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Boss L, Kędzierska B. Bacterial Toxin-Antitoxin Systems' Cross-Interactions-Implications for Practical Use in Medicine and Biotechnology. Toxins (Basel) 2023; 15:380. [PMID: 37368681 DOI: 10.3390/toxins15060380] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2023] [Revised: 05/30/2023] [Accepted: 06/02/2023] [Indexed: 06/29/2023] Open
Abstract
Toxin-antitoxin (TA) systems are widely present in bacterial genomes. They consist of stable toxins and unstable antitoxins that are classified into distinct groups based on their structure and biological activity. TA systems are mostly related to mobile genetic elements and can be easily acquired through horizontal gene transfer. The ubiquity of different homologous and non-homologous TA systems within a single bacterial genome raises questions about their potential cross-interactions. Unspecific cross-talk between toxins and antitoxins of non-cognate modules may unbalance the ratio of the interacting partners and cause an increase in the free toxin level, which can be deleterious to the cell. Moreover, TA systems can be involved in broadly understood molecular networks as transcriptional regulators of other genes' expression or modulators of cellular mRNA stability. In nature, multiple copies of highly similar or identical TA systems are rather infrequent and probably represent a transition stage during evolution to complete insulation or decay of one of them. Nevertheless, several types of cross-interactions have been described in the literature to date. This implies a question of the possibility and consequences of the TA system cross-interactions, especially in the context of the practical application of the TA-based biotechnological and medical strategies, in which such TAs will be used outside their natural context, will be artificially introduced and induced in the new hosts. Thus, in this review, we discuss the prospective challenges of system cross-talks in the safety and effectiveness of TA system usage.
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Affiliation(s)
- Lidia Boss
- Department of Bacterial Molecular Genetics, Faculty of Biology, University of Gdańsk, 80-309 Gdańsk, Poland
| | - Barbara Kędzierska
- Department of Bacterial Molecular Genetics, Faculty of Biology, University of Gdańsk, 80-309 Gdańsk, Poland
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Abstract
Toxin-antitoxin systems are widespread in bacterial genomes. They are usually composed of two elements: a toxin that inhibits an essential cellular process and an antitoxin that counteracts its cognate toxin. In the past decade, a number of new toxin-antitoxin systems have been described, bringing new growth inhibition mechanisms to light as well as novel modes of antitoxicity. However, recent advances in the field profoundly questioned the role of these systems in bacterial physiology, stress response and antimicrobial persistence. This shifted the paradigm of the functions of toxin-antitoxin systems to roles related to interactions between hosts and their mobile genetic elements, such as viral defence or plasmid stability. In this Review, we summarize the recent progress in understanding the biology and evolution of these small genetic elements, and discuss how genomic conflicts could shape the diversification of toxin-antitoxin systems.
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Srivastava A, Pati S, Kaushik H, Singh S, Garg LC. Toxin-antitoxin systems and their medical applications: current status and future perspective. Appl Microbiol Biotechnol 2021; 105:1803-1821. [PMID: 33582835 DOI: 10.1007/s00253-021-11134-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2020] [Revised: 01/13/2021] [Accepted: 01/20/2021] [Indexed: 12/11/2022]
Abstract
Almost all bacteria synthesize two types of toxins-one for its survival by regulating different cellular processes and another as a strategy to interact with host cells for pathogenesis. Usually, "bacterial toxins" are contemplated as virulence factors that harm the host organism. However, toxins produced by bacteria, as a survival strategy against the host, also hamper its cellular processes. To overcome this, the bacteria have evolved with the production of a molecule, referred to as antitoxin, to negate the deleterious effect of the toxin against itself. The toxin and antitoxins are encoded by a two-component toxin-antitoxin (TA) system. The antitoxin, a protein or RNA, sequesters the toxins of the TA system for neutralization within the bacterial cell. In this review, we have described different TA systems of bacteria and their potential medical and biotechnological applications. It is of interest to note that while bacterial toxin-antitoxin systems have been well studied, the TA system in unicellular eukaryotes, though predicted by the investigators, have never been paid the desired attention. In the present review, we have also touched upon the TA system of eukaryotes identified to date. KEY POINTS: Bacterial toxins harm the host and also affect the bacterial cellular processes. The antitoxin produced by bacteria protect it from the toxin's harmful effects. The toxin-antitoxin systems can be targeted for various medical applications.
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Affiliation(s)
- Akriti Srivastava
- Department of Life Sciences, Shiv Nadar University, Gautam Buddha Nagar, Greater Noida, Uttar Pradesh, 201314, India
| | - Soumya Pati
- Department of Life Sciences, Shiv Nadar University, Gautam Buddha Nagar, Greater Noida, Uttar Pradesh, 201314, India
| | - Himani Kaushik
- Gene Regulation Laboratory, National Institute of Immunology, New Delhi, 110067, India
| | - Shailja Singh
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, 110067, India.
| | - Lalit C Garg
- Gene Regulation Laboratory, National Institute of Immunology, New Delhi, 110067, India.
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Targeting Type II Toxin-Antitoxin Systems as Antibacterial Strategies. Toxins (Basel) 2020; 12:toxins12090568. [PMID: 32899634 PMCID: PMC7551001 DOI: 10.3390/toxins12090568] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 08/31/2020] [Accepted: 08/31/2020] [Indexed: 12/13/2022] Open
Abstract
The identification of novel targets for antimicrobial agents is crucial for combating infectious diseases caused by evolving bacterial pathogens. Components of bacterial toxin–antitoxin (TA) systems have been recognized as promising therapeutic targets. These widespread genetic modules are usually composed of two genes that encode a toxic protein targeting an essential cellular process and an antitoxin that counteracts the activity of the toxin. Uncontrolled toxin expression may elicit a bactericidal effect, so they may be considered “intracellular molecular bombs” that can lead to elimination of their host cells. Based on the molecular nature of antitoxins and their mode of interaction with toxins, TA systems have been classified into six groups. The most prevalent are type II TA systems. Due to their ubiquity among clinical isolates of pathogenic bacteria and the essential processes targeted, they are promising candidates for the development of novel antimicrobial strategies. In this review, we describe the distribution of type II TA systems in clinically relevant human pathogens, examine how these systems could be developed as the targets for novel antibacterials, and discuss possible undesirable effects of such therapeutic intervention, such as the induction of persister cells, biofilm formation and toxicity to eukaryotic cells.
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A Systematic Overview of Type II and III Toxin-Antitoxin Systems with a Focus on Druggability. Toxins (Basel) 2018; 10:toxins10120515. [PMID: 30518070 PMCID: PMC6315513 DOI: 10.3390/toxins10120515] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 11/29/2018] [Accepted: 11/30/2018] [Indexed: 02/07/2023] Open
Abstract
Toxin-antitoxin (TA) systems are known to play various roles in physiological processes, such as gene regulation, growth arrest and survival, in bacteria exposed to environmental stress. Type II TA systems comprise natural complexes consisting of protein toxins and antitoxins. Each toxin and antitoxin participates in distinct regulatory mechanisms depending on the type of TA system. Recently, peptides designed by mimicking the interfaces between TA complexes showed its potential to activate the activity of toxin by competing its binding counterparts. Type II TA systems occur more often in pathogenic bacteria than in their nonpathogenic kin. Therefore, they can be possible drug targets, because of their high abundance in some pathogenic bacteria, such as Mycobacterium tuberculosis. In addition, recent bioinformatic analyses have shown that type III TA systems are highly abundant in the intestinal microbiota, and recent clinical studies have shown that the intestinal microbiota is linked to inflammatory diseases, obesity and even several types of cancer. We therefore focused on exploring the putative relationship between intestinal microbiota-related human diseases and type III TA systems. In this paper, we review and discuss the development of possible druggable materials based on the mechanism of type II and type III TA system.
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Shapira S, Shapira A, Kazanov D, Hevroni G, Kraus S, Arber N. Selective eradication of cancer cells by delivery of adenovirus-based toxins. Oncotarget 2018; 8:38581-38591. [PMID: 28445136 PMCID: PMC5503555 DOI: 10.18632/oncotarget.16934] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 03/13/2017] [Indexed: 01/17/2023] Open
Abstract
Background and objective KRAS mutation is an early event in colorectal cancer carcinogenesis. We previously reported that a recombinant adenovirus, carrying a pro-apoptotic gene (PUMA) under the regulation of Ets/AP1 (RAS-responsive elements) suppressed the growth of cancer cells harboring hyperactive KRAS. We propose to exploit the hyperactive RAS pathway, rather than to inhibit it as was previously tried and failed repeatedly. We aim to improve efficacy by substituting PUMA with a more potent toxin, the bacterial MazF-MazE toxin-antitoxin system, under a very tight regulation. Results A massive cell death, in a dose-dependent manner, reaching 73% at MOI 10 was seen in KRAS cells as compared to 22% in WT cells. Increase expression of MazE (the anti-toxin) protected normal cells from any possible internal or external leakage of the system and confirmed the selectivity, specificity and safety of the targeting system. Considerable tumor shrinkage (61%) was demonstrated in vivo following MazEF-encoding adenovirus treatment without any side effects. Design Efficient vectors for cancer-directed gene delivery were constructed; “pAdEasy-Py4-SV40mP-mCherry-MazF”“pAdEasy-Py4-SV40mP-mCherry-MazF-IRES-TetR-CMVmp-MazE-IRES-EGFP“,“pAdEasy-ΔPy4-SV40mP-mCherry-MazF-IRES-TetR-CMVmp-MazE-IRES-EGFP “and “pAdEasy-mCherry”. Virus particles were produced and their potency was tested. Cell death was measured qualitatively by using the fluorescent microscopy and colony formation assay, and was quantified by MTT. FACS analysis using annexin V and RedDot2 dyes was performed for measuring apoptotic and dead cells, respectively. In vivo tumor formation was measured in a xenograft model. Conclusions A proof of concept for a novel cancer safe and effective gene therapy exploiting an aberrant hyperactive pathway is achievable.
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Affiliation(s)
- Shiran Shapira
- Laboratory of Molecular Biology, The Integrated Cancer Prevention Center, Tel Aviv Sourasky Medical Center, Affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Tel-Aviv, Israel
| | - Assaf Shapira
- Department of Molecular Microbiology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel-Aviv, Israel
| | - Diana Kazanov
- Laboratory of Molecular Biology, The Integrated Cancer Prevention Center, Tel Aviv Sourasky Medical Center, Affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Tel-Aviv, Israel
| | - Gil Hevroni
- Laboratory of Molecular Biology, The Integrated Cancer Prevention Center, Tel Aviv Sourasky Medical Center, Affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Tel-Aviv, Israel
| | - Sarah Kraus
- Laboratory of Molecular Biology, The Integrated Cancer Prevention Center, Tel Aviv Sourasky Medical Center, Affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Tel-Aviv, Israel
| | - Nadir Arber
- Laboratory of Molecular Biology, The Integrated Cancer Prevention Center, Tel Aviv Sourasky Medical Center, Affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Tel-Aviv, Israel
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Klimina KM, Poluektova EU, Danilenko VN. Bacterial toxin–antitoxin systems: Properties, functional significance, and possibility of use (Review). APPL BIOCHEM MICRO+ 2017. [DOI: 10.1134/s0003683817050076] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Jahanban-Esfahlan R, Seidi K, Zarghami N. Tumor vascular infarction: prospects and challenges. Int J Hematol 2017; 105:244-256. [DOI: 10.1007/s12185-016-2171-3] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Revised: 12/19/2016] [Accepted: 12/21/2016] [Indexed: 12/21/2022]
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Baldacci-Cresp F, Houbaert A, Metuor Dabire A, Mol A, Monteyne D, El Jaziri M, Van Melderen L, Baucher M. Escherichia colimazEF Toxin-Antitoxin System as a Tool to Target Cell Ablation in Plants. J Mol Microbiol Biotechnol 2016; 26:277-83. [PMID: 27245477 DOI: 10.1159/000446112] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 03/08/2016] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS The Escherichia coli MazF is an endoribonuclease that cleaves mRNA at ACA sequences, thereby triggering inhibition of protein synthesis. The aim of this study is to evaluate the efficiency of the mazEF toxin-antitoxin system in plants to develop biotechnological tools for targeted cell ablation. METHODS A double transformation strategy, combining expression of the mazE antitoxin gene under the control of the CaMV 35S promoter, reported to drive expression in all plant cells except within the tapetum, together with the expression of the mazF gene under the control of the TA29 tapetum-specific promoter in transgenic tobacco, was applied. RESULTS No transgenic TA29-mazF line could be regenerated, suggesting that the TA29 promoter is not strictly tapetum specific and that MazF is toxic for plant cells. The regenerated 35S-mazE/TA29-mazF double-transformed lines gave a unique phenotype where the tapetal cell layer was necrosed resulting in the absence of pollen. CONCLUSION These results show that the E. colimazEF system can be used to induce death of specific plant cell types and can provide a new tool to plant cell ablation.
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Affiliation(s)
- Fabien Baldacci-Cresp
- Laboratoire de Biotechnologie Vx00E9;gx00E9;tale, Universitx00E9; libre de Bruxelles (ULB), Gosselies, Belgium
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Chan WT, Espinosa M, Yeo CC. Keeping the Wolves at Bay: Antitoxins of Prokaryotic Type II Toxin-Antitoxin Systems. Front Mol Biosci 2016; 3:9. [PMID: 27047942 PMCID: PMC4803016 DOI: 10.3389/fmolb.2016.00009] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 03/04/2016] [Indexed: 12/21/2022] Open
Abstract
In their initial stages of discovery, prokaryotic toxin-antitoxin (TA) systems were confined to bacterial plasmids where they function to mediate the maintenance and stability of usually low- to medium-copy number plasmids through the post-segregational killing of any plasmid-free daughter cells that developed. Their eventual discovery as nearly ubiquitous and repetitive elements in bacterial chromosomes led to a wealth of knowledge and scientific debate as to their diversity and functionality in the prokaryotic lifestyle. Currently categorized into six different types designated types I–VI, type II TA systems are the best characterized. These generally comprised of two genes encoding a proteic toxin and its corresponding proteic antitoxin, respectively. Under normal growth conditions, the stable toxin is prevented from exerting its lethal effect through tight binding with the less stable antitoxin partner, forming a non-lethal TA protein complex. Besides binding with its cognate toxin, the antitoxin also plays a role in regulating the expression of the type II TA operon by binding to the operator site, thereby repressing transcription from the TA promoter. In most cases, full repression is observed in the presence of the TA complex as binding of the toxin enhances the DNA binding capability of the antitoxin. TA systems have been implicated in a gamut of prokaryotic cellular functions such as being mediators of programmed cell death as well as persistence or dormancy, biofilm formation, as defensive weapons against bacteriophage infections and as virulence factors in pathogenic bacteria. It is thus apparent that these antitoxins, as DNA-binding proteins, play an essential role in modulating the prokaryotic lifestyle whilst at the same time preventing the lethal action of the toxins under normal growth conditions, i.e., keeping the proverbial wolves at bay. In this review, we will cover the diversity and characteristics of various type II TA antitoxins. We shall also look into some interesting deviations from the canonical type II TA systems such as tripartite TA systems where the regulatory role is played by a third party protein and not the antitoxin, and a unique TA system encoding a single protein with both toxin as well as antitoxin domains.
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Affiliation(s)
- Wai Ting Chan
- Molecular Microbiology and Infection Biology, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas Madrid, Spain
| | - Manuel Espinosa
- Molecular Microbiology and Infection Biology, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas Madrid, Spain
| | - Chew Chieng Yeo
- Faculty of Medicine, Biomedical Research Centre, Universiti Sultan Zainal Abidin Kuala Terengganu, Malaysia
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Chan WT, Balsa D, Espinosa M. One cannot rule them all: Are bacterial toxins-antitoxins druggable? FEMS Microbiol Rev 2015; 39:522-40. [PMID: 25796610 PMCID: PMC4487406 DOI: 10.1093/femsre/fuv002] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/02/2015] [Indexed: 01/31/2023] Open
Abstract
Type II (proteic) toxin–antitoxin (TA) operons are widely spread in bacteria and archaea. They are organized as operons in which, usually, the antitoxin gene precedes the cognate toxin gene. The antitoxin generally acts as a transcriptional self-repressor, whereas the toxin acts as a co-repressor, both proteins constituting a harmless complex. When bacteria encounter a stressful environment, TAs are triggered. The antitoxin protein is unstable and will be degraded by host proteases, releasing the free toxin to halt essential processes. The result is a cessation of cell growth or even death. Because of their ubiquity and the essential processes targeted, TAs have been proposed as good candidates for development of novel antimicrobials. We discuss here the possible druggability of TAs as antivirals and antibacterials, with focus on the potentials and the challenges that their use may find in the ‘real’ world. We present strategies to develop TAs as antibacterials in view of novel technologies, such as the use of very small molecules (fragments) as inhibitors of protein–protein interactions. Appropriate fragments could disrupt the T:A interfaces leading to the release of the targeted TA pair. Possible ways of delivery and formulation of Tas are also discussed. We consider various approaches to develop the toxins of the type II family as possible candidates to drug discovery; druggability of toxins-antitoxins could be possible as antivirals. As antibacterials, they might be considered as druggable but delivery and formulation may not be simple so far.
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Affiliation(s)
- Wai Ting Chan
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu, 9, 28006-Madrid, Spain
| | - Dolors Balsa
- Immunology & Vaccines, Laboratorios LETI, Gran Via de les Corts Catalanes 184. 08034-Barcelona, Spain
| | - Manuel Espinosa
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu, 9, 28006-Madrid, Spain
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