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Popoff MR. Overview of Bacterial Protein Toxins from Pathogenic Bacteria: Mode of Action and Insights into Evolution. Toxins (Basel) 2024; 16:182. [PMID: 38668607 PMCID: PMC11054074 DOI: 10.3390/toxins16040182] [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: 02/16/2024] [Revised: 03/29/2024] [Accepted: 03/30/2024] [Indexed: 04/29/2024] Open
Abstract
Bacterial protein toxins are secreted by certain bacteria and are responsible for mild to severe diseases in humans and animals. They are among the most potent molecules known, which are active at very low concentrations. Bacterial protein toxins exhibit a wide diversity based on size, structure, and mode of action. Upon recognition of a cell surface receptor (protein, glycoprotein, and glycolipid), they are active either at the cell surface (signal transduction, membrane damage by pore formation, or hydrolysis of membrane compound(s)) or intracellularly. Various bacterial protein toxins have the ability to enter cells, most often using an endocytosis mechanism, and to deliver the effector domain into the cytosol, where it interacts with an intracellular target(s). According to the nature of the intracellular target(s) and type of modification, various cellular effects are induced (cell death, homeostasis modification, cytoskeleton alteration, blockade of exocytosis, etc.). The various modes of action of bacterial protein toxins are illustrated with representative examples. Insights in toxin evolution are discussed.
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Affiliation(s)
- Michel R Popoff
- Unité des Toxines Bactériennes, Institut Pasteur, Université Paris Cité, CNRS UMR 2001 INSERM U1306, F-75015 Paris, France
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2
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Yin L, Thaker H. Cancer Drug Delivery Systems Using Bacterial Toxin Translocation Mechanisms. Bioengineering (Basel) 2023; 10:813. [PMID: 37508840 PMCID: PMC10376142 DOI: 10.3390/bioengineering10070813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 06/16/2023] [Accepted: 06/21/2023] [Indexed: 07/30/2023] Open
Abstract
Recent advances in targeted cancer therapy hold great promise for both research and clinical applications and push the boundaries in finding new treatments for various currently incurable cancers. However, these therapies require specific cell-targeting mechanisms for the efficient delivery of drug cargo across the cell membrane to reach intracellular targets and avoid diffusion to unwanted tissues. Traditional drug delivery systems suffer from a limited ability to travel across the barriers posed by cell membranes and, therefore, there is a need for high doses, which are associated with adverse reactions and safety concerns. Bacterial toxins have evolved naturally to specifically target cell subtypes via their receptor binding module, penetrating the cell membrane efficiently through the membrane translocation process and then successfully delivering the toxic cargo into the host cytosol. They have, thus, been harnessed for the delivery of various drugs. In this review, we focus on bacterial toxin translocation mechanisms and recent progress in the targeted delivery systems of cancer therapy drugs that have been inspired by the receptor binding and membrane translocation processes of the anthrax toxin protective antigen, diphtheria toxin, and Pseudomonas exotoxin A. We also discuss the challenges and limitations of these studies that should be addressed before bacterial toxin-based drug delivery systems can become a viable new generation of drug delivery approaches in clinical translation.
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Affiliation(s)
- Linxiang Yin
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA
- Department of Surgery, Harvard Medical School, Boston, MA 02115, USA
- Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA
| | - Hatim Thaker
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA
- Department of Surgery, Harvard Medical School, Boston, MA 02115, USA
- Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA
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3
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Solution Structures of Bacillus anthracis Protective Antigen Proteins Using Small Angle Neutron Scattering and Protective Antigen 63 Ion Channel Formation Kinetics. Toxins (Basel) 2021; 13:toxins13120888. [PMID: 34941724 PMCID: PMC8708185 DOI: 10.3390/toxins13120888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 12/03/2021] [Accepted: 12/06/2021] [Indexed: 11/17/2022] Open
Abstract
We are studying the structures of bacterial toxins that form ion channels and enable macromolecule transport across membranes. For example, the crystal structure of the Staphylococcus aureus α-hemolysin (α-HL) channel in its functional state was confirmed using neutron reflectometry (NR) with the protein reconstituted in membranes tethered to a solid support. This method, which provides sub-nanometer structural information, could also test putative structures of the Bacillus anthracis protective antigen 63 (PA63) channel, locate where B. anthracis lethal factor and edema factor toxins (LF and EF, respectively) bind to it, and determine how certain small molecules can inhibit the interaction of LF and EF with the channel. We report here the solution structures of channel-forming PA63 and its precursor PA83 (which does not form channels) obtained with small angle neutron scattering. At near neutral pH, PA83 is a monomer and PA63 a heptamer. The latter is compared to two cryo-electron microscopy structures. We also show that although the α-HL and PA63 channels have similar structural features, unlike α-HL, PA63 channel formation in lipid bilayer membranes ceases within minutes of protein addition, which currently precludes the use of NR for elucidating the interactions between PA63, LF, EF, and potential therapeutic agents.
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Hirschenberger M, Stadler N, Fellermann M, Sparrer KMJ, Kirchhoff F, Barth H, Papatheodorou P. CRISPA: A Non-viral, Transient Cas9 Delivery System Based on Reengineered Anthrax Toxin. Front Pharmacol 2021; 12:770283. [PMID: 34733166 PMCID: PMC8558532 DOI: 10.3389/fphar.2021.770283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 10/01/2021] [Indexed: 11/13/2022] Open
Abstract
Translating the CRISPR/Cas9 genome editing technology into clinics is still hampered by rather unspecific, unsafe and/or inconvenient approaches for the delivery of its main components - the Cas9 endonuclease and a guide RNA - into cells. Here, we describe the development of a novel transient and non-viral Cas9 delivery strategy based on the translocation machinery of the Bacillus anthracis anthrax toxin, PA (protective antigen). We show that Cas9 variants fused to the N-terminus of the lethal factor or to a hexahistidine tag are shuttled through channels formed by PA into the cytosol of human cells. As proof-of-principle, we applied our new approach, denoted as CRISPA, to knock out lipolysis-stimulated lipoprotein receptor (LSR) in the human colon cancer cell line HCT116 and green-fluorescent protein (GFP) in human embryonic kidney 293T cells stably expressing GFP. Notably, we confirmed that the transporter PA can be adapted to recognize specific host cell-surface receptor proteins and may be optimized for cell type-selective delivery of Cas9. Altogether, CRISPA provides a novel, transient and non-viral way to deliver Cas9 into specific cells. Thus, this system is an additional step towards safe translation of the CRISPR/Cas9 technology into clinics.
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Affiliation(s)
- Maximilian Hirschenberger
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm, Germany.,Institute of Molecular Virology, Ulm University Medical Center, Ulm, Germany
| | - Nicole Stadler
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm, Germany
| | - Maximilian Fellermann
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm, Germany
| | | | - Frank Kirchhoff
- Institute of Molecular Virology, Ulm University Medical Center, Ulm, Germany
| | - Holger Barth
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm, Germany
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Liu W, Nestorovich EM. Anthrax toxin channel: What we know based on over 30 years of research. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183715. [PMID: 34332985 DOI: 10.1016/j.bbamem.2021.183715] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Revised: 07/21/2021] [Accepted: 07/24/2021] [Indexed: 10/20/2022]
Abstract
Protective antigen channel is the central component of the deadly anthrax exotoxin responsible for binding and delivery of the toxin's enzymatic lethal and edema factor components into the cytosol. The channel, which is more than three times longer than the lipid bilayer membrane thickness and has a 6-Å limiting diameter, is believed to provide a sophisticated unfoldase and translocase machinery for the foreign protein transport into the host cell cytosol. The tripartite toxin can be reengineered, one component at a time or collectively, to adapt it for the targeted cancer therapeutic treatments. In this review, we focus on the biophysical studies of the protective antigen channel-forming activity, small ion transport properties, enzymatic factor translocation, and blockage comparing it with the related clostridial binary toxin channels. We address issues linked to the anthrax toxin channel structural dynamics and lipid dependence, which are yet to become generally recognized as parts of the toxin translocation machinery.
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Affiliation(s)
- Wenxing Liu
- Department of Biology, The Catholic University of America, 620 Michigan Ave, Washington, DC 20064, USA
| | - Ekaterina M Nestorovich
- Department of Biology, The Catholic University of America, 620 Michigan Ave, Washington, DC 20064, USA.
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6
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Abstract
Anthrax toxin is a major virulence factor of Bacillus anthracis, a Gram-positive bacterium which can form highly stable spores that are the causative agents of the disease, anthrax. While chiefly a disease of livestock, spores can be "weaponized" as a bio-terrorist agent, and can be deadly if not recognized and treated early with antibiotics. The intracellular pathways affected by the enzymes are broadly understood and are not discussed here. This chapter focuses on what is known about the assembly of secreted toxins on the host cell surface and how the toxin is delivered into the cytosol. The central component is the "Protective Antigen", which self-oligomerizes and forms complexes with its pay-load, either Lethal Factor or Edema Factor. It binds a host receptor, CMG2, or a close relative, triggering receptor-mediated endocytosis, and forms a remarkably elegant yet powerful machine that delivers toxic enzymes into the cytosol, powered only by the pH gradient across the membrane. We now have atomic structures of most of the starting, intermediate and final assemblies in the infectious process. Together with a major body of biophysical, mutational and biochemical work, these studies reveal a remarkable story of both how toxin assembly is choreographed in time and space.
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Tournier JN, Rougeaux C. Anthrax Toxin Detection: From In Vivo Studies to Diagnostic Applications. Microorganisms 2020; 8:microorganisms8081103. [PMID: 32717946 PMCID: PMC7464488 DOI: 10.3390/microorganisms8081103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 07/19/2020] [Accepted: 07/21/2020] [Indexed: 11/16/2022] Open
Abstract
Anthrax toxins are produced by Bacillus anthracis throughout infection and shape the physiopathogenesis of the disease. They are produced in low quantities but are highly efficient. They have thus been long ignored, but recent biochemical methods have improved our knowledge in animal models. This article reviews the various methods that have been used and how they could be applied to clinical diagnosis.
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Affiliation(s)
- Jean-Nicolas Tournier
- Unité Bactériologie Biothérapies Anti-infectieuses et Immunité, Institut de Recherche Biomédicale des Armées (IRBA), 1 place Général Valérie André, 91220 Brétigny sur Orge, France;
- Centre National de Référence-Laboratoire Expert Charbon, 1 place Général Valérie André, 91220 Brétigny sur Orge, France
- Innovative Vaccine Laboratory, Institut Pasteur, 28 rue du docteur Roux, 75015 Paris, France
- Ecole du Val-de-Grâce, 1 place Alphonse Laveran, 75005 Paris, France
| | - Clémence Rougeaux
- Unité Bactériologie Biothérapies Anti-infectieuses et Immunité, Institut de Recherche Biomédicale des Armées (IRBA), 1 place Général Valérie André, 91220 Brétigny sur Orge, France;
- Centre National de Référence-Laboratoire Expert Charbon, 1 place Général Valérie André, 91220 Brétigny sur Orge, France
- Correspondence: ; Tel.: +33-178-651-891
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Majumder S, Das S, Kingston J, Shivakiran MS, Batra HV, Somani VK, Bhatnagar R. Functional characterization and evaluation of protective efficacy of EA752-862 monoclonal antibody against B. anthracis vegetative cell and spores. Med Microbiol Immunol 2019; 209:125-137. [PMID: 31811379 DOI: 10.1007/s00430-019-00650-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2019] [Accepted: 11/22/2019] [Indexed: 08/30/2023]
Abstract
The most promising means of controlling anthrax, a lethal zoonotic disease during the early infection stages, entail restricting the resilient infectious form, i.e., the spores from proliferating to replicating bacilli in the host. The extractible antigen (EA1), a major S-layer protein present on the vegetative cells and spores of Bacillus anthracis, is highly immunogenic and protects mice against lethal challenge upon immunization. In the present study, mice were immunized with r-EA1C, the C terminal crystallization domain of EA1, to generate a neutralizing monoclonal antibody EA752-862, that was evaluated for its anti-spore and anti-bacterial properties. The monoclonal antibody EA752-862 had a minimum inhibitory concentration of 0.08 mg/ml, was bactericidal at a concentration of 0.1 mg/ml and resulted in 100% survival of mice against challenge with B. anthracis vegetative cells. Bacterial cell lysis as observed by scanning electron microscopy and nucleic acid leakage assay could be attributed as a possible mechanism for the bactericidal property. The association of mAb EA752-862 with spores inhibits their subsequent germination to vegetative cells in vitro, enhances phagocytosis of the spores and killing of the vegetative cells within the macrophage, and subsequently resulted in 90% survival of mice upon B. anthracis Ames spore challenge. Therefore, owing to its anti-spore and bactericidal properties, the present study demonstrates mAb EA752-862 as an efficient neutralizing antibody that hinders the establishment of early infection before massive multiplication and toxin release takes place.
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Affiliation(s)
- Saugata Majumder
- Microbiology Division, Defence Food Research Laboratory, Mysore, 570011, India
| | - Shreya Das
- Microbiology Division, Defence Food Research Laboratory, Mysore, 570011, India
| | - Joseph Kingston
- Microbiology Division, Defence Food Research Laboratory, Mysore, 570011, India.
| | - M S Shivakiran
- Microbiology Division, Defence Food Research Laboratory, Mysore, 570011, India
| | - H V Batra
- Microbiology Division, Defence Food Research Laboratory, Mysore, 570011, India
| | - Vikas Kumar Somani
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Rakesh Bhatnagar
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067, India
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Stiles BG. Clostridial Binary Toxins: Basic Understandings that Include Cell Surface Binding and an Internal "Coup de Grâce". Curr Top Microbiol Immunol 2019; 406:135-162. [PMID: 27380267 DOI: 10.1007/82_2016_11] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Clostridium species can make a remarkable number of different protein toxins, causing many diverse diseases in humans and animals. The binary toxins of Clostridium botulinum, C. difficile, C. perfringens, and C. spiroforme are one group of enteric-acting toxins that attack the actin cytoskeleton of various cell types. These enterotoxins consist of A (enzymatic) and B (cell binding/membrane translocation) components that assemble on the targeted cell surface or in solution, forming a multimeric complex. Once translocated into the cytosol via endosomal trafficking and acidification, the A component dismantles the filamentous actin-based cytoskeleton via mono-ADP-ribosylation of globular actin. Knowledge of cell surface receptors and how these usurped, host-derived molecules facilitate intoxication can lead to novel ways of defending against these clostridial binary toxins. A molecular-based understanding of the various steps involved in toxin internalization can also unveil therapeutic intervention points that stop the intoxication process. Furthermore, using these bacterial proteins as medicinal shuttle systems into cells provides intriguing possibilities in the future. The pertinent past and state-of-the-art present, regarding clostridial binary toxins, will be evident in this chapter.
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Affiliation(s)
- Bradley G Stiles
- Biology Department, Wilson College, Chambersburg, PA, 17201, USA.
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Zeptomole per milliliter detection and quantification of edema factor in plasma by LC-MS/MS yields insights into toxemia and the progression of inhalation anthrax. Anal Bioanal Chem 2019; 411:2493-2509. [PMID: 30911800 DOI: 10.1007/s00216-019-01730-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 02/06/2019] [Accepted: 02/26/2019] [Indexed: 12/28/2022]
Abstract
Inhalation of Bacillus anthracis spores can cause a rapidly progressing fatal infection. B. anthracis secretes three protein toxins: lethal factor (LF), edema factor (EF), and protective antigen (PA). EF and LF may circulate as free or PA-bound forms. Both free EF (EF) and PA-bound-EF (ETx) have adenylyl cyclase activity converting ATP to cAMP. We developed an adenylyl cyclase activity-based method for detecting and quantifying total EF (EF+ETx) in plasma. The three-step method includes magnetic immunocapture with monoclonal antibodies, reaction with ATP generating cAMP, and quantification of cAMP by isotope-dilution HPLC-MS/MS. Total EF was quantified from 5PL regression of cAMP vs ETx concentration. The detection limit was 20 fg/mL (225 zeptomoles/mL for the 89 kDa protein). Relative standard deviations for controls with 0.3, 6.0, and 90 pg/mL were 11.7-16.6% with 91.2-99.5% accuracy. The method demonstrated 100% specificity in 238 human serum/plasma samples collected from unexposed healthy individuals, and 100% sensitivity in samples from 3 human and 5 rhesus macaques with inhalation anthrax. Analysis of EF in the rhesus macaques showed that it was detected earlier post-exposure than B. anthracis by culture and PCR. Similar to LF, the kinetics of EF over the course of infection were triphasic, with an initial rise (phase-1), decline (phase-2), and final rapid rise (phase-3). EF levels were ~ 2-4 orders of magnitude lower than LF during phase-1 and phase-2 and only ~ 6-fold lower at death/euthanasia. Analysis of EF improves early diagnosis and adds to our understanding of anthrax toxemia throughout infection. The LF/EF ratio may also indicate the stage of infection and need for advanced treatments.
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Kalu N, Atsmon-Raz Y, Momben Abolfath S, Lucas L, Kenney C, Leppla SH, Tieleman DP, Nestorovich EM. Effect of late endosomal DOBMP lipid and traditional model lipids of electrophysiology on the anthrax toxin channel activity. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:2192-2203. [PMID: 30409515 DOI: 10.1016/j.bbamem.2018.08.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 07/09/2018] [Accepted: 08/19/2018] [Indexed: 01/26/2023]
Abstract
Anthrax toxin action requires triggering of natural endocytic transport mechanisms whereby the binding component of the toxin forms channels (PA63) within endosomal limiting and intraluminal vesicle membranes to deliver the toxin's enzymatic components into the cytosol. Membrane lipid composition varies at different stages of anthrax toxin internalization, with intraluminal vesicle membranes containing ~70% of anionic bis(monoacylglycero)phosphate lipid. Using model bilayer measurements, we show that membrane lipids can have a strong effect on the anthrax toxin channel properties, including the channel-forming activity, voltage-gating, conductance, selectivity, and enzymatic factor binding. Interestingly, the highest PA63 insertion rate was observed in bis(monoacylglycero)phosphate membranes. The molecular dynamics simulation data show that the conformational properties of the channel are different in bis(monoacylglycero)phosphate compared to PC, PE, and PS lipids. The anthrax toxin protein/lipid bilayer system can be advanced as a novel robust model to directly investigate lipid influence on membrane protein properties and protein/protein interactions.
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Affiliation(s)
- Nnanya Kalu
- Department of Biology, The Catholic University of America, 620 Michigan Ave NE, Washington 20064, DC, USA
| | - Yoav Atsmon-Raz
- Department of Biological Sciences, Centre for Molecular Simulation, University of Calgary, 2500 University Drive NW, Calgary T2N 1N4, Alberta, Canada.
| | - Sanaz Momben Abolfath
- Department of Biology, The Catholic University of America, 620 Michigan Ave NE, Washington 20064, DC, USA
| | - Laura Lucas
- Department of Biology, The Catholic University of America, 620 Michigan Ave NE, Washington 20064, DC, USA
| | - Clare Kenney
- Department of Biology, The Catholic University of America, 620 Michigan Ave NE, Washington 20064, DC, USA
| | - Stephen H Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda 20892, MD, USA
| | - D Peter Tieleman
- Department of Biological Sciences, Centre for Molecular Simulation, University of Calgary, 2500 University Drive NW, Calgary T2N 1N4, Alberta, Canada
| | - Ekaterina M Nestorovich
- Department of Biology, The Catholic University of America, 620 Michigan Ave NE, Washington 20064, DC, USA.
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Kalu N, Alcaraz A, Yamini G, Momben Abolfath S, Lucas L, Kenney C, Aguilella VM, Nestorovich EM. Effect of endosomal acidification on small ion transport through the anthrax toxin PA 63 channel. FEBS Lett 2017; 591:3481-3492. [PMID: 28963849 DOI: 10.1002/1873-3468.12866] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 09/20/2017] [Accepted: 09/21/2017] [Indexed: 11/12/2022]
Abstract
Tight regulation of pH is critical for the structure and function of cells and organelles. The pH environment changes dramatically along the endocytic pathway, an internalization transport process that is 'hijacked' by many intracellularly active bacterial exotoxins, including the anthrax toxin. Here, we investigate the role of pH on single-channel properties of the anthrax toxin protective antigen (PA63 ). Using conductance and current noise analysis, blocker binding, ion selectivity, and poly(ethylene glycol) partitioning measurements, we show that the channel exists in two different open states ('maximum' and 'main') at pH ≥ 5.5, while only a maximum conductance state is detected at pH < 5.5. We describe two substantially distinct patterns of PA63 conductance dependence on KCl concentration uncovered at pH 6.5 and 4.5.
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Affiliation(s)
- Nnanya Kalu
- Department of Biology, The Catholic University of America, Washington, DC, USA
| | - Antonio Alcaraz
- Laboratory of Molecular Biophysics, Department of Physics, Universitat Jaume I, Castellón, Spain
| | - Goli Yamini
- Department of Biology, The Catholic University of America, Washington, DC, USA
| | | | - Laura Lucas
- Department of Biology, The Catholic University of America, Washington, DC, USA
| | - Clare Kenney
- Department of Biology, The Catholic University of America, Washington, DC, USA
| | - Vicente M Aguilella
- Laboratory of Molecular Biophysics, Department of Physics, Universitat Jaume I, Castellón, Spain
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Rabideau AE, Pentelute BL. Delivery of Non-Native Cargo into Mammalian Cells Using Anthrax Lethal Toxin. ACS Chem Biol 2016; 11:1490-501. [PMID: 27055654 DOI: 10.1021/acschembio.6b00169] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The intracellular delivery of peptide and protein therapeutics is a major challenge due to the plasma membrane, which acts as a barrier between the extracellular environment and the intracellular milieu. Over the past two decades, a nontoxic PA/LFN delivery platform derived from anthrax lethal toxin has been developed for the transport of non-native cargo into the cytosol of cells in order to understand the translocation process through a protective antigen (PA) pore and to probe intracellular biological functions. Enzyme-mediated ligation using sortase A and native chemical ligation are two facile methods used to synthesize these non-native conjugates, inaccessible by recombinant technology. Cargo molecules that translocate efficiently include enzymes from protein toxins, antibody mimic proteins, and peptides of varying lengths and non-natural amino acid compositions. The PA pore has been found to effectively convey over 30 known cargos other than native lethal factor (LF; i.e., non-native) with diverse sequences and functionalities on the LFN transporter protein. All together these studies demonstrated that non-native cargos must adopt an unfolded or extended conformation and contain a suitable charge composition in order to efficiently pass through the PA pore. This review provides insight into design parameters for the efficient delivery of new cargos using PA and LFN.
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Affiliation(s)
- Amy E. Rabideau
- Massachusetts Institute of Technology, Department of Chemistry, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Bradley Lether Pentelute
- Massachusetts Institute of Technology, Department of Chemistry, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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Sun J, Jacquez P. Roles of Anthrax Toxin Receptor 2 in Anthrax Toxin Membrane Insertion and Pore Formation. Toxins (Basel) 2016; 8:34. [PMID: 26805886 PMCID: PMC4773787 DOI: 10.3390/toxins8020034] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Revised: 01/18/2016] [Accepted: 01/19/2016] [Indexed: 12/04/2022] Open
Abstract
Interaction between bacterial toxins and cellular surface receptors is an important component of the host-pathogen interaction. Anthrax toxin protective antigen (PA) binds to the cell surface receptor, enters the cell through receptor-mediated endocytosis, and forms a pore on the endosomal membrane that translocates toxin enzymes into the cytosol of the host cell. As the major receptor for anthrax toxin in vivo, anthrax toxin receptor 2 (ANTXR2) plays an essential role in anthrax toxin action by providing the toxin with a high-affinity binding anchor on the cell membrane and a path of entry into the host cell. ANTXR2 also acts as a molecular clamp by shifting the pH threshold of PA pore formation to a more acidic pH range, which prevents premature pore formation at neutral pH before the toxin reaches the designated intracellular location. Most recent studies have suggested that the disulfide bond in the immunoglobulin (Ig)-like domain of ANTXR2 plays an essential role in anthrax toxin action. Here we will review the roles of ANTXR2 in anthrax toxin action, with an emphasis on newly updated knowledge.
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Affiliation(s)
- Jianjun Sun
- Department of Biological Sciences, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, TX 79968, USA.
| | - Pedro Jacquez
- Department of Biological Sciences, Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, TX 79968, USA.
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15
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Molecular assembly of lethal factor enzyme and pre-pore heptameric protective antigen in early stage of translocation. J Mol Model 2015; 22:7. [PMID: 26659402 DOI: 10.1007/s00894-015-2878-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 11/25/2015] [Indexed: 10/22/2022]
Abstract
During intoxication, the anthrax toxin lethal (LF) and edema (EF) factors initially assemble with the protective antigen (PA) on the plasma membrane of cells expressing the membrane-bound surface-exposed anthrax toxin receptor (ATR). This takes place at the physiological pH prior to entering the acidic environment of the endosome. We elucidated the molecular dynamics (MD) behaviors of the three-dimensional structure of the (PA63)7LF3 complex in various conformations and analyzed the dynamical properties of the fully loaded pre-pore complex on the plasma membrane at the physiological pH. The analysis points to the interaction networks of amino acids conserved between PA63 octamer and heptamer, which are not affected during the initial stage of the LFs binding. The simulations show an asymmetrical movement of the complex domains that directly affect LFs conformations. The conformational and structural alterations of the 2β2-2β3 loops of PA subunits are associated with pore formation. The early conformational changes of the loops appear as they peel off from the domain 2 toward domain 4 of each PA subunit. The LFs unfold in 1α1 segments of their N-terminal initiating the early stage of the pre-pore formation. The results indicate instable regions within the complex and provide important clues concerning the detail of fluctuating residues of the LF-PA interface regions at the early steps of toxins translocation.
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Williamson ED, Dyson EH. Anthrax prophylaxis: recent advances and future directions. Front Microbiol 2015; 6:1009. [PMID: 26441934 PMCID: PMC4585224 DOI: 10.3389/fmicb.2015.01009] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 09/07/2015] [Indexed: 11/13/2022] Open
Abstract
Anthrax is a serious, potentially fatal disease that can present in four distinct clinical patterns depending on the route of infection (cutaneous, gastrointestinal, pneumonic, or injectional); effective strategies for prophylaxis and therapy are therefore required. This review addresses the complex mechanisms of pathogenesis employed by the bacterium and describes how, as understanding of these has developed over many years, so too have current strategies for vaccination and therapy. It covers the clinical and veterinary use of live attenuated strains of anthrax and the subsequent identification of protein sub-units for incorporation into vaccines, as well as combinations of protein sub-units with spore or other components. It also addresses the application of these vaccines for conventional prophylactic use, as well as post-exposure use in conjunction with antibiotics. It describes the licensed acellular vaccines AVA and AVP and discusses the prospects for a next generation of recombinant sub-unit vaccines for anthrax, balancing the regulatory requirement and current drive for highly defined vaccines, against the risk of losing the “danger” signals required to induce protective immunity in the vaccinee. It considers novel approaches to reduce time to immunity by means of combining, for example, dendritic cell vaccination with conventional approaches and considers current opportunities for the immunotherapy of anthrax.
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Affiliation(s)
| | - Edward Hugh Dyson
- Defence Science and Technology Laboratory Porton Down, Salisbury, UK
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17
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Pore-forming activity of clostridial binary toxins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:512-25. [PMID: 26278641 DOI: 10.1016/j.bbamem.2015.08.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 07/13/2015] [Accepted: 08/11/2015] [Indexed: 11/24/2022]
Abstract
Clostridial binary toxins (Clostridium perfringens Iota toxin, Clostridium difficile transferase, Clostridium spiroforme toxin, Clostridium botulinum C2 toxin) as Bacillus binary toxins, including Bacillus anthracis toxins consist of two independent proteins, one being the binding component which mediates the internalization into cell of the intracellularly active component. Clostridial binary toxins induce actin cytoskeleton disorganization through mono-ADP-ribosylation of globular actin and are responsible for enteric diseases. Clostridial and Bacillus binary toxins share structurally and functionally related binding components which recognize specific cell receptors, oligomerize, form pores in endocytic vesicle membrane, and mediate the transport of the enzymatic component into the cytosol. Binding components retain the global structure of pore-forming toxins (PFTs) from the cholesterol-dependent cytotoxin family such as perfringolysin. However, their pore-forming activity notably that of clostridial binding components is more related to that of heptameric PFT family including aerolysin and C. perfringens epsilon toxin. This review focuses upon pore-forming activity of clostridial binary toxins compared to other related PFTs. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Mauro Dalla Serra and Franco Gambale.
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Micropatterned macrophage analysis reveals global cytoskeleton constraints induced by Bacillus anthracis edema toxin. Infect Immun 2015; 83:3114-25. [PMID: 26015478 DOI: 10.1128/iai.00479-15] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 05/16/2015] [Indexed: 12/20/2022] Open
Abstract
Bacillus anthracis secretes the edema toxin (ET) that disrupts the cellular physiology of endothelial and immune cells, ultimately affecting the adherens junction integrity of blood vessels that in turn leads to edema. The effects of ET on the cytoskeleton, which is critical in cell physiology, have not been described thus far on macrophages. In this study, we have developed different adhesive micropatterned surfaces (L and crossbow) to control the shape of bone marrow-derived macrophages (BMDMs) and primary peritoneal macrophages. We found that macrophage F-actin cytoskeleton adopts a specific polar organization slightly different from classical human HeLa cells on the micropatterns. Moreover, ET induced a major quantitative reorganization of F-actin within 16 h with a collapse at the nonadhesive side of BMDMs along the nucleus. There was an increase in size and deformation into a kidney-like shape, followed by a decrease in size that correlates with a global cellular collapse. The collapse of F-actin was correlated with a release of focal adhesion on the patterns and decreased cell size. Finally, the cell nucleus was affected by actin reorganization. By using this technology, we could describe many previously unknown macrophage cellular dysfunctions induced by ET. This novel tool could be used to analyze more broadly the effects of toxins and other virulence factors that target the cytoskeleton.
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19
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Ohanjanian L, Remy KE, Li Y, Cui X, Eichacker PQ. An overview of investigational toxin-directed therapies for the adjunctive management of Bacillus anthracis infection and sepsis. Expert Opin Investig Drugs 2015; 24:851-65. [PMID: 25920540 DOI: 10.1517/13543784.2015.1041587] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
INTRODUCTION Sepsis with Bacillus anthracis infection has a very high mortality rate despite appropriate antibiotic and supportive therapies. Over the past 15 years, recent outbreaks in the US and in Europe, coupled with anthrax's bioterrorism weapon potential, have stimulated efforts to develop adjunctive therapies to improve clinical outcomes. Since lethal toxin and edema toxin (LT and ET) make central contributions to the pathogenesis of B. anthracis, these have been major targets in this effort. AREAS COVERED Here, the authors review different investigative biopharmaceuticals that have been recently identified for their therapeutic potential as inhibitors of LT or ET. Among these inhibitors are two antibody preparations that have been included in the Strategic National Stockpile (SNS) and several more that have reached Phase I testing. Presently, however, many of these candidate agents have only been studied in vitro and very few tested in bacteria-challenged models. EXPERT OPINION Although a large number of drugs have been identified as potential therapeutic inhibitors of LT and ET, in most cases their testing has been limited. The use of the two SNS antibody therapies during a large-scale exposure to B. anthracis will be difficult. Further testing and development of agents with oral bioavailability and relatively long shelf lives should be a focus for future research.
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Affiliation(s)
- Lernik Ohanjanian
- National Institutes of Health, Clinical Center, Critical Care Medicine Department , Building 10, Room 2C145, Bethesda, MD 20892 , USA +1 301 402 2914 ; +1 301 402 1213 ;
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20
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Moayeri M, Leysath CE, Tremblay JM, Vrentas C, Crown D, Leppla SH, Shoemaker CB. A heterodimer of a VHH (variable domains of camelid heavy chain-only) antibody that inhibits anthrax toxin cell binding linked to a VHH antibody that blocks oligomer formation is highly protective in an anthrax spore challenge model. J Biol Chem 2015; 290:6584-95. [PMID: 25564615 DOI: 10.1074/jbc.m114.627943] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Anthrax disease is caused by a toxin consisting of protective antigen (PA), lethal factor, and edema factor. Antibodies against PA have been shown to be protective against the disease. Variable domains of camelid heavy chain-only antibodies (VHHs) with affinity for PA were obtained from immunized alpacas and screened for anthrax neutralizing activity in macrophage toxicity assays. Two classes of neutralizing VHHs were identified recognizing distinct, non-overlapping epitopes. One class recognizes domain 4 of PA at a well characterized neutralizing site through which PA binds to its cellular receptor. A second neutralizing VHH (JKH-C7) recognizes a novel epitope. This antibody inhibits conversion of the PA oligomer from "pre-pore" to its SDS and heat-resistant "pore" conformation while not preventing cleavage of full-length 83-kDa PA (PA83) by cell surface proteases to its oligomer-competent 63-kDa form (PA63). The antibody prevents endocytosis of the cell surface-generated PA63 subunit but not preformed PA63 oligomers formed in solution. JKH-C7 and the receptor-blocking VHH class (JIK-B8) were expressed as a heterodimeric VHH-based neutralizing agent (VNA2-PA). This VNA displayed improved neutralizing potency in cell assays and protected mice from anthrax toxin challenge with much better efficacy than the separate component VHHs. The VNA protected virtually all mice when separately administered at a 1:1 ratio to toxin and protected mice against Bacillus anthracis spore infection. Thus, our studies show the potential of VNAs as anthrax therapeutics. Due to their simple and stable nature, VNAs should be amenable to genetic delivery or administration via respiratory routes.
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Affiliation(s)
- Mahtab Moayeri
- From the Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine at Tufts University North Grafton, Massachusetts 01536 and
| | - Clinton E Leysath
- From the Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine at Tufts University North Grafton, Massachusetts 01536 and
| | - Jacqueline M Tremblay
- Laboratory of Parasitic Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892
| | - Catherine Vrentas
- From the Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine at Tufts University North Grafton, Massachusetts 01536 and
| | - Devorah Crown
- From the Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine at Tufts University North Grafton, Massachusetts 01536 and
| | - Stephen H Leppla
- From the Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine at Tufts University North Grafton, Massachusetts 01536 and
| | - Charles B Shoemaker
- Laboratory of Parasitic Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892
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21
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Gurnev PA, Nestorovich EM. Channel-forming bacterial toxins in biosensing and macromolecule delivery. Toxins (Basel) 2014; 6:2483-540. [PMID: 25153255 PMCID: PMC4147595 DOI: 10.3390/toxins6082483] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 08/08/2014] [Accepted: 08/08/2014] [Indexed: 12/19/2022] Open
Abstract
To intoxicate cells, pore-forming bacterial toxins are evolved to allow for the transmembrane traffic of different substrates, ranging from small inorganic ions to cell-specific polypeptides. Recent developments in single-channel electrical recordings, X-ray crystallography, protein engineering, and computational methods have generated a large body of knowledge about the basic principles of channel-mediated molecular transport. These discoveries provide a robust framework for expansion of the described principles and methods toward use of biological nanopores in the growing field of nanobiotechnology. This article, written for a special volume on "Intracellular Traffic and Transport of Bacterial Protein Toxins", reviews the current state of applications of pore-forming bacterial toxins in small- and macromolecule-sensing, targeted cancer therapy, and drug delivery. We discuss the electrophysiological studies that explore molecular details of channel-facilitated protein and polymer transport across cellular membranes using both natural and foreign substrates. The review focuses on the structurally and functionally different bacterial toxins: gramicidin A of Bacillus brevis, α-hemolysin of Staphylococcus aureus, and binary toxin of Bacillus anthracis, which have found their "second life" in a variety of developing medical and technological applications.
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Affiliation(s)
- Philip A Gurnev
- Physics Department, University of Massachusetts, Amherst, MA 01003, USA.
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22
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Liu S, Moayeri M, Leppla SH. Anthrax lethal and edema toxins in anthrax pathogenesis. Trends Microbiol 2014; 22:317-25. [PMID: 24684968 DOI: 10.1016/j.tim.2014.02.012] [Citation(s) in RCA: 144] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 02/23/2014] [Accepted: 02/26/2014] [Indexed: 10/25/2022]
Abstract
The pathophysiological effects resulting from many bacterial diseases are caused by exotoxins released by the bacteria. Bacillus anthracis, a spore-forming bacterium, is such a pathogen, causing anthrax through a combination of bacterial infection and toxemia. B. anthracis causes natural infection in humans and animals and has been a top bioterrorism concern since the 2001 anthrax attacks in the USA. The exotoxins secreted by B. anthracis use capillary morphogenesis protein 2 (CMG2) as the major toxin receptor and play essential roles in pathogenesis during the entire course of the disease. This review focuses on the activities of anthrax toxins and their roles in initial and late stages of anthrax infection.
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Affiliation(s)
- Shihui Liu
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
| | - Mahtab Moayeri
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
| | - Stephen H Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
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23
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Abrami L, Brandi L, Moayeri M, Brown MJ, Krantz BA, Leppla SH, van der Goot FG. Hijacking multivesicular bodies enables long-term and exosome-mediated long-distance action of anthrax toxin. Cell Rep 2013; 5:986-96. [PMID: 24239351 PMCID: PMC3866279 DOI: 10.1016/j.celrep.2013.10.019] [Citation(s) in RCA: 141] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 10/01/2013] [Accepted: 10/11/2013] [Indexed: 12/21/2022] Open
Abstract
Anthrax lethal toxin is a classical AB toxin comprised of two components: protective antigen (PA) and lethal factor (LF). Here, we show that following assembly and endocytosis, PA forms a channel that translocates LF, not only into the cytosol, but also into the lumen of endosomal intraluminal vesicles (ILVs). These ILVs can fuse and release LF into the cytosol, where LF can proteolyze and disable host targets. We find that LF can persist in ILVs for days, fully sheltered from proteolytic degradation, both in vitro and in vivo. During this time, ILV-localized LF can be transmitted to daughter cells upon cell division. In addition, LF-containing ILVs can be delivered to the extracellular medium as exosomes. These can deliver LF to the cytosol of naive cells in a manner that is independent of the typical anthrax toxin receptor-mediated trafficking pathway, while being sheltered from neutralizing extracellular factors of the immune system.
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Affiliation(s)
- Laurence Abrami
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 19, CH-1015 Lausanne, Switzerland
| | - Lucia Brandi
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 19, CH-1015 Lausanne, Switzerland
| | - Mahtab Moayeri
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, 20892, U.S.A
| | - Michael J. Brown
- Department of Molecular & Cell Biology, University of California, Berkeley, CA, 94720, U.S.A
| | - Bryan A. Krantz
- Department of Molecular & Cell Biology, University of California, Berkeley, CA, 94720, U.S.A
- Department of Chemistry, University of California, Berkeley, CA, 94720, U.S.A
| | - Stephen H. Leppla
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, 20892, U.S.A
| | - F. G. van der Goot
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 19, CH-1015 Lausanne, Switzerland
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24
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Jeong SY, Martchenko M, Cohen SN. Calpain-dependent cytoskeletal rearrangement exploited for anthrax toxin endocytosis. Proc Natl Acad Sci U S A 2013; 110:E4007-15. [PMID: 24085852 PMCID: PMC3801034 DOI: 10.1073/pnas.1316852110] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The protective antigen component of Bacillus anthracis toxins can interact with at least three distinct proteins on the host cell surface, capillary morphogenesis gene 2 (CMG2), tumor endothelial marker 8, and β1-integrin, and, with the assistance of other host proteins, enters targeted cells by receptor-mediated endocytosis. Using an antisense-based phenotypic screen, we discovered the role of calpains in this process. We show that functions of a ubiquitous Ca(2+)-dependent cysteine protease, calpain-2, and of the calpain substrate talin-1 are exploited for association of anthrax toxin and its principal receptor, CMG2, with higher-order actin filaments and consequently for toxin entry into host cells. Down-regulated expression of calpain-2 or talin-1, or pharmacological interference with calpain action, did not affect toxin binding but reduced endocytosis and increased the survival of cells exposed to anthrax lethal toxin. Adventitious expression of wild-type talin-1 promoted toxin endocytosis and lethality, whereas expression of a talin-1 mutant (L432G) that is insensitive to calpain cleavage did not. Disruption of talin-1, which links integrin-containing focal adhesion complexes to the actin cytoskeleton, facilitated association of toxin bound to its principal cell-surface receptor, CMG2, with higher-order actin filaments undergoing dynamic disassembly and reassembly during endocytosis. Our results reveal a mechanism by which a bacterial toxin uses constitutively occurring calpain-mediated cytoskeletal rearrangement for internalization.
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Affiliation(s)
| | | | - Stanley N. Cohen
- Departments of Genetics and
- Medicine, Stanford University School of Medicine, Stanford, CA 94305
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25
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Toxin inhibition of antimicrobial factors induced by Bacillus anthracis peptidoglycan in human blood. Infect Immun 2013; 81:3693-702. [PMID: 23876807 DOI: 10.1128/iai.00709-13] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Here, we describe the capacity of Bacillus anthracis peptidoglycan (BaPGN) to trigger an antimicrobial response in human white blood cells (WBCs). Analysis of freshly isolated human blood cells found that monocytes and neutrophils, but not B and T cells, were highly responsive to BaPGN and produced a variety of cytokines and chemokines. This BaPGN-induced response was suppressed by anthrax lethal toxin (LT) and edema toxin (ET), with the most pronounced effect on human monocytes, and this corresponded with the higher levels of anthrax toxin receptor 1 (ANTXR1) in these cells than in neutrophils. The supernatant from BaPGN-treated cells altered the growth of B. anthracis Sterne, and this effect was blocked by LT, but not by ET. An FtsX mutant of B. anthracis known to be resistant to the antimicrobial effects of interferon-inducible Glu-Leu-Arg (ELR)-negative CXC chemokines was not affected by the BaPGN-induced antimicrobial effects. Collectively, these findings describe a system in which BaPGN triggers expression of antimicrobial factors in human WBCs and reveal a distinctive role, not shared with ET, in LT's capacity to suppress this response.
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26
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Yan SE, Lemmin T, Salvi S, Lausch E, Superti-Furga A, Rokicki D, Dal Peraro M, van der Goot FG. In-depth analysis of hyaline fibromatosis syndrome frameshift mutations at the same site reveal the necessity of personalized therapy. Hum Mutat 2013; 34:1005-17. [PMID: 23554269 DOI: 10.1002/humu.22324] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Accepted: 03/20/2013] [Indexed: 11/07/2022]
Abstract
Hyaline fibromatosis syndrome is an autosomal recessive disease caused by mutations in ANTXR2, a gene involved in extracellular matrix homeostasis. Sixty percent of patients carry frameshift mutations at a mutational hotspot in exon 13. We show in patient cells that these mutations lead to low ANTXR2 mRNA and undetectable protein levels. Ectopic expression of the proteins encoded by the mutated genes reveals that a two base insertion leads to the synthesis of a protein that is rapidly targeted to the ER-associated degradation pathway due to the modified structure of the cytosolic tail, which instead of being hydrophilic and highly disordered as in wild type ANTXR2, is folded and exposes hydrophobic patches. In contrast, one base insertion leads to a truncated protein that properly localizes to the plasma membrane and retains partial function. We next show that targeting the nonsense mediated mRNA decay pathway in patient cells leads to a rescue of ANTXR2 protein in patients carrying one base insertion but not in those carrying two base insertions. This study highlights the importance of in-depth analysis of the molecular consequences of specific patient mutations, which even when they occur at the same site can have drastically different consequences.
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Affiliation(s)
- Shixu E Yan
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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27
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CCT chaperonin complex is required for efficient delivery of anthrax toxin into the cytosol of host cells. Proc Natl Acad Sci U S A 2013; 110:9932-7. [PMID: 23716698 DOI: 10.1073/pnas.1302257110] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Bacterial toxins have evolved successful strategies for coopting host proteins to access the cytosol of host cells. Anthrax lethal factor (LF) enters the cytosol through pores in the endosomal membrane formed by anthrax protective antigen. Although in vitro models using planar lipid bilayers have shown that translocation can occur in the absence of cellular factors, recent studies using intact endosomes indicate that host factors are required for translocation in the cellular environment. In this study, we describe a high-throughput shRNA screen to identify host factors required for anthrax lethal toxin-induced cell death. The cytosolic chaperonin complex chaperonin containing t-complex protein 1 (CCT) was identified, and subsequent studies showed that CCT is required for efficient delivery of LF and related fusion proteins into the cytosol. We further show that knockdown of CCT inhibits the acid-induced delivery of LF and the fusion protein LFN-Bla (N terminal domain of LF fused to β-lactamase) across the plasma membrane of intact cells. Together, these results suggest that CCT is required for efficient delivery of enzymatically active toxin to the cytosol and are consistent with a direct role for CCT in translocation of LF through the protective antigen pore.
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28
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D'Agnillo F, Williams MC, Moayeri M, Warfel JM. Anthrax lethal toxin downregulates claudin-5 expression in human endothelial tight junctions. PLoS One 2013; 8:e62576. [PMID: 23626836 PMCID: PMC3633853 DOI: 10.1371/journal.pone.0062576] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 03/22/2013] [Indexed: 01/22/2023] Open
Abstract
Vascular leakage pathologies such as pleural effusion and hemorrhage are hallmarks of anthrax pathogenesis. We previously reported that anthrax lethal toxin (LT), the major virulence factor of anthrax, reduces barrier function in cultured primary human microvascular endothelial cells. Here, we show that LT-induced barrier dysfunction is accompanied by the reduced expression of the endothelial tight junction (TJ) protein claudin-5 but no change in the expression of other TJ components occludin, ZO-1, ZO-2, or the adherens junction (AJ) protein VE-cadherin. The downregulation of claudin-5 correlated temporally and dose-dependently with the reduction of transendothelial electrical resistance. LT-induced loss of claudin-5 was independent of cell death and preceded the appearance of actin stress fibers and altered AJ morphology. Pharmacological inhibition of MEK-1/2, two kinases that are proteolytically inactivated by LT, showed a similar reduction in claudin-5 expression. We found that LT reduced claudin-5 mRNA levels but did not accelerate the rate of claudin-5 degradation. Mice challenged with LT also showed significant reduction in claudin-5 expression. Together, these findings support a possible role for LT disruption of endothelial TJs in the vascular leakage pathologies of anthrax.
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Affiliation(s)
- Felice D'Agnillo
- Laboratory of Biochemistry and Vascular Biology, Division of Hematology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland, United States of America.
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29
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Slater LH, Hett EC, Mark K, Chumbler NM, Patel D, Lacy DB, Collier RJ, Hung DT. Identification of novel host-targeted compounds that protect from anthrax lethal toxin-induced cell death. ACS Chem Biol 2013; 8:812-22. [PMID: 23343607 DOI: 10.1021/cb300555n] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Studying how pathogens subvert the host to cause disease has contributed to the understanding of fundamental cell biology. Bacillus anthracis, the causative agent of anthrax, produces the virulence factor lethal toxin to disarm host immunity and cause pathology. We conducted a phenotypic small molecule screen to identify inhibitors of lethal toxin-induced macrophage cell death and used an ordered series of secondary assays to characterize the hits and determine their effects on cellular function. We identified a structurally diverse set of small molecules that act at various points along the lethal toxin pathway, including inhibitors of endocytosis, natural product inhibitors of organelle acidification (e.g., the botulinum neurotoxin inhibitor, toosendanin), and a novel proteasome inhibitor, 4MNB (4-methoxy-2-[2-(5-methoxy-2-nitrosophenyl)ethyl]-1-nitrosobenzene). Many of the compounds, including three drugs approved for use in humans, also protected against the related Clostridium difficile toxin TcdB, further demonstrating their value as novel tools for perturbation and study of toxin biology and host cellular processes and highlighting potential new strategies for intervening on toxin-mediated diseases.
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Affiliation(s)
- Louise H. Slater
- Department of Molecular Biology
and Center for Computational and Integrative Biology, Massachusetts General Hospital, 185 Cambridge Street,
Boston, Massachusetts 02114, United States
- Infectious Disease Initiative, Broad Institute, 7 Cambridge Center, Cambridge, Massachusetts
02142, United States
- Department
of Microbiology and
Immunobiology, Harvard Medical School,
77 Ave. Louis Pasteur Boston, Massachusetts 02115, United States
| | - Erik C. Hett
- Department of Molecular Biology
and Center for Computational and Integrative Biology, Massachusetts General Hospital, 185 Cambridge Street,
Boston, Massachusetts 02114, United States
- Infectious Disease Initiative, Broad Institute, 7 Cambridge Center, Cambridge, Massachusetts
02142, United States
- Department
of Microbiology and
Immunobiology, Harvard Medical School,
77 Ave. Louis Pasteur Boston, Massachusetts 02115, United States
| | - Kevin Mark
- Department of Molecular Biology
and Center for Computational and Integrative Biology, Massachusetts General Hospital, 185 Cambridge Street,
Boston, Massachusetts 02114, United States
- Infectious Disease Initiative, Broad Institute, 7 Cambridge Center, Cambridge, Massachusetts
02142, United States
- Department
of Microbiology and
Immunobiology, Harvard Medical School,
77 Ave. Louis Pasteur Boston, Massachusetts 02115, United States
| | - Nicole M. Chumbler
- Department of Microbiology and
Immunology, Vanderbilt University Medical Center, A-5301 Medical Center North, 1161 21st Avenue South, Nashville,
Tennessee 37232, United States
| | - Deepa Patel
- Department
of Microbiology and
Immunobiology, Harvard Medical School,
77 Ave. Louis Pasteur Boston, Massachusetts 02115, United States
| | - D. Borden Lacy
- Department of Microbiology and
Immunology, Vanderbilt University Medical Center, A-5301 Medical Center North, 1161 21st Avenue South, Nashville,
Tennessee 37232, United States
| | - R. John Collier
- Department
of Microbiology and
Immunobiology, Harvard Medical School,
77 Ave. Louis Pasteur Boston, Massachusetts 02115, United States
| | - Deborah T. Hung
- Department of Molecular Biology
and Center for Computational and Integrative Biology, Massachusetts General Hospital, 185 Cambridge Street,
Boston, Massachusetts 02114, United States
- Infectious Disease Initiative, Broad Institute, 7 Cambridge Center, Cambridge, Massachusetts
02142, United States
- Department
of Microbiology and
Immunobiology, Harvard Medical School,
77 Ave. Louis Pasteur Boston, Massachusetts 02115, United States
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30
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Studies in mice reveal a role for anthrax toxin receptors in matrix metalloproteinase function and extracellular matrix homeostasis. Toxins (Basel) 2013; 5:315-26. [PMID: 23389402 PMCID: PMC3640537 DOI: 10.3390/toxins5020315] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Accepted: 01/31/2013] [Indexed: 02/07/2023] Open
Abstract
The genes encoding Anthrax Toxin Receptors (ANTXRs) were originally identified based on expression in endothelial cells suggesting a role in angiogenesis. The focus of this review is to discuss what has been learned about the physiological roles of these receptors through evaluation of the Antxr knockout mouse phenotypes. Mice mutant in Antxr genes have defects in extracellular matrix homeostasis. We discuss how knowledge of physiological ANTXR function relates to what is already known about anthrax intoxication.
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Bischofberger M, Iacovache I, van der Goot FG. Pathogenic pore-forming proteins: function and host response. Cell Host Microbe 2013; 12:266-75. [PMID: 22980324 DOI: 10.1016/j.chom.2012.08.005] [Citation(s) in RCA: 146] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Organisms from all kingdoms produce pore-forming proteins, with the best-characterized being of bacterial origin. The last decade of research has revealed that the channels formed by these proteins can be very diverse, thus differentially affecting target cell-membrane permeability and consequent cellular outcome. The responses to these toxins are also extremely diverse due to multiple downstream effects of pore-induced changes in ion balance. Determining the secondary effects of pore-forming toxins is essential to understand their contribution to infection.
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Affiliation(s)
- Mirko Bischofberger
- Ecole Polytechnique Fédérale de Lausanne, Global Health Institute, Station 15, CH-1015 Lausanne, Switzerland
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Singh NK, Pakkkianathan BC, Kumar M, Daddam JR, Jayavel S, Kannan M, Pillai GG, Krishnan M. Computational studies on molecular interactions of 6-thioguanosine analogs with anthrax toxin receptor 1. Interdiscip Sci 2013; 4:183-9. [PMID: 23292691 DOI: 10.1007/s12539-012-0126-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Revised: 01/27/2012] [Accepted: 04/06/2012] [Indexed: 02/06/2023]
Abstract
Dormant endospores of Bacillus anthracis are the causative agent of anthrax, which is an acute disease for both human and animals. Anthrax has been practised as biological weapon because of two attributes: i) short duration of spore germination, and ii) lethal toxaemia of the vegetative stage. Pathogenesis is caused by the activity of edema toxin and lethal toxin. Protective antigen (PA), is an essential component of both complexes, binds to Anthrax Toxin Receptor (ATR) and mediates the lethality in mammals. The combination of vaccine and antibiotics are preferred to be effective treatment for destruction of the vegetative cell wall but could not be a successive destructor for endospores. So the present study is intended to identify the small molecules as a potential inhibitor for ATR1. 3D structure of Anthrax Toxin Receptor 1 (ATR1) was built by using the crystal structure of Anthrax Toxin Receptor 2 (ATR2) from Homo sapiens as template. Molecular docking of 6-thiogunaosine (6-TG) analogs was performed on the ATR1 model and effective inhibitor was selected based on the docking results. The docking results showed that the three residues in the ATR1 binding pocket (Phe162, Asp160, and Phe22) were essential for making hydrogen bond with the 2-(2-bromo-6-chloro-4H-purin-9(5H)-yl)- 5-(hydroxymethyl) tetrahydrofuran-3,4-diol (C(11)H(13)N(3)O(5)). The data presented here strongly indicate that the interactions of these four residues are necessary for a stronger binding of the ATR1 with C(11)H(13)N(3)O(5). Also, the study proposed C(11)H(13)N(3)O(5) as an effective inhibitor by the comparison of docking energy.
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Affiliation(s)
- Nitin K Singh
- Department of Environmental Biotechnology, Bharathidasan University, Tiruchirappalli, 620024, India
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Wigelsworth DJ, Ruthel G, Schnell L, Herrlich P, Blonder J, Veenstra TD, Carman RJ, Wilkins TD, Van Nhieu GT, Pauillac S, Gibert M, Sauvonnet N, Stiles BG, Popoff MR, Barth H. CD44 Promotes intoxication by the clostridial iota-family toxins. PLoS One 2012; 7:e51356. [PMID: 23236484 PMCID: PMC3517468 DOI: 10.1371/journal.pone.0051356] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 10/31/2012] [Indexed: 12/16/2022] Open
Abstract
Various pathogenic clostridia produce binary protein toxins associated with enteric diseases of humans and animals. Separate binding/translocation (B) components bind to a protein receptor on the cell surface, assemble with enzymatic (A) component(s), and mediate endocytosis of the toxin complex. Ultimately there is translocation of A component(s) from acidified endosomes into the cytosol, leading to destruction of the actin cytoskeleton. Our results revealed that CD44, a multifunctional surface protein of mammalian cells, facilitates intoxication by the iota family of clostridial binary toxins. Specific antibody against CD44 inhibited cytotoxicity of the prototypical Clostridium perfringens iota toxin. Versus CD44+ melanoma cells, those lacking CD44 bound less toxin and were dose-dependently resistant to C. perfringens iota, as well as Clostridium difficile and Clostridium spiroforme iota-like, toxins. Purified CD44 specifically interacted in vitro with iota and iota-like, but not related Clostridium botulinum C2, toxins. Furthermore, CD44 knockout mice were resistant to iota toxin lethality. Collective data reveal an important role for CD44 during intoxication by a family of clostridial binary toxins.
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Affiliation(s)
- Darran J. Wigelsworth
- Integrated Toxicology Division, Medical Research Institute of Infectious Diseases, Frederick, Maryland, United States of America
| | - Gordon Ruthel
- Core Imaging Facility, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania, United States of America
| | - Leonie Schnell
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Ulm, Germany
| | - Peter Herrlich
- Leibniz Institute for Age Research, Fritz Lipmann Institute, Jena, Germany
| | - Josip Blonder
- Laboratory of Proteomics and Analytical Technologies, National Cancer Institute, Frederick, Maryland, United States of America
| | - Timothy D. Veenstra
- Laboratory of Proteomics and Analytical Technologies, National Cancer Institute, Frederick, Maryland, United States of America
| | | | | | - Guy Tran Van Nhieu
- Department of Intracellular Communications and Infectious Microorganisms, College of France, Paris, France
| | - Serge Pauillac
- Institut Pasteur, Unité des Bactéries anaérobies et Toxines, Paris, France
| | - Maryse Gibert
- Institut Pasteur, Unité des Bactéries anaérobies et Toxines, Paris, France
| | - Nathalie Sauvonnet
- Institut Pasteur, Unité de Biologie des Interactions Cellulaires, Paris, France
| | - Bradley G. Stiles
- Biology Department, Wilson College, Chambersburg, Pennsylvania, United States of America
- * E-mail: (BGS); (HB); (MRP)
| | - Michel R. Popoff
- Institut Pasteur, Unité des Bactéries anaérobies et Toxines, Paris, France
- * E-mail: (BGS); (HB); (MRP)
| | - Holger Barth
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Ulm, Germany
- * E-mail: (BGS); (HB); (MRP)
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Vargas M, Karamsetty R, Leppla SH, Chaudry GJ. Broad expression analysis of human ANTXR1/TEM8 transcripts reveals differential expression and novel splizce variants. PLoS One 2012; 7:e43174. [PMID: 22912819 PMCID: PMC3422265 DOI: 10.1371/journal.pone.0043174] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 07/20/2012] [Indexed: 01/25/2023] Open
Abstract
Tumor endothelial marker 8 (TEM8; ANTXR1) is one of two anthrax toxin receptors; the other is capillary morphogenesis gene 2 protein (CMG2; ANTXR2). TEM8 shows enhanced expression in certain tumor endothelia, and is thought to be a player in tumor vasculature formation. However, a comprehensive expression profile of individual TEM8 variants in normal or cancerous tissues is lacking. In this work we carried out an extensive analysis of all splice variants of human TEM8 in 12 digestive tissues, and 8 each fetal and adult tissues, 6 of them cognate pairs. Using variant-specific primers, we first ascertained the status of full-length transcripts by nested PCR. We then carried out quantitative analysis of each transcript by real-time PCR. Three splice variants of TEM8 were reported before, two single-pass integral membrane forms (V1 and V2) and one secreted (V3). Our analysis has revealed two new variants, one encoding a membrane-bound form of the receptor and the other secreted, which we have designated V4 and V5, respectively. All tissues had V1, V2, V3, and V4, but only prostate had V5. Real-time PCR revealed that all variants are present at different levels in various tissues. V3 appeared the most abundant of all. To ascertain its functionality for anthrax toxin, we expressed the newly identified form V4 in a receptor-negative host cell, and included V1 and V2 for comparison. Cytotoxicity, toxin binding, and internalization assays showed V4 to be as efficient a receptor as V1 and V2.
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Affiliation(s)
- Micaela Vargas
- Cell and Molecular Biology Program, Department of Biology, The University of Texas at San Antonio, San Antonio, Texas, United States of America
| | - Raghavendra Karamsetty
- Cell and Molecular Biology Program, Department of Biology, The University of Texas at San Antonio, San Antonio, Texas, United States of America
| | - Stephen H. Leppla
- Microbial Pathogenesis Section, The Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - G. Jilani Chaudry
- Cell and Molecular Biology Program, Department of Biology, The University of Texas at San Antonio, San Antonio, Texas, United States of America
- * E-mail:
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Bacillus anthracis factors for phagosomal escape. Toxins (Basel) 2012; 4:536-53. [PMID: 22852067 PMCID: PMC3407891 DOI: 10.3390/toxins4070536] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 06/21/2012] [Accepted: 07/02/2012] [Indexed: 12/27/2022] Open
Abstract
The mechanism of phagosome escape by intracellular pathogens is an important step in the infectious cycle. During the establishment of anthrax, Bacillus anthracis undergoes a transient intracellular phase in which spores are engulfed by local phagocytes. Spores germinate inside phagosomes and grow to vegetative bacilli, which emerge from their resident intracellular compartments, replicate and eventually exit from the plasma membrane. During germination, B. anthracis secretes multiple factors that can help its resistance to the phagocytes. Here the possible role of B. anthracis toxins, phospholipases, antioxidant enzymes and capsules in the phagosomal escape and survival, is analyzed and compared with that of factors of other microbial pathogens involved in the same type of process.
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Ivarsson ME, Leroux JC, Castagner B. Targeting bacterial toxins. Angew Chem Int Ed Engl 2012; 51:4024-45. [PMID: 22441768 DOI: 10.1002/anie.201104384] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Revised: 09/21/2011] [Indexed: 12/18/2022]
Abstract
Protein toxins constitute the main virulence factors of several species of bacteria and have proven to be attractive targets for drug development. Lead candidates that target bacterial toxins range from small molecules to polymeric binders, and act at each of the multiple steps in the process of toxin-mediated pathogenicity. Despite recent and significant advances in the field, a rationally designed drug that targets toxins has yet to reach the market. This Review presents the state of the art in bacterial toxin targeted drug development with a critical consideration of achieved breakthroughs and withstanding challenges. The discussion focuses on A-B-type protein toxins secreted by four species of bacteria, namely Clostridium difficile (toxins A and B), Vibrio cholerae (cholera toxin), enterohemorrhagic Escherichia coli (Shiga toxin), and Bacillus anthracis (anthrax toxin), which are the causative agents of diseases for which treatments need to be improved.
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Affiliation(s)
- Mattias E Ivarsson
- Institute of Pharmaceutical Sciences, Swiss Federal Institute of Technology Zurich, Wolfgang-Pauli-Strasse 10, Zurich, Switzerland
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Wolf JM, Rivera J, Casadevall A. Serum albumin disrupts Cryptococcus neoformans and Bacillus anthracis extracellular vesicles. Cell Microbiol 2012; 14:762-73. [PMID: 22289081 DOI: 10.1111/j.1462-5822.2012.01757.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
For both pathogenic fungi and bacteria, extracellular vesicles have been shown to contain many microbial components associated with virulence, suggesting a role in pathogenesis. However, there are many unresolved issues regarding vesicle synthesis and stability, including the fact that vesicular packaging for extracellular factors involved in virulence must also have a mechanism for vesicle unloading. Consequently, we studied the kinetics of vesicle production and stability using [1-(14) C] palmitic acid metabolic labelling and dynamic light scattering techniques. Cryptococcus neoformans vesicles were produced throughout all stages of fungal culture growth and they were stable once isolated. Density gradient analysis revealed that only a portion of the vesicle population carried cryptococcal polysaccharide, implying heterogeneity in vesicular cargo. Vesicle incubation with macrophages resulted in rapid vesicle instability, a phenomenon that was ultimately associated with serum albumin. Additionally, albumin, along with mouse serum and murine immunoglobulin destabilized Bacillus anthracis vesicles, but the effect was not observed with ovalbumin or keyhole limpet haemocyanin, demonstrating that this phenomenon is neither host-, microbe- nor protein-specific. Our findings strongly suggest that cryptococcal vesicles are short-lived in vivo and vesicle destabilization is mediated by albumin. The ability of albumin to promote vesicular offload through destabilization indicates a new activity for this abundant serum protein.
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Affiliation(s)
- Julie M Wolf
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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Trescos Y, Tournier JN. Cytoskeleton as an emerging target of anthrax toxins. Toxins (Basel) 2012; 4:83-97. [PMID: 22474568 PMCID: PMC3317109 DOI: 10.3390/toxins4020083] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Revised: 01/21/2012] [Accepted: 01/26/2012] [Indexed: 01/29/2023] Open
Abstract
Bacillus anthracis, the agent of anthrax, has gained virulence through its exotoxins produced by vegetative bacilli and is composed of three components forming lethal toxin (LT) and edema toxin (ET). So far, little is known about the effects of these toxins on the eukaryotic cytoskeleton. Here, we provide an overview on the general effects of toxin upon the cytoskeleton architecture. Thus, we shall discuss how anthrax toxins interact with their receptors and may disrupt the interface between extracellular matrix and the cytoskeleton. We then analyze what toxin molecular effects on cytoskeleton have been described, before discussing how the cytoskeleton may help the pathogen to corrupt general cell processes such as phagocytosis or vascular integrity.
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Affiliation(s)
- Yannick Trescos
- Unité Interactions Hôte-Agents pathogènes, Institut de Recherche Biomédicale des Armées, Centre de Recherche du Service de Santé des Armées, BP 87, 24 avenue des Maquis du Grésivaudan 38702 La Tronche Cedex, France;
- Ecole du Val-de-Grâce, 1 place Alphonse Lavéran, 75005 Paris, France
| | - Jean-Nicolas Tournier
- Unité Interactions Hôte-Agents pathogènes, Institut de Recherche Biomédicale des Armées, Centre de Recherche du Service de Santé des Armées, BP 87, 24 avenue des Maquis du Grésivaudan 38702 La Tronche Cedex, France;
- Ecole du Val-de-Grâce, 1 place Alphonse Lavéran, 75005 Paris, France
- Author to whom correspondence should be addressed; ; Tel.: +33-4-76636850; Fax: +33-4-76636917
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Deuquet J, Lausch E, Superti-Furga A, van der Goot FG. The dark sides of capillary morphogenesis gene 2. EMBO J 2012; 31:3-13. [PMID: 22215446 PMCID: PMC3252584 DOI: 10.1038/emboj.2011.442] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Accepted: 11/07/2011] [Indexed: 11/08/2022] Open
Abstract
Capillary morphogenesis gene 2 (CMG2) is a type I membrane protein involved in the homeostasis of the extracellular matrix. While it shares interesting similarities with integrins, its exact molecular role is unknown. The interest and knowledge about CMG2 largely stems from the fact that it is involved in two diseases, one infectious and one genetic. CMG2 is the main receptor of the anthrax toxin, and knocking out this gene in mice renders them insensitive to infection with Bacillus anthracis spores. On the other hand, mutations in CMG2 lead to a rare but severe autosomal recessive disorder in humans called Hyaline Fibromatosis Syndrome (HFS). We will here review what is known about the structure of CMG2 and its ability to mediate anthrax toxin entry into cell. We will then describe the limited knowledge available concerning the physiological role of CMG2. Finally, we will describe HFS and the consequences of HFS-associated mutations in CMG2 at the molecular and cellular level.
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Affiliation(s)
- Julie Deuquet
- Ecole Polytechnique Fédérale de Lausanne, Institute of Global Health, Lausanne, Switzerland
| | - Ekkehart Lausch
- Department of Pediatrics, University of Freiburg, Freiburg, Germany
| | - Andrea Superti-Furga
- Division of Molecular Pediatrics, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland
| | - F Gisou van der Goot
- Ecole Polytechnique Fédérale de Lausanne, Institute of Global Health, Lausanne, Switzerland
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In situ gastrointestinal protection against anthrax edema toxin by single-chain antibody fragment producing lactobacilli. BMC Biotechnol 2011; 11:126. [PMID: 22185669 PMCID: PMC3295704 DOI: 10.1186/1472-6750-11-126] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Accepted: 12/20/2011] [Indexed: 11/10/2022] Open
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The effect of deletion of the edema factor on Bacillus anthracis pathogenicity in guinea pigs and rabbits. Microb Pathog 2011; 52:55-60. [PMID: 22020310 DOI: 10.1016/j.micpath.2011.10.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 10/06/2011] [Accepted: 10/10/2011] [Indexed: 11/21/2022]
Abstract
Bacillus anthracis secretes three major components, which assemble into two bipartite toxins: lethal toxin (LT), composed of lethal factor (LF) and protective antigen (PA) and edema toxin (ET), composed of edema factor (EF) and PA. EF is a potent calmodulin-dependent adenylate cyclase, which is internalized into the target cell following PA binding. Once inside the cell, EF elevates cAMP levels, interrupting intracellular signaling. Effects of ET were demonstrated on monocytes, neutrophils and T-cells. In an earlier work we demonstrated that a deletion of LF in a fully virulent strain had no effect in guinea pigs and a significant, but not major, effect in the rabbit model. These results suggested that EF might play an important role in the development of infection and mortality following exposure to B. anthracis spores. To evaluate the role of EF in B. anthracis pathogenicity we deleted the cya gene, which encodes the EF protein, in the fully virulent Vollum strain. The Δcya mutant was fully virulent in the guinea pig model as determined by LD(50) experiments. In the rabbit model, when infected subcutaneously, the absence of EF had no effect on the virulence of the mutant. However an increase of two orders of magnitude in the LD(50) was demonstrated when the rabbits were infected by intranasal instillation accompanied with partial mortality and increased mean time to death. These results argue that in the guinea pig model the presence of one of the toxins, ET or LT is sufficient for the development of the infection. In the rabbit model ET plays a role in respiratory infection, most probably mediating the early steps of host colonization.
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Hicks CW, Cui X, Sweeney DA, Li Y, Barochia A, Eichacker PQ. The potential contributions of lethal and edema toxins to the pathogenesis of anthrax associated shock. Toxins (Basel) 2011; 3:1185-202. [PMID: 22069762 PMCID: PMC3202877 DOI: 10.3390/toxins3091185] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2011] [Revised: 09/08/2011] [Accepted: 09/09/2011] [Indexed: 12/22/2022] Open
Abstract
Outbreaks of Bacillus anthracis in the US and Europe over the past 10 years have emphasized the health threat this lethal bacteria poses even for developed parts of the world. In contrast to cutaneous anthrax, inhalational disease in the US during the 2001 outbreaks and the newly identified injectional drug use form of disease in the UK and Germany have been associated with relatively high mortality rates. One notable aspect of these cases has been the difficulty in supporting patients once shock has developed. Anthrax bacilli produce several different components which likely contribute to this shock. Growing evidence indicates that both major anthrax toxins may produce substantial cardiovascular dysfunction. Lethal toxin (LT) can alter peripheral vascular function; it also has direct myocardial depressant effects. Edema toxin (ET) may have even more pronounced peripheral vascular effects than LT, including the ability to interfere with the actions of conventional vasopressors. Additionally, ET also appears capable of interfering with renal sodium and water retention. Importantly, the two toxins exert their actions via quite different mechanisms and therefore have the potential to worsen shock and outcome in an additive fashion. Finally, both toxins have the ability to inhibit host defense and microbial clearance, possibly contributing to the very high bacterial loads noted in patients dying with anthrax. This last point is clinically relevant since emerging data has begun to implicate other bacterial components such as anthrax cell wall in the shock and organ injury observed with infection. Taken together, accumulating evidence regarding the potential contribution of LT and ET to anthrax-associated shock supports efforts to develop adjunctive therapies that target both toxins in patients with progressive shock.
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Affiliation(s)
- Caitlin W. Hicks
- Cleveland Clinic Lerner College of Medicine, Cleveland, OH 44195, USA;
- Howard Hughes Medical Institute-National Institutes of Health Research Scholar, National Institutes of Health, Bethesda, MD 20814, USA
| | - Xizhong Cui
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA; (X.C.); (Y.L.); (A.B.)
| | - Daniel A. Sweeney
- Medical Intensivist Program, Washington Hospital, Fremont, CA 94538, USA;
| | - Yan Li
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA; (X.C.); (Y.L.); (A.B.)
| | - Amisha Barochia
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA; (X.C.); (Y.L.); (A.B.)
| | - Peter Q. Eichacker
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA; (X.C.); (Y.L.); (A.B.)
- Author to whom correspondence should be addressed; ; Tel.: +1-301-496-9320; Fax: +1-301-402-1213
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Dumas EK, Cox PM, Fullenwider CO, Nguyen M, Centola M, Frank MB, Dozmorov I, James JA, Farris AD. Anthrax lethal toxin-induced gene expression changes in mouse lung. Toxins (Basel) 2011; 3:1111-30. [PMID: 22039574 PMCID: PMC3202878 DOI: 10.3390/toxins3091111] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 08/24/2011] [Accepted: 09/06/2011] [Indexed: 11/16/2022] Open
Abstract
A major virulence factor of Bacillus anthracis is the anthrax Lethal Toxin (LeTx), a bipartite toxin composed of Protective Antigen and Lethal Factor. Systemic administration of LeTx to laboratory animals leads to death associated with vascular leakage and pulmonary edema. In this study, we investigated whether systemic exposure of mice to LeTx would induce gene expression changes associated with vascular/capillary leakage in lung tissue. We observed enhanced susceptibility of A/J mice to death by systemic LeTx administration compared to the C57BL/6 strain. LeTx-induced groups of both up- and down-regulated genes were observed in mouse lungs 6 h after systemic administration of wild type toxin compared to lungs of mice exposed to an inactive mutant form of the toxin. Lungs of the less susceptible C57BL/6 strain showed 80% fewer differentially expressed genes compared to lungs of the more sensitive A/J strain. Expression of genes known to regulate vascular permeability was modulated by LeTx in the lungs of the more susceptible A/J strain. Unexpectedly, the largest set of genes with altered expression was immune specific, characterized by the up-regulation of lymphoid genes and the down-regulation of myeloid genes. Transcripts encoding neutrophil chemoattractants, modulators of tumor regulation and angiogenesis were also differentially expressed in both mouse strains. These studies provide new directions for the investigation of vascular leakage and pulmonary edema induced by anthrax LeTx.
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Affiliation(s)
- Eric K. Dumas
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, 1100 N. Lindsay, Oklahoma City, OK 73104, USA; (E.K.D.); (M.N.); (J.A.J.)
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
| | - Philip M. Cox
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
| | - Charles O’Connor Fullenwider
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
| | - Melissa Nguyen
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, 1100 N. Lindsay, Oklahoma City, OK 73104, USA; (E.K.D.); (M.N.); (J.A.J.)
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
| | - Michael Centola
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
- Microarray Research Facility, Oklahoma Medical Research Foundation, 825 NE 13th Street, MS 53, Oklahoma City, OK 73104, USA
| | - Mark Barton Frank
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
- Microarray Research Facility, Oklahoma Medical Research Foundation, 825 NE 13th Street, MS 53, Oklahoma City, OK 73104, USA
| | - Igor Dozmorov
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
| | - Judith A. James
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, 1100 N. Lindsay, Oklahoma City, OK 73104, USA; (E.K.D.); (M.N.); (J.A.J.)
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
| | - A. Darise Farris
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, 1100 N. Lindsay, Oklahoma City, OK 73104, USA; (E.K.D.); (M.N.); (J.A.J.)
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
- Author to whom correspondence should be addressed; ; Tel.: +1-405-271-7389; Fax: +1-405-271-706
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Monoclonal antibody therapies against anthrax. Toxins (Basel) 2011; 3:1004-19. [PMID: 22069754 PMCID: PMC3202866 DOI: 10.3390/toxins3081004] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Revised: 08/06/2011] [Accepted: 08/10/2011] [Indexed: 12/15/2022] Open
Abstract
Anthrax is a highly lethal infectious disease caused by the spore-forming bacterium Bacillus anthracis. It not only causes natural infection in humans but also poses a great threat as an emerging bioterror agent. The lethality of anthrax is primarily attributed to the two major virulence factors: toxins and capsule. An extensive effort has been made to generate therapeutically useful monoclonal antibodies to each of the virulence components: protective antigen (PA), lethal factor (LF) and edema factor (EF), and the capsule of B. anthracis. This review summarizes the current status of anti-anthrax mAb development and argues for the potential therapeutic advantage of a cocktail of mAbs that recognize different epitopes or different virulence factors.
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Bacillus anthracis: Molecular taxonomy, population genetics, phylogeny and patho-evolution. INFECTION GENETICS AND EVOLUTION 2011; 11:1218-24. [DOI: 10.1016/j.meegid.2011.05.013] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Revised: 05/18/2011] [Accepted: 05/18/2011] [Indexed: 11/17/2022]
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Levy H, Weiss S, Altboum Z, Schlomovitz J, Rothschild N, Blachinsky E, Kobiler D. Lethal factor is not required for Bacillus anthracis virulence in guinea pigs and rabbits. Microb Pathog 2011; 51:345-51. [PMID: 21791242 DOI: 10.1016/j.micpath.2011.07.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Revised: 06/26/2011] [Accepted: 07/06/2011] [Indexed: 11/26/2022]
Abstract
The major virulence factor of Bacillus anthracis is the tripartite anthrax toxin, comprising the protective antigen (PA), lethal factor (LF) and edema factor (EF). The LF of B. anthracis is a metalloprotease that has been shown to play an important role in pathogenicity. Deletion of this gene (lef) in the Sterne strain was reported to dramatically reduce the pathogenicity of this strain in mice, and was reported to be as dramatic as the deletion of PA. We evaluated the effect on pathogenicity of the lef deletion in the fully virulent Vollum strain in guinea pigs and NZW rabbits by either subcutaneous injection or intranasal instillation. In guinea pigs, no major differences between the mutant strain and the wild type could be detected in the LD(50) or mean time to death values. On the other hand, the lef deletion caused death of 50-70% of all rabbits infected with the mutant spores at doses equivalent or higher than the wild type LD(50). The surviving rabbits, which were infected with spore doses higher than the wild type LD(50), developed a protective immune response that conferred resistance to challenge with the wild type strain. These findings may indicate that the mutant lacking the LF is capable of host colonization which causes death in 50-70% of the animals and a protective immune response in the others. These results indicate that unlike the data obtained in mice, the LF mutation does not abolish B. anthracis pathogenicity.
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Affiliation(s)
- Haim Levy
- Department of Infectious Diseases, Israel Institute for Biological Research, 74100 Ness Ziona, Israel.
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Paccani SR, Baldari CT. T cell targeting by anthrax toxins: two faces of the same coin. Toxins (Basel) 2011; 3:660-71. [PMID: 22069732 PMCID: PMC3202842 DOI: 10.3390/toxins3060660] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Revised: 06/03/2011] [Accepted: 06/07/2011] [Indexed: 12/24/2022] Open
Abstract
Bacillus anthracis, similar to other bacterial pathogens, has evolved effective immune evasion strategies to prolong its survival in the host, thus ensuring the unchecked spread of the infection. This function is subserved by lethal (LT) and edema (ET) toxins, two exotoxins produced by vegetative anthrax bacilli following germination of the spores. The structure of these toxins and the mechanism of cell intoxication are topics covered by other reviews in this issue. Here we shall discuss how B. anthracis uses LT and ET to suppress the immune defenses of the host, focusing on T lymphocytes, the key players in adaptive immunity. We shall also summarize recent findings showing that, depending on its concentration, ET has the ability not only to suppress T cell activation but also to promote the polarization of CD4(+) T cells to the Th2 and Th17 subsets, highlighting the potential use of this toxin as an immunomodulator.
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Affiliation(s)
- Silvia Rossi Paccani
- Department of Evolutionary Biology, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy;
- Novartis Vaccines, Via Fiorentina 1, 53100 Siena, Italy
- Author to whom correspondence should be addressed; or ; Tel.: +39-0577-234396; Fax: +39-0577-234476
| | - Cosima T. Baldari
- Department of Evolutionary Biology, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy;
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Gautier M, Naves M. Footprints of selection in the ancestral admixture of a New World Creole cattle breed. Mol Ecol 2011; 20:3128-43. [PMID: 21689193 DOI: 10.1111/j.1365-294x.2011.05163.x] [Citation(s) in RCA: 111] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Admixed populations represent attractive biological models to study adaptive selection. Originating from several waves of recent introduction from European (EUT), African (AFT) and zebus (ZEB) cattle, New World Creole cattle allow investigating the response to tropical environmental challenges of these three ancestries. We here provide a detailed assessment of their genetic contributions to the Creole breed from Guadeloupe (CGU). We subsequently look for footprints of selection by combining results from tests based on the extent of haplotype homozygosity and the identification of excess/deficiency of local ancestry. To tackle these issues, 140 CGU individuals and 25 Brahman zebus from Martinique were genotyped at 44 057 SNPs. These data were combined to those available on 23 populations representative of EUT, AFT or ZEB. We found average proportions of 26.1%, 36.0% and 37.9% of EUT, AFT and ZEB ancestries in the CGU genome indicating a higher level of African and zebu ancestries than suggested by historical records. We further identified 23 genomic regions displaying strong signal of selection, most of them being characterized by an excess of ZEB local ancestry. Among the candidate gene underlying these regions, several are associated with reproductive functions (RXFP2, PMEPA1, IGFBP3, KDR, PPP1R8, TBXA2R and SLC7A5) and metabolism (PDE1B and CYP46A1). Finally, two genes (CENTD3 and SAMD12) are involved in cellular signalization of immune response. This study illustrates the relevance of admixed populations to identify footprints of selection by combining several tests straightforward to implement on large data sets.
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Affiliation(s)
- Mathieu Gautier
- INRA, UMR CBGP (INRA/CIRAD/IRD/Supagro), Montferrier-sur-Lez, France.
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Xie T, Auth RD, Frucht DM. The effects of anthrax lethal toxin on host barrier function. Toxins (Basel) 2011; 3:591-607. [PMID: 22069727 PMCID: PMC3202839 DOI: 10.3390/toxins3060591] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Revised: 06/02/2011] [Accepted: 06/07/2011] [Indexed: 01/08/2023] Open
Abstract
The pathological actions of anthrax toxin require the activities of its edema factor (EF) and lethal factor (LF) enzyme components, which gain intracellular access via its receptor-binding component, protective antigen (PA). LF is a metalloproteinase with specificity for selected mitogen-activated protein kinase kinases (MKKs), but its activity is not directly lethal to many types of primary and transformed cells in vitro. Nevertheless, in vivo treatment of several animal species with the combination of LF and PA (termed lethal toxin or LT) leads to morbidity and mortality, suggesting that LT-dependent toxicity is mediated by cellular interactions between host cells. Decades of research have revealed that a central hallmark of this toxicity is the disruption of key cellular barriers required to maintain homeostasis. This review will focus on the current understanding of the effects of LT on barrier function, highlighting recent progress in establishing the molecular mechanisms underlying these effects.
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Affiliation(s)
- Tao Xie
- Laboratory of Cell Biology, Division of Monoclonal Antibodies, Office of Biotechnology Products, Office of Pharmaceutical Science, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Bethesda, MD 20892, USA.
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