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Krantz BA. Anthrax Toxin: Model System for Studying Protein Translocation. J Mol Biol 2024; 436:168521. [PMID: 38458604 DOI: 10.1016/j.jmb.2024.168521] [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: 11/17/2023] [Revised: 02/08/2024] [Accepted: 03/04/2024] [Indexed: 03/10/2024]
Abstract
Dedicated translocase channels are nanomachines that often, but not always, unfold and translocate proteins through narrow pores across the membrane. Generally, these molecular machines utilize external sources of free energy to drive these reactions, since folded proteins are thermodynamically stable, and once unfolded they contain immense diffusive configurational entropy. To catalyze unfolding and translocate the unfolded state at appreciable timescales, translocase channels often utilize analogous peptide-clamp active sites. Here we describe how anthrax toxin has been used as a biophysical model system to study protein translocation. The tripartite bacterial toxin is composed of an oligomeric translocase channel, protective antigen (PA), and two enzymes, edema factor (EF) and lethal factor (LF), which are translocated by PA into mammalian host cells. Unfolding and translocation are powered by the endosomal proton gradient and are catalyzed by three peptide-clamp sites in the PA channel: the α clamp, the ϕ clamp, and the charge clamp. These clamp sites interact nonspecifically with the chemically complex translocating chain, serve to minimize unfolded state configurational entropy, and work cooperatively to promote translocation. Two models of proton gradient driven translocation have been proposed: (i) an extended-chain Brownian ratchet mechanism and (ii) a proton-driven helix-compression mechanism. These models are not mutually exclusive; instead the extended-chain Brownian ratchet likely operates on β-sheet sequences and the helix-compression mechanism likely operates on α-helical sequences. Finally, we compare and contrast anthrax toxin with other related and unrelated translocase channels.
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Affiliation(s)
- Bryan A Krantz
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, 650 W. Baltimore Street, Baltimore, MD 21201, USA.
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Park SG, Lee HB, Kang S. Development of plug-and-deliverable intracellular protein delivery platforms based on botulinum neurotoxin. Int J Biol Macromol 2024; 261:129622. [PMID: 38266854 DOI: 10.1016/j.ijbiomac.2024.129622] [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: 10/24/2023] [Revised: 01/04/2024] [Accepted: 01/18/2024] [Indexed: 01/26/2024]
Abstract
Intracellular protein delivery systems have great potential in the fields of therapeutics development and biomedical research. However, targeted delivery, passing through the cell membrane without damaging the cells, and escaping from endosomal entrapment of endocytosed molecular cargos are major challenges of the system. Here, we present a novel intracellular protein delivery system based on modularly engineered botulinum neurotoxin type A (BoNT/A). LHNA domain, consisting of light chain and endosomal escape machinery of BoNT/A, was genetically fused with SpyCatcher (SC) and EGFR targeting affibody (EGFRAfb) to create SC-LHNA-EGFRAfb, a target-specific and protein cargo-switchable BoNT/A-based intracellular protein delivery platform. SC-LHNA-EGFRAfb was purely purified in large quantities, efficiently ligated with multiple ST-fused protein cargos individually, generating a variety of protein cargo-containing intracellular delivery complexes, and successfully delivered ligated protein cargos into the cytosol of target cells via receptor-mediated endocytosis, followed by endosomal escape and subsequent cytosolic delivery. SC-LHNA-EGFRAfb enhanced intracellular delivery efficiency of protein toxin, gelonin, by approximately 100-fold, highlighting the crucial roles of EGFRAfb and LHNA domain as a targeting ligand and an endosomal escape machinery, respectively, in the delivery process. The BoNT-based plug-and-deliverable intracellular protein delivery system has the potential to expand its applications in protein therapeutics and manipulating cellular processes.
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Affiliation(s)
- Seong Guk Park
- Department of Biological Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Hyun Bin Lee
- Department of Biological Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Sebyung Kang
- Department of Biological Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea.
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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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Heber S, Borho J, Stadler N, Wondany F, König I, Michaelis J, Papatheodorou P, Barth H, Fellermann M. The Clostridium botulinum C2 Toxin Subunit C2IIa Delivers Enzymes with Positively Charged N-Termini into the Cytosol of Target Cells. Toxins (Basel) 2023; 15:390. [PMID: 37368691 DOI: 10.3390/toxins15060390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 06/05/2023] [Accepted: 06/07/2023] [Indexed: 06/29/2023] Open
Abstract
The binary Clostridium (C.) botulinum C2 toxin consists of two non-linked proteins. The proteolytically activated binding/transport subunit C2IIa forms barrel-shaped homoheptamers, which bind to cell surface receptors, mediate endocytosis, and translocate the enzyme subunit C2I into the cytosol of target cells. Here, we investigate whether C2IIa can be harnessed as a transporter for proteins/enzymes fused to polycationic tags, as earlier demonstrated for the related anthrax toxin transport subunit PA63. To test C2IIa-mediated transport in cultured cells, reporter enzymes are generated by fusing different polycationic tags to the N- or C-terminus of other bacterial toxins' catalytic A subunits. C2IIa as well as PA63 deliver N-terminally polyhistidine-tagged proteins more efficiently compared to C-terminally tagged ones. However, in contrast to PA63, C2IIa does not efficiently deliver polylysine-tagged proteins into the cytosol of target cells. Moreover, untagged enzymes with a native cationic N-terminus are efficiently transported by both C2IIa and PA63. In conclusion, the C2IIa-transporter serves as a transport system for enzymes that harbor positively charged amino acids at their N-terminus. The charge distribution at the N-terminus of cargo proteins and their ability to unfold in the endosome and subsequently refold in the cytosol determine transport feasibility and efficiency.
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Affiliation(s)
- Sebastian Heber
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, 89081 Ulm, Germany
| | - Joscha Borho
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, 89081 Ulm, Germany
| | - Nicole Stadler
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, 89081 Ulm, Germany
| | - Fanny Wondany
- Institute of Biophysics, Ulm University, 89081 Ulm, Germany
| | - Irina König
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, 89081 Ulm, Germany
| | - Jens Michaelis
- Institute of Biophysics, Ulm University, 89081 Ulm, Germany
| | - Panagiotis Papatheodorou
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, 89081 Ulm, Germany
| | - Holger Barth
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, 89081 Ulm, Germany
| | - Maximilian Fellermann
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, 89081 Ulm, Germany
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Sharma S, Bahl V, Srivastava G, Shamim R, Bhatnagar R, Gaur D. Recombinant full-length Bacillus Anthracis protective antigen and its 63 kDa form elicits protective response in formulation with addavax. Front Immunol 2023; 13:1075662. [PMID: 36713362 PMCID: PMC9877290 DOI: 10.3389/fimmu.2022.1075662] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Accepted: 12/16/2022] [Indexed: 01/14/2023] Open
Abstract
Introduction Bacillus anthracis is the causative agent for the lethal disease anthrax, primarily affecting animals and humans in close contact with an infected host. The pathogenicity of B. anthracis is attributed to the secreted exotoxins and their outer capsule. The host cell-binding exotoxin component "protective antigen" (PA) is reported to be a potent vaccine candidate. The aim of our study is to produce several PA constructs and analyze their vaccine potential. Methods We have designed the various subunit, PA-based recombinant proteins, i.e., full-length Protective antigen (PA-FL), C-terminal 63 kDa fragment (PA63), Protective antigen domain 1-domain 4 chimeras (PA-D1-4) and protective antigen domain 4 (PA-D4) and analyzed their vaccine potential with different human-compatible adjuvants in the mouse model. We have optimized the process and successfully expressed our recombinant antigens as soluble proteins, except full-length PA. All the recombinant antigen formulations with three different adjuvants i.e., Addavax, Alhydrogel, and Montanide ISA 720, were immunized in different mouse groups. The vaccine efficacy of the formulations was analyzed by mouse serum antigen-specific antibody titer, toxin neutralization assay, and survival analysis of mouse groups challenged with a lethal dose of B. anthracis virulent spores. Results We have demonstrated that the PA-FL addavax and PA63 addavax formulations were most effective in protecting spore-challenged mice and serum from the mice immunized with PAFL addavax, PA-FL alhydrogel, PA63 addavax, and PA63 alhydrogel formulations were equivalently efficient in neutralizing the anthrax lethal toxin. The higher levels of serum Th1, Th2, and Th17 cytokines in PA-FL addavax immunized mice correspond to the enhanced protection provided by the formulation in challenged mice. Discussion We have demonstrated that the PA-FL addavax and PA63 addavax formulations exhibit equivalent efficiency as vaccine formulation both in a mouse model of anthrax and mammalian cell lines. However, PA63 is a smaller antigen than PA-FL and more importantly, PA63 is expressed as a soluble protein in E. coli, which imparts a translational advantage to PA63-based formulation. Thus, the outcome of our study has significant implications for the development of protective antigen-based vaccine formulations for human use against the lethal disease anthrax.
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Affiliation(s)
- Shikhar Sharma
- Laboratory of Malaria & Vaccine Research, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India,Department of Oncology Science, University of Oklahoma Health Science Center, Oklahoma City, OK, United States,*Correspondence: Shikhar Sharma, ;
| | - Vanndita Bahl
- Laboratory of Malaria & Vaccine Research, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | - Gaurav Srivastava
- Food Technology Division, Bhabha Atomic Research Centre, Mumbai, Maharashtra, India
| | - Risha Shamim
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Rakesh Bhatnagar
- Molecular Biology and Genetic Engineering Laboratory, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | - Deepak Gaur
- Laboratory of Malaria & Vaccine Research, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
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Anwar MU, Sergeeva OA, Abrami L, Mesquita FS, Lukonin I, Amen T, Chuat A, Capolupo L, Liberali P, D'Angelo G, van der Goot FG. ER-Golgi-localized proteins TMED2 and TMED10 control the formation of plasma membrane lipid nanodomains. Dev Cell 2022; 57:2334-2346.e8. [PMID: 36174556 DOI: 10.1016/j.devcel.2022.09.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 07/24/2022] [Accepted: 09/08/2022] [Indexed: 11/03/2022]
Abstract
To promote infections, pathogens exploit host cell machineries such as structural elements of the plasma membrane. Studying these interactions and identifying molecular players are ideal for gaining insights into the fundamental biology of the host cell. Here, we used the anthrax toxin to screen a library of 1,500 regulatory, cell-surface, and membrane trafficking genes for their involvement in the intoxication process. We found that endoplasmic reticulum (ER)-Golgi-localized proteins TMED2 and TMED10 are required for toxin oligomerization at the plasma membrane of human cells, an essential step dependent on localization to cholesterol-rich lipid nanodomains. Biochemical, morphological, and mechanistic analyses showed that TMED2 and TMED10 are essential components of a supercomplex that operates the exchange of both cholesterol and ceramides at ER-Golgi membrane contact sites. Overall, this study of anthrax intoxication led to the discovery that lipid compositional remodeling at ER-Golgi interfaces fully controls the formation of functional membrane nanodomains at the cell surface.
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Affiliation(s)
- Muhammad U Anwar
- Global Health Institute, School of Life Sciences, EPFL, 1015 Lausanne, Switzerland
| | - Oksana A Sergeeva
- Global Health Institute, School of Life Sciences, EPFL, 1015 Lausanne, Switzerland
| | - Laurence Abrami
- Global Health Institute, School of Life Sciences, EPFL, 1015 Lausanne, Switzerland
| | - Francisco S Mesquita
- Global Health Institute, School of Life Sciences, EPFL, 1015 Lausanne, Switzerland
| | - Ilya Lukonin
- Friedrich Miescher Institute for Biomedical Research (FMI), 4058 Basel, Switzerland; University of Basel, 4056 Basel, Switzerland
| | - Triana Amen
- Global Health Institute, School of Life Sciences, EPFL, 1015 Lausanne, Switzerland
| | - Audrey Chuat
- Global Health Institute, School of Life Sciences, EPFL, 1015 Lausanne, Switzerland
| | - Laura Capolupo
- Institute of Bioengineering, School of Life Sciences, EPFL, 1015 Lausanne, Switzerland
| | - Prisca Liberali
- Friedrich Miescher Institute for Biomedical Research (FMI), 4058 Basel, Switzerland; University of Basel, 4056 Basel, Switzerland
| | - Giovanni D'Angelo
- Institute of Bioengineering, School of Life Sciences, EPFL, 1015 Lausanne, Switzerland.
| | - F Gisou van der Goot
- Global Health Institute, School of Life Sciences, EPFL, 1015 Lausanne, Switzerland.
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7
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Solution Structures of Bacillus anthracis Protective Antigen Proteins Using Small Angle Neutron Scattering and Protective Antigen 63 Ion Channel Formation Kinetics. Toxins (Basel) 2021; 13:toxins13120888. [PMID: 34941724 PMCID: PMC8708185 DOI: 10.3390/toxins13120888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 12/03/2021] [Accepted: 12/06/2021] [Indexed: 11/17/2022] Open
Abstract
We are studying the structures of bacterial toxins that form ion channels and enable macromolecule transport across membranes. For example, the crystal structure of the Staphylococcus aureus α-hemolysin (α-HL) channel in its functional state was confirmed using neutron reflectometry (NR) with the protein reconstituted in membranes tethered to a solid support. This method, which provides sub-nanometer structural information, could also test putative structures of the Bacillus anthracis protective antigen 63 (PA63) channel, locate where B. anthracis lethal factor and edema factor toxins (LF and EF, respectively) bind to it, and determine how certain small molecules can inhibit the interaction of LF and EF with the channel. We report here the solution structures of channel-forming PA63 and its precursor PA83 (which does not form channels) obtained with small angle neutron scattering. At near neutral pH, PA83 is a monomer and PA63 a heptamer. The latter is compared to two cryo-electron microscopy structures. We also show that although the α-HL and PA63 channels have similar structural features, unlike α-HL, PA63 channel formation in lipid bilayer membranes ceases within minutes of protein addition, which currently precludes the use of NR for elucidating the interactions between PA63, LF, EF, and potential therapeutic agents.
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Lu Z, Truex NL, Melo MB, Cheng Y, Li N, Irvine DJ, Pentelute BL. IgG-Engineered Protective Antigen for Cytosolic Delivery of Proteins into Cancer Cells. ACS CENTRAL SCIENCE 2021; 7:365-378. [PMID: 33655074 PMCID: PMC7908032 DOI: 10.1021/acscentsci.0c01670] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Indexed: 05/05/2023]
Abstract
Therapeutic immunotoxins composed of antibodies and bacterial toxins provide potent activity against malignant cells, but joining them with a defined covalent bond while maintaining the desired function is challenging. Here, we develop novel immunotoxins by dovetailing full-length immunoglobulin G (IgG) antibodies and nontoxic anthrax proteins, in which the C terminus of the IgG heavy chain is connected to the side chain of anthrax toxin protective antigen. This strategy enabled efficient conjugation of protective antigen variants to trastuzumab (Tmab) and cetuximab (Cmab) antibodies. The conjugates effectively perform intracellular delivery of edema factor and N terminus of lethal factor (LFN) fused with diphtheria toxin and Ras/Rap1-specific endopeptidase. Each conjugate shows high specificity for cells expressing human epidermal growth factor receptor 2 (HER2) and epidermal growth factor receptor (EGFR), respectively, and potent activity across six Tmab- and Cmab-resistant cell lines. The conjugates also exhibit increased pharmacokinetics and pronounced in vivo safety, which shows promise for further therapeutic development.
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Affiliation(s)
- Zeyu Lu
- Department
of Chemistry, Massachusetts Institute of
Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Nicholas L. Truex
- Department
of Chemistry, Massachusetts Institute of
Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Mariane B. Melo
- The
Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 500 Main Street, Cambridge, Massachusetts 02142, United States
- Ragon
Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Yiran Cheng
- Department
of Chemistry, Massachusetts Institute of
Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Na Li
- The
Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 500 Main Street, Cambridge, Massachusetts 02142, United States
| | - Darrell J. Irvine
- The
Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 500 Main Street, Cambridge, Massachusetts 02142, United States
- Ragon
Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
- Department
of Materials Science and Engineering, Massachusetts
Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
- Department
of Biological Engineering, Massachusetts
Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
- Howard Hughes
Medical Institute, 4000
Jones Bridge Road, Chevy Chase, Maryland 20815, United
States
| | - Bradley L. Pentelute
- Department
of Chemistry, Massachusetts Institute of
Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
- The
Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 500 Main Street, Cambridge, Massachusetts 02142, United States
- Center
for Environmental Health Sciences, Massachusetts
Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
- Broad
Institute of MIT and Harvard, 415 Main Street, Cambridge, Massachusetts 02142, United States
- E-mail:
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The Buzz about ADP-Ribosylation Toxins from Paenibacillus larvae, the Causative Agent of American Foulbrood in Honey Bees. Toxins (Basel) 2021; 13:toxins13020151. [PMID: 33669183 PMCID: PMC7919650 DOI: 10.3390/toxins13020151] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 02/02/2021] [Accepted: 02/11/2021] [Indexed: 11/26/2022] Open
Abstract
The Gram-positive, spore-forming bacterium Paenibacillus larvae is the etiological agent of American Foulbrood, a highly contagious and often fatal honey bee brood disease. The species P. larvae comprises five so-called ERIC-genotypes which differ in virulence and pathogenesis strategies. In the past two decades, the identification and characterization of several P. larvae virulence factors have led to considerable progress in understanding the molecular basis of pathogen-host-interactions during P. larvae infections. Among these virulence factors are three ADP-ribosylating AB-toxins, Plx1, Plx2, and C3larvin. Plx1 is a phage-born toxin highly homologous to the pierisin-like AB-toxins expressed by the whites-and-yellows family Pieridae (Lepidoptera, Insecta) and to scabin expressed by the plant pathogen Streptomyces scabiei. These toxins ADP-ribosylate DNA and thus induce apoptosis. While the presumed cellular target of Plx1 still awaits final experimental proof, the classification of the A subunits of the binary AB-toxins Plx2 and C3larvin as typical C3-like toxins, which ADP-ribosylate Rho-proteins, has been confirmed experimentally. Normally, C3-exoenzymes do not occur together with a B subunit partner, but as single domain toxins. Interestingly, the B subunits of the two P. larvae C3-like toxins are homologous to the B-subunits of C2-like toxins with striking structural similarity to the PA-63 protomer of Bacillus anthracis.
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Harnessing the Membrane Translocation Properties of AB Toxins for Therapeutic Applications. Toxins (Basel) 2021; 13:toxins13010036. [PMID: 33418946 PMCID: PMC7825107 DOI: 10.3390/toxins13010036] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 12/28/2020] [Accepted: 01/01/2021] [Indexed: 12/31/2022] Open
Abstract
Over the last few decades, proteins and peptides have become increasingly more common as FDA-approved drugs, despite their inefficient delivery due to their inability to cross the plasma membrane. In this context, bacterial two-component systems, termed AB toxins, use various protein-based membrane translocation mechanisms to deliver toxins into cells, and these mechanisms could provide new insights into the development of bio-based drug delivery systems. These toxins have great potential as therapies both because of their intrinsic properties as well as the modular characteristics of both subunits, which make them highly amenable to conjugation with various drug classes. This review focuses on the therapeutical approaches involving the internalization mechanisms of three representative AB toxins: botulinum toxin type A, anthrax toxin, and cholera toxin. We showcase several specific examples of the use of these toxins to develop new therapeutic strategies for numerous diseases and explain what makes these toxins promising tools in the development of drugs and drug delivery systems.
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Transcriptional Regulators in Bacillus anthracis: A Potent Biothreat Agent. RECENT DEVELOPMENTS IN MICROBIAL TECHNOLOGIES 2021. [DOI: 10.1007/978-981-15-4439-2_17] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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12
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Abstract
The cholesterol-dependent cytolysins’ pore-forming mechanism relies on the ability to sense the completion of the oligomeric prepore structure and initiate the insertion of the β-barrel pore from the assembled prepore structure. These studies show that a conserved motif is an important component of the sensor that triggers the prepore-to-pore transition and that it is conserved in a large family of previously unidentified CDC-like proteins, the genes for which are present in a vast array of microbial species that span most terrestrial environments, as well as most animal and human microbiomes. These studies establish the foundation for future investigations that will probe the contribution of this large family of CDC-like proteins to microbial survival and human disease. The cholesterol-dependent cytolysins (CDCs) are bacterial, β-barrel, pore-forming toxins. A central enigma of the pore-forming mechanism is how completion of the prepore is sensed to initiate its conversion to the pore. We identified a motif that is conserved between the CDCs and a diverse family of nearly 300 uncharacterized proteins present in over 220 species that span at least 10 bacterial and 2 eukaryotic phyla. Except for this motif, these proteins exhibit little similarity to the CDCs at the primary structure level. Studies herein show this motif is a critical component of the sensor that initiates the prepore-to-pore transition in the CDCs. We further show by crystallography, single particle analysis, and biochemical studies of one of these CDC-like (CDCL) proteins from Elizabethkingia anophelis, a commensal of the malarial mosquito midgut, that a high degree of structural similarity exists between the CDC and CDCL monomer structures and both form large oligomeric pore complexes. Furthermore, the conserved motif in the E. anophelis CDCL crystal structure occupies a nearly identical position and makes similar contacts to those observed in the structure of the archetype CDC, perfringolysin O (PFO). This suggests a common function in the CDCs and CDCLs and may explain why only this motif is conserved in the CDCLs. Hence, these studies identify a critical component of the sensor involved in initiating the prepore-to-pore transition in the CDCs, which is conserved in a large and diverse group of distant relatives of the CDCs.
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13
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Cryo-EM structure of the fully-loaded asymmetric anthrax lethal toxin in its heptameric pre-pore state. PLoS Pathog 2020; 16:e1008530. [PMID: 32810181 PMCID: PMC7462287 DOI: 10.1371/journal.ppat.1008530] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Revised: 09/01/2020] [Accepted: 06/27/2020] [Indexed: 12/20/2022] Open
Abstract
Anthrax toxin is the major virulence factor secreted by Bacillus anthracis, causing high mortality in humans and other mammals. It consists of a membrane translocase, known as protective antigen (PA), that catalyzes the unfolding of its cytotoxic substrates lethal factor (LF) and edema factor (EF), followed by translocation into the host cell. Substrate recruitment to the heptameric PA pre-pore and subsequent translocation, however, are not well understood. Here, we report three high-resolution cryo-EM structures of the fully-loaded anthrax lethal toxin in its heptameric pre-pore state, which differ in the position and conformation of LFs. The structures reveal that three LFs interact with the heptameric PA and upon binding change their conformation to form a continuous chain of head-to-tail interactions. As a result of the underlying symmetry mismatch, one LF binding site in PA remains unoccupied. Whereas one LF directly interacts with a part of PA called α-clamp, the others do not interact with this region, indicating an intermediate state between toxin assembly and translocation. Interestingly, the interaction of the N-terminal domain with the α-clamp correlates with a higher flexibility in the C-terminal domain of the protein. Based on our data, we propose a model for toxin assembly, in which the relative position of the N-terminal α-helices in the three LFs determines which factor is translocated first.
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Lu Z, Paolella BR, Truex NL, Loftis AR, Liao X, Rabideau AE, Brown MS, Busanovich J, Beroukhim R, Pentelute BL. Targeting Cancer Gene Dependencies with Anthrax-Mediated Delivery of Peptide Nucleic Acids. ACS Chem Biol 2020; 15:1358-1369. [PMID: 32348107 PMCID: PMC7521945 DOI: 10.1021/acschembio.9b01027] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Antisense oligonucleotide therapies are important cancer treatments, which can suppress genes in cancer cells that are critical for cell survival. SF3B1 has recently emerged as a promising gene target that encodes a key splicing factor in the SF3B protein complex. Over 10% of cancers have lost one or more copies of the SF3B1 gene, rendering these cancers vulnerable after further suppression. SF3B1 is just one example of a CYCLOPS (Copy-number alterations Yielding Cancer Liabilities Owing to Partial losS) gene, but over 120 additional candidate CYCLOPS genes are known. Antisense oligonucleotide therapies for cancer offer the promise of effective suppression for CYCLOPS genes, but developing these treatments is difficult due to their limited permeability into cells and poor cytosolic stability. Here, we develop an effective approach to suppress CYCLOPS genes by delivering antisense peptide nucleic acids (PNAs) into the cytosol of cancer cells. We achieve efficient cytosolic PNA delivery with the two main nontoxic components of the anthrax toxin: protective antigen (PA) and the 263-residue N-terminal domain of lethal factor (LFN). Sortase-mediated ligation readily enables the conjugation of PNAs to the C terminus of the LFN protein. LFN and PA work together in concert to translocate PNAs into the cytosol of mammalian cells. Antisense SF3B1 PNAs delivered with the LFN/PA system suppress the SF3B1 gene and decrease cell viability, particularly of cancer cells with partial copy-number loss of SF3B1. Moreover, antisense SF3B1 PNAs delivered with a HER2-binding PA variant selectively target cancer cells that overexpress the HER2 cell receptor, demonstrating receptor-specific targeting of cancer cells. Taken together, our efforts illustrate how PA-mediated delivery of PNAs provides an effective and general approach for delivering antisense PNA therapeutics and for targeting gene dependencies in cancer.
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Affiliation(s)
- Zeyu Lu
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - Brenton R. Paolella
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02139, USA
| | - Nicholas L. Truex
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - Alexander R. Loftis
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - Xiaoli Liao
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - Amy E. Rabideau
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - Meredith S. Brown
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02139, USA
| | - John Busanovich
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02139, USA
| | - Rameen Beroukhim
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02139, USA
| | - Bradley L. Pentelute
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
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Abstract
The anthrax toxin receptors-capillary morphogenesis gene 2 (CMG2) and tumor endothelial marker 8 (TEM8)-were identified almost 20 years ago, although few studies have moved beyond their roles as receptors for the anthrax toxins to address their physiological functions. In the last few years, insight into their endogenous roles has come from two rare diseases: hyaline fibromatosis syndrome, caused by mutations in CMG2, and growth retardation, alopecia, pseudo-anodontia, and optic atrophy (GAPO) syndrome, caused by loss-of-function mutations in TEM8. Although CMG2 and TEM8 are highly homologous at the protein level, the difference in disease symptoms points to variations in the physiological roles of the two anthrax receptors. Here, we focus on the similarities between these receptors in their ability to regulate extracellular matrix homeostasis, angiogenesis, cell migration, and skin elasticity. In this way, we shed light on how mutations in these two related proteins cause such seemingly different diseases and we highlight the existing knowledge gaps that could form the focus of future studies.
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Affiliation(s)
- Oksana A. Sergeeva
- Global Health Institute, School of Life Sciences, EPFL, Lausanne, Switzerland
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Fischer ES, Campbell WA, Liu S, Ghirlando R, Fattah RJ, Bugge TH, Leppla SH. Bismaleimide cross-linked anthrax toxin forms functional octamers with high specificity in tumor targeting. Protein Sci 2019; 28:1059-1070. [PMID: 30942916 PMCID: PMC6511737 DOI: 10.1002/pro.3613] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Accepted: 04/01/2019] [Indexed: 12/12/2022]
Abstract
In recent years, anthrax toxin has been reengineered to act as a highly specific antiangiogenic cancer therapeutic, shown to kill tumors in animal models. This has been achieved by modifying protective antigen (PA) so that its activation and toxicity require the presence of two proteases, matrix metalloproteinase (MMP) and urokinase plasminogen activator (uPA), which are upregulated in tumor microenvironments. These therapeutics consist of intercomplementing PA variants, which are individually nontoxic, but form functional toxins upon complementary oligomerization. Here, we have created a dual-protease requiring PA targeting system which utilizes bismaleimide cross-linked PA (CLPA) rather than the intercomplementing PA variants. Three different CLPA agents were tested and, as expected, found to exclusively form octamers. Two of the CLPA agents have in vitro toxicities equal to those of previous intercomplementing agents, while the third CLPA agent had compromised in vitro cleavage and was significantly less cytotoxic. We hypothesize this difference was due to steric hindrance caused by cross-linking two PA monomers in close proximity to the PA cleavage site. Overall, this work advances the development and use of the PA and LF tumor-targeting system as a practical cancer therapeutic, as it provides a way to reduce the drug components of the anthrax toxin drug delivery system from three to two, which may lower the cost and simplify testing in clinical trials. HIGHLIGHT: Previously, anthrax toxin has been reengineered to act as a highly specific antiangiogenic cancer therapeutic. Here, we present a version, which utilizes bismaleimide cross-linked protective antigen (PA) rather than intercomplementing PA variants. This advances the development of anthrax toxin as a practical cancer therapeutic as it reduces the components of the drug delivery system to two, which may lower the cost and simplify testing in clinical trials.
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Affiliation(s)
- Elyse S. Fischer
- Laboratory of Parasitic DiseasesNational Institute of Allergy and Infectious DiseasesBethesdaMaryland
| | - Warren A. Campbell
- Laboratory of Parasitic DiseasesNational Institute of Allergy and Infectious DiseasesBethesdaMaryland
| | - Shihui Liu
- Oral and Pharyngeal Cancer BranchNational Institute of Dental and Craniofacial ResearchBethesdaMaryland
| | - Rodolfo Ghirlando
- Laboratory of Molecular BiologyNational Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of HealthBethesdaMaryland, 20892
| | - Rasem J. Fattah
- Laboratory of Parasitic DiseasesNational Institute of Allergy and Infectious DiseasesBethesdaMaryland
| | - Thomas H. Bugge
- Oral and Pharyngeal Cancer BranchNational Institute of Dental and Craniofacial ResearchBethesdaMaryland
| | - Stephen H. Leppla
- Laboratory of Parasitic DiseasesNational Institute of Allergy and Infectious DiseasesBethesdaMaryland
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Mamedov T, Musayeva I, Acsora R, Gun N, Gulec B, Mammadova G, Cicek K, Hasanova G. Engineering, and production of functionally active human Furin in N. benthamiana plant: In vivo post-translational processing of target proteins by Furin in plants. PLoS One 2019; 14:e0213438. [PMID: 30861020 PMCID: PMC6413912 DOI: 10.1371/journal.pone.0213438] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 02/21/2019] [Indexed: 11/19/2022] Open
Abstract
A plant expression platform with eukaryotic post-translational modification (PTM) machinery has many advantages compared to other protein expression systems. This promising technology is useful for the production of a variety of recombinant proteins including, therapeutic proteins, vaccine antigens, native additives, and industrial enzymes. However, plants lack some of the important PTMs, including furin processing, which limits this system for the production of certain mammalian complex proteins of therapeutic value. Furin is a ubiquitous proprotein convertase that is involved in the processing (activation) of a wide variety of precursor proteins, including blood coagulation factors, cell surface receptors, hormones and growth factors, viral envelope glycoproteins, etc. and plays a critical regulatory role in a wide variety of cellular events. In this study, we engineered the human furin gene for expression in plants and demonstrated the production of a functional active recombinant truncated human furin in N. benthamiana plant. We demonstrate that plant produced human furin is highly active both in vivo and in vitro and specifically cleaved the tested target proteins, Factor IX (FIX) and Protective Antigen (PA83). We also demonstrate that both, enzymatic deglycosylation and proteolytic processing of target proteins can be achieved in vivo by co-expression of deglycosylating and furin cleavage enzymes in a single cell to produce deglycosylated and furin processed target proteins. It is highly expected that this strategy will have many potential applications in pharmaceutical industry and can be used to produce safe and affordable therapeutic proteins, antibodies, and vaccines using a plant expression system.
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Affiliation(s)
- Tarlan Mamedov
- Akdeniz University, Department of Agricultural Biotechnology, Antalya, Turkey
- Azerbaijan National Academy of Science, Department of Biology and Medical Science, Baku, Azerbaijan
| | - Ilaha Musayeva
- Akdeniz University, Department of Agricultural Biotechnology, Antalya, Turkey
| | - Rabia Acsora
- Akdeniz University, Department of Agricultural Biotechnology, Antalya, Turkey
| | - Nilufer Gun
- Akdeniz University, Department of Agricultural Biotechnology, Antalya, Turkey
| | - Burcu Gulec
- Akdeniz University, Department of Agricultural Biotechnology, Antalya, Turkey
| | - Gulshan Mammadova
- Akdeniz University, Department of Agricultural Biotechnology, Antalya, Turkey
| | - Kader Cicek
- Akdeniz University, Department of Agricultural Biotechnology, Antalya, Turkey
| | - Gulnara Hasanova
- Akdeniz University, Department of Agricultural Biotechnology, Antalya, Turkey
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Anthrax toxin requires ZDHHC5-mediated palmitoylation of its surface-processing host enzymes. Proc Natl Acad Sci U S A 2019; 116:1279-1288. [PMID: 30610172 PMCID: PMC6347675 DOI: 10.1073/pnas.1812588116] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Toxins exploit numerous pathways of their host cells to gain cellular entry and promote intoxication. Therefore, studying the action of toxins allows us to better understand basic mechanisms in cell biology. In this study, we found that ZDHHC5, an enzyme that adds a lipid posttranslational modification to cysteines of proteins, is responsible for allowing anthrax toxin to enter cells. This enzyme acts on proprotein convertases that are needed to cleave these toxins to their active forms. ZDHHC5 does not affect the enzymatic activity of these proteases, but allows them to encounter the toxin by favoring their partitioning in microdomains on the cell surface, domains where the toxin has previously been shown to preferentially reside. The protein acyl transferase ZDHHC5 was recently proposed to regulate trafficking in the endocytic pathway. Therefore, we explored the function of this enzyme in controlling the action of bacterial toxins. We found that ZDHHC5 activity is required for two very different toxins: the anthrax lethal toxin and the pore-forming toxin aerolysin. Both of these toxins have precursor forms, the protoxins, which can use the proprotein convertases Furin and PC7 for activation. We show that ZDHHC5 indeed affects the processing of the protoxins to their active forms. We found that Furin and PC7 can both be S-palmitoylated and are substrates of ZDHHC5. The impact of ZDHHC5 on Furin/PC7-mediated anthrax toxin cleavage is dual, having an indirect and a direct component. First, ZDHHC5 affects the homeostasis and trafficking of a subset of cellular proteins, including Furin and PC7, presumably by affecting the endocytic/recycling pathway. Second, while not inhibiting the protease activity per se, ZDHHC5-mediated Furin/PC7 palmitoylation is required for the cleavage of the anthrax toxin. Finally, we show that palmitoylation of Furin and PC7 promotes their association with plasma membrane microdomains. Both the receptor-bound toxin and the convertases are of very low abundance at the cell surface. Their encounter is unlikely on reasonable time scales. This work indicates that palmitoylation drives their encounter in specific domains, allowing processing and thereby intoxication of the cell.
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Shali A, Hasannia S, Gashtasbi F, Abdous M, Shahangian SS, Jalili S. Generation and screening of efficient neutralizing single domain antibodies (VHHs) against the critical functional domain of anthrax protective antigen (PA). Int J Biol Macromol 2018. [DOI: 10.1016/j.ijbiomac.2018.03.034] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Certhrax Is an Antivirulence Factor for the Anthrax-Like Organism Bacillus cereus Strain G9241. Infect Immun 2018; 86:IAI.00207-18. [PMID: 29610258 DOI: 10.1128/iai.00207-18] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 03/28/2018] [Indexed: 11/20/2022] Open
Abstract
Bacillus cereus G9241 caused a life-threatening anthrax-like lung infection in a previously healthy human. This strain harbors two large virulence plasmids, pBCXO1 and pBC210, that are absent from typical B. cereus isolates. The pBCXO1 plasmid is nearly identical to pXO1 from Bacillus anthracis and carries genes (pagA1, lef, and cya) for anthrax toxin components (protective antigen [called PA1 in G9241], lethal factor [LF], and edema factor [EF], respectively). The plasmid also has an intact hyaluronic acid capsule locus. The pBC210 plasmid has a tetrasaccharide capsule locus, a gene for a PA1 homolog called PA2 (pagA2), and a gene (cer) for Certhrax, an ADP-ribosyltransferase toxin that inactivates vinculin. LF, EF, and Certhrax require PA for entry into cells. In this study, we asked what role PA1, PA2, LF, and Certhrax play in the pathogenicity of G9241. To answer this, we generated isogenic deletion mutations in the targeted toxin gene components and then assessed the strains for virulence in highly G9241-susceptible (A/J) and moderately G9241-sensitive (C57BL/6) mice. We found that full virulence of G9241 required PA1 and LF, while PA2 contributed minimally to pathogenesis of G9241 but could not functionally replace PA1 as a toxin-binding subunit in vivo Surprisingly, we discovered that Certhrax attenuated the virulence of G9241; i.e., a Δcer Δlef mutant strain was more virulent than a Δlef mutant strain following subcutaneous inoculation of A/J mice. Moreover, the enzymatic activity of Certhrax contributed to this phenotype. We concluded that Certhrax acts as an antivirulence factor in the anthrax-like organism B. cereus G9241.
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Abstract
Bacillus anthracis, the anthrax agent, is a member of the Bacillus cereus sensu lato group, which includes invasive pathogens of mammals or insects as well as nonpathogenic environmental strains. The genes for anthrax pathogenesis are located on two large virulence plasmids. Similar virulence plasmids have been acquired by other B. cereus strains and enable the pathogenesis of anthrax-like diseases. Among the virulence factors of B. anthracis is the S-layer-associated protein BslA, which endows bacilli with invasive attributes for mammalian hosts. BslA surface display and function are dependent on the bacterial S-layer, whose constituents assemble by binding to the secondary cell wall polysaccharide (SCWP) via S-layer homology (SLH) domains. B. anthracis and other pathogenic B. cereus isolates harbor genes for the secretion of S-layer proteins, for S-layer assembly, and for synthesis of the SCWP. We review here recent insights into the assembly and function of the S-layer and the SCWP.
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Affiliation(s)
- Dominique Missiakas
- Howard Taylor Ricketts Laboratory, Argonne National Laboratory, Lemont, Illinois 60649.,Department of Microbiology, University of Chicago, Chicago, Illinois 60637;
| | - Olaf Schneewind
- Howard Taylor Ricketts Laboratory, Argonne National Laboratory, Lemont, Illinois 60649.,Department of Microbiology, University of Chicago, Chicago, Illinois 60637;
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22
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Majumder S, Das S, Somani V, Makam SS, Joseph KJ, Bhatnagar R. A bivalent protein r-PB, comprising PA and BclA immunodominant regions for comprehensive protection against Bacillus anthracis. Sci Rep 2018; 8:7242. [PMID: 29740033 PMCID: PMC5940697 DOI: 10.1038/s41598-018-25502-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 04/23/2018] [Indexed: 01/09/2023] Open
Abstract
Anthrax infection is primarily initiated by B. anthracis endospores that on entry into the host germinate to vegetative cells and cause severe bacteremia and toxaemia employing an array of host colonisation factors and the lethal tripartite toxin. The protective efficacy of conventional protective antigen (PA) based anthrax vaccines is improved by co-administration with inactivated spores or its components. In the present study, using structural vaccinology rationale we synthesized a bivalent protein r-PB encompassing toxin (PAIV) and spore components (BclACTD) and characterized its protective efficacy against B. anthracis infection. Active immunization of mice with r-PB generated high titer circulating antibodies which facilitated the phagocytic uptake of spores, inhibited their germination to vegetative cells and completely neutralized anthrax toxins in vivo resulting in 100 % survival against anthrax toxin challenge. Proliferation of CD4+ T cell subsets with up-regulation of Th1 (IFN-γ, IL-2, and IL-12), Th2 (IL-5, IL-10) cytokines and balanced expression of IgG1:IgG2a antibody isotypes indicated the stimulation of both Th1 and Th2 subsets. The immunized mice exhibited 100 % survival upon challenge with B. anthracis spores or toxin indicating the ability of r-PB to provide comprehensive protection against anthrax. Our results thus demonstrate r-PB an efficient vaccine candidate against anthrax infection.
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Affiliation(s)
- Saugata Majumder
- Microbiology Division, Defence Food Research Laboratory, Defence Research Development Organisation, Mysore, 570011, India
| | - Shreya Das
- Microbiology Division, Defence Food Research Laboratory, Defence Research Development Organisation, Mysore, 570011, India
| | - Vikas Somani
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Shivakiran S Makam
- Microbiology Division, Defence Food Research Laboratory, Defence Research Development Organisation, Mysore, 570011, India
| | - Kingston J Joseph
- Microbiology Division, Defence Food Research Laboratory, Defence Research Development Organisation, Mysore, 570011, India.
| | - Rakesh Bhatnagar
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067, India
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23
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Fabre L, Santelli E, Mountassif D, Donoghue A, Biswas A, Blunck R, Hanein D, Volkmann N, Liddington R, Rouiller I. Structure of anthrax lethal toxin prepore complex suggests a pathway for efficient cell entry. J Gen Physiol 2017; 148:313-24. [PMID: 27670897 PMCID: PMC5037343 DOI: 10.1085/jgp.201611617] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 08/25/2016] [Indexed: 01/20/2023] Open
Abstract
Anthrax toxin comprises three soluble proteins: protective antigen (PA), lethal factor (LF), and edema factor (EF). PA must be cleaved by host proteases before it oligomerizes and forms a prepore, to which LF and EF bind. After endocytosis of this tripartite complex, the prepore transforms into a narrow transmembrane pore that delivers unfolded LF and EF into the host cytosol. Here, we find that translocation of multiple 90-kD LF molecules is rapid and efficient. To probe the molecular basis of this translocation, we calculated a three-dimensional map of the fully loaded (PA63)7-(LF)3 prepore complex by cryo-electron microscopy (cryo-EM). The map shows three LFs bound in a similar way to one another, via their N-terminal domains, to the surface of the PA heptamer. The model also reveals contacts between the N- and C-terminal domains of adjacent LF molecules. We propose that this molecular arrangement plays an important role in the maintenance of translocation efficiency through the narrow PA pore.
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Affiliation(s)
- Lucien Fabre
- Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada Groupe de Recherche Axé sur la Structure des Protéines (GRASP), Groupe d'Étude des Protéines Membranaires (GÉPROM), McGill University, Montréal, Québec H3A 0C7, Canada
| | - Eugenio Santelli
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037
| | - Driss Mountassif
- Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada Groupe de Recherche Axé sur la Structure des Protéines (GRASP), Groupe d'Étude des Protéines Membranaires (GÉPROM), McGill University, Montréal, Québec H3A 0C7, Canada
| | - Annemarie Donoghue
- Departments of Physics, Université de Montréal, Montréal, Québec H3T 1J4, Canada Department of Physiology, Université de Montréal, Montréal, Québec H3T 1J4, Canada Groupe d'Étude des Protéines Membranaires (GÉPROM), Université de Montréal, Montréal, Québec H3T 1J4, Canada
| | - Aviroop Biswas
- Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada Groupe de Recherche Axé sur la Structure des Protéines (GRASP), Groupe d'Étude des Protéines Membranaires (GÉPROM), McGill University, Montréal, Québec H3A 0C7, Canada
| | - Rikard Blunck
- Departments of Physics, Université de Montréal, Montréal, Québec H3T 1J4, Canada Department of Physiology, Université de Montréal, Montréal, Québec H3T 1J4, Canada Groupe d'Étude des Protéines Membranaires (GÉPROM), Université de Montréal, Montréal, Québec H3T 1J4, Canada
| | - Dorit Hanein
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037
| | - Niels Volkmann
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037
| | - Robert Liddington
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037
| | - Isabelle Rouiller
- Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada Groupe de Recherche Axé sur la Structure des Protéines (GRASP), Groupe d'Étude des Protéines Membranaires (GÉPROM), McGill University, Montréal, Québec H3A 0C7, Canada
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Comparative Studies of Actin- and Rho-Specific ADP-Ribosylating Toxins: Insight from Structural Biology. Curr Top Microbiol Immunol 2017; 399:69-86. [PMID: 27540723 DOI: 10.1007/82_2016_23] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Mono-ADP-ribosylation is a major post-translational modification performed by bacterial toxins, which transfer an ADP-ribose moiety to a substrate acceptor residue. Actin- and Rho-specific ADP-ribosylating toxins (ARTs) are typical ARTs known to have very similar tertiary structures but totally different targets. Actin-specific ARTs are the A components of binary toxins, ADP-ribosylate actin at Arg177, leading to the depolymerization of the actin cytoskeleton. On the other hand, C3-like exoenzymes are Rho-specific ARTs, ADP-ribosylate Rho GTPases at Asn41, exerting an indirect effect on the actin cytoskeleton. This review focuses on the differences and similarities of actin- and Rho-specific ARTs, especially with respect to their substrate recognition and cell entry mechanisms, based on structural studies.
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25
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Liang X, Zhu J, Zhao Z, Zheng F, Zhang H, Wei J, Ji Y, Ji Y. The pag Gene of pXO1 Is Involved in Capsule Biosynthesis of Bacillus anthracis Pasteur II Strain. Front Cell Infect Microbiol 2017; 7:203. [PMID: 28603695 PMCID: PMC5445325 DOI: 10.3389/fcimb.2017.00203] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Accepted: 05/08/2017] [Indexed: 11/13/2022] Open
Abstract
The poly-γ-D-glutamic acid capsule and anthrax toxins are major virulence factors of Bacillus anthracis. Genes responsible for capsule biosynthesis are located on pXO2, whereas genes encoding the toxins, which are composed of edema factors, lethal factors, and protective antigens (PA), are located on pXO1. In this study, we found that the pag null mutation not only eliminated the production of the protective antigen, it also eliminated the ability of the B. anthracis Pasteur II strain to form capsules. qPCR analysis revealed that the deletion of pag decreased the transcription levels of the capABCD operon and its regulatory genes acpA and acpB. The introduction of the acpA or acpB plasmid complemented the effect of the pag null mutation on capsule formation. Taken together, the above results suggest that PA probably affects capsule biosynthesis by altering the expression of acpA and acpB. In addition, we found that the deletion mutation of pag remarkably attenuated bacterial pathogenicity in a mouse model of infection. Our results indicate that besides encoding the protective antigen, the pag gene of pXO1 is also involved in the modulation of capsule biosynthesis. Our findings provide new insight into the regulation mechanisms of capsule formation in B. anthracis Pasteur II strain.
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Affiliation(s)
- Xudong Liang
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and PreventionBeijing, China
| | - Jin Zhu
- Huadong Medical Institute of BiotechniquesNanjing, China
| | - Zhongzhi Zhao
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and PreventionBeijing, China
| | - Feng Zheng
- Huadong Medical Institute of BiotechniquesNanjing, China
| | - Huijuan Zhang
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and PreventionBeijing, China
| | - Jianchun Wei
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and PreventionBeijing, China
| | - Yon Ji
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and PreventionBeijing, China
| | - Yinduo Ji
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of MinnesotaSt. Paul, MN, United States
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26
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Secondary Structure Preferences of the Anthrax Toxin Protective Antigen Translocase. J Mol Biol 2017; 429:753-762. [DOI: 10.1016/j.jmb.2017.01.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 01/13/2017] [Accepted: 01/15/2017] [Indexed: 01/14/2023]
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Ghosal K, Colby JM, Das D, Joy ST, Arora PS, Krantz BA. Dynamic Phenylalanine Clamp Interactions Define Single-Channel Polypeptide Translocation through the Anthrax Toxin Protective Antigen Channel. J Mol Biol 2017; 429:900-910. [PMID: 28192089 DOI: 10.1016/j.jmb.2017.02.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 02/03/2017] [Accepted: 02/08/2017] [Indexed: 10/20/2022]
Abstract
Anthrax toxin is an intracellularly acting toxin where sufficient detail is known about the structure of its channel, allowing for molecular investigations of translocation. The toxin is composed of three proteins, protective antigen (PA), lethal factor (LF), and edema factor (EF). The toxin's translocon, PA, translocates the large enzymes, LF and EF, across the endosomal membrane into the host cell's cytosol. Polypeptide clamps located throughout the PA channel catalyze the translocation of LF and EF. Here, we show that the central peptide clamp, the ϕ clamp, is a dynamic site that governs the overall peptide translocation pathway. Single-channel translocations of a 10-residue, guest-host peptide revealed that there were four states when peptide interacted with the channel. Two of the states had intermediate conductances of 10% and 50% of full conductance. With aromatic guest-host peptides, the 50% conducting intermediate oscillated with the fully blocked state. A Trp guest-host peptide was studied by manipulating its stereochemistry and prenucleating helix formation with a covalent linkage in the place of a hydrogen bond or hydrogen-bond surrogate (HBS). The Trp peptide synthesized with ʟ-amino acids translocated more efficiently than peptides synthesized with D- or alternating D,ʟ-amino acids. HBS stapled Trp peptide exhibited signs of steric hindrance and difficulty translocating. However, when mutant ϕ clamp (F427A) channels were tested, the HBS peptide translocated normally. Overall, peptide translocation is defined by dynamic interactions between the peptide and ϕ clamp. These dynamics require conformational flexibility, such that the peptide productively forms both extended-chain and helical states during translocation.
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Affiliation(s)
- Koyel Ghosal
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, 650 W, Baltimore Street, Baltimore, MD 21201, USA
| | - Jennifer M Colby
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Debasis Das
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, 650 W, Baltimore Street, Baltimore, MD 21201, USA
| | - Stephen T Joy
- Department of Chemistry, New York University, New York, NY 10003, USA
| | - Paramjit S Arora
- Department of Chemistry, New York University, New York, NY 10003, USA
| | - Bryan A Krantz
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, 650 W, Baltimore Street, Baltimore, MD 21201, USA.
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Harris JR, Soliakov A, Watkinson A, Lakey JH. Recombinant anthrax protective antigen: Observation of aggregation phenomena by TEM reveals specific effects of sterols. Micron 2016; 93:1-8. [PMID: 27883989 DOI: 10.1016/j.micron.2016.10.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2016] [Accepted: 10/12/2016] [Indexed: 10/20/2022]
Abstract
Negatively stained transmission electron microscope images are presented that depict the aggregation of recombinant anthrax protective antigen (rPA83 monomer and the PA63 prepore oligomer) under varying in vitro biochemical conditions. Heat treatment (50°C) of rPA83 produced clumped fibrils, but following heating the PA63 prepore formed disordered aggregates. Freeze-thaw treatment of the PA63 prepore generated linear flexuous aggregates of the heptameric oligomers. Aqueous suspensions of cholesterol microcrystals were shown to bind small rPA83 aggregates at the edges of the planar bilayers. With PA63 a more discrete binding of the prepores to the crystalline cholesterol bilayer edges occurs. Sodium deoxycholate (NaDOC) treatment of rPA83 produced quasi helical fibrillar aggregate, similar but not identical to that produced by heat treatment. Remarkably, NaDOC treatment of the PA63 prepores induced transformation into pores, with a characteristic extended ß-barrel. The PA63 pores aggregated as dimers, that aggregated further as angular chains and closed structures in higher NaDOC concentrations. The significance of the sterol interaction is discussed in relation to its likely importance for PA action in vivo.
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Affiliation(s)
- J Robin Harris
- Institute of Zoology, University of Mainz, 55099 Mainz, Germany.
| | - Andrei Soliakov
- Fujifilm Diosynth Biotechnologies, Belasis Avenue, Billingham TS23 1LH, UK
| | - Allan Watkinson
- Envigo, Wooley Road, Alcon bury, Huntingdon, Cambridgeshire PE28 4HS, UK
| | - Jeremy H Lakey
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle-upon-Tyne NE2 4HH, UK
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Krantz BA. Anthrax lethal toxin co-complexes are stabilized by contacts between adjacent lethal factors. J Gen Physiol 2016; 148:273-5. [PMID: 27670896 PMCID: PMC5037347 DOI: 10.1085/jgp.201611681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Accepted: 08/26/2016] [Indexed: 11/20/2022] Open
Affiliation(s)
- Bryan A Krantz
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, MD 21201
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Corbi-Verge C, Garton M, Nim S, Kim PM. Strategies to Develop Inhibitors of Motif-Mediated Protein-Protein Interactions as Drug Leads. Annu Rev Pharmacol Toxicol 2016; 57:39-60. [PMID: 27618737 DOI: 10.1146/annurev-pharmtox-010716-104805] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Protein-protein interactions are fundamental for virtually all functions of the cell. A large fraction of these interactions involve short peptide motifs, and there has been increased interest in targeting them using peptide-based therapeutics. Peptides benefit from being specific, relatively safe, and easy to produce. They are also easy to modify using chemical synthesis and molecular biology techniques. However, significant challenges remain regarding the use of peptides as therapeutic agents. Identification of peptide motifs is difficult, and peptides typically display low cell permeability and sensitivity to enzymatic degradation. In this review, we outline the principal high-throughput methodologies for motif discovery and describe current methods for overcoming pharmacokinetic and bioavailability limitations.
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Affiliation(s)
- Carles Corbi-Verge
- Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario M5S 3E1, Canada; , , ,
| | - Michael Garton
- Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario M5S 3E1, Canada; , , ,
| | - Satra Nim
- Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario M5S 3E1, Canada; , , ,
| | - Philip M Kim
- Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario M5S 3E1, Canada; , , , .,Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 3E1, Canada.,Department of Computer Science, University of Toronto, Toronto, Ontario M5S 3E1, Canada
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31
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Bachran C, Leppla SH. Tumor Targeting and Drug Delivery by Anthrax Toxin. Toxins (Basel) 2016; 8:toxins8070197. [PMID: 27376328 PMCID: PMC4963830 DOI: 10.3390/toxins8070197] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 06/21/2016] [Accepted: 06/23/2016] [Indexed: 12/17/2022] Open
Abstract
Anthrax toxin is a potent tripartite protein toxin from Bacillus anthracis. It is one of the two virulence factors and causes the disease anthrax. The receptor-binding component of the toxin, protective antigen, needs to be cleaved by furin-like proteases to be activated and to deliver the enzymatic moieties lethal factor and edema factor to the cytosol of cells. Alteration of the protease cleavage site allows the activation of the toxin selectively in response to the presence of tumor-associated proteases. This initial idea of re-targeting anthrax toxin to tumor cells was further elaborated in recent years and resulted in the design of many modifications of anthrax toxin, which resulted in successful tumor therapy in animal models. These modifications include the combination of different toxin variants that require activation by two different tumor-associated proteases for increased specificity of toxin activation. The anthrax toxin system has proved to be a versatile system for drug delivery of several enzymatic moieties into cells. This highly efficient delivery system has recently been further modified by introducing ubiquitin as a cytosolic cleavage site into lethal factor fusion proteins. This review article describes the latest developments in this field of tumor targeting and drug delivery.
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Affiliation(s)
| | - Stephen H Leppla
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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Rabideau AE, Pentelute BL. Delivery of Non-Native Cargo into Mammalian Cells Using Anthrax Lethal Toxin. ACS Chem Biol 2016; 11:1490-501. [PMID: 27055654 DOI: 10.1021/acschembio.6b00169] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The intracellular delivery of peptide and protein therapeutics is a major challenge due to the plasma membrane, which acts as a barrier between the extracellular environment and the intracellular milieu. Over the past two decades, a nontoxic PA/LFN delivery platform derived from anthrax lethal toxin has been developed for the transport of non-native cargo into the cytosol of cells in order to understand the translocation process through a protective antigen (PA) pore and to probe intracellular biological functions. Enzyme-mediated ligation using sortase A and native chemical ligation are two facile methods used to synthesize these non-native conjugates, inaccessible by recombinant technology. Cargo molecules that translocate efficiently include enzymes from protein toxins, antibody mimic proteins, and peptides of varying lengths and non-natural amino acid compositions. The PA pore has been found to effectively convey over 30 known cargos other than native lethal factor (LF; i.e., non-native) with diverse sequences and functionalities on the LFN transporter protein. All together these studies demonstrated that non-native cargos must adopt an unfolded or extended conformation and contain a suitable charge composition in order to efficiently pass through the PA pore. This review provides insight into design parameters for the efficient delivery of new cargos using PA and LFN.
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Affiliation(s)
- Amy E. Rabideau
- Massachusetts Institute of Technology, Department of Chemistry, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Bradley Lether Pentelute
- Massachusetts Institute of Technology, Department of Chemistry, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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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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Rabideau AE, Pentelute BL. A d-Amino Acid at the N-Terminus of a Protein Abrogates Its Degradation by the N-End Rule Pathway. ACS CENTRAL SCIENCE 2015; 1:423-430. [PMID: 26807441 PMCID: PMC4711398 DOI: 10.1021/acscentsci.5b00308] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Indexed: 06/05/2023]
Abstract
Eukaryotes have evolved the ubiquitin (Ub)/proteasome system to degrade polypeptides. The Ub/proteasome system is one way that cells regulate cytosolic protein and amino acids levels through the recognition and ubiquitination of a protein's N-terminus via E1, E2, and E3 enzymes. The process by which the N-terminus stimulates intracellular protein degradation is referred to as the N-end rule. Characterization of the N-end rule has been limited to only the natural l-amino acids. Using a cytosolic delivery platform derived from anthrax lethal toxin, we probed the stability of mixed chirality proteins, containing one d-amino acid on the N-terminus of otherwise all l-proteins. In all cases, we observed that one N-terminal d-amino acid stabilized the cargo protein to proteasomal degradation with respect to the N-end rule. We found that since the mixed chirality proteins were not polyubiquitinated, they evaded N-end-mediated proteasomal degradation. Evidently, a subtle change on the N-terminus of a natural protein can enhance its intracellular lifetime.
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35
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McComb RC, Martchenko M. Neutralizing antibody and functional mapping of Bacillus anthracis protective antigen-The first step toward a rationally designed anthrax vaccine. Vaccine 2015; 34:13-9. [PMID: 26611201 DOI: 10.1016/j.vaccine.2015.11.025] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 10/05/2015] [Accepted: 11/09/2015] [Indexed: 12/14/2022]
Abstract
Anthrax is defined by the Centers for Disease Control and Prevention as a Category A pathogen for its potential use as a bioweapon. Current prevention treatments include Anthrax Vaccine Adsorbed (AVA). AVA is an undefined formulation of Bacillus anthracis culture supernatant adsorbed to aluminum hydroxide. It has an onerous vaccination schedule, is slow and cumbersome to produce and is slightly reactogenic. Next-generation vaccines are focused on producing recombinant forms of anthrax toxin in a well-defined formulation but these vaccines have been shown to lose potency as they are stored. In addition, studies have shown that a proportion of the antibody response against these vaccines is focused on non-functional, non-neutralizing regions of the anthrax toxin while some essential functional regions are shielded from eliciting an antibody response. Rational vaccinology is a developing field that focuses on designing vaccine antigens based on structural information provided by neutralizing antibody epitope mapping, crystal structure analysis, and functional mapping through amino acid mutations. This information provides an opportunity to design antigens that target only functionally important and conserved regions of a pathogen in order to make a more optimal vaccine product. This review provides an overview of the literature related to functional and neutralizing antibody epitope mapping of the Protective Antigen (PA) component of anthrax toxin.
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Affiliation(s)
- Ryan C McComb
- Keck Graduate Institute, School of Applied Life Science, 535 Watson Dr., Claremont, CA, United States
| | - Mikhail Martchenko
- Keck Graduate Institute, School of Applied Life Science, 535 Watson Dr., Claremont, CA, United States.
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36
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McComb RC, Ho CL, Bradley KA, Grill LK, Martchenko M. Presentation of peptides from Bacillus anthracis protective antigen on Tobacco Mosaic Virus as an epitope targeted anthrax vaccine. Vaccine 2015; 33:6745-51. [PMID: 26514421 DOI: 10.1016/j.vaccine.2015.10.075] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 09/26/2015] [Accepted: 10/14/2015] [Indexed: 10/22/2022]
Abstract
The current anthrax vaccine requires improvements for rapidly invoking longer-lasting neutralizing antibody responses with fewer doses from a well-defined formulation. Designing antigens that target neutralizing antibody epitopes of anthrax protective antigen, a component of anthrax toxin, may offer a solution for achieving a vaccine that can induce strong and long lasting antibody responses with fewer boosters. Here we report implementation of a strategy for developing epitope focused virus nanoparticle vaccines against anthrax by using immunogenic virus particles to present peptides derived from anthrax toxin previously identified in (1) neutralizing antibody epitope mapping studies, (2) toxin crystal structure analyses to identify functional regions, and (3) toxin mutational analyses. We successfully expressed two of three peptide epitopes from anthrax toxin that, in previous reports, bound antibodies that were partially neutralizing against toxin activity, discovered cross-reactivity between vaccine constructs and toxin specific antibodies raised in goats against native toxin and showed that antibodies induced by our vaccine constructs also cross-react with native toxin. While protection against intoxication in cellular and animal studies were not as effective as in previous studies, partial toxin neutralization was observed in animals, demonstrating the feasibility of using plant-virus nanoparticles as a platform for epitope defined anthrax vaccines.
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Affiliation(s)
| | - Chi-Lee Ho
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA, USA
| | - Kenneth A Bradley
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA, USA
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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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38
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Zhan C, Li C, Wei X, Lu W, Lu W. Toxins and derivatives in molecular pharmaceutics: Drug delivery and targeted therapy. Adv Drug Deliv Rev 2015; 90:101-18. [PMID: 25959429 DOI: 10.1016/j.addr.2015.04.025] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Revised: 04/20/2015] [Accepted: 04/29/2015] [Indexed: 01/13/2023]
Abstract
Protein and peptide toxins offer an invaluable source for the development of actively targeted drug delivery systems. They avidly bind to a variety of cognate receptors, some of which are expressed or even up-regulated in diseased tissues and biological barriers. Protein and peptide toxins or their derivatives can act as ligands to facilitate tissue- or organ-specific accumulation of therapeutics. Some toxins have evolved from a relatively small number of structural frameworks that are particularly suitable for addressing the crucial issues of potency and stability, making them an instrumental source of leads and templates for targeted therapy. The focus of this review is on protein and peptide toxins for the development of targeted drug delivery systems and molecular therapies. We summarize disease- and biological barrier-related toxin receptors, as well as targeted drug delivery strategies inspired by those receptors. The design of new therapeutics based on protein and peptide toxins is also discussed.
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Affiliation(s)
- Changyou Zhan
- Department of Pharmaceutics, School of Pharmacy, Fudan University & Key Laboratory of Smart Drug Delivery (Fudan University), Ministry of Education, Shanghai 201203, PR China
| | - Chong Li
- College of Pharmaceutical Sciences, Southwest University & Chongqing Engineering Research Center for Pharmaceutical Process and Quality Control, Chongqing 400716, PR China
| | - Xiaoli Wei
- Department of Pharmaceutics, School of Pharmacy, Fudan University & Key Laboratory of Smart Drug Delivery (Fudan University), Ministry of Education, Shanghai 201203, PR China; State Key Laboratory of Medical Neurobiology and the Collaborative Innovation Center for Brain Science, Fudan University, Shanghai 200032, PR China
| | - Wuyuan Lu
- Institute of Human Virology and Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Weiyue Lu
- Department of Pharmaceutics, School of Pharmacy, Fudan University & Key Laboratory of Smart Drug Delivery (Fudan University), Ministry of Education, Shanghai 201203, PR China; State Key Laboratory of Medical Neurobiology and the Collaborative Innovation Center for Brain Science, Fudan University, Shanghai 200032, PR China; State Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai 200433, PR China.
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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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40
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Translocation of Non-Canonical Polypeptides into Cells Using Protective Antigen. Sci Rep 2015; 5:11944. [PMID: 26178180 PMCID: PMC4503955 DOI: 10.1038/srep11944] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 04/09/2015] [Indexed: 11/09/2022] Open
Abstract
A variety of pathogenic bacteria infect host eukaryotic cells using protein toxins, which enter the cytosol and exert their cytotoxic effects. Anthrax lethal toxin, for example, utilizes the membrane-spanning translocase, protective antigen (PA) pore, to deliver the protein toxin lethal factor (LF) from the endosome into the cytosol of cells. Previous work has investigated the delivery of natural peptides and enzymatic domains appended to the C-terminus of the PA-binding domain of lethal factor (LFN) into the cytosol via PA pore. Here, we move beyond natural amino acids and systematically investigate the translocation of polypeptide cargo containing non-canonical amino acids and functionalities through PA pore. Our results indicate translocation is not perturbed with alterations to the peptide backbone or side-chain. Moreover, despite their structural complexity, we found that the small molecule drugs, doxorubicin and monomethyl auristatin F (MMAF) translocated efficiently through PA pore. However, we found cyclic peptides and the small molecule drug docetaxel abrogated translocation due to their large size and structural rigidity. For cargos that reached the cytosol, we demonstrated that each remained intact after translocation. These studies show PA is capable of translocating non-canonical cargo provided it is in a conformational state conducive for passage through the narrow pore.
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41
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Jacquez P, Avila G, Boone K, Altiyev A, Puschhof J, Sauter R, Arigi E, Ruiz B, Peng X, Almeida I, Sherman M, Xiao C, Sun J. The Disulfide Bond Cys255-Cys279 in the Immunoglobulin-Like Domain of Anthrax Toxin Receptor 2 Is Required for Membrane Insertion of Anthrax Protective Antigen Pore. PLoS One 2015; 10:e0130832. [PMID: 26107617 PMCID: PMC4479931 DOI: 10.1371/journal.pone.0130832] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2015] [Accepted: 05/25/2015] [Indexed: 11/19/2022] Open
Abstract
Anthrax toxin receptors act as molecular clamps or switches that control anthrax toxin entry, pH-dependent pore formation, and translocation of enzymatic moieties across the endosomal membranes. We previously reported that reduction of the disulfide bonds in the immunoglobulin-like (Ig) domain of the anthrax toxin receptor 2 (ANTXR2) inhibited the function of the protective antigen (PA) pore. In the present study, the disulfide linkage in the Ig domain was identified as Cys255-Cys279 and Cys230-Cys315. Specific disulfide bond deletion mutants were achieved by replacing Cys residues with Ala residues. Deletion of the disulfide bond C255-C279, but not C230-C315, inhibited the PA pore-induced release of the fluorescence dyes from the liposomes, suggesting that C255-C279 is essential for PA pore function. Furthermore, we found that deletion of C255-C279 did not affect PA prepore-to-pore conversion, but inhibited PA pore membrane insertion by trapping the PA membrane-inserting loops in proteinaceous hydrophobic pockets. Fluorescence spectra of Trp59, a residue adjacent to the PA-binding motif in von Willebrand factor A (VWA) domain of ANTXR2, showed that deletion of C255-C279 resulted in a significant conformational change on the receptor ectodomain. The disulfide deletion-induced conformational change on the VWA domain was further confirmed by single-particle 3D reconstruction of the negatively stained PA-receptor heptameric complexes. Together, the biochemical and structural data obtained in this study provides a mechanistic insight into the role of the receptor disulfide bond C255-C279 in anthrax toxin action. Manipulation of the redox states of the receptor, specifically targeting to C255-C279, may become a novel strategy to treat anthrax.
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Affiliation(s)
- Pedro Jacquez
- Department of Biological Sciences & Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas, 79968, United States of America
| | - Gustavo Avila
- Department of Chemistry, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas, 79968, United States of America
| | - Kyle Boone
- Bioinformatics Program of University of Texas at El Paso, 500 West University Avenue, El Paso, Texas, 79968, United States of America
| | - Agamyrat Altiyev
- Bioinformatics Program of University of Texas at El Paso, 500 West University Avenue, El Paso, Texas, 79968, United States of America
| | - Jens Puschhof
- Department of Biological Sciences & Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas, 79968, United States of America
| | - Roland Sauter
- Department of Biological Sciences & Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas, 79968, United States of America
| | - Emma Arigi
- Department of Biological Sciences & Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas, 79968, United States of America
| | - Blanca Ruiz
- Department of Biological Sciences & Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas, 79968, United States of America
| | - Xiuli Peng
- China National Key Laboratory of Agricultural Microbiology, Huazhong Agriculture University, Wuhan, 430070, P. R. China
| | - Igor Almeida
- Department of Biological Sciences & Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas, 79968, United States of America
| | - Michael Sherman
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas, 77555, United States of America
| | - Chuan Xiao
- Department of Chemistry, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas, 79968, United States of America
- * E-mail: (CX); (JS)
| | - Jianjun Sun
- Department of Biological Sciences & Border Biomedical Research Center, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas, 79968, United States of America
- * E-mail: (CX); (JS)
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42
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Leone P, Bebeacua C, Opota O, Kellenberger C, Klaholz B, Orlov I, Cambillau C, Lemaitre B, Roussel A. X-ray and Cryo-electron Microscopy Structures of Monalysin Pore-forming Toxin Reveal Multimerization of the Pro-form. J Biol Chem 2015; 290:13191-201. [PMID: 25847242 DOI: 10.1074/jbc.m115.646109] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Indexed: 11/06/2022] Open
Abstract
β-Barrel pore-forming toxins (β-PFT), a large family of bacterial toxins, are generally secreted as water-soluble monomers and can form oligomeric pores in membranes following proteolytic cleavage and interaction with cell surface receptors. Monalysin has been recently identified as a β-PFT that contributes to the virulence of Pseudomonas entomophila against Drosophila. It is secreted as a pro-protein that becomes active upon cleavage. Here we report the crystal and cryo-electron microscopy structure of the pro-form of Monalysin as well as the crystal structures of the cleaved form and of an inactive mutant lacking the membrane-spanning region. The overall structure of Monalysin displays an elongated shape, which resembles those of β-pore-forming toxins, such as Aerolysin, but is devoid of a receptor-binding domain. X-ray crystallography, cryo-electron microscopy, and light-scattering studies show that pro-Monalysin forms a stable doughnut-like 18-mer complex composed of two disk-shaped nonamers held together by N-terminal swapping of the pro-peptides. This observation is in contrast with the monomeric pro-form of the other β-PFTs that are receptor-dependent for membrane interaction. The membrane-spanning region of pro-Monalysin is fully buried in the center of the doughnut, suggesting that upon cleavage of pro-peptides, the two disk-shaped nonamers can, and have to, dissociate to leave the transmembrane segments free to deploy and lead to pore formation. In contrast with other toxins, the delivery of 18 subunits at once, nearby the cell surface, may be used to bypass the requirement of receptor-dependent concentration to reach the threshold for oligomerization into the pore-forming complex.
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Affiliation(s)
- Philippe Leone
- From the CNRS, Architecture et Fonction des Macromolécules Biologiques (AFMB), Unité Mixte de Recherche (UMR) 7257, 13288 Marseille, France, the Aix-Marseille Université, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, 13288 Marseille, France
| | - Cecilia Bebeacua
- From the CNRS, Architecture et Fonction des Macromolécules Biologiques (AFMB), Unité Mixte de Recherche (UMR) 7257, 13288 Marseille, France, the Aix-Marseille Université, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, 13288 Marseille, France
| | - Onya Opota
- the Global Health Institute, School of Life Sciences, École Polytechnique Fédérale Lausanne (EPFL), CH-1015 Lausanne, Switzerland, and
| | - Christine Kellenberger
- From the CNRS, Architecture et Fonction des Macromolécules Biologiques (AFMB), Unité Mixte de Recherche (UMR) 7257, 13288 Marseille, France, the Aix-Marseille Université, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, 13288 Marseille, France
| | - Bruno Klaholz
- the Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), CNRS, UMR 7104/INSERM U964/Université de Strasbourg, 1 rue Laurent Fries, 67404 Illkirch, France
| | - Igor Orlov
- the Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), CNRS, UMR 7104/INSERM U964/Université de Strasbourg, 1 rue Laurent Fries, 67404 Illkirch, France
| | - Christian Cambillau
- From the CNRS, Architecture et Fonction des Macromolécules Biologiques (AFMB), Unité Mixte de Recherche (UMR) 7257, 13288 Marseille, France, the Aix-Marseille Université, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, 13288 Marseille, France
| | - Bruno Lemaitre
- the Global Health Institute, School of Life Sciences, École Polytechnique Fédérale Lausanne (EPFL), CH-1015 Lausanne, Switzerland, and
| | - Alain Roussel
- From the CNRS, Architecture et Fonction des Macromolécules Biologiques (AFMB), Unité Mixte de Recherche (UMR) 7257, 13288 Marseille, France, the Aix-Marseille Université, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, 13288 Marseille, France,
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43
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Liao X, Rabideau AE, Pentelute BL. Delivery of antibody mimics into mammalian cells via anthrax toxin protective antigen. Chembiochem 2014; 15:2458-66. [PMID: 25250705 PMCID: PMC4498471 DOI: 10.1002/cbic.201402290] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Indexed: 11/06/2022]
Abstract
Antibody mimics have significant scientific and therapeutic utility for the disruption of protein-protein interactions inside cells; however, their delivery to the cell cytosol remains a major challenge. Here we show that protective antigen (PA), a component of anthrax toxin, efficiently transports commonly used antibody mimics to the cytosol of mammalian cells when conjugated to the N-terminal domain of LF (LFN). In contrast, a cell-penetrating peptide (CPP) was not able to deliver any of these antibody mimics into the cell cytosol. The refolding and binding of a transported tandem monobody to Bcr-Abl (its protein target) in chronic myeloid leukemia cells were confirmed by co-immunoprecipitation. We also observed inhibition of Bcr-Abl kinase activity and induction of apoptosis caused by the monobody. In a separate case, we show disruption of key interactions in the MAPK signaling pathway after PA-mediated delivery of an affibody binder that targets hRaf-1. We show for the first time that PA can deliver bioactive antibody mimics to disrupt intracellular protein-protein interactions. This technology adds a useful tool to expand the applications of these modern agents to the intracellular milieu.
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Affiliation(s)
- Xiaoli Liao
- Department of Chemistry, Massachusetts Institute of Technology77 Massachusetts Avenue 18-596, Cambridge, MA 02193 (USA) E-mail:
| | - Amy E Rabideau
- Department of Chemistry, Massachusetts Institute of Technology77 Massachusetts Avenue 18-596, Cambridge, MA 02193 (USA) E-mail:
| | - Bradley L Pentelute
- Department of Chemistry, Massachusetts Institute of Technology77 Massachusetts Avenue 18-596, Cambridge, MA 02193 (USA) E-mail:
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44
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Sharma O, Collier RJ. Polylysine-mediated translocation of the diphtheria toxin catalytic domain through the anthrax protective antigen pore. Biochemistry 2014; 53:6934-40. [PMID: 25317832 PMCID: PMC4230326 DOI: 10.1021/bi500985v] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The protective antigen (PA) moiety of anthrax toxin forms oligomeric pores in the endosomal membrane, which translocate the effector proteins of the toxin to the cytosol. Effector proteins bind to oligomeric PA via their respective N-terminal domains and undergo N- to C-terminal translocation through the pore. Earlier we reported that a tract of basic amino acids fused to the N-terminus of an unrelated effector protein (the catalytic domain diphtheria toxin, DTA) potentiated that protein to undergo weak PA-dependent translocation. In this study, we varied the location of the tract (N-terminal or C-terminal) and the length of a poly-Lys tract fused to DTA and examined the effects of these variations on PA-dependent translocation into cells and across planar bilayers in vitro. Entry into cells was most efficient with ∼12 Lys residues (K12) fused to the N-terminus but also occurred, albeit 10-100-fold less efficiently, with a C-terminal tract of the same length. Similarly, K12 tracts at either terminus occluded PA pores in planar bilayers, and occlusion was more efficient with the N-terminal tag. We used biotin-labeled K12 constructs in conjunction with streptavidin to show that a biotinyl-K12 tag at either terminus is transiently exposed to the trans compartment of planar bilayers at 20 mV; this partial translocation in vitro was more efficient with an N-terminal tag than a C-terminal tag. Significantly, our studies with polycationic tracts fused to the N- and C-termini of DTA suggest that PA-mediated translocation can occur not only in the N to C direction but also in the C to N direction.
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Affiliation(s)
- Onkar Sharma
- Department of Microbiology and Immunobiology, Harvard Medical School , 77 Avenue Louis Pasteur, Boston, Massachusetts 02115, United States
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45
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Hutt JA, Lovchik JA, Drysdale M, Sherwood RL, Brasel T, Lipscomb MF, Lyons CR. Lethal factor, but not edema factor, is required to cause fatal anthrax in cynomolgus macaques after pulmonary spore challenge. THE AMERICAN JOURNAL OF PATHOLOGY 2014; 184:3205-16. [PMID: 25285720 DOI: 10.1016/j.ajpath.2014.08.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 08/01/2014] [Accepted: 08/21/2014] [Indexed: 11/27/2022]
Abstract
Inhalational anthrax is caused by inhalation of Bacillus anthracis spores. The ability of B. anthracis to cause anthrax is attributed to the plasmid-encoded A/B-type toxins, edema toxin (edema factor and protective antigen) and lethal toxin (lethal factor and protective antigen), and a poly-d-glutamic acid capsule. To better understand the contribution of these toxins to the disease pathophysiology in vivo, we used B. anthracis Ames strain and isogenic toxin deletion mutants derived from the Ames strain to examine the role of lethal toxin and edema toxin after pulmonary spore challenge of cynomolgus macaques. Lethal toxin, but not edema toxin, was required to induce sustained bacteremia and death after pulmonary challenge with spores delivered via bronchoscopy. After intravenous challenge with bacilli to model the systemic phase of infection, lethal toxin contributed to bacterial proliferation and subsequent host death to a greater extent than edema toxin. Deletion of protective antigen resulted in greater loss of virulence after intravenous challenge with bacilli than deletion of lethal toxin or edema toxin alone. These findings are consistent with the ability of anti-protective antigen antibodies to prevent anthrax and suggest that lethal factor is the dominant toxin that contributes to the escape of significant numbers of bacilli from the thoracic cavity to cause anthrax after inhalation challenge with spores.
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Affiliation(s)
- Julie A Hutt
- Lovelace Respiratory Research Institute, Albuquerque, New Mexico; Center for Infectious Disease & Immunity, University of New Mexico Health Science Center, Albuquerque, New Mexico.
| | - Julie A Lovchik
- Center for Infectious Disease & Immunity, University of New Mexico Health Science Center, Albuquerque, New Mexico; Department of Internal Medicine, University of New Mexico Health Science Center, Albuquerque, New Mexico
| | - Melissa Drysdale
- Center for Infectious Disease & Immunity, University of New Mexico Health Science Center, Albuquerque, New Mexico; Department of Internal Medicine, University of New Mexico Health Science Center, Albuquerque, New Mexico
| | | | - Trevor Brasel
- Lovelace Respiratory Research Institute, Albuquerque, New Mexico
| | - Mary F Lipscomb
- Department of Pathology, University of New Mexico Health Science Center, Albuquerque, New Mexico
| | - C Rick Lyons
- Center for Infectious Disease & Immunity, University of New Mexico Health Science Center, Albuquerque, New Mexico; Department of Internal Medicine, University of New Mexico Health Science Center, Albuquerque, New Mexico
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46
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Rabideau AE, Liao X, Pentelute BL. Delivery of mirror image polypeptides into cells. Chem Sci 2014; 6:648-653. [PMID: 28706631 PMCID: PMC5492103 DOI: 10.1039/c4sc02078b] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 09/09/2014] [Indexed: 11/21/2022] Open
Abstract
Mirror image peptides have unique stability and immunogenic properties in mammals, making them attractive agents to investigate. Their properties inside cells have been mostly unexplored because biopolymers are difficult to transport across cellular membranes. Here, we used protective antigen (PA) from anthrax toxin to deliver mirror image polypeptide cargo into the cytosol of mammalian cells when conjugated to the C-terminus of the PA-binding domain of lethal factor, LFN. We found mirror image polypeptides and proteins were translocated as efficiently into cells as their L counterparts. Once in the cytosol, by the use of western blot, we found that d peptides at the C-terminus of LFN were able to achieve higher steady state concentrations when compared to the l-peptide conjugate. With this platform, we delivered a d-peptide MDM2 antagonist to disrupt the p53/MDM2 interaction in cancer cells. For the first time, we show the PA/LFN system is adaptable for the intracellular delivery of mirror image peptides and proteins.
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Affiliation(s)
- Amy E Rabideau
- Department of Chemistry , Massachusetts Institute of Technology , 77 Massachusetts Ave. 18-596 , Cambridge , MA 02139 , USA .
| | - Xiaoli Liao
- Department of Chemistry , Massachusetts Institute of Technology , 77 Massachusetts Ave. 18-596 , Cambridge , MA 02139 , USA .
| | - Bradley L Pentelute
- Department of Chemistry , Massachusetts Institute of Technology , 77 Massachusetts Ave. 18-596 , Cambridge , MA 02139 , USA .
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47
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Lowe DE, Ya J, Glomski IJ. In trans complementation of lethal factor reveal roles in colonization and dissemination in a murine mouse model. PLoS One 2014; 9:e95950. [PMID: 24763227 PMCID: PMC3999102 DOI: 10.1371/journal.pone.0095950] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 04/02/2014] [Indexed: 12/04/2022] Open
Abstract
Lethal factor (LF) is a component of the B. anthracis exotoxin and critical for pathogenesis. The roles of LF in early anthrax pathogenesis, such as colonization and dissemination from the initial site of infection, are poorly understood. In mice models of infection, LF-deficient strains either have altered dissemination patterns or do not colonize, precluding analysis of the role of LF in colonization and dissemination from the portal of entry. Previous reports indicate rabbit and guinea pig models infected with LF-deficient strains have decreased virulence, yet the inability to use bioluminescent imaging techniques to track B. anthracis growth and dissemination in these hosts makes analysis of early pathogenesis challenging. In this study, the roles of LF early in infection were analyzed using bioluminescent signature tagged libraries of B. anthracis with varying ratios of LF-producing and LF-deficient clones. Populations where all clones produced LF and populations where only 40% of clones produce LF were equally virulent. The 40% LF-producing clones trans complimented the LF mutants and permitted them to colonize and disseminate. Decreases of the LF producing strains to 10% or 0.3% of the population led to increased host survival and decreased trans complementation of the LF mutants. A library with 10% LF producing clones could replicate and disseminate, but fewer clones disseminated and the mutant clones were less competitive than wild type. The inoculum with 0.3% LF producing clones could not colonize the host. This strongly suggests that between 10% and 0.3% of the population must produce LF in order to colonize. In total, these findings suggest that a threshold of LF must be produced in order for colonization and dissemination to occur in vivo. These observations suggest that LF has a major role in the early stages of colonization and dissemination.
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Affiliation(s)
- David E. Lowe
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Jason Ya
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Ian J. Glomski
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, Virginia, United States of America
- * E-mail:
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48
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Kaur M, Singh S, Bhatnagar R. Anthrax vaccines: present status and future prospects. Expert Rev Vaccines 2014; 12:955-70. [PMID: 23984963 DOI: 10.1586/14760584.2013.814860] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The management of anthrax remains a top priority among the biowarfare/bioterror agents. It was the Bacillus anthracis spore attack through the US mail system after the September 11, 2001, terrorist attacks in the USA that highlighted the potential of B. anthracis as a bioterrorism agent and the threat posed by its deliberate dissemination. These attacks invigorated the efforts toward understanding the anthrax pathogenesis and development of more comprehensive medical intervention strategies for its containment in case of both natural disease and manmade, accidental or deliberate infection of a non-suspecting population. Currently, efforts are directed toward the development of safe and efficacious vaccines as well as intervention tools for controlling the disease in the advanced fulminant stage when toxemia has already developed. This work presents an overview of the current understanding of anthrax pathogenesis and recent advances made, particularly after 2001, for the successful management of anthrax and outlines future perspectives.
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Affiliation(s)
- Manpreet Kaur
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University, New Delhi 110067, Delhi, India
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49
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Dennis MK, Mogridge J. A protective antigen mutation increases the pH threshold of anthrax toxin receptor 2-mediated pore formation. Biochemistry 2014; 53:2166-71. [PMID: 24641616 PMCID: PMC3985898 DOI: 10.1021/bi5000756] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Anthrax toxin protective antigen
(PA) binds cellular receptors
and self-assembles into oligomeric prepores. A prepore converts to
a protein translocating pore after it has been transported to an endosome
where the low pH triggers formation of a membrane-spanning β-barrel
channel. Formation of this channel occurs after some PA–receptor
contacts are broken to allow pore formation, while others are retained
to preserve receptor association. The interaction between PA and anthrax
toxin receptor 1 (ANTXR1) is weaker than its interaction with ANTXR2
such that the pH threshold of ANTXR1-mediated pore formation is higher
by 1 pH unit. Here we examine receptor-specific differences in toxin
binding and pore formation by mutating PA residue G342 that selectively
abuts ANTXR2. Mutation of G342 to valine, leucine, isoleucine, or
tryptophan increased the amount of PA bound to ANTXR1-expressing cells
and decreased the amount of PA bound to ANTXR2-expressing cells. The
more conservative G342A mutation did not affect the level of binding
to ANTXR2, but ANTXR2-bound PA-G342A prepores exhibited a pH threshold
higher than that of wild-type prepores. Mixtures of wild-type PA and
PA-G342A were functional in toxicity assays, and the pH threshold
of ANTXR2-mediated pore formation was dictated by the relative amounts
of the two proteins in the hetero-oligomers. These results suggest
that PA subunits within an oligomer do not have to be triggered simultaneously
for a productive membrane insertion event to occur.
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Affiliation(s)
- Melissa K Dennis
- Department of Laboratory Medicine and Pathobiology, University of Toronto , Toronto, Ontario M5S 1A8, Canada
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50
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Simon NC, Barbieri JT. Bacillus cereus Certhrax ADP-ribosylates vinculin to disrupt focal adhesion complexes and cell adhesion. J Biol Chem 2014; 289:10650-10659. [PMID: 24573681 DOI: 10.1074/jbc.m113.500710] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bacillus cereus is often associated with mild to moderate gastroenteritis; however, some recent isolates cause inhalational anthrax-like diseases and death. These potential emerging human pathogens express multiple virulence factors. B. cereus strain G9241 expresses anthrax toxin, several polysaccharide capsules, and the novel ADP-ribosyltransferase, Certhrax. In this study, we show that Certhrax ADP-ribosylates Arg-433 of vinculin, a protein that coordinates actin cytoskeleton and extracellular matrix interactions. ADP-ribosylation of vinculin disrupted focal adhesion complexes and redistributed vinculin to the cytoplasm. Exogenous vinculin rescued these phenotypes. This provides a mechanism for strain G9241 to breach host barrier defenses and promote bacterial growth and spread. Certhrax is the first bacterial toxin to add a post-translational modification to vinculin to disrupt the actin cytoskeleton.
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Affiliation(s)
- Nathan C Simon
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Joseph T Barbieri
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226.
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