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Tessier E, Cheutin L, Garnier A, Vigne C, Tournier JN, Rougeaux C. Early Circulating Edema Factor in Inhalational Anthrax Infection: Does It Matter? Microorganisms 2024; 12:308. [PMID: 38399712 PMCID: PMC10891819 DOI: 10.3390/microorganisms12020308] [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: 11/29/2023] [Revised: 01/22/2024] [Accepted: 01/26/2024] [Indexed: 02/25/2024] Open
Abstract
Anthrax toxins are critical virulence factors of Bacillus anthracis and Bacillus cereus strains that cause anthrax-like disease, composed of a common binding factor, the protective antigen (PA), and two enzymatic proteins, lethal factor (LF) and edema factor (EF). While PA is required for endocytosis and activity of EF and LF, several studies showed that these enzymatic factors disseminate within the body in the absence of PA after intranasal infection. In an effort to understand the impact of EF in the absence of PA, we used a fluorescent EF chimera to facilitate the study of endocytosis in different cell lines. Unexpectedly, EF was found inside cells in the absence of PA and showed a pole-dependent endocytosis. However, looking at enzymatic activity, PA was still required for EF to induce an increase in intracellular cAMP levels. Interestingly, the sequential delivery of EF and then PA rescued the rise in cAMP levels, indicating that PA and EF may functionally associate during intracellular trafficking, as well as it did at the cell surface. Our data shed new light on EF trafficking and the potential location of PA and EF association for optimal cytosolic delivery.
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Affiliation(s)
- Emilie Tessier
- Département des Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France (C.R.)
| | - Laurence Cheutin
- Département des Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France (C.R.)
| | - Annabelle Garnier
- Département des Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France (C.R.)
| | - Clarisse Vigne
- Département des Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France (C.R.)
| | - Jean-Nicolas Tournier
- Département des Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France (C.R.)
- Institut Pasteur, 75015 Paris, France
| | - Clémence Rougeaux
- Département des Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France (C.R.)
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Beitzinger C, Kronhardt A, Benz R. Chloroquine-analogues block anthrax protective antigen channels in steady-state and kinetic studies. Toxicology 2023; 492:153547. [PMID: 37201861 DOI: 10.1016/j.tox.2023.153547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 05/11/2023] [Accepted: 05/15/2023] [Indexed: 05/20/2023]
Abstract
The tripartite anthrax toxin from Bacillus anthracis represents the prototype of A-B type of toxins, where the effector A (an enzymatic subunit) is transported with the help of a binding component B into a target cell. Anthrax toxin consists of three different molecules, two effectors, lethal factor (LF) and edema factor (EF) and the binding component also known as protective antigen (PA). PA forms heptamers or octamers following binding to host cell's receptors and mediates the translocation of the effectors into the cytosol via the endosomal pathway. The cation-selective PA63-channel is able to reconstitute in lipid membranes and can be blocked by chloroquine and other heterocyclic compounds. This suggests that the PA63-channel contains a binding site for quinolines. In this study, we investigated the structure-function relationship of different quinolines for the block of the PA63-channel. The affinity of the different chloroquine analogues to the PA63-channel as provided by the equilibrium dissociation constant was measured using titrations. Some quinolines had a much higher affinity to the PA63-channel than chloroquine itself. We also performed ligand-induced current noise measurements using fast Fourier transformation to get insight in the kinetics of the binding of some quinolines to the PA63-channel. The on-rate constants of ligand binding were around 108M-1·s-1 at 150mM KCl and were only little dependent on the individual quinoline. The off-rates varied between 4s-1 and 160s-1 and depended much more on the structure of the molecules than the on-rate constants. The possible use of the 4-aminoquinolines as a therapy is discussed.
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Affiliation(s)
- Christoph Beitzinger
- Rudolf Virchow Center, Research Center for Experimental Biomedicine, University of Würzburg, Versbacher Straße 9, 97078 Würzburg, Germany
| | - Angelika Kronhardt
- Rudolf Virchow Center, Research Center for Experimental Biomedicine, University of Würzburg, Versbacher Straße 9, 97078 Würzburg, Germany
| | - Roland Benz
- Science Faculty, Constructor University Bremen, Campus-Ring 1, 28759 Bremen, Germany.
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Heber S, Barthold L, Baier J, Papatheodorou P, Fois G, Frick M, Barth H, Fischer S. Inhibition of Clostridioides difficile Toxins TcdA and TcdB by Ambroxol. Front Pharmacol 2022; 12:809595. [PMID: 35058787 PMCID: PMC8764291 DOI: 10.3389/fphar.2021.809595] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 12/10/2021] [Indexed: 02/04/2023] Open
Abstract
Clostridioides (C.) difficile produces the exotoxins TcdA and TcdB, which are the predominant virulence factors causing C. difficile associated disease (CDAD). TcdA and TcdB bind to target cells and are internalized via receptor-mediated endocytosis. Translocation of the toxins’ enzyme subunits from early endosomes into the cytosol depends on acidification of endosomal vesicles, which is a prerequisite for the formation of transmembrane channels. The enzyme subunits of the toxins translocate into the cytosol via these channels where they are released after auto-proteolytic cleavage. Once in the cytosol, both toxins target small GTPases of the Rho/Ras-family and inactivate them by mono-glucosylation. This in turn interferes with actin-dependent processes and ultimately leads to the breakdown of the intestinal epithelial barrier and inflammation. So far, therapeutic approaches to treat CDAD are insufficient, since conventional antibiotic therapy does not target the bacterial protein toxins, which are the causative agents for the clinical symptoms. Thus, directly targeting the exotoxins represents a promising approach for the treatment of CDAD. Lately, it was shown that ambroxol (Ax) prevents acidification of intracellular organelles. Therefore, we investigated the effect of Ax on the cytotoxic activities of TcdA and TcdB. Ax significantly reduced toxin-induced morphological changes as well as the glucosylation of Rac1 upon intoxication with TcdA and TcdB. Most surprisingly, Ax, independent of its effects on endosomal acidification, decreased the toxins’ intracellular enzyme activity, which is mediated by a catalytic glucosyltransferase domain. Considering its undoubted safety profile, Ax might be taken into account as therapeutic option in the context of CDAD.
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Affiliation(s)
- Sebastian Heber
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm, Germany
| | - Lara Barthold
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm, Germany
| | - Jan Baier
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm, Germany
| | | | - Giorgio Fois
- Institute of General Physiology, Ulm University, Ulm, Germany
| | - Manfred Frick
- Institute of General Physiology, Ulm University, Ulm, Germany
| | - Holger Barth
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm, Germany
| | - Stephan Fischer
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm, Germany
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Chui AJ, Okondo MC, Rao SD, Gai K, Griswold AR, Johnson DC, Ball DP, Taabazuing CY, Orth EL, Vittimberga BA, Bachovchin DA. N-terminal degradation activates the NLRP1B inflammasome. Science 2019; 364:82-85. [PMID: 30872531 PMCID: PMC6610862 DOI: 10.1126/science.aau1208] [Citation(s) in RCA: 204] [Impact Index Per Article: 40.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Revised: 11/02/2018] [Accepted: 03/05/2019] [Indexed: 12/29/2022]
Abstract
Intracellular pathogens and danger signals trigger the formation of inflammasomes, which activate inflammatory caspases and induce pyroptosis. The anthrax lethal factor metalloprotease and small-molecule DPP8/9 inhibitors both activate the NLRP1B inflammasome, but the molecular mechanism of NLRP1B activation is unknown. In this study, we used genome-wide CRISPR-Cas9 knockout screens to identify genes required for NLRP1B-mediated pyroptosis. We discovered that lethal factor induces cell death via the N-end rule proteasomal degradation pathway. Lethal factor directly cleaves NLRP1B, inducing the N-end rule-mediated degradation of the NLRP1B N terminus and freeing the NLRP1B C terminus to activate caspase-1. DPP8/9 inhibitors also induce proteasomal degradation of the NLRP1B N terminus but not via the N-end rule pathway. Thus, N-terminal degradation is the common activation mechanism of this innate immune sensor.
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Affiliation(s)
- Ashley J Chui
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Marian C Okondo
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Sahana D Rao
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Kuo Gai
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Andrew R Griswold
- Pharmacology Program of the Weill Cornell Graduate School of Medical Sciences, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Darren C Johnson
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Daniel P Ball
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Cornelius Y Taabazuing
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Elizabeth L Orth
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Brooke A Vittimberga
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Daniel A Bachovchin
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
- Pharmacology Program of the Weill Cornell Graduate School of Medical Sciences, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
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Friebe S, van der Goot FG, Bürgi J. The Ins and Outs of Anthrax Toxin. Toxins (Basel) 2016; 8:toxins8030069. [PMID: 26978402 PMCID: PMC4810214 DOI: 10.3390/toxins8030069] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 02/28/2016] [Accepted: 03/01/2016] [Indexed: 12/21/2022] Open
Abstract
Anthrax is a severe, although rather rare, infectious disease that is caused by the Gram-positive, spore-forming bacterium Bacillus anthracis. The infectious form is the spore and the major virulence factors of the bacterium are its poly-γ-D-glutamic acid capsule and the tripartite anthrax toxin. The discovery of the anthrax toxin receptors in the early 2000s has allowed in-depth studies on the mechanisms of anthrax toxin cellular entry and translocation from the endocytic compartment to the cytoplasm. The toxin generally hijacks the endocytic pathway of CMG2 and TEM8, the two anthrax toxin receptors, in order to reach the endosomes. From there, the pore-forming subunit of the toxin inserts into endosomal membranes and enables translocation of the two catalytic subunits. Insertion of the pore-forming unit preferentially occurs in intraluminal vesicles rather than the limiting membrane of the endosome, leading to the translocation of the enzymatic subunits in the lumen of these vesicles. This has important consequences that will be discussed. Ultimately, the toxins reach the cytosol where they act on their respective targets. Target modification has severe consequences on cell behavior, in particular on cells of the immune system, allowing the spread of the bacterium, in severe cases leading to host death. Here we will review the literature on anthrax disease with a focus on the structure of the toxin, how it enters cells and its immunological effects.
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Affiliation(s)
- Sarah Friebe
- Faculty of Life Sciences, Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne 1015, Switzerland.
| | - F Gisou van der Goot
- Faculty of Life Sciences, Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne 1015, Switzerland.
| | - Jérôme Bürgi
- Faculty of Life Sciences, Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne 1015, Switzerland.
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Noskov AN. [Molecular model of anthrax toxin translocation into target-cells]. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2015; 40:399-404. [PMID: 25898749 DOI: 10.1134/s1068162014040098] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Anthrax toxin is formed from three components: protective antigen (PA), lethal (LF) and edema (EF) factors. PA83 is cleaved by cell surface protease furin to produce a 63-kDa fragment (PA63). PA63 and LF/EF molecules are assembled to anthrax toxin complexes: oligomer PA63 x 7 + LF/EF x 3. Assembly is occurred during of binding with cellular receptor or near surface of target-cell. This toxin complex forms pore and induces receptor-mediated endocytosis. Formed endosome consists extracellular liquid with LF/EF and membrane-associated ferments (H+ and K+/Na+-ATPases) and proteins (receptors and others). H+ concentration is increased into endosome as result of K/Na-ATPase-dependent- activity of H+-ATPase. Difference of potentials (between endosome and intracellular liquid) is increased and LF/EF molecules are moved to pore and bound with PA63-oligomer to PA63 x 7 + LF/EF x 7 and full block pore (ion-selective channel). Endosome is increased in volume and induces increasing of PA63-oligomer pore to.size of effector complex: LF/EF x 7 + PAl7 x 7 = 750 kDa. Effector complex is translocated from endosome to cytosol by means high difference of potentials (H+) and dissociates from PA47 x 7 complex after cleavage of FFD315-sait by intracellular chymotrypsin-like proteases in all 7 molecules PA63. PA47 x 7 complex (strongly fixed in membrane with debris of hydrophobic loops) return into endosome and pore is destroyed. Endosome pH is decreased rapidly and PA47 x 7 complex is destroyed by endosomal/lysosomal proteases. Receptor-mediated endocytosis is ended by endosome recycling in cell-membrane.
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Stiles BG, Pradhan K, Fleming JM, Samy RP, Barth H, Popoff MR. Clostridium and bacillus binary enterotoxins: bad for the bowels, and eukaryotic being. Toxins (Basel) 2014; 6:2626-56. [PMID: 25198129 PMCID: PMC4179152 DOI: 10.3390/toxins6092626] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 08/22/2014] [Accepted: 08/27/2014] [Indexed: 12/18/2022] Open
Abstract
Some pathogenic spore-forming bacilli employ a binary protein mechanism for intoxicating the intestinal tracts of insects, animals, and humans. These Gram-positive bacteria and their toxins include Clostridium botulinum (C2 toxin), Clostridium difficile (C. difficile toxin or CDT), Clostridium perfringens (ι-toxin and binary enterotoxin, or BEC), Clostridium spiroforme (C. spiroforme toxin or CST), as well as Bacillus cereus (vegetative insecticidal protein or VIP). These gut-acting proteins form an AB complex composed of ADP-ribosyl transferase (A) and cell-binding (B) components that intoxicate cells via receptor-mediated endocytosis and endosomal trafficking. Once inside the cytosol, the A components inhibit normal cell functions by mono-ADP-ribosylation of globular actin, which induces cytoskeletal disarray and death. Important aspects of each bacterium and binary enterotoxin will be highlighted in this review, with particular focus upon the disease process involving the biochemistry and modes of action for each toxin.
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Affiliation(s)
- Bradley G Stiles
- Biology Department, Wilson College, 1015 Philadelphia Avenue, Chambersburg, PA 17201, USA.
| | - Kisha Pradhan
- Environmental Science Department, Wilson College, 1015 Philadelphia Avenue, Chambersburg, PA 17201, USA.
| | - Jodie M Fleming
- Department of Biology, North Carolina Central University, 1801 Fayetteville Street, Durham, NC 27707, USA.
| | - Ramar Perumal Samy
- Venom and Toxin Research Programme, Department of Anatomy, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Kent Ridge 117597, Singapore.
| | - Holger Barth
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, Ulm D-89081, Germany.
| | - Michel R Popoff
- Bacteries Anaerobies et Toxines, Institut Pasteur, 28 Rue du Docteur Roux, Paris 75724, France.
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Noskov AN. [Molecular mechanism of AB5 toxin A-subunit translocation into the target cells]. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2013; 39:671-9. [PMID: 25696929 DOI: 10.1134/s1068162013050129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
AB5 toxins are pore-forming protein complexes, which destroy eukaryotic target cells inactivating essential enzyme complexes through protein ADP-ribosylation or glycosylation by enzymatically active A1 subunits. The B-subunit pentamer interacts with the target cell receptor, induces membrane pore formation, and initiates receptor-mediated endocytosis. In the present article, we propose a model of A1-subunit translocation in the form of a globular structure, as opposed to the generally accepted hypothesis of A-subunit unfolding in the acidic milieu of the endosome followed by its transport in the form of unfolded polypeptide and refolding in the cytoplasm. This model is based on physical-chemical processes and explains why an endosome, but not an exosome, is formed. A-subunit translocation into the cytosol is driven by the proton potential difference generated by K/Na- and H(+)-ATPases. After reduction of the disulphide bond between A1 and A2 fragments by intracellular enzymes, B-subunit returns back into the endosome, where they are destroyed by endosomal proteases, and the pore is closed. Endosome integrates into the cellular membrane, and membrane-bound enzymatic complexes (ATPases and others) return back to their initial position. The proposed model of receptor-mediated endocytosis is a universal molecular mechanism of translocation of effector toxin molecule subunits or any other proteins into the target cell, as well as of cell membrane reparation after any cell membrane injury by pore-forming complexes.
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Beitzinger C, Bronnhuber A, Duscha K, Riedl Z, Huber-Lang M, Benz R, Hajós G, Barth H. Designed azolopyridinium salts block protective antigen pores in vitro and protect cells from anthrax toxin. PLoS One 2013; 8:e66099. [PMID: 23840407 PMCID: PMC3688708 DOI: 10.1371/journal.pone.0066099] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Accepted: 05/02/2013] [Indexed: 11/28/2022] Open
Abstract
Background Several intracellular acting bacterial protein toxins of the AB-type, which are known to enter cells by endocytosis, are shown to produce channels. This holds true for protective antigen (PA), the binding component of the tripartite anthrax-toxin of Bacillus anthracis. Evidence has been presented that translocation of the enzymatic components of anthrax-toxin across the endosomal membrane of target cells and channel formation by the heptameric/octameric PA63 binding/translocation component are related phenomena. Chloroquine and some 4-aminoquinolones, known as potent drugs against Plasmodium falciparium infection of humans, block efficiently the PA63-channel in a dose dependent way. Methodology/Principal Findings Here we demonstrate that related positively charged heterocyclic azolopyridinium salts block the PA63-channel in the µM range, when both, inhibitor and PA63 are added to the same side of the membrane, the cis-side, which corresponds to the lumen of acidified endosomal vesicles of target cells. Noise-analysis allowed the study of the kinetics of the plug formation by the heterocycles. In vivo experiments using J774A.1 macrophages demonstrated that the inhibitors of PA63-channel function also efficiently block intoxication of the cells by the combination lethal factor and PA63 in the same concentration range as they block the channels in vitro. Conclusions/Significance These results strongly argue in favor of a transport of lethal factor through the PA63-channel and suggest that the heterocycles used in this study could represent attractive candidates for development of novel therapeutic strategies against anthrax.
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Affiliation(s)
- Christoph Beitzinger
- Rudolf-Virchow-Center, DFG-Research Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany
| | - Anika Bronnhuber
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Ulm, Germany
| | - Kerstin Duscha
- Rudolf-Virchow-Center, DFG-Research Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany
| | - Zsuzsanna Riedl
- Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary
| | - Markus Huber-Lang
- Institute of Traumatology, Hand- and Reconstructive Surgery, University of Ulm Medical Center, Ulm, Germany
| | - Roland Benz
- Rudolf-Virchow-Center, DFG-Research Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany
- School of Engineering and Science, Jacobs University Bremen, Bremen, Germany
- * E-mail: (RB); (HB)
| | - György Hajós
- Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary
| | - Holger Barth
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Ulm, Germany
- * E-mail: (RB); (HB)
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Botulinum Neurotoxin Type A is Internalized and Translocated from Small Synaptic Vesicles at the Neuromuscular Junction. Mol Neurobiol 2013; 48:120-7. [DOI: 10.1007/s12035-013-8423-9] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 02/05/2013] [Indexed: 10/27/2022]
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Acid and base stress and transcriptomic responses in Bacillus subtilis. Appl Environ Microbiol 2008; 75:981-90. [PMID: 19114526 DOI: 10.1128/aem.01652-08] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Acid and base environmental stress responses were investigated in Bacillus subtilis. B. subtilis AG174 cultures in buffered potassium-modified Luria broth were switched from pH 8.5 to pH 6.0 and recovered growth rapidly, whereas cultures switched from pH 6.0 to pH 8.5 showed a long lag time. Log-phase cultures at pH 6.0 survived 60 to 100% at pH 4.5, whereas cells grown at pH 7.0 survived <15%. Cells grown at pH 9.0 survived 40 to 100% at pH 10, whereas cells grown at pH 7.0 survived <5%. Thus, growth in a moderate acid or base induced adaptation to a more extreme acid or base, respectively. Expression indices from Affymetrix chip hybridization were obtained for 4,095 protein-encoding open reading frames of B. subtilis grown at external pH 6, pH 7, and pH 9. Growth at pH 6 upregulated acetoin production (alsDS), dehydrogenases (adhA, ald, fdhD, and gabD), and decarboxylases (psd and speA). Acid upregulated malate metabolism (maeN), metal export (czcDO and cadA), oxidative stress (catalase katA; OYE family namA), and the SigX extracytoplasmic stress regulon. Growth at pH 9 upregulated arginine catabolism (roc), which generates organic acids, glutamate synthase (gltAB), polyamine acetylation and transport (blt), the K(+)/H(+) antiporter (yhaTU), and cytochrome oxidoreductases (cyd, ctaACE, and qcrC). The SigH, SigL, and SigW regulons were upregulated at high pH. Overall, greater genetic adaptation was seen at pH 9 than at pH 6, which may explain the lag time required for growth shift to high pH. Low external pH favored dehydrogenases and decarboxylases that may consume acids and generate basic amines, whereas high external pH favored catabolism-generating acids.
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Leuber M, Kronhardt A, Tonello F, Dal Molin F, Benz R. Binding of N-terminal fragments of anthrax edema factor (EF(N)) and lethal factor (LF(N)) to the protective antigen pore. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:1436-43. [PMID: 18243126 DOI: 10.1016/j.bbamem.2008.01.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Revised: 01/07/2008] [Accepted: 01/08/2008] [Indexed: 12/23/2022]
Abstract
Anthrax toxin consists of three different molecules: the binding component protective antigen (PA, 83 kDa), and the enzymatic components lethal factor (LF, 90 kDa) and edema factor (EF, 89 kDa). The 63 kDa C-terminal part of PA, PA(63), forms heptameric channels that insert in endosomal membranes at low pH, necessary to translocate EF and LF into the cytosol of target cells. In many studies, about 30 kDa N-terminal fragments of the enzymatic components EF (254 amino acids) and LF (268 amino acids) were used to study their interaction with PA(63)-channels. Here, in experiments with artificial lipid bilayer membranes, EF(N) and LF(N) show block of PA(63)-channels in a dose, voltage and ionic strength dependent way with high affinity. However, when compared to their full-length counterparts EF and LF, they exhibit considerably lower binding affinity. Decreasing ionic strength and, in the case of EF(N), increasing transmembrane voltage at the cis side of the membranes, resulted in a strong decrease of half saturation constants. Our results demonstrate similarities but also remarkable differences between the binding kinetics of both truncated and full-length effectors to the PA(63)-channel.
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Affiliation(s)
- Michael Leuber
- Lehrstuhl für Biotechnologie, Theodor-Boveri-Institut (Biozentrum) der Universität Würzburg, Am Hubland, Würzburg, Germany
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Where and how do anthrax toxins exit endosomes to intoxicate host cells? Trends Microbiol 2007; 15:477-82. [PMID: 17983750 DOI: 10.1016/j.tim.2007.10.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2007] [Revised: 08/06/2007] [Accepted: 10/25/2007] [Indexed: 01/19/2023]
Abstract
The role of Bacillus anthracis virulence factors in its pathogenesis has been subjected to intense investigation with the aim of finding novel preventive and therapeutic protocols. Toxins that are endocytosed and act in the cytosol of host cells have a central role in B. anthracis infection. Understanding of anthrax toxin cell entry has increased during the past few years and a composite picture is emerging. Nevertheless, unanswered and controversial questions remain, particularly concerning the site and mode of anthrax toxin cell entry, the role of anthrax toxin receptors in the process and the possible involvement of cytosolic chaperones, which might affect entry efficiency. Here, the current model of anthrax toxin cell entry, an alternative model and experimental approaches for clarifying unanswered questions will be discussed.
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14
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Chalton DA, Kelly IF, McGregor A, Ridley H, Watkinson A, Miller J, Lakey JH. Unfolding transitions of Bacillus anthracis protective antigen. Arch Biochem Biophys 2007; 465:1-10. [PMID: 17531947 DOI: 10.1016/j.abb.2007.04.030] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Revised: 04/24/2007] [Accepted: 04/24/2007] [Indexed: 10/23/2022]
Abstract
Protective antigen (PA) is an 83kDa protein which, although essential for toxicity of Bacillus anthracis, is harmless and an effective vaccine component. In vivo it undergoes receptor binding, proteolysis, heptamerisation and membrane insertion. Here we probe the response of PA to denaturants, temperature and pH. We present analyses (including barycentric mean) of the unfolding and refolding behavior of PA and reveal the origin of two critical steps in the denaturant unfolding pathway in which the first step is a calcium and pH dependent rearrangement of domain 1. Thermal unfolding fits a single transition near 50 degrees C. We show for the first time circular dichroism (CD) spectra of the heptameric, furin-cleaved PA63 and the low-pH forms of both PA83 and PA63. Although only PA63 should reach the acidic endosome, both PA83 and PA63 undergo similar acidic transitions and an unusual change from a beta II to a beta I CD spectrum.
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Affiliation(s)
- David A Chalton
- Institute of Cell and Molecular Biosciences, University of Newcastle upon Tyne, Framlington Place, Newcastle NE2 4HH, UK
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15
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Dal Molin F, Tonello F, Ladant D, Zornetta I, Zamparo I, Di Benedetto G, Zaccolo M, Montecucco C. Cell entry and cAMP imaging of anthrax edema toxin. EMBO J 2006; 25:5405-13. [PMID: 17082768 PMCID: PMC1636612 DOI: 10.1038/sj.emboj.7601408] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2006] [Accepted: 10/05/2006] [Indexed: 02/07/2023] Open
Abstract
The entry and enzymatic activity of the anthrax edema factor (EF) in different cell types was studied by monitoring EF-induced changes in intracellular cAMP with biochemical and microscopic methods. cAMP was imaged in live cells, transfected with a fluorescence resonance energy transfer biosensor based on the protein kinase A regulatory and catalytic subunits fused to CFP and YFP, respectively. The cAMP biosensor was located either in the cytosol or was membrane-bound owing to the addition of a tag determining its myristoylation/palmitoylation. Real-time imaging of cells expressing the cAMP biosensors provided the time course of EF catalytic activity and an indication of its subcellular localization. Bafilomycin A1, an inhibitor of the vacuolar ATPase proton pump, completely prevented EF activity, even when added long after the toxin. The time course of appearance of the adenylate cyclase activity and of bafilomycin A1 action suggests that EF enters the cytosol from late endosomes. EF remains associated to these compartments and its activity shows a perinuclear localization generating intracellular cAMP concentration gradients from the cell centre to the periphery.
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Affiliation(s)
- Federica Dal Molin
- Dipartimento di Scienze Biomediche ed Istituto CNR Neuroscienze, Padova, Italy
| | - Fiorella Tonello
- Dipartimento di Scienze Biomediche ed Istituto CNR Neuroscienze, Padova, Italy
| | - Daniel Ladant
- Departement de Biologie Structurale et Chimie, Institut Pasteur, Paris Cedex, France
| | - Irene Zornetta
- Dipartimento di Scienze Biomediche ed Istituto CNR Neuroscienze, Padova, Italy
| | - Ilaria Zamparo
- Dulbecco Telethon Institute, Padova, Italy
- Istituto Veneto di Medicina Molecolare, Padova, Italy
| | - Giulietta Di Benedetto
- Dulbecco Telethon Institute, Padova, Italy
- Istituto Veneto di Medicina Molecolare, Padova, Italy
| | - Manuela Zaccolo
- Dulbecco Telethon Institute, Padova, Italy
- Istituto Veneto di Medicina Molecolare, Padova, Italy
- These authors share senior authorship
| | - Cesare Montecucco
- Dipartimento di Scienze Biomediche ed Istituto CNR Neuroscienze, Padova, Italy
- These authors share senior authorship
- Dipartimento di Scienze Biomediche, Viale G Colombo 3, 35121 Padova, Italy. Tel.: +39 049 827 6058; Fax: +39 049 827 6049; E-mails: or
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16
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Sapra R, Gaucher SP, Lachmann JS, Buffleben GM, Chirica GS, Comer JE, Peterson JW, Chopra AK, Singh AK. Proteomic analyses of murine macrophages treated with Bacillus anthracis lethal toxin. Microb Pathog 2006; 41:157-67. [PMID: 16950595 DOI: 10.1016/j.micpath.2006.07.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2006] [Revised: 06/22/2006] [Accepted: 07/10/2006] [Indexed: 11/30/2022]
Abstract
Bacillus anthracis is the etiological agent of anthrax and the bacterium produces a tripartite anthrax toxin composed of protective antigen (PA), lethal factor (LF) and edema factor (EF). PA represents the binding domain of the toxin and acts in concert with either LF, a metalloprotease, or EF, an adenylate cyclase, to form lethal toxin (LeTx) or edema toxin (EdTx), respectively. We analyzed the proteomics response of two murine macrophage cell lines (J774.1A and RAW264.7) following B. anthracis LeTx treatment to detect unique host proteins involved in anthrax infection using difference in-gel electrophoresis (DIGE) followed by nanoLC-MS for identification of the proteins. The comparative proteomics approach identified a set of proteins in each cell line that was consistently upregulated when the two macrophage cell lines were treated with LeTx. The upregulated proteins include those involved in energy metabolism, cytoskeleton structure and stress response. A subset of five proteins (ATP synthase beta subunit, beta-actin, Hsp70, vimentin, and Hsp60 homolog) was identified that were commonly upregulated in both cell lines. The proteomic data suggest the involvement of reactive oxygen species (ROS) in cell lysis as seen by the upregulation of proteins that lead to the production of ROS in both the cell lines used in our study. However, proteins that afford protection against ROS may play an important role in the survival of the macrophage to LeTx infection as shown by the differences in proteomic responses of the two cell lines to the action of LeTx. These identified proteins may have the potential to be used as biomarkers for diagnostics and therapeutics.
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Affiliation(s)
- R Sapra
- Sandia National Laboratories, 7011 East Avenue, Livermore, CA 94551, USA
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17
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Moayeri M, Wickliffe KE, Wiggins JF, Leppla SH. Oxidized ATP protection against anthrax lethal toxin. Infect Immun 2006; 74:3707-14. [PMID: 16790743 PMCID: PMC1489720 DOI: 10.1128/iai.00051-06] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacillus anthracis lethal toxin (LT) induces rapid lysis (<90 min) of murine macrophages from certain inbred strains. The mechanism for LT-induced cytolysis is currently unknown. We hypothesized that the ATP-activated macrophage P2X7 receptors implicated in nucleotide-mediated macrophage lysis could play a role in LT-mediated cytolysis and discovered that a potent P2X7 antagonist, oxidized ATP (o-ATP), protects macrophages against LT. Other P2X7 receptor antagonists, however, had no effect on LT function, while oxidized nucleotides, o-ADP, o-GTP, and o-ITP, which did not act as receptor ligands, provided protection. Cleavage of the LT substrates, the mitogen-activated protein kinases, was inhibited by o-ATP in RAW274.6 macrophages and CHO cells. We investigated the various steps in the intoxication pathway and found that binding of the protective-antigen (PA) component of LT to cells and the enzymatic proteolytic ability of the lethal factor (LF) component of LT were unaffected by o-ATP. Instead, the drug inhibited formation of the sodium dodecyl sulfate-resistant PA oligomer, which occurs in acidified endosomes, but did not prevent cell surface PA oligomerization, as evidenced by binding and translocation of LF to a protease-resistant intracellular location. We found that o-ATP also protected cells from anthrax edema toxin and diphtheria toxin, which also require an acidic environment for escape from endosomes. Confocal microscopy using pH-sensitive fluorescent dyes showed that o-ATP increased endosomal pH. Finally, BALB/cJ mice injected with o-ATP and LT were completely protected against lethality.
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Affiliation(s)
- Mahtab Moayeri
- Microbial Pathogenesis Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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18
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Jiao GS, Simo O, Nagata M, O'Malley S, Hemscheidt T, Cregar L, Millis SZ, Goldman ME, Tang C. Selectively guanidinylated derivatives of neamine. Syntheses and inhibition of anthrax lethal factor protease. Bioorg Med Chem Lett 2006; 16:5183-9. [PMID: 16870442 DOI: 10.1016/j.bmcl.2006.07.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Revised: 06/26/2006] [Accepted: 07/05/2006] [Indexed: 11/25/2022]
Abstract
A series of mono-, di-, and tri-guanidinylated derivatives of neamine were prepared via selective guanidinylation of neamine. These molecules represent a novel scaffold as inhibitors of anthrax lethal factor zinc metalloprotease. Methods for the synthesis of these compounds are described, and structure-activity relationships among the series are analyzed. In addition, initial findings regarding the mechanism of LF inhibition for these molecules are presented.
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Affiliation(s)
- Guan-Sheng Jiao
- Department of Chemistry, Hawaii Biotech, Inc., 99-193 Aiea Heights Dr., Suite 200, Aiea, 96701, USA.
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19
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Neumeyer T, Tonello F, Dal Molin F, Schiffler B, Orlik F, Benz R. Anthrax Lethal Factor (LF) Mediated Block of the Anthrax Protective Antigen (PA) Ion Channel: Effect of Ionic Strength and Voltage. Biochemistry 2006; 45:3060-8. [PMID: 16503661 DOI: 10.1021/bi0524316] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The anthrax toxin complex consists of three different molecules, protective antigen (PA), lethal factor (LF), and edema factor (EF). The activated form of PA, PA(63), forms heptamers that insert at low pH in biological membranes forming ion channels and that are necessary to translocate EF and LF in the cell cytosol. LF and EF are intracellular active enzymes that inhibit the host immune system promoting bacterial outgrowth. Here, PA(63) was reconstituted into artificial lipid bilayer membranes and formed ion-permeable channels. The heptameric PA(63) channel contains a binding site for LF on the cis side of the channel. Full-size LF was found to block the PA(63) channel in a dose- and ionic-strength-dependent way with half-saturation constants in the nanomolar concentration range. The binding curves suggest a 1:1 relationship between (PA(63))(7) and bound LF that blocks the channel. The presence of a His(6) tag at the N-terminal end of LF strongly increases the affinity of LF toward the PA(63) channel, indicating that the interaction between LF and the PA(63) channel occurs at the N terminus of the enzyme. The LF-mediated block of the PA(63)-induced membrane conductance is highly asymmetric with respect to the sign of the applied transmembrane potential. The result suggested that the PA(63) heptamers contain a high-affinity binding site for LF inside domain 1 or the channel vestibule and that the binding is ionic-strength-dependent.
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Affiliation(s)
- Tobias Neumeyer
- Lehrstuhl für Biotechnologie, Theodor-Boveri-Institut (Biozentrum) der Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
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20
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Jiao GS, Cregar L, Goldman ME, Millis SZ, Tang C. Guanidinylated 2,5-dideoxystreptamine derivatives as anthrax lethal factor inhibitors. Bioorg Med Chem Lett 2006; 16:1527-31. [PMID: 16386899 DOI: 10.1016/j.bmcl.2005.12.038] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2005] [Revised: 12/09/2005] [Accepted: 12/09/2005] [Indexed: 11/23/2022]
Abstract
Anthrax lethal factor is a Zn(2+)-dependent metalloprotease and the key virulence factor of tripartite anthrax toxin secreted by Bacillus anthracis, the causative agent of anthrax. A series of guanidinylated 2,5-dideoxystreptamine derivatives were designed and synthesized as inhibitors of lethal factor, some of which show strong inhibitory activity against lethal factor in an in vitro FRET assay. Preparation and structure-activity relationships of these compounds are presented.
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Affiliation(s)
- Guan-Sheng Jiao
- Department of Chemistry, Hawaii Biotech Inc., 99-193 Aiea Heights Drive, Suite 200, Aiea, HI 96701, USA.
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21
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Rainey GJA, Wigelsworth DJ, Ryan PL, Scobie HM, Collier RJ, Young JAT. Receptor-specific requirements for anthrax toxin delivery into cells. Proc Natl Acad Sci U S A 2005; 102:13278-83. [PMID: 16141341 PMCID: PMC1201603 DOI: 10.1073/pnas.0505865102] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The three proteins that constitute anthrax toxin self-assemble into toxic complexes after one of these proteins, protective antigen (PA), binds to tumor endothelial marker 8 (TEM8) or capillary morphogenesis protein 2 (CMG2) cellular receptors. The toxin receptor complexes are internalized, and acidic endosomal pH triggers pore formation by PA and translocation of the catalytic subunits into the cytosol. In this study we show that the pH threshold for conversion of the PA prepore to the pore and for translocation differs by approximately a pH unit, depending on whether the TEM8 or CMG2 receptor is used. For TEM8-associated toxin, these events can occur at close to neutral pH values, and they show relatively low sensitivity to ammonium chloride treatment in cells. In contrast, with CMG2-associated toxin, these events require more acidic conditions and are highly sensitive to ammonium chloride. We show, furthermore, that PA dissociates from TEM8 and CMG2 upon pore formation. Our results are consistent with a model in which translocation depends on pore formation and pore formation, in turn, depends on release of PA from its receptor. We propose that because PA binds to CMG2 with much higher affinity than it does to TEM8, a lower pH is needed to attenuate CMG2 binding to allow pore formation. Our results suggest that toxin can form pores at different points in the endocytic pathway, depending on which receptor is used for entry.
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Affiliation(s)
- G Jonah A Rainey
- Infectious Disease Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
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22
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Orlik F, Schiffler B, Benz R. Anthrax toxin protective antigen: inhibition of channel function by chloroquine and related compounds and study of binding kinetics using the current noise analysis. Biophys J 2004; 88:1715-24. [PMID: 15596516 PMCID: PMC1305228 DOI: 10.1529/biophysj.104.050336] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Protective antigen (PA) of the tripartite anthrax toxin binds to a cell surface receptor and mediates the transport of two enzymatic components, edema factor and lethal factor, into the cytosol of host cells. Here recombinant PA(63) from Bacillus anthracis was reconstituted into artificial lipid bilayer membranes and formed ion permeable channels. The heptameric PA(63)-channel contains a binding site for 4-aminoquinolones, which block ion transport through PA in vitro. This result allowed a detailed investigation of ligand binding and the stability constants for the binding of chloroquine, fluphenazine, and quinacrine to the binding site inside the PA(63)-channel were determined using titration experiments. Open PA(63)-channels exhibit 1/f noise in the frequency range between 1 and 100 Hz, whereas the spectral density of the ligand-induced current noise was of Lorentzian type. The analysis of the power density spectra allowed the evaluation of the on- and off-rate constants (k(1) and k(-1)) of ligand binding. The on-rate constants of ligand binding were between 10(6) and 10(8) M(-1) s(-1) and were dependent on the ionic strength of the aqueous phase, sidedness of ligand addition, as well as the orientation and intensity of the applied electric field. The off-rates varied between approximately 10 s(-1) and 2600 s(-1) and depended mainly on the structure of the ligand.
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Affiliation(s)
- Frank Orlik
- Lehrstuhl für Biotechnologie, Theodor-Boveri-Institut (Biozentrum) der Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
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23
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Barth H, Aktories K, Popoff MR, Stiles BG. Binary bacterial toxins: biochemistry, biology, and applications of common Clostridium and Bacillus proteins. Microbiol Mol Biol Rev 2004; 68:373-402, table of contents. [PMID: 15353562 PMCID: PMC515256 DOI: 10.1128/mmbr.68.3.373-402.2004] [Citation(s) in RCA: 285] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Certain pathogenic species of Bacillus and Clostridium have developed unique methods for intoxicating cells that employ the classic enzymatic "A-B" paradigm for protein toxins. The binary toxins produced by B. anthracis, B. cereus, C. botulinum, C. difficile, C. perfringens, and C. spiroforme consist of components not physically associated in solution that are linked to various diseases in humans, animals, or insects. The "B" components are synthesized as precursors that are subsequently activated by serine-type proteases on the targeted cell surface and/or in solution. Following release of a 20-kDa N-terminal peptide, the activated "B" components form homoheptameric rings that subsequently dock with an "A" component(s) on the cell surface. By following an acidified endosomal route and translocation into the cytosol, "A" molecules disable a cell (and host organism) via disruption of the actin cytoskeleton, increasing intracellular levels of cyclic AMP, or inactivation of signaling pathways linked to mitogen-activated protein kinase kinases. Recently, B. anthracis has gleaned much notoriety as a biowarfare/bioterrorism agent, and of primary interest has been the edema and lethal toxins, their role in anthrax, as well as the development of efficacious vaccines and therapeutics targeting these virulence factors and ultimately B. anthracis. This review comprehensively surveys the literature and discusses the similarities, as well as distinct differences, between each Clostridium and Bacillus binary toxin in terms of their biochemistry, biology, genetics, structure, and applications in science and medicine. The information may foster future studies that aid novel vaccine and drug development, as well as a better understanding of a conserved intoxication process utilized by various gram-positive, spore-forming bacteria.
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Affiliation(s)
- Holger Barth
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie der Albert-Ludwigs-Universität Freiburg, Otto-Krayer-Haus, Albertstrasse 25, D-79104 Freiburg, Germany.
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24
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Abrami L, Lindsay M, Parton RG, Leppla SH, van der Goot FG. Membrane insertion of anthrax protective antigen and cytoplasmic delivery of lethal factor occur at different stages of the endocytic pathway. ACTA ACUST UNITED AC 2004; 166:645-51. [PMID: 15337774 PMCID: PMC2172425 DOI: 10.1083/jcb.200312072] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
The protective antigen (PA) of anthrax toxin binds to a cell surface receptor, undergoes heptamerization, and binds the enzymatic subunits, the lethal factor (LF) and the edema factor (EF). The resulting complex is then endocytosed. Via mechanisms that depend on the vacuolar ATPase and require membrane insertion of PA, LF and EF are ultimately delivered to the cytoplasm where their targets reside. Here, we show that membrane insertion of PA already occurs in early endosomes, possibly only in the multivesicular regions, but that subsequent delivery of LF to the cytoplasm occurs preferentially later in the endocytic pathway and relies on the dynamics of internal vesicles of multivesicular late endosomes.
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Affiliation(s)
- Laurence Abrami
- Department of Microbiology and Molecular Medicine, University of Geneva, 1 rue Michel Servet, Geneva, Switzerland 1211
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25
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Abstract
Bacillus anthracis, the etiological agent of anthrax, secretes three polypeptides that assemble into toxic complexes on the cell surfaces of the host it infects. One of these polypeptides, protective antigen (PA), binds to the integrin-like domains of ubiquitously expressed membrane proteins of mammalian cells. PA is then cleaved by membrane endoproteases of the furin family. Cleaved PA molecules assemble into heptamers, which can then associate with the two other secreted polypeptides: edema factor (EF) and/or lethal factor (LF). The heptamers of PA are relocalized to lipid rafts where they are quickly endocytosed and routed to an acidic compartment. The low pH triggers a conformational change in the heptamers, resulting in the formation of cation-specific channels and the translocation of EF/LF. EF is a calcium- and calmodulin-dependent adenylate cyclase that dramatically raises the intracellular concentration of cyclic adenosine monophosphate (cAMP). LF is a zinc-dependent endoprotease that cleaves the amino terminus of mitogen-activated protein kinase kinases (Meks). Cleaved Meks cannot bind to their substrates and have reduced kinase activity, resulting in alterations of the signaling pathways they govern. The structures of PA, PA heptamer, EF, and LF have been solved and much is now known about the molecular details of the intoxication mechanism. The in vivo action of the toxins, on the other hand, is still poorly understood and hotly debated. A better understanding of the toxins will help in the design of much-needed anti-toxin drugs and the development of new toxin-based medical applications.
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Affiliation(s)
- M Mourez
- Faculté de Médecine Vétérinaire, Département de Pathologie et Microbiologie, Université de Montréal, J2S 7C6, Saint Hyacinthe, QC, Canada.
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26
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Dell'Aica I, Donà M, Tonello F, Piris A, Mock M, Montecucco C, Garbisa S. Potent inhibitors of anthrax lethal factor from green tea. EMBO Rep 2004; 5:418-22. [PMID: 15031715 PMCID: PMC1299029 DOI: 10.1038/sj.embor.7400118] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2003] [Revised: 01/27/2004] [Accepted: 01/28/2004] [Indexed: 11/09/2022] Open
Abstract
The anthrax lethal factor (LF) has a major role in the development of anthrax. LF is delivered by the protective antigen (PA) inside the cell, where it exerts its metalloprotease activity on the N-terminus of MAPK-kinases. PA+LF are cytotoxic to macrophages in culture and kill the Fischer 344 rat when injected intravenously. We describe here the properties of some polyphenols contained in green tea as powerful inhibitors of LF metalloproteolytic activity, and how the main catechin of green tea, (-)epigallocatechin-3-gallate, prevents the LF-induced death of macrophages and Fischer 344 rats.
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Affiliation(s)
| | - Massimo Donà
- Dipartimento di Scienze Biomediche, Università di Padova, Padova, Italy
| | | | - Alejandro Piris
- Toxines et Pathogénie Bactérienne (CNRS URA 2172), Institut Pasteur, Paris, France
| | - Michèle Mock
- Toxines et Pathogénie Bactérienne (CNRS URA 2172), Institut Pasteur, Paris, France
| | - Cesare Montecucco
- Dipartimento di Scienze Biomediche, Università di Padova, Padova, Italy
- Tel: +39 049 8276058; Fax: +39 049 8276049; E-mail:
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27
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Abstract
Anthrax toxin consists of three nontoxic proteins that associate in binary or ternary combinations to form toxic complexes at the surface of mammalian cells. One of these proteins, protective antigen (PA), transports the other two, edema factor (EF) and lethal factor (LF), to the cytosol. LF is a Zn2+-protease that cleaves certain MAP kinase kinases, leading to death of the host via a poorly defined sequence of events. EF, a calmodulin- and Ca2+-dependent adenylate cyclase, is responsible for the edema seen in the disease. Both enzymes are believed to benefit the bacteria by inhibiting cells of the host's innate immune system. Assembly of toxic complexes begins after PA binds to cellular receptors and is cleaved into two fragments by furin proteases. The smaller fragment dissociates, allowing the receptor-bound fragment, PA63 (63 kDa), to self-associate and form a ring-shaped, heptameric pore precursor (prepore). The prepore binds up to three molecules of EF and/or LF, and the resulting complexes are endocytosed and trafficked to an acidic compartment. There, the prepore converts to a transmembrane pore, mediating translocation of EF and LF to the cytosol. Recent studies have revealed (a) the identity of receptors; (b) crystallographic structures of the three toxin proteins and the heptameric PA63 prepore; and (c) information about toxin assembly, entry, and action within the cytosol. Knowledge of the structure and mode of action of the toxin has unveiled potential applications in medicine, including approaches to treating anthrax infections.
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Affiliation(s)
- R John Collier
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
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28
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Tonello F, Naletto L, Romanello V, Dal Molin F, Montecucco C. Tyrosine-728 and glutamic acid-735 are essential for the metalloproteolytic activity of the lethal factor of Bacillus anthracis. Biochem Biophys Res Commun 2004; 313:496-502. [PMID: 14697216 DOI: 10.1016/j.bbrc.2003.11.134] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The lethal factor (LF) of Bacillus anthracis is a Zn2+-endopeptidase specific for the MAPK-kinase family of proteins. The catalytic zinc atom is coordinated by a first shell of residues including the two histidines and the glutamate of the zinc-binding motif HExxH and by Glu-735. A characteristic feature of LF is the presence, within the second shell of residues, of a tyrosine (Tyr-728) in close proximity (3.3 A) to the zinc atom. To investigate the role of Tyr-728 and Glu-735, LF mutants with one or both of these two residues replaced by Ala were cloned, expressed, and purified from Escherichia coli. A fourth mutant was obtained by replacing Tyr-728 with Phe. Spectroscopic analysis of these mutants indicates that they fold in the same way as the parental molecule and that zinc stabilizes the structure of LF. These mutants have neither proteolytic activity nor in vivo toxicity. The possible role of Tyr-728 in catalysis is discussed.
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Affiliation(s)
- Fiorella Tonello
- Istituto di Neuroscienze del CNR, Università di Padova, Via G Colombo 3, 35121 Padua, Italy.
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29
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Salles II, Tucker AE, Voth DE, Ballard JD. Toxin-induced resistance in Bacillus anthracis lethal toxin-treated macrophages. Proc Natl Acad Sci U S A 2003; 100:12426-31. [PMID: 14519843 PMCID: PMC218774 DOI: 10.1073/pnas.2134042100] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
In the current study, we show that macrophages adaptively resist anthrax lethal toxin (LT) through a toxin-activated process termed toxin-induced resistance (TIR). TIR was triggered by pretreatment of RAW 264.7 or J774A.1 macrophages with a low dose of LT for at least 6 h, which resulted in resistance to high doses of LT for 96 h. Activation of TIR required functional toxin, because LT subunits, mutants, and heat-inactivated toxin were unable to trigger resistance. TIR macrophages were not altered in toxin receptor levels or cell cycle profiles. Treatment of TIR macrophages with high doses of LT resulted in a sustained decline in full-length mitogen-activated protein kinase kinase 2, a known target of lethal factor, and a marked reduction in diphosphorylated extracellular response kinases 1,2 for 24 h. However, despite the sustained loss of full-length mitogen-activated protein kinase kinase 2, by 48 h, TIR macrophages regained diphosphorylated extracellular response kinases 1,2, suggesting an adaptation led to recovery of this signaling pathway. TIR macrophages were also able to maintain normal levels of ubiquitinylated proteins, whereas sensitive cells show a rapid reduction in ubiquitin-modified proteins before cell death, indicating a possible alteration in proteasome activity contributed to resistance. These results provide a paradigm for toxin-cell interactions and suggest macrophages are capable of adapting to and tolerating toxic doses of LT.
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Affiliation(s)
- Isabelle I Salles
- Department of Botany and Microbiology, 770 Van Vleet Oval, University of Oklahoma, Norman, OK 73019, USA
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30
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Abstract
Anthrax toxin is a key virulence factor for Bacillus anthracis, the causative agent of anthrax. Here we discuss what is known about the anthrax toxin receptor (ATR), the cellular receptor for anthrax toxin, and how this information is being used to develop treatments for anthrax as well as to understand aspects of cancer. ATR was identified recently as a type I transmembrane protein with unknown function that contains an extracellular integrin-like inserted (I) domain. The ATR I domain contains the toxin binding site, and a soluble form of this domain was shown to serve as an effective antitoxin to protect cultured cells from toxin action. ATR is encoded by the tumor endothelial marker 8 (TEM8) gene, which is selectively up-regulated during blood vessel formation and in tumor vasculature, raising the possibility that this protein normally functions in angiogenesis. Therefore, identification of the cellular receptor for anthrax toxin has made possible new avenues of research in the areas of anthrax pathogenesis, antitoxin development, and cancer biology.
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Affiliation(s)
- Kenneth A Bradley
- McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, 1400 University Avenue, Madison, WI 53706, USA.
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31
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Abstract
Anthrax toxin is a binary A-B toxin comprised of protective antigen (PA) and two enzymatic moieties, edema factor (EF) and lethal factor (LF). In the presence of a host cell-surface receptor, PA can mediate the delivery of EF and LF from the extracellular milieu into the host cell cytosol to effect toxicity. In this delivery, PA undergoes multiple structural changes--from a monomer to a heptameric prepore to a membrane-spanning heptameric pore. The catalytic factors also undergo dramatic structural changes as they unfold to allow for their translocation across the endosomal membrane and refold to preserve their catalytic activity within the cytosol. In addition to these gross structural changes, the intoxication mechanism depends on the ability of PA to form specific interactions with the host cell receptor, EF, and LF. This chapter presents a review of experiments probing these structural interactions and rearrangements in the hopes of gaining a molecular understanding of toxin action.
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Affiliation(s)
- D B Lacy
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA
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32
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Ascenzi P, Visca P, Ippolito G, Spallarossa A, Bolognesi M, Montecucco C. Anthrax toxin: a tripartite lethal combination. FEBS Lett 2002; 531:384-8. [PMID: 12435580 DOI: 10.1016/s0014-5793(02)03609-8] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Anthrax is a severe bacterial infection that occurs when Bacillus anthracis spores gain access into the body and germinate in macrophages, causing septicemia and toxemia. Anthrax toxin is a binary A-B toxin composed of protective antigen (PA), lethal factor (LF), and edema factor (EF). PA mediates the entry of either LF or EF into the cytosol of host cells. LF is a zinc metalloprotease that inactivates mitogen-activated protein kinase kinase inducing cell death, and EF is an adenylyl cyclase impairing host defences. Inhibitors targeting different steps of toxin activity have recently been developed. Anthrax toxin has also been exploited as a therapeutic agent against cancer.
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Affiliation(s)
- Paolo Ascenzi
- Department of Biology and Interdepartmental Laboratory for Electron Microscopy, University Roma Tre, Viale G. Marconi 446, 00146, Rome, Italy.
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33
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Welkos S, Friedlander A, Weeks S, Little S, Mendelson I. In-vitro characterisation of the phagocytosis and fate of anthrax spores in macrophages and the effects of anti-PA antibody. J Med Microbiol 2002; 51:821-831. [PMID: 12435060 DOI: 10.1099/0022-1317-51-10-821] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Antibodies (Abs) to the protective antigen (PA) component of the anthrax toxins have anti-spore as well as anti-toxin activities. Anti-PA antisera and purified anti-PA Abs enhance the phagocytosis by murine-derived macrophages (MQs) of spores of the Ames and Sterne strains and retard the germination of extracellular spores in vitro. The fate after phagocytosis of untreated and anti-PA-treated spores was further studied in culture medium that supported phagocytosis without stimulating spore germination (Dulbecco's minimal essential medium with horse serum 10%). The spores germinated within cells of primary peritoneal murine MQs (C3H/HeN) and MQs of the RAW264.7 MQ-like cell line; germination was associated with a rapid decline in spore viability. Exposure of MQs to inhibitors of phago-endosomal acidification (bafilomycin A and chloroquine) reduced the efficiency of MQ killing and allowed outgrowth and replication of the organisms. Treatment of spores with anti-PA Abs stimulated their phagocytosis and was associated with enhanced MQ killing of the spores. The enhanced killing of spores correlated with the greater extent of germination of anti-PA-treated spores after phagocytosis. A PA null mutant of the Ames strain exhibited none of the effects associated with anti-PA Ab treatment ofthe parental strain. Thus, the anti-PA Ab-specific immunity induced by vaccines has anti-spore activities and its role in impeding the early stages of infection with Bacillusanthracis needs to be assessed.
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Affiliation(s)
| | - A Friedlander
- Division of Bacteriology and *Headquarters, US Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD 21702-5011, USA
| | | | | | - I Mendelson
- Division of Bacteriology and *Headquarters, US Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD 21702-5011, USA
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34
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Beauregard KE, Collier RJ, Swanson JA. Proteolytic activation of receptor-bound anthrax protective antigen on macrophages promotes its internalization. Cell Microbiol 2000; 2:251-8. [PMID: 11207581 DOI: 10.1046/j.1462-5822.2000.00052.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Immunofluorescence and other methods have been used to probe the self-assembly and internalization of the binary toxin, anthrax lethal toxin (LeTx), in primary murine macrophages. Proteolytic activation of protective antigen (PA; 83 kDa, the B moiety of the toxin) by furin was the rate-limiting step in internalization of LeTx and promoted clearance of PA from the cell surface. A furin-resistant form of PA remained at the cell surface for at least 90 min. Oligomerization of receptor-bound PA63, the 63 kDa active fragment of PA, was manifested by its conversion to a pronase-resistant state, characteristic of the heptameric prepore form in solution. That oligomerization of PA63 triggers toxin internalization is supported by the observation that PA20, the complementary 20 kDa fragment of PA, inhibited clearance of nicked PA. The PA63 prepore, with or without lethal factor (LF), cleared slowly from the cell surface. These studies show that proteolytic cleavage of PA, in addition to permitting oligomerization and LF binding, also promotes internalization of the protein. The relatively long period of activation and internalization of PA at the cell surface may reflect adaptation of this binary toxin that maximizes self-assembly.
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Affiliation(s)
- K E Beauregard
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA
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35
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Qa'Dan M, Spyres LM, Ballard JD. pH-induced conformational changes in Clostridium difficile toxin B. Infect Immun 2000; 68:2470-4. [PMID: 10768933 PMCID: PMC97448 DOI: 10.1128/iai.68.5.2470-2474.2000] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Toxin B from Clostridium difficile is a monoglucosylating toxin that targets substrates within the cytosol of mammalian cells. In this study, we investigated the impact of acidic pH on cytosolic entry and structural changes within toxin B. Bafilomycin A1 was used to block endosomal acidification and subsequent toxin B translocation. Cytopathic effects could be completely blocked by addition of bafilomycin A1 up to 20 min following toxin treatment. Furthermore, providing a low extracellular pH could circumvent the effect of bafilomycin A1 and other lysosomotropic agents. Acid pH-induced structural changes were monitored by using the fluorescent probe 2-(p-toluidinyl) naphthalene-6-sulfonic acid, sodium salt (TNS), inherent tryptophan fluorescence, and relative susceptibility to a specific protease. As the toxin was exposed to lower pH there was an increase in TNS fluorescence, suggesting the exposure of hydrophobic domains by toxin B. The change in hydrophobicity appeared to be reversible, since returning the pH to neutrality abrogated TNS fluorescence. Furthermore, tryptophan fluorescence was quenched at the acidic pH, indicating that domains may have been moving into more aqueous environments. Toxin B also demonstrated variable susceptibility to Staphylococcus aureus V8 protease at neutral and acidic pH, further suggesting pH-induced structural changes in this protein.
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Affiliation(s)
- M Qa'Dan
- Department of Botany and Microbiology, The University of Oklahoma, Norman, Oklahoma 73019, USA
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Pellizzari R, Guidi-Rontani C, Vitale G, Mock M, Montecucco C. Anthrax lethal factor cleaves MKK3 in macrophages and inhibits the LPS/IFNgamma-induced release of NO and TNFalpha. FEBS Lett 1999; 462:199-204. [PMID: 10580119 DOI: 10.1016/s0014-5793(99)01502-1] [Citation(s) in RCA: 240] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The lethal toxin of Bacillus anthracis consists of two proteins, PA and LF, which together induce lethal effects in animals and cause macrophage lysis. LF is a zinc-endopeptidase which cleaves two mitogen-activated protein kinase kinases (MAPKKs), Mek1 and Mek2, within the cytosol. Here, we show that also MKK3, another dual-specificity kinase that phosphorylates and activates p38 MAP kinase, is cleaved by LF in macrophages. No direct correlation between LF-induced cell death and cleavage of these MAPKKs was found in macrophage cell lines and primary peritoneal cells exhibiting different sensitivity to LF. However, we present the first evidence that sublytic doses of LF cleave Meks and cause a substantial reduction in the production of NO and tumour necrosis factor-alpha induced by lipopolysaccharide/interferon gamma. We suggest that this effect of LF is relevant during the first stages of B. anthracis infection, when a reduction of the inflammatory response would permit growth and diffusion of the bacterium.
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Affiliation(s)
- R Pellizzari
- Centro CNR Biomembrane and Dipartimento di Scienze Biomediche, Università di Padova, via Colombo 3, 35121, Padua, Italy
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37
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Beauregard KE, Wimer-Mackin S, Collier RJ, Lencer WI. Anthrax toxin entry into polarized epithelial cells. Infect Immun 1999; 67:3026-30. [PMID: 10338515 PMCID: PMC96616 DOI: 10.1128/iai.67.6.3026-3030.1999] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/1999] [Accepted: 03/16/1999] [Indexed: 11/20/2022] Open
Abstract
We examined the entry of anthrax edema toxin (EdTx) into polarized human T84 epithelial cells using cyclic AMP-regulated Cl- secretion as an index of toxin entry. EdTx is a binary A/B toxin which self assembles at the cell surface from anthrax edema factor and protective antigen (PA). PA binds to cell surface receptors and delivers EF, an adenylate cyclase, to the cytosol. EdTx elicited a strong Cl- secretory response when it was applied to the basolateral surface of T84 cells but no response when it was applied to the apical surface. PA alone had no effect when it was applied to either surface. T84 cells exposed basolaterally bound at least 30-fold-more PA than did T84 cells exposed apically, indicating that the PA receptor is largely or completely restricted to the basolateral membrane of these cells. The PA receptor did not fractionate with detergent-insoluble caveola-like membranes as cholera toxin receptors do. These findings have implications regarding the nature of the PA receptor and confirm the view that EdTx and CT coopt fundamentally different subcellular systems to enter the cell and cause disease.
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Affiliation(s)
- K E Beauregard
- Departments of Microbiology, Harvard Medical School, Boston, Massachusetts, USA
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38
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Abstract
Legionella pneumophila is the cause of Legionnaires' pneumonia. After Internalization by macrophages, it bypasses the normal endocytic pathway and occupies a replicative phagosome bound by endoplasmic reticulum. Here, we show that lysis of macrophages and red blood cells by L. pneumophila was dependent on dotA and other loci known to be required for proper targeting of the phagosome and replication within the host cell. Cytotoxicity occurred rapidly during a high-multiplicity infection, required close association of the bacteria with the eukaryotic cell and was a form of necrotic cell death accompanied by osmotic lysis. The differential cytoprotective ability of high-molecular-weight polyethylene glycols suggested that osmotic lysis resulted from insertion of a pore less than 3 nm in diameter into the plasma membrane. Results concerning the uptake of membrane-impermeant fluorescent compounds of various sizes are consistent with the osmoprotection analysis. Therefore, kinetic and genetic evidence suggested that the apparent ability of L. pneumophila to insert a pore into eukaryotic membranes on initial contact may play a role in altering endocytic trafficking events within the host cell and in the establishment of a replicative vacuole.
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Affiliation(s)
- J E Kirby
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111, USA
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