20850, United States,
| | - Yuchun Du
- †Department
of Chemistry and Biochemistry and ⬡Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, United States,
| | - Caroline Demangel
- Immunobiology
of Infection Unit, Institut Pasteur, 75015 Paris, France,INSERM, U1221, 75005 Paris, France,
| | - Stephen High
- School
of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, United Kingdom,
| | - Ville O. Paavilainen
- University
of Helsinki, HiLIFE, Helsinki, Finland,Institute
of Biotechnology, Helsinki, Finland,
| | - Wei Q. Shi
- †Department
of Chemistry and Biochemistry and ⬡Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, United States,Department
of Chemistry, Ball State University, Muncie, Indiana 47306, United States,;
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12
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Kubicek-Sutherland JZ, Vu DM, Anderson AS, Sanchez TC, Converse PJ, Martí-Arbona R, Nuermberger EL, Swanson BI, Mukundan H. Understanding the Significance of Biochemistry in the Storage, Handling, Purification, and Sampling of Amphiphilic Mycolactone. Toxins (Basel) 2019; 11:toxins11040202. [PMID: 30987300 PMCID: PMC6520765 DOI: 10.3390/toxins11040202] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 02/26/2019] [Accepted: 04/01/2019] [Indexed: 12/29/2022] Open
Abstract
Mycolactone, the amphiphilic macrolide toxin secreted by Mycobacterium ulcerans, plays a significant role in the pathology and manifestations of Buruli ulcer (BU). Consequently, it follows that the toxin is a suitable target for the development of diagnostics and therapeutics for this disease. Yet, several challenges have deterred such development. For one, the lipophilic nature of the toxin makes it difficult to handle and store and contributes to variability associated with laboratory experimentation and purification yields. In this manuscript, we have attempted to incorporate our understanding of the lipophilicity of mycolactone in order to define the optimal methods for the storage, handling, and purification of this toxin. We present a systematic correlation of variability associated with measurement techniques (thin-layer chromatography (TLC), mass spectrometry (MS), and UV-Vis spectrometry), storage conditions, choice of solvents, as well as the impact of each of these on toxin function as assessed by cellular cytotoxicity. We also compared natural mycolactone extracted from bacterial culture with synthesized toxins in laboratory (solvents, buffers) and physiologically relevant (serum) matrices. Our results point to the greater stability of mycolactone in organic, as well as detergent-containing, solvents, regardless of the container material (plastic, glass, or silanized tubes). They also highlight the presence of toxin in samples that may be undetectable by any one technique, suggesting that each detection approach captures different configurations of the molecule with varying specificity and sensitivity. Most importantly, our results demonstrate for the very first time that amphiphilic mycolactone associates with host lipoproteins in serum, and that this association will likely impact our ability to study, diagnose, and treat Buruli ulcers in patients.
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Affiliation(s)
| | - Dung M Vu
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
| | - Aaron S Anderson
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
| | - Timothy C Sanchez
- Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
| | - Paul J Converse
- Department of Medicine, Johns Hopkins University Center for Tuberculosis Research, Baltimore, MD 21218, USA.
| | | | - Eric L Nuermberger
- Department of Medicine, Johns Hopkins University Center for Tuberculosis Research, Baltimore, MD 21218, USA.
| | - Basil I Swanson
- Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
| | - Harshini Mukundan
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
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13
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Heravi MM, Mohammadkhani L. Recent applications of Stille reaction in total synthesis of natural products: An update. J Organomet Chem 2018. [DOI: 10.1016/j.jorganchem.2018.05.018] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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14
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Saint-Auret S, Abdelkafi H, Le Nouen D, Guenin-Macé L, Demangel C, Bisseret P, Blanchard N. Modular total syntheses of mycolactone A/B and its [ 2H]-isotopologue. Org Biomol Chem 2018; 15:7518-7522. [PMID: 28871293 DOI: 10.1039/c7ob01943b] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A modular total synthesis of mycolactone A/B, the exotoxin produced by Mycobacterium ulcerans, has been achieved through the orchestration of several Pd-catalyzed key steps. While this route leads to a mixture of the natural product and its C12 epimer (4 : 1 ratio), this was inconsequential from the biological activity standpoint. Compared to the previously reported routes, this synthetic blueprint allows the late-stage modification of the toxin, as exemplified by the preparation of [22,22,22-2H3]-mycolactone A/B.
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Affiliation(s)
- Sarah Saint-Auret
- Université de Strasbourg, CNRS, Laboratoire de Chimie Moléculaire UMR 7509, 67000 Strasbourg, France.
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15
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Gehringer M, Altmann KH. The chemistry and biology of mycolactones. Beilstein J Org Chem 2017; 13:1596-1660. [PMID: 28904608 PMCID: PMC5564285 DOI: 10.3762/bjoc.13.159] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 07/21/2017] [Indexed: 12/21/2022] Open
Abstract
Mycolactones are a group of macrolides excreted by the human pathogen Mycobacterium ulcerans, which exhibit cytotoxic, immunosuppressive and analgesic properties. As the virulence factor of M. ulcerans, mycolactones are central to the pathogenesis of the neglected disease Buruli ulcer, a chronic and debilitating medical condition characterized by necrotic skin ulcers. Due to their complex structure and fascinating biology, mycolactones have inspired various total synthesis endeavors and structure-activity relationship studies. Although this review intends to cover all synthesis efforts in the field, special emphasis is given to the comparison of conceptually different approaches and to the discussion of more recent contributions. Furthermore, a detailed discussion of molecular targets and structure-activity relationships is provided.
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Affiliation(s)
- Matthias Gehringer
- Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, ETH Zürich, Vladimir-Prelog-Weg 4, 8093 Zürich, Switzerland
| | - Karl-Heinz Altmann
- Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, ETH Zürich, Vladimir-Prelog-Weg 4, 8093 Zürich, Switzerland
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16
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Babu VS, Zhou Y, Kishi Y. Design, synthesis, and cytotoxicity of stabilized mycolactone analogs. Bioorg Med Chem Lett 2017; 27:1274-1277. [PMID: 28159417 DOI: 10.1016/j.bmcl.2017.01.036] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 01/11/2017] [Accepted: 01/12/2017] [Indexed: 11/16/2022]
Abstract
On exposure to visible light, mycolactone A/B, the causative toxin of Buruli ulcer, rearranges to a mixture of four photo-mycolactones apparently via a rare photochemically-induced [4πs+2πa] cycloaddition. In order to prevent the rearrangement, two C6'-C7' dihydromycolactone analogs 6'α-15 and 6'β-15 were designed and synthesized. 6'α-15 and 6'β-15 were shown to be stable under not only photochemical, but also acidic and basic conditions. Cytotoxicity was tested against arbitrarily chosen four cell lines (human Hek-293, human lung carcinoma A-549, human melanoma LOX-IMVI, and mouse L-929), thereby revealing that: (1) both analogs maintain potent cytotoxicity; (2) 6'β-15 exhibits significantly higher potency against human cell lines than 6'α-15; (3) in comparison with parent mycolactone A/B, 6'β-15 exhibits equal potency against human Hek-293, whereas significantly lower potency against human lung carcinoma A-549 and human melanoma LOX-IMVI.
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Affiliation(s)
- Vaddela Sudheer Babu
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
| | - Ya Zhou
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
| | - Yoshito Kishi
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA.
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17
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Saint-Auret S, Abdelkafi H, Le Nouen D, Bisseret P, Blanchard N. Synthetic strategies towards mycolactone A/B, an exotoxin secreted by Mycobacterium ulcerans. Org Chem Front 2017. [DOI: 10.1039/c7qo00608j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Pitfalls and dead-ends pave the way to mycolactone A/B. This full account reports synthetic efforts towards this natural product that eventually culminated in a de novo total synthesis.
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Affiliation(s)
- Sarah Saint-Auret
- Université de Strasbourg
- CNRS
- Laboratoire de Chimie Moléculaire UMR 7509
- 67000 Strasbourg
- France
| | - Hajer Abdelkafi
- Université de Strasbourg
- CNRS
- Laboratoire de Chimie Moléculaire UMR 7509
- 67000 Strasbourg
- France
| | - Didier Le Nouen
- Université de Haute-Alsace
- Laboratoire de Chimie Organique et Bioorganique EA 4566
- 68093 Mulhouse Cedex
- France
| | - Philippe Bisseret
- Université de Strasbourg
- CNRS
- Laboratoire de Chimie Moléculaire UMR 7509
- 67000 Strasbourg
- France
| | - Nicolas Blanchard
- Université de Strasbourg
- CNRS
- Laboratoire de Chimie Moléculaire UMR 7509
- 67000 Strasbourg
- France
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18
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Sarfo FS, Phillips R, Wansbrough-Jones M, Simmonds RE. Recent advances: role of mycolactone in the pathogenesis and monitoring of Mycobacterium ulcerans infection/Buruli ulcer disease. Cell Microbiol 2016; 18:17-29. [PMID: 26572803 PMCID: PMC4705457 DOI: 10.1111/cmi.12547] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 11/10/2015] [Accepted: 11/13/2015] [Indexed: 02/03/2023]
Abstract
Infection of subcutaneous tissue with Mycobacterium ulcerans can lead to chronic skin ulceration known as Buruli ulcer. The pathogenesis of this neglected tropical disease is dependent on a lipid‐like toxin, mycolactone, which diffuses through tissue away from the infecting organisms. Since its identification in 1999, this molecule has been intensely studied to elucidate its cytotoxic and immunosuppressive properties. Two recent major advances identifying the underlying molecular targets for mycolactone have been described. First, it can target scaffolding proteins (such as Wiskott Aldrich Syndrome Protein), which control actin dynamics in adherent cells and therefore lead to detachment and cell death by anoikis. Second, it prevents the co‐translational translocation (and therefore production) of many proteins that pass through the endoplasmic reticulum for secretion or placement in cell membranes. These pleiotropic effects underpin the range of cell‐specific functional defects in immune and other cells that contact mycolactone during infection. The dose and duration of mycolactone exposure for these different cells explains tissue necrosis and the paucity of immune cells in the ulcers. This review discusses recent advances in the field, revisits older findings in this context and highlights current developments in structure‐function studies as well as methodology that make mycolactone a promising diagnostic biomarker.
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Affiliation(s)
- Fred Stephen Sarfo
- Department of Medicine, Kwame Nkrumah University of Science & Technology, Kumasi, Ghana
| | - Richard Phillips
- Department of Medicine, Kwame Nkrumah University of Science & Technology, Kumasi, Ghana
| | - Mark Wansbrough-Jones
- Division of Cellular and Molecular Medicine, St George's, University of London, London, UK
| | - Rachel E Simmonds
- School of Biosciences and Medicine, University of Surrey, Guildford, UK
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Guenin-Macé L, Baron L, Chany AC, Tresse C, Saint-Auret S, Jönsson F, Le Chevalier F, Bruhns P, Bismuth G, Hidalgo-Lucas S, Bisson JF, Blanchard N, Demangel C. Shaping mycolactone for therapeutic use against inflammatory disorders. Sci Transl Med 2016; 7:289ra85. [PMID: 26019221 DOI: 10.1126/scitranslmed.aab0458] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Inflammation adversely affects the health of millions of people worldwide, and there is an unmet medical need for better anti-inflammatory drugs. We evaluated the therapeutic interest of mycolactone, a polyketide-derived macrolide produced by Mycobacterium ulcerans. Bacterial production of mycolactone in human skin causes a combination of ulcerative, analgesic, and anti-inflammatory effects. Whereas ulcer formation is mediated by the proapoptotic activity of mycolactone on skin cells via hyperactivation of Wiskott-Aldrich syndrome proteins, analgesia results from neuronal hyperpolarization via signaling through angiotensin II type 2 receptors. Mycolactone also blunts the capacity of immune cells to produce inflammatory mediators by an independent mechanism of protein synthesis blockade. In an attempt to isolate the structural determinants of mycolactone's immunosuppressive activity, we screened a library of synthetic subunits of mycolactone for inhibition of cytokine production by activated T cells. The minimal structure retaining immunosuppressive activity was a truncated version of mycolactone, missing one of the two core-branched polyketide chains. This compound inhibited the inflammatory cytokine responses of human primary cells at noncytotoxic doses and bound to angiotensin II type 2 receptors comparably to mycolactone in vitro. Notably, it was considerably less toxic than mycolactone in human primary dermal fibroblasts modeling ulcerative activity. In mouse models of human diseases, it conferred systemic protection against chronic skin inflammation and inflammatory pain, with no apparent side effects. In addition to establishing the anti-inflammatory potency of mycolactone in vivo, our study therefore highlights the translational potential of mycolactone core-derived structures as prospective immunosuppressants.
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Affiliation(s)
- Laure Guenin-Macé
- Institut Pasteur, Unité d'Immunobiologie de l'Infection, Paris 75015, France. CNRS URA 1961, Paris 75015, France
| | - Ludivine Baron
- Institut Pasteur, Unité d'Immunobiologie de l'Infection, Paris 75015, France. CNRS URA 1961, Paris 75015, France
| | - Anne-Caroline Chany
- Université de Strasbourg, Laboratoire de Chimie Moléculaire, ECPM-CNRS UMR 7509, Strasbourg 67087, France
| | - Cédric Tresse
- Université de Strasbourg, Laboratoire de Chimie Moléculaire, ECPM-CNRS UMR 7509, Strasbourg 67087, France
| | - Sarah Saint-Auret
- Université de Strasbourg, Laboratoire de Chimie Moléculaire, ECPM-CNRS UMR 7509, Strasbourg 67087, France
| | - Friederike Jönsson
- Institut Pasteur, Unité Anticorps en Thérapie et Pathologie, Paris 75015, France. INSERM U760, Paris 75015, France
| | - Fabien Le Chevalier
- Institut Pasteur, Unité d'Immunobiologie de l'Infection, Paris 75015, France
| | - Pierre Bruhns
- Institut Pasteur, Unité Anticorps en Thérapie et Pathologie, Paris 75015, France. INSERM U760, Paris 75015, France
| | - Georges Bismuth
- INSERM U1016, Institut Cochin, Paris 75014, France. Université Paris Descartes, Paris 75014, France. CNRS UMR 8104, Paris 75014, France
| | - Sophie Hidalgo-Lucas
- ETAP, Inflammation, Dermatologie et Toxicologie, Vandœuvre-lès-Nancy 54500, France
| | - Jean-François Bisson
- ETAP, Inflammation, Dermatologie et Toxicologie, Vandœuvre-lès-Nancy 54500, France
| | - Nicolas Blanchard
- Université de Strasbourg, Laboratoire de Chimie Moléculaire, ECPM-CNRS UMR 7509, Strasbourg 67087, France
| | - Caroline Demangel
- Institut Pasteur, Unité d'Immunobiologie de l'Infection, Paris 75015, France. CNRS URA 1961, Paris 75015, France.
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20
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Brown CA, Aggarwal VK. Short Convergent Synthesis of the Mycolactone Core Through Lithiation-Borylation Homologations. Chemistry 2015; 21:13900-3. [PMID: 26332797 PMCID: PMC6519258 DOI: 10.1002/chem.201503122] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Indexed: 12/17/2022]
Abstract
Using iterative lithiation-borylation homologations, the mycolactone toxin core has been synthesized in 13 steps and 17% overall yield. The rapid build-up of molecular complexity, high convergence and high stereoselectivity are noteworthy features of this synthesis.
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Affiliation(s)
- Christopher A Brown
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS (UK)
| | - Varinder K Aggarwal
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS (UK).
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21
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Li X, Babu VS, Kishi Y. Stereoselective total synthesis and stereochemistry confirmation of photo-mycolactones. Tetrahedron Lett 2015. [DOI: 10.1016/j.tetlet.2014.12.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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