1
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Kumari M, Subbarao N. Convolutional neural network-based quantitative structure-activity relationship and fingerprint analysis against inhibitors of anthrax lethal factor. Future Med Chem 2023; 15:853-866. [PMID: 37248697 DOI: 10.4155/fmc-2023-0093] [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: 03/27/2023] [Accepted: 05/10/2023] [Indexed: 05/31/2023] Open
Abstract
Aim: To develop a one-dimensional convolutional neural network-based quantitative structure-activity relationship (1D-CNN-QSAR) model to identify novel anthrax inhibitors and analyze chemical space. Methods: We developed a 1D-CNN-QSAR model to identify novel anthrax inhibitors. Results: The statistical results of the 1D-CNN-QSAR model showed a mean square error of 0.045 and a predicted correlation coefficient of 0.79 for the test set. Further, chemical space analysis showed more than 80% fragment pair similarity, with activity cliffs associated with carboxylic acid, 2-phenylfurans, N-phenyldihydropyrazole, N-phenylpyrrole, furan, 4-methylene-1H-pyrazol-5-one, phenylimidazole, phenylpyrrole and phenylpyrazolidine. Conclusion: These fragments may serve as the basis for developing potent novel drug candidates for anthrax. Finally, we concluded that our proposed 1D-CNN-QSAR model and fingerprint analysis might be used to discover potential anthrax drug candidates.
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Affiliation(s)
- Madhulata Kumari
- Amity Institute of Biotechnology, Amity University, Rajasthan, Jaipur, India
| | - Naidu Subbarao
- School of Computational & Integrative Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
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2
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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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3
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Desikan R, Maiti PK, Ayappa KG. Predicting interfacial hot-spot residues that stabilize protein-protein interfaces in oligomeric membrane-toxin pores through hydrogen bonds and salt bridges. J Biomol Struct Dyn 2020; 39:20-34. [DOI: 10.1080/07391102.2020.1711806] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Rajat Desikan
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, India
| | - Prabal K. Maiti
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore, India
| | - K. Ganapathy Ayappa
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, India
- Centre for Biosystems Science and Engineering, Indian Institute of Science, Bangalore, India
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4
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Exploring the Nature of Cationic Blocker Recognition by the Anthrax Toxin Channel. Biophys J 2019; 117:1751-1763. [PMID: 31587826 DOI: 10.1016/j.bpj.2019.08.041] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 07/11/2019] [Accepted: 08/05/2019] [Indexed: 01/20/2023] Open
Abstract
Obstructing conductive pathways of the channel-forming toxins with targeted blockers is a promising drug design approach. Nearly all tested positively charged ligands have been shown to reversibly block the cation-selective channel-forming protective antigen (PA63) component of the binary anthrax toxin. The cationic ligands with more hydrophobic surfaces, particularly those carrying aromatic moieties, inhibited PA63 more effectively. To understand the physical basis of PA63 selectivity for a particular ligand, detailed information is required on how the blocker structural elements (e.g., positively charged and aromatic groups) influence the molecular kinetics of the blocker/channel binding reactions. In this study, we address this problem using the high-resolution single-channel planar lipid bilayer technique. Several structurally distinct cationic blockers, namely per-6-S-(3-amino) propyl-β-cyclodextrin, per-6-S-(3-aminomethyl) benzyl-α-cyclodextrin, per-6-S-(3-aminomethyl) benzyl-β-cyclodextrin, per-6-S-(3-aminomethyl) benzyl-γ-cyclodextrin, methyltriphenylphosphonium ion, and G0 polyamidoamine dendrimer are tested for their ability to inhibit the heptameric and octameric PA63 variants and PA63F427A mutant. The F427 residues form a hydrophobic constriction region inside the channel, known as the "ϕ-clamp." We show that the cationic blockers interact with PA63 through a combination of forces. Analysis of the binding reaction kinetics suggests the involvement of cation-π, Coulomb, and salt-concentration-independent π-π or hydrophobic interactions in the cationic cyclodextrin binding. It is possible that these blockers bind to the ϕ-clamp and are also stabilized by the Coulomb interactions of their terminal amino groups with the water-exposed negatively charged channel residues. In PA63F427A, only the suggested Coulomb component of the cyclodextrin interaction remains. Methyltriphenylphosphonium ion and G0 polyamidoamine dendrimer, despite being positively charged, interact primarily with the ϕ-clamp. We also show that seven- and eightfold symmetric cyclodextrins effectively block the heptameric and octameric forms of PA63 interchangeably, adding flexibility to the earlier formulated blocker/target symmetry match requirement.
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5
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Workman AM, Chitko-McKown CG, Smith TPL, Bennett GL, Kalbfleisch TS, Basnayake V, Heaton MP. A bovine CD18 signal peptide variant with increased binding activity to Mannheimia hemolytica leukotoxin. F1000Res 2018; 7:1985. [PMID: 30881690 PMCID: PMC6406179 DOI: 10.12688/f1000research.17187.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/13/2018] [Indexed: 11/20/2022] Open
Abstract
Background: Mannheimia haemolytica is the major bacterial infectious agent of bovine respiratory disease complex and causes severe morbidity and mortality during lung infections.
M. haemolytica secretes a protein leukotoxin (Lkt) that binds to the CD18 receptor on leukocytes, initiates lysis, induces inflammation, and causes acute fibrinous bronchopneumonia. Lkt binds the 22-amino acid CD18 signal peptide domain, which remains uncleaved in ruminant species. Our aim was to identify missense variation in the bovine CD18 signal peptide and measure the effects on Lkt binding. Methods: Missense variants in the integrin beta 2 gene (
ITGB2) encoding CD18 were identified by whole genome sequencing of 96 cattle from 19 breeds, and targeted Sanger sequencing of 1238 cattle from 46 breeds. The ability of different CD18 signal peptide variants to bind Lkt was evaluated by preincubating the toxin with synthetic peptides and applying the mixture to susceptible bovine cell cultures in cytotoxicity-blocking assays. Results: We identified 14 missense variants encoded on 15 predicted haplotypes, including a rare signal peptide variant with a cysteine at position 5 (C
5) instead of arginine (R
5). Preincubating Lkt with synthetic signal peptides with C
5 blocked cytotoxicity significantly better than those with R
5. The most potent synthetic peptide (C
5PQLLLLAGLLA) had 30-fold more binding activity compared to that with R
5. Conclusions: The results suggest that missense variants in the CD18 signal peptide affect Lkt binding, and animals carrying the C
5 allele may be more susceptible to the effects of Lkt. The results also identify a potent class of non-antibiotic Lkt inhibitors that could potentially protect cattle from cytotoxic effects during acute lung infections.
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Affiliation(s)
- Aspen M Workman
- USDA, US Meat Animal Research Center (USMARC), Clay Center, Nebraska, 68933, USA
| | | | - Timothy P L Smith
- USDA, US Meat Animal Research Center (USMARC), Clay Center, Nebraska, 68933, USA
| | - Gary L Bennett
- USDA, US Meat Animal Research Center (USMARC), Clay Center, Nebraska, 68933, USA
| | - Theodore S Kalbfleisch
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Louisville, Louisville, Kentucky, 40292, USA
| | | | - Michael P Heaton
- USDA, US Meat Animal Research Center (USMARC), Clay Center, Nebraska, 68933, USA
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6
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Englert C, Brendel JC, Majdanski TC, Yildirim T, Schubert S, Gottschaldt M, Windhab N, Schubert US. Pharmapolymers in the 21st century: Synthetic polymers in drug delivery applications. Prog Polym Sci 2018. [DOI: 10.1016/j.progpolymsci.2018.07.005] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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7
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Baker CA, Schudel B, Chaudhari MI, Wu K, Dunford D, Singh AK, Rempe SB, Hatch AV. Nanoporous Hydrogels for the Observation of Anthrax Exotoxin Translocation Dynamics. ACS APPLIED MATERIALS & INTERFACES 2018; 10:13342-13349. [PMID: 29595948 DOI: 10.1021/acsami.8b01871] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The ability to observe lethal anthrax exotoxins translocating through size-constricting nanopores in vitro, combined with detailed sequence and structural data, has aided in elucidated mechanisms of exotoxin cell entry and toxicity. However, due to limited observations of anthrax exotoxins translocating through protective antigen nanopores in vitro and the instability of protective antigen-functionalized suspended lipid bilayers, questions remain regarding the native mechanisms of cell entry. Nanoporous hydrogel membranes offer a robust tool for studying protein translocation with ensemble measurements that complement conventional single-molecule translocation measurements. Here, we utilize nanoporous hydrogel membranes to assess the translocation of full-length anthrax lethal and edema factors through nanopores similar in diameter to protective antigen translocons. We find that, relative to globular serum and other proteins that do not translocate natively through nanopores, anthrax exotoxins demonstrate significantly reduced barriers to pore entry. Computed free-energy barriers to the unfolding of proteins and the dissociation of macromolecular complexes are generally found to coincide with translocation. Finally, a nanopore-blocking strategy is developed that utilizes nonspecific synthetic peptide constructs and effectively prevents LF translocation within the nanoporous hydrogel.
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Affiliation(s)
- Christopher A Baker
- Department of Chemistry , University of Tennessee , Knoxville , Tennessee 37996 , United States
| | - Ben Schudel
- Natera , San Carlos , California 94070 , United States
| | - Mangesh I Chaudhari
- Center for Biological and Engineering Sciences , Sandia National Laboratories , Albuquerque , New Mexico 87185 , United States
| | - Kerrie Wu
- Massachusetts Institute of Technology , Cambridge , Massachusetts 02129 , United States
| | - Derek Dunford
- University of Utah , Salt Lake City , Utah 84112 , United States
| | - Anup K Singh
- Center for Biological and Engineering Sciences , Sandia National Laboratories , Albuquerque , New Mexico 87185 , United States
| | - Susan B Rempe
- Center for Biological and Engineering Sciences , Sandia National Laboratories , Albuquerque , New Mexico 87185 , United States
| | - Anson V Hatch
- Center for Biological and Engineering Sciences , Sandia National Laboratories , Albuquerque , New Mexico 87185 , United States
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8
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Dickey SW, Cheung GYC, Otto M. Different drugs for bad bugs: antivirulence strategies in the age of antibiotic resistance. Nat Rev Drug Discov 2017; 16:457-471. [PMID: 28337021 DOI: 10.1038/nrd.2017.23] [Citation(s) in RCA: 451] [Impact Index Per Article: 64.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The rapid evolution and dissemination of antibiotic resistance among bacterial pathogens are outpacing the development of new antibiotics, but antivirulence agents provide an alternative. These agents can circumvent antibiotic resistance by disarming pathogens of virulence factors that facilitate human disease while leaving bacterial growth pathways - the target of traditional antibiotics - intact. Either as stand-alone medications or together with antibiotics, these drugs are intended to treat bacterial infections in a largely pathogen-specific manner. Notably, development of antivirulence drugs requires an in-depth understanding of the roles that diverse virulence factors have in disease processes. In this Review, we outline the theory behind antivirulence strategies and provide examples of bacterial features that can be targeted by antivirulence approaches. Furthermore, we discuss the recent successes and failures of this paradigm, and new developments that are in the pipeline.
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Affiliation(s)
- Seth W Dickey
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland 20814, USA
| | - Gordon Y C Cheung
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland 20814, USA
| | - Michael Otto
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland 20814, USA
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9
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Culp E, Wright GD. Bacterial proteases, untapped antimicrobial drug targets. J Antibiot (Tokyo) 2016; 70:366-377. [PMID: 27899793 DOI: 10.1038/ja.2016.138] [Citation(s) in RCA: 141] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 09/29/2016] [Accepted: 10/06/2016] [Indexed: 01/05/2023]
Abstract
Bacterial proteases are an extensive collection of enzymes that have vital roles in cell viability, stress response and pathogenicity. Although their perturbation clearly offers the potential for antimicrobial drug development, both as traditional antibiotics and anti-virulence drugs, they are not yet the target of any clinically used therapeutics. Here we describe the potential for and recent progress in the development of compounds targeting bacterial proteases with a focus on AAA+ family proteolytic complexes and signal peptidases (SPs). Caseinolytic protease (ClpP) belongs to the AAA+ family of proteases, a group of multimeric barrel-shaped complexes whose activity is tightly regulated by associated AAA+ ATPases. The opportunity for chemical perturbation of these complexes is demonstrated by compounds targeting ClpP for inhibition, activation or perturbation of its associated ATPase. Meanwhile, SPs are also a proven antibiotic target. Responsible for the cleavage of targeting peptides during protein secretion, both type I and type II SPs have been successfully targeted by chemical inhibitors. As the threat of pan-antibiotic resistance continues to grow, these and other bacterial proteases offer an arsenal of novel antibiotic targets ripe for development.
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Affiliation(s)
- Elizabeth Culp
- Michael G. DeGroote Institute for Infectious Disease Research and the Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Gerard D Wright
- Michael G. DeGroote Institute for Infectious Disease Research and the Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
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10
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Impact of Dendrimer Terminal Group Chemistry on Blockage of the Anthrax Toxin Channel: A Single Molecule Study. Toxins (Basel) 2016; 8:toxins8110337. [PMID: 27854272 PMCID: PMC5127133 DOI: 10.3390/toxins8110337] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 11/07/2016] [Accepted: 11/07/2016] [Indexed: 12/19/2022] Open
Abstract
Nearly all the cationic molecules tested so far have been shown to reversibly block K⁺ current through the cation-selective PA63 channels of anthrax toxin in a wide nM-mM range of effective concentrations. A significant increase in channel-blocking activity of the cationic compounds was achieved when multiple copies of positively charged ligands were covalently linked to multivalent scaffolds, such as cyclodextrins and dendrimers. Even though multivalent binding can be strong when the individual bonds are relatively weak, for drug discovery purposes we often strive to design multivalent compounds with high individual functional group affinity toward the respective binding site on a multivalent target. Keeping this requirement in mind, here we perform a single-channel/single-molecule study to investigate kinetic parameters of anthrax toxin PA63 channel blockage by second-generation (G2) poly(amido amine) (PAMAM) dendrimers functionalized with different surface ligands, including G2-NH₂, G2-OH, G2-succinamate, and G2-COONa. We found that the previously reported difference in IC50 values of the G2-OH/PA63 and G2-NH₂/PA63 binding was determined by both on- and off-rates of the reversible dendrimer/channel binding reaction. In 1 M KCl, we observed a decrease of about three folds in k o n and a decrease of only about ten times in t r e s with G2-OH compared to G2-NH₂. At the same time for both blockers, k o n and t r e s increased dramatically with transmembrane voltage increase. PAMAM dendrimers functionalized with negatively charged succinamate, but not carboxyl surface groups, still had some residual activity in inhibiting the anthrax toxin channels. At 100 mV, the on-rate of the G2-succinamate binding was comparable with that of G2-OH but showed weaker voltage dependence when compared to G2-OH and G2-NH₂. The residence time of G2-succinamate in the channel exhibited opposite voltage dependence compared to G2-OH and G2-NH₂, increasing with the cis-negative voltage increase. We also describe kinetics of the PA63 ion current modulation by two different types of the "imperfect" PAMAM dendrimers, the mixed-surface G2 75% OH 25% NH₂ dendrimer and G3-NH₂ dendron. At low voltages, both "imperfect" dendrimers show similar rate constants but significantly weaker voltage sensitivity when compared with the intact G2-NH₂ PAMAM dendrimer.
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11
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Power BH, Smith N, Downer B, Alisaraie L. Insight into the mechanism of chemical modification of antibacterial agents by antibiotic resistance enzymeO-phosphotransferase-IIIA. Chem Biol Drug Des 2016; 89:84-97. [DOI: 10.1111/cbdd.12835] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 07/22/2016] [Accepted: 07/25/2016] [Indexed: 11/30/2022]
Affiliation(s)
- Blake Hollett Power
- School of Pharmacy; Memorial University of Newfoundland; St. John's Newfoundland Canada
| | - Nathan Smith
- School of Pharmacy; Memorial University of Newfoundland; St. John's Newfoundland Canada
| | - Brandon Downer
- School of Pharmacy; Memorial University of Newfoundland; St. John's Newfoundland Canada
| | - Laleh Alisaraie
- School of Pharmacy; Memorial University of Newfoundland; St. John's Newfoundland Canada
- Department of Chemistry; Memorial University of Newfoundland; St. John's Newfoundland Canada
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12
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Maxson T, Mitchell DA. Targeted Treatment for Bacterial Infections: Prospects for Pathogen-Specific Antibiotics Coupled with Rapid Diagnostics. Tetrahedron 2016; 72:3609-3624. [PMID: 27429480 PMCID: PMC4941824 DOI: 10.1016/j.tet.2015.09.069] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Antibiotics are a cornerstone of modern medicine and have significantly reduced the burden of infectious diseases. However, commonly used broad-spectrum antibiotics can cause major collateral damage to the human microbiome, causing complications ranging from antibiotic-associated colitis to the rapid spread of resistance. Employing narrower spectrum antibiotics targeting specific pathogens may alleviate this predicament as well as provide additional tools to expand an antibiotic repertoire threatened by the inevitability of resistance. Improvements in clinical diagnosis will be required to effectively utilize pathogen-specific antibiotics and new molecular diagnostics are poised to fulfill this need. Here we review recent trends and the future prospects of deploying narrower spectrum antibiotics coupled with rapid diagnostics. Further, we discuss the theoretical advantages and limitations of this emerging approach to controlling bacterial infectious diseases.
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Affiliation(s)
- Tucker Maxson
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Douglas A. Mitchell
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
- Carle R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
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13
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Hauser AR, Mecsas J, Moir DT. Beyond Antibiotics: New Therapeutic Approaches for Bacterial Infections. Clin Infect Dis 2016; 63:89-95. [PMID: 27025826 DOI: 10.1093/cid/ciw200] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 03/23/2016] [Indexed: 01/07/2023] Open
Abstract
The utility of conventional antibiotics for the treatment of bacterial infections has become increasingly strained due to increased rates of resistance coupled with reduced rates of development of new agents. As a result, multidrug-resistant, extensively drug-resistant, and pandrug-resistant bacterial strains are now frequently encountered. This has led to fears of a "postantibiotic era" in which many bacterial infections will be untreatable. Alternative nonantibiotic treatment strategies need to be explored to ensure that a robust pipeline of effective therapies is available to clinicians. In this review, we highlight some of the recent developments in this area, such as the targeting of bacterial virulence factors, utilization of bacteriophages to kill bacteria, and manipulation of the microbiome to combat infections.
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Affiliation(s)
- Alan R Hauser
- Departments of Microbiology/Immunology and Medicine, Northwestern University, Chicago, Illinois
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14
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Li L, Guo Q, Liu J, Zhang J, Yin Y, Dong D, Fu L, Xu J, Chen W. Recombinant HSA-CMG2 Is a Promising Anthrax Toxin Inhibitor. Toxins (Basel) 2016; 8:toxins8010028. [PMID: 26805881 PMCID: PMC4728550 DOI: 10.3390/toxins8010028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 12/25/2015] [Accepted: 01/13/2016] [Indexed: 12/20/2022] Open
Abstract
Anthrax toxin is the major virulence factor produced by Bacillus anthracis. Protective antigen (PA) is the key component of the toxin and has been confirmed as the main target for the development of toxin inhibitors. The inhibition of the binding of PA to its receptor, capillary morphogenesis protein-2 (CMG2), can effectively block anthrax intoxication. The recombinant, soluble von Willebrand factor type A (vWA) domain of CMG2 (sCMG2) has demonstrated potency against anthrax toxin. However, the short half-life of sCMG2 in vivo is a disadvantage for its development as a new anthrax drug. In the present study, we report that HSA-CMG2, a protein combining human serum albumin (HSA) and sCMG2, produced in the Pichia pastoris expression system prolonged the half-life of sCMG2 while maintaining PA binding ability. The IC50 of HSA-CMG2 is similar to those of sCMG2 and CMG2-Fc in in vitro toxin neutralization assays, and HSA-CMG2 completely protects rats from lethal doses of anthrax toxin challenge; these same challenge doses exceed sCMG2 at a sub-equivalent dose ratio and overwhelm CMG2-Fc. Our results suggest that HSA-CMG2 is a promising inhibitor of anthrax toxin and may contribute to the development of novel anthrax drugs.
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Affiliation(s)
- Liangliang Li
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
- Center for Disease Control and Prevention of Navy, Beijing 101113, China.
| | - Qiang Guo
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
| | - Ju Liu
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
| | - Jun Zhang
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
| | - Ying Yin
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
| | - Dayong Dong
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
| | - Ling Fu
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
| | - Junjie Xu
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
| | - Wei Chen
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
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15
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Ravulapalli R, Lugo MR, Pfoh R, Visschedyk D, Poole A, Fieldhouse RJ, Pai EF, Merrill AR. Characterization of Vis Toxin, a Novel ADP-Ribosyltransferase from Vibrio splendidus. Biochemistry 2015; 54:5920-36. [PMID: 26352925 DOI: 10.1021/acs.biochem.5b00921] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Vis toxin was identified by a bioinformatics strategy as a putative virulence factor produced by Vibrio splendidus with mono-ADP-ribosyltransferase activity. Vis was purified to homogeneity as a 28 kDa single-domain enzyme and was shown to possess NAD(+)-glycohydrolase [KM(NAD(+)) = 276 ± 12 μM] activity and with an R-S-E-X-E motif; it targets arginine-related compounds [KM(agmatine) = 272 ± 18 mM]. Mass spectrometry analysis revealed that Vis labels l-arginine with ADP-ribose from the NAD(+) substrate at the amino nitrogen of the guanidinium side chain. Vis is toxic to yeast when expressed in the cytoplasm under control of the CUP1 promotor, and catalytic variants lost the ability to kill the yeast host, indicating that the toxin exerts its lethality through its enzyme activity. Several small molecule inhibitors were identified from a virtual screen, and the most potent compounds were found to inhibit the transferase activity of the enzyme with Ki values ranging from 25 to 134 μM. Inhibitor compound M6 bears the necessary attributes of a solid candidate as a lead compound for therapeutic development. Vis toxin was crystallized, and the structures of the apoenzyme (1.4 Å) and the enzyme bound with NAD(+) (1.8 Å) and with the M6 inhibitor (1.5 Å) were determined. The structures revealed that Vis represents a new subgroup within the mono-ADP-ribosyltransferase toxin family.
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Affiliation(s)
- Ravikiran Ravulapalli
- Department of Molecular and Cellular Biology, University of Guelph , Guelph, Ontario, Canada N1G 2W1
| | - Miguel R Lugo
- Department of Molecular and Cellular Biology, University of Guelph , Guelph, Ontario, Canada N1G 2W1
| | - Roland Pfoh
- Department of Biology, York University , Toronto, ON, Canada M3J 1P3.,Department of Biochemistry, University of Toronto , Toronto, ON, Canada M5S 1A8.,Campbell Family Institute for Cancer Research, Princess Margaret Hospital , Toronto, ON, Canada M5G 1L7
| | - Danielle Visschedyk
- Department of Molecular and Cellular Biology, University of Guelph , Guelph, Ontario, Canada N1G 2W1
| | - Amanda Poole
- Department of Molecular and Cellular Biology, University of Guelph , Guelph, Ontario, Canada N1G 2W1
| | - Robert J Fieldhouse
- Computational Biology Center, Memorial Sloan-Kettering Cancer Center , New York, New York 10065, United States.,Department of Systems Biology, Harvard Medical School , Boston, Massachusetts 02115, United States
| | - Emil F Pai
- Department of Biochemistry, University of Toronto , Toronto, ON, Canada M5S 1A8.,Campbell Family Institute for Cancer Research, Princess Margaret Hospital , Toronto, ON, Canada M5G 1L7.,Departments of Medical Biophysics and Molecular Genetics, University of Toronto , Toronto, ON, Canada M5S 1A8
| | - A Rod Merrill
- Department of Molecular and Cellular Biology, University of Guelph , Guelph, Ontario, Canada N1G 2W1
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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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Abstract
Anthrax is caused by the spore-forming, gram-positive bacterium Bacillus anthracis. The bacterium's major virulence factors are (a) the anthrax toxins and (b) an antiphagocytic polyglutamic capsule. These are encoded by two large plasmids, the former by pXO1 and the latter by pXO2. The expression of both is controlled by the bicarbonate-responsive transcriptional regulator, AtxA. The anthrax toxins are three polypeptides-protective antigen (PA), lethal factor (LF), and edema factor (EF)-that come together in binary combinations to form lethal toxin and edema toxin. PA binds to cellular receptors to translocate LF (a protease) and EF (an adenylate cyclase) into cells. The toxins alter cell signaling pathways in the host to interfere with innate immune responses in early stages of infection and to induce vascular collapse at late stages. This review focuses on the role of anthrax toxins in pathogenesis. Other virulence determinants, as well as vaccines and therapeutics, are briefly discussed.
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Affiliation(s)
- Mahtab Moayeri
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892; , , , ,
| | - Stephen H Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892; , , , ,
| | - Catherine Vrentas
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892; , , , ,
| | - Andrei P Pomerantsev
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892; , , , ,
| | - Shihui Liu
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892; , , , ,
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Abstract
The number of intoxications from xenobiotics—natural or synthetic foreign chemicals, or substances given in higher doses than typically present in humans—has risen tremendously in the last decade, placing poisoning as the leading external cause of death in the United States. This epidemic has fostered the development of antidotal nanomedicines, which we call “nano-antidotes,” capable of efficiently neutralizing offending compounds in situ. Although prototype nano-antidotes have shown efficacy in proof-of-concept studies, the gap to clinical translation can only be filled if issues such as the clinical relevance of intoxication models and the safety profile of nano-antidotes are properly addressed. As the unmet medical needs in resuscitative care call for better treatments, this Perspective critically reviews the recent progress in antidotal medicine and emerging nanotechnologies.
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Affiliation(s)
- Vincent Forster
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 1-5/10, 8093 Zurich, Switzerland
| | - Jean-Christophe Leroux
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 1-5/10, 8093 Zurich, Switzerland
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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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Abstract
Resistance of important bacterial pathogens to common antimicrobial therapies and the emergence of multidrug-resistant bacteria are increasing at an alarming rate and constitute one of our greatest challenges in the combat of bacterial infection and accompanied diseases. The current shortage of effective drugs, lack of successful prevention measures and only a few new antibiotics in the clinical pipeline demand the development of novel treatment options and alternative antimicrobial therapies. Our increasing understanding of bacterial virulence strategies and the induced molecular pathways of the infectious disease provides novel opportunities to target and interfere with crucial pathogenicity factors or virulence-associated traits of the bacteria while bypassing the evolutionary pressure on the bacterium to develop resistance. In the past decade, numerous new bacterial targets for anti-virulence therapies have been identified, and structure-based tailoring of intervention strategies and screening assays for small-molecule inhibitors of such pathways were successfully established. In this chapter, we will take a closer look at the bacterial virulence-related factors and processes that present promising targets for anti-virulence therapies, recently discovered inhibitory substances and their promises and discuss the challenges, and problems that have to be faced.
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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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Roeder M, Nestorovich EM, Karginov VA, Schwan C, Aktories K, Barth H. Tailored cyclodextrin pore blocker protects mammalian cells from clostridium difficile binary toxin CDT. Toxins (Basel) 2014; 6:2097-114. [PMID: 25029374 PMCID: PMC4113744 DOI: 10.3390/toxins6072097] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 06/16/2014] [Accepted: 06/27/2014] [Indexed: 12/11/2022] Open
Abstract
Some Clostridium difficile strains produce, in addition to toxins A and B, the binary toxin Clostridium difficile transferase (CDT), which ADP-ribosylates actin and may contribute to the hypervirulence of these strains. The separate binding and translocation component CDTb mediates transport of the enzyme component CDTa into mammalian target cells. CDTb binds to its receptor on the cell surface, CDTa assembles and CDTb/CDTa complexes are internalised. In acidic endosomes, CDTb mediates the delivery of CDTa into the cytosol, most likely by forming a translocation pore in endosomal membranes. We demonstrate that a seven-fold symmetrical positively charged β-cyclodextrin derivative, per-6-S-(3-aminomethyl)benzylthio-β-cyclodextrin, which was developed earlier as a potent inhibitor of the translocation pores of related binary toxins of Bacillus anthracis, Clostridium botulinum and Clostridium perfringens, protects cells from intoxication with CDT. The pore blocker did not interfere with the CDTa-catalyzed ADP-ribosylation of actin or toxin binding to Vero cells but inhibited the pH-dependent membrane translocation of CDTa into the cytosol. In conclusion, the cationic β-cyclodextrin could serve as the lead compound in a development of novel pharmacological strategies against the CDT-producing strains of C. difficile.
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Affiliation(s)
- Maurice Roeder
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
| | | | - Vladimir A Karginov
- Innovative Biologics, Inc., 13455 Sunrise Valley Dr., Suite 200, Herndon, VA 20171, USA.
| | - Carsten Schwan
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, 79104 Freiburg, Germany.
| | - Klaus Aktories
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, 79104 Freiburg, Germany.
| | - Holger Barth
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
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