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Wang S, Fang R, Wang H, Li X, Xing J, Li Z, Song N. The role of transcriptional regulators in metal ion homeostasis of Mycobacterium tuberculosis. Front Cell Infect Microbiol 2024; 14:1360880. [PMID: 38529472 PMCID: PMC10961391 DOI: 10.3389/fcimb.2024.1360880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2023] [Accepted: 02/27/2024] [Indexed: 03/27/2024] Open
Abstract
Metal ions are essential trace elements for all living organisms and play critical catalytic, structural, and allosteric roles in many enzymes and transcription factors. Mycobacterium tuberculosis (MTB), as an intracellular pathogen, is usually found in host macrophages, where the bacterium can survive and replicate. One of the reasons why Tuberculosis (TB) is so difficult to eradicate is the continuous adaptation of its pathogen. It is capable of adapting to a wide range of harsh environmental stresses, including metal ion toxicity in the host macrophages. Altering the concentration of metal ions is the common host strategy to limit MTB replication and persistence. This review mainly focuses on transcriptional regulatory proteins in MTB that are involved in the regulation of metal ions such as iron, copper and zinc. The aim is to offer novel insights and strategies for screening targets for TB treatment, as well as for the development and design of new therapeutic interventions.
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Affiliation(s)
- Shuxian Wang
- Key Laboratory of Respiratory Tract Pathogens and Drug Therapy, School of Life Science and Technology, Shandong Second Medical University, Weifang, China
| | - Ren Fang
- Key Laboratory of Respiratory Tract Pathogens and Drug Therapy, School of Life Science and Technology, Shandong Second Medical University, Weifang, China
| | - Hui Wang
- Key Laboratory of Respiratory Tract Pathogens and Drug Therapy, School of Life Science and Technology, Shandong Second Medical University, Weifang, China
| | - Xiaotian Li
- Key Laboratory of Respiratory Tract Pathogens and Drug Therapy, School of Life Science and Technology, Shandong Second Medical University, Weifang, China
| | - Jiayin Xing
- Key Laboratory of Respiratory Tract Pathogens and Drug Therapy, School of Life Science and Technology, Shandong Second Medical University, Weifang, China
| | - Zhaoli Li
- Drug Innovation Research Center, SAFE Pharmaceutical Technology Co. Ltd., Beijing, China
| | - Ningning Song
- Key Laboratory of Respiratory Tract Pathogens and Drug Therapy, School of Life Science and Technology, Shandong Second Medical University, Weifang, China
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2
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Kumari R S, Sethi G, Krishna R. Development of multi-epitope based subunit vaccine against Mycobacterium Tuberculosis using immunoinformatics approach. J Biomol Struct Dyn 2023:1-20. [PMID: 37880982 DOI: 10.1080/07391102.2023.2270065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 10/07/2023] [Indexed: 10/27/2023]
Abstract
The etiological agent of tuberculosis (TB), Mycobacterium tuberculosis, is a deadly pathogen that adapts to thrive within the host. Since 2020, the COVID-19 pandemic has had colossal health, societal, and economic consequences, which have affected the reporting of new incidences and mortality cases of TB. As per the WHO 2022 report, 10.6 million people were diagnosed with TB, and 1.6 million died worldwide. The increase in resistant strains of tuberculosis is making it more burdensome to reach the End TB strategy. A reliable and efficient TB vaccine that may avert both primary infection and recurrence of latent TB in adults and adolescents is of the utmost importance. In this study, we used computational techniques to predict the ability of HLA molecules to display epitopes for six TB proteins (PPE68, PE_PGRS17, EspC, LDT4, RpfD, and RpfC) to design the multi-epitope subunit vaccine. From the aimed proteins, the potential B-cell, helper T lymphocyte (HTL), and cytotoxic T lymphocyte (CTL) epitopes were predicted and linked together with LPA adjuvant, and the vaccine was designed. The vaccine's physicochemical analysis demonstrates that it is non-allergic, non-toxic, and antigenic. Then, the vaccine structure was predicted, improved, and verified to yield the optimal structure. The developed vaccine's binding mechanism with distinct immunogenic receptors (Tlr2 and MHC-II) was assessed utilizing molecular docking. The molecular dynamic simulation and MMPBSA analysis were performed to comprehend the complexes' dynamics and stability. The immune simulation was utilized to anticipate the vaccine's immunogenic attributes. In silico cloning was employed to demonstrate the efficient expression of the designed vaccine in E. coli as a host. Moreover, in vitro and in vivo animal testing is required to determine the efficacy of the in silico developed vaccine.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Savita Kumari R
- Department of Bioinformatics, Pondicherry University, Puducherry, India
| | - Guneswar Sethi
- Department of Bioinformatics, Pondicherry University, Puducherry, India
- Department of Predictive Toxicology, Korea Institute of Toxicology (KIT), Republic of Korea
| | - Ramadas Krishna
- Department of Bioinformatics, Pondicherry University, Puducherry, India
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3
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Li X, Chen L, Wang Y, Guo X, He ZG. Zinc excess impairs Mycobacterium bovis growth through triggering a Zur-IdeR-iron homeostasis signal pathway. Microbiol Spectr 2023; 11:e0106923. [PMID: 37668384 PMCID: PMC10580935 DOI: 10.1128/spectrum.01069-23] [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: 03/10/2023] [Accepted: 07/15/2023] [Indexed: 09/06/2023] Open
Abstract
Zinc excess is toxic to bacteria and, thus, represents an important innate defense mechanism of host cells, especially against mycobacterial infections. However, the signaling pathway triggered by zinc excess and its relationship with iron homeostasis remain poorly understood in mycobacteria. Here, we characterize a novel Zur-IdeR-iron homeostasis signaling pathway that modulates the growth of Mycobacterium bovis under zinc toxicity. We found that the regulator Zur interacts with the iron-homeostasis regulator IdeR, enhancing the DNA-binding ability of IdeR. Excess zinc disrupts this interaction and represses ideR transcription through Zur, which promotes the expression of iron uptake genes and leads to the accumulation of intracellular iron in M. bovis. The elevated iron levels lower the bacterial survival ability under excess zinc stress. Consistently, deleting zur hinders intracellular iron accumulation of M. bovis and enhances bacterial growth under stress, while silencing ideR impairs the growth of the wild-type and zur-deleted strains under the same conditions. Interestingly, both Zur and IdeR are conserved in bacteria facing zinc toxicity. Overall, our work uncovers a novel antimicrobial signal pathway whereby zinc excess disrupts iron homeostasis, which may deepen our understanding of the crosstalk mechanism between iron and zinc homeostasis in bacteria.IMPORTANCEAs a catalytic and structural cofactor of proteins, zinc is essential for almost all living organisms. However, zinc excess is toxic and represents a vital innate immunity strategy of macrophages to combat intracellular pathogens, especially against mycobacterial pathogens such as Mycobacterium tuberculosis, the causative agent of tuberculosis. Here, we first characterize an antibacterial signaling pathway of zinc excess and its relationship with iron homeostasis in M. bovis. We found that excess zinc inhibits the transcription of ideR and its DNA-binding activity through Zur, which, in turn, promotes the expression of iron uptake genes, causes intracellular iron accumulation, and finally impairs the bacterial growth. This study reveals the existence of the Zur-IdeR-iron homeostasis pathway triggered by zinc excess in M. bovis, which will shed light on the crosstalk mechanisms between zinc and iron homeostasis in bacteria and the antimicrobial mechanisms of host-mediated zinc toxicity.
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Affiliation(s)
- Xiaohui Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Research Center for Microbial and Enzyme Engineering Technology, College of Life Science and Technology, Guangxi University, Nanning, Guangxi, China
| | - Liu Chen
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Yuankun Wang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Research Center for Microbial and Enzyme Engineering Technology, College of Life Science and Technology, Guangxi University, Nanning, Guangxi, China
| | - Xiao Guo
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Research Center for Microbial and Enzyme Engineering Technology, College of Life Science and Technology, Guangxi University, Nanning, Guangxi, China
| | - Zheng-Guo He
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Research Center for Microbial and Enzyme Engineering Technology, College of Life Science and Technology, Guangxi University, Nanning, Guangxi, China
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4
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Famelis N, Geibel S, van Tol D. Mycobacterial type VII secretion systems. Biol Chem 2023; 0:hsz-2022-0350. [PMID: 37276364 DOI: 10.1515/hsz-2022-0350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Accepted: 05/22/2023] [Indexed: 06/07/2023]
Abstract
Mycobacteria, such as the pathogen M. tuberculosis, utilize up to five paralogous type VII secretion systems to transport proteins across their cell envelope. Since these proteins associate in pairs that depend on each other for transport to a different extent, the secretion pathway to the bacterial surface remained challenging to address. Structural characterization of the inner-membrane embedded secretion machineries along with recent advances on the substrates' co-dependencies for transport allow for the first time more detailed and testable models for secretion.
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Affiliation(s)
- Nikolaos Famelis
- Institute for Molecular Infection Biology, Julius Maximilian University of Würzburg, D-97080 Würzburg, Germany
| | - Sebastian Geibel
- Leiden Institute of Chemistry, Leiden University, NL-2333 CC Leiden, Netherlands
| | - Daan van Tol
- Leiden Institute of Chemistry, Leiden University, NL-2333 CC Leiden, Netherlands
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5
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The Antibacterial Type VII Secretion System of Bacillus subtilis: Structure and Interactions of the Pseudokinase YukC/EssB. mBio 2022; 13:e0013422. [PMID: 36154281 PMCID: PMC9600267 DOI: 10.1128/mbio.00134-22] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Type VIIb secretion systems (T7SSb) were recently proposed to mediate different aspects of Firmicutes physiology, including bacterial pathogenicity and competition. However, their architecture and mechanism of action remain largely obscure. Here, we present a detailed analysis of the T7SSb-mediated bacterial competition in Bacillus subtilis, using the effector YxiD as a model for the LXG secreted toxins. By systematically investigating protein-protein interactions, we reveal that the membrane subunit YukC contacts all T7SSb components, including the WXG100 substrate YukE and the LXG effector YxiD. YukC’s crystal structure shows unique features, suggesting an intrinsic flexibility that is required for T7SSb antibacterial activity. Overall, our results shed light on the role and molecular organization of the T7SSb and demonstrate the potential of B. subtilis as a model system for extensive structure-function studies of these secretion machineries.
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Gauthier DT, Doss JH, LaGatta M, Gupta T, Karls RK, Quinn FD. Genomic Degeneration and Reduction in the Fish Pathogen Mycobacterium shottsii. Microbiol Spectr 2022; 10:e0115821. [PMID: 35579461 PMCID: PMC9241763 DOI: 10.1128/spectrum.01158-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 04/26/2022] [Indexed: 01/17/2023] Open
Abstract
Mycobacterium shottsii is a dysgonic, nonpigmented mycobacterium originally isolated from diseased striped bass (Morone saxatilis) in the Chesapeake Bay, USA. Genomic analysis reveals that M. shottsii is a Mycobacterium ulcerans/Mycobacterium marinum clade (MuMC) member, but unlike the superficially similar M. pseudoshottsii, also isolated from striped bass, it is not an M. ulcerans ecovar, instead belonging to a transitional group of strains basal to proposed "Aronson" and "M" lineages. Although phylogenetically distinct from the human pathogen M. ulcerans, the M. shottsii genome shows parallel but nonhomologous genomic degeneration, including massive accumulation of pseudogenes accompanied by proliferation of unique insertion sequences (ISMysh01, ISMysh03), large-scale deletions, and genomic reorganization relative to typical M. marinum strains. Coupled with its observed ecological characteristics and loss of chromogenicity, the genomic structure of M. shottsii is suggestive of evolution toward a state of obligate pathogenicity, as observed for other Mycobacterium spp., including M. ulcerans, M. tuberculosis, and M. leprae. IMPORTANCE Morone saxatilis (striped bass) is an ecologically and economically important finfish species on the United States east coast. Mycobacterium shottsii and Mycobacterium pseudoshottsii were originally described in the early 2000s as novel species from outbreaks of visceral and dermal mycobacteriosis in this species. Biochemical and genetic characterization place these species within the Mycobacterium ulcerans/M. marinum clade (MuMC), and M. pseudoshottsii has been proposed as an ecovar of M. ulcerans. Here, we describe the complete genome of M. shottsii, demonstrating that it is clearly not an M. ulcerans ecovar; however, it has undergone parallel genomic modification suggestive of a transition to obligate pathogenicity. As in M. ulcerans, the M. shottsii genome demonstrates widespread pseudogene formation driven by proliferation of insertion sequences, as well as genomic reorganization. This work clarifies the phylogenetic position of M. shottsii relative to other MuMC members and provides insight into processes shaping its genomic structure.
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Affiliation(s)
- D. T. Gauthier
- Department of Biological Sciences, Old Dominion University, Norfolk, Virginia, USA
| | - J. H. Doss
- Department of Biological Sciences, Old Dominion University, Norfolk, Virginia, USA
| | - M. LaGatta
- Department of Infectious Diseases, University of Georgia, Athens, Georgia, USA
- Pathens Incorporated, Athens, Georgia, USA
| | - T. Gupta
- Department of Infectious Diseases, University of Georgia, Athens, Georgia, USA
| | - R. K. Karls
- Department of Infectious Diseases, University of Georgia, Athens, Georgia, USA
- Pathens Incorporated, Athens, Georgia, USA
| | - F. D. Quinn
- Department of Infectious Diseases, University of Georgia, Athens, Georgia, USA
- Pathens Incorporated, Athens, Georgia, USA
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7
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Multiple genetic paths including massive gene amplification allow Mycobacterium tuberculosis to overcome loss of ESX-3 secretion system substrates. Proc Natl Acad Sci U S A 2022; 119:2112608119. [PMID: 35193958 PMCID: PMC8872769 DOI: 10.1073/pnas.2112608119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/18/2021] [Indexed: 01/18/2023] Open
Abstract
The Mycobacterium tuberculosis (Mtb) ESX-3 type VII secretion system plays a critical role in iron acquisition. Infection of mice with highly attenuated Mtb deletion mutants lacking esxG or esxH, genes encoding key ESX-3 substrates, unexpectedly yielded suppressor mutants with restored capacity to grow in vivo and in vitro in the absence of iron supplementation. Whole-genome sequencing identified two mechanisms of suppression, the disruption of a transcriptional repressor that regulates expression of an ESX-3 paralogous region encoding EsxR and EsxS, and a massive 38- to 60-fold gene amplification of this same region. These data are significant because they reveal a previously unrecognized iron acquisition regulon and inform mechanisms of Mtb chromosome evolution. Mycobacterium tuberculosis (Mtb) possesses five type VII secretion systems (T7SS), virulence determinants that include the secretion apparatus and associated secretion substrates. Mtb strains deleted for the genes encoding substrates of the ESX-3 T7SS, esxG or esxH, require iron supplementation for in vitro growth and are highly attenuated in vivo. In a subset of infected mice, suppressor mutants of esxG or esxH deletions were isolated, which enabled growth to high titers or restored virulence. Suppression was conferred by mechanisms that cause overexpression of an ESX-3 paralogous region that lacks genes for the secretion apparatus but encodes EsxR and EsxS, apparent ESX-3 orphan substrates that functionally compensate for the lack of EsxG or EsxH. The mechanisms include the disruption of a transcriptional repressor and a massive 38- to 60-fold gene amplification. These data identify an iron acquisition regulon, provide insight into T7SS, and reveal a mechanism of Mtb chromosome evolution involving “accordion-type” amplification.
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8
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Jia P, Zhang Y, Xu J, Zhu M, Peng S, Zhang Y, Zhao J, Li X, Mi K, Yan D, Wang Y, Yu L, Lu Y, Shi H, Cen S. IMB-BZ as an Inhibitor Targeting ESX-1 Secretion System to Control Mycobacterial Infection. J Infect Dis 2021; 225:608-616. [PMID: 34558604 DOI: 10.1093/infdis/jiab486] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 09/23/2021] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Resistance to anti-tuberculosis (TB) drug is a major issue in TB control, and demands the discovery of new drugs targeting virulence factor ESX-1. METHODS We first established a high-throughput screen (HTS) assay for the discovery of ESX-1 secretion inhibitors. The positive hits were then evaluated for the potency of diminishing the survival of virulent mycobacterium and reducing bacterial virulence. We further investigated the probability of inducing drug-resistance and the underlying mechanism using M-PFC. RESULTS A robust HTS assay was developed to identify small molecules that inhibit ESX-1 secretion without impairing bacterial growth in vitro. A hit named IMB-BZ specifically inhibits the secretion of CFP-10 and reduces virulence in an ESX-1-dependent manner, therefore resulting in significant reduction in intracellular and in vivo survival of mycobacteria. Blocking the CFP-10-EccCb1 interaction directly or indirectly underlies the inhibitory effect of IMB-BZ on the secretion of CFP-10. Importantly, our finding shows that the ESX-1 inhibitors pose low risk of drug resistance development by mycobacteria in vitro as compared with traditional anti-TB drug, and exhibit high potency against chronic mycobacterial infection. CONCLUSION Targeting ESX-1 may lead to the development of novel therapeutics for tuberculosis. IMB-BZ holds the potential for future development into a new anti-TB drug.
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Affiliation(s)
- Pingping Jia
- Department of Clinical Nutrition, Department of Gastrointestinal Surgery, Beijing Shijitan Hospital, Capital Medical University, Beijing, 100038, China; Department of Oncology, Capital Medical University, Beijing, 100038, China.,Institute of Medicinal Biotechnology Chinese Academy of Medical Sciences, Beijing, 100050, China
| | - Yi Zhang
- Institute of Medicinal Biotechnology Chinese Academy of Medical Sciences, Beijing, 100050, China
| | - Jian Xu
- Institute of Medicinal Biotechnology Chinese Academy of Medical Sciences, Beijing, 100050, China.,Beijing Tuberculosis and Thoracic Tumor Research Institute, Beijing, 101149, China
| | - Mei Zhu
- Institute of Medicinal Biotechnology Chinese Academy of Medical Sciences, Beijing, 100050, China
| | - Shize Peng
- Institute of Medicinal Biotechnology Chinese Academy of Medical Sciences, Beijing, 100050, China
| | - Yongxin Zhang
- Institute of Medicinal Biotechnology Chinese Academy of Medical Sciences, Beijing, 100050, China
| | - Jianyuan Zhao
- Institute of Medicinal Biotechnology Chinese Academy of Medical Sciences, Beijing, 100050, China
| | - Xiaoyu Li
- Institute of Medicinal Biotechnology Chinese Academy of Medical Sciences, Beijing, 100050, China
| | - Kaixia Mi
- The Institute of Microbiology of the Chinese Academy of Sciences, Beijing 100101, China
| | - Dan Yan
- Beijing Friendship Hospital, Capital Medical University, Beijing, China
| | - Yucheng Wang
- Institute of Medicinal Biotechnology Chinese Academy of Medical Sciences, Beijing, 100050, China
| | - Liyan Yu
- Institute of Medicinal Biotechnology Chinese Academy of Medical Sciences, Beijing, 100050, China
| | - Yu Lu
- Beijing Tuberculosis and Thoracic Tumor Research Institute, Beijing, 101149, China
| | - Hanping Shi
- Department of Clinical Nutrition, Department of Gastrointestinal Surgery, Beijing Shijitan Hospital, Capital Medical University, Beijing, 100038, China; Department of Oncology, Capital Medical University, Beijing, 100038, China
| | - Shan Cen
- Institute of Medicinal Biotechnology Chinese Academy of Medical Sciences, Beijing, 100050, China.,Beijing Friendship Hospital, Capital Medical University, Beijing, China
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9
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Gupta A, Alland D. Reversible gene silencing through frameshift indels and frameshift scars provide adaptive plasticity for Mycobacterium tuberculosis. Nat Commun 2021; 12:4702. [PMID: 34349104 PMCID: PMC8339072 DOI: 10.1038/s41467-021-25055-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 07/16/2021] [Indexed: 12/15/2022] Open
Abstract
Mycobacterium tuberculosis can adapt to changing environments by non-heritable mechanisms. Frame-shifting insertions and deletions (indels) may also participate in adaptation through gene disruption, which could be reversed by secondary introduction of a frame-restoring indel. We present ScarTrek, a program that scans genomic data for indels, including those that together disrupt and restore a gene's reading frame, producing "frame-shift scars" suggestive of reversible gene inactivation. We use ScarTrek to analyze 5977 clinical M. tuberculosis isolates. We show that indel frequency inversely correlates with genomic linguistic complexity and varies with gene-position and gene-essentiality. Using ScarTrek, we detect 74 unique frame-shift scars in 48 genes, with a 3.74% population-level incidence of unique scar events. We find multiple scars in the ESX-1 gene cluster. Six scars show evidence of convergent evolution while the rest shared a common ancestor. Our results suggest that sequential indels are a mechanism for reversible gene silencing and adaptation in M. tuberculosis.
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Affiliation(s)
- Aditi Gupta
- Center for Emerging Pathogens, New Jersey Medical School, Rutgers University, Newark, NJ, USA.
| | - David Alland
- Center for Emerging Pathogens, New Jersey Medical School, Rutgers University, Newark, NJ, USA.
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10
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Izquierdo Lafuente B, Ummels R, Kuijl C, Bitter W, Speer A. Mycobacterium tuberculosis Toxin CpnT Is an ESX-5 Substrate and Requires Three Type VII Secretion Systems for Intracellular Secretion. mBio 2021; 12:e02983-20. [PMID: 33653883 PMCID: PMC8092274 DOI: 10.1128/mbio.02983-20] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 01/25/2021] [Indexed: 11/20/2022] Open
Abstract
CpnT, a NAD+ glycohydrolase, is the only known toxin that is secreted by Mycobacterium tuberculosis CpnT is composed of two domains; the C-terminal domain is the toxin, whereas the N-terminal domain is required for secretion. CpnT shows characteristics of type VII secretion (T7S) substrates, including a predicted helix-turn-helix domain followed by a secretion motif (YxxxE). Disruption of this motif indeed abolished CpnT secretion. By analyzing different mutants, we established that CpnT is specifically secreted by the ESX-5 system in Mycobacterium marinum under axenic conditions and during macrophage infection. Surprisingly, intracellular secretion of CpnT was also dependent on both ESX-1 and ESX-4. These secretion defects could be partially rescued by coinfection with wild-type bacteria, indicating that secreted effectors are involved in this process. In summary, our data reveal that three different type VII secretion systems have to be functional in order to observe intracellular secretion of the toxin CpnT.IMPORTANCE For decades, it was believed that the intracellular pathogen M. tuberculosis does not possess toxins. Only fairly recently it was discovered that CpnT is a potent secreted toxin of M. tuberculosis, causing necrotic cell death in host cells. However, until now the secretion pathway remained unknown. In our study, we were able to identify CpnT as a substrate of the mycobacterial type VII secretion system. Pathogenic mycobacteria have up to five different type VII secretion systems, called ESX-1 to ESX-5, which play distinct roles for the pathogen during growth or infection. We were able to elucidate that CpnT is exclusively secreted by the ESX-5 system in bacterial culture. However, to our surprise we discovered that, during infection studies, CpnT secretion relies on intact ESX-1, ESX-4, and ESX-5 systems. We elucidate for the first time the intertwined interplay of three different and independent secretion systems to secrete one substrate during infection.
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Affiliation(s)
- B Izquierdo Lafuente
- Section of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - R Ummels
- Department of Medical Microbiology and Infection Control, Amsterdam UMC, Location VU Medical Center, Amsterdam, The Netherlands
| | - C Kuijl
- Department of Medical Microbiology and Infection Control, Amsterdam UMC, Location VU Medical Center, Amsterdam, The Netherlands
| | - W Bitter
- Section of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
- Department of Medical Microbiology and Infection Control, Amsterdam UMC, Location VU Medical Center, Amsterdam, The Netherlands
| | - A Speer
- Department of Medical Microbiology and Infection Control, Amsterdam UMC, Location VU Medical Center, Amsterdam, The Netherlands
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11
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Li X, Chen L, Liao J, Hui J, Li W, He ZG. A novel stress-inducible CmtR-ESX3-Zn 2+ regulatory pathway essential for survival of Mycobacterium bovis under oxidative stress. J Biol Chem 2020; 295:17083-17099. [PMID: 33033071 PMCID: PMC7863910 DOI: 10.1074/jbc.ra120.013017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 09/28/2020] [Indexed: 11/06/2022] Open
Abstract
Reactive oxygen species (ROS) are an unavoidable host environmental cue for intracellular pathogens such as Mycobacterium tuberculosis and Mycobacterium bovis; however, the signaling pathway in mycobacteria for sensing and responding to environmental stress remains largely unclear. Here, we characterize a novel CmtR-Zur-ESX3-Zn2+ regulatory pathway in M. bovis that aids mycobacterial survival under oxidative stress. We demonstrate that CmtR functions as a novel redox sensor and that its expression can be significantly induced under H2O2 stress. CmtR can physically interact with the negative regulator Zur and de-represses the expression of the esx-3 operon, which leads to Zn2+ accumulation and promotion of reactive oxygen species detoxication in mycobacterial cells. Zn2+ can also act as an effector molecule of the CmtR regulator, using which the latter can de-repress its own expression for further inducing bacterial antioxidant adaptation. Consistently, CmtR can induce the expression of EsxH, a component of esx-3 operon involved in Zn2+ transportation that has been reported earlier, and inhibit phagosome maturation in macrophages. Lastly, CmtR significantly contributes to bacterial survival in macrophages and in the lungs of infected mice. Our findings reveal the existence of an antioxidant regulatory pathway in mycobacteria and provide novel information on stress-triggered gene regulation and its association with host-pathogen interaction.
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Affiliation(s)
- Xiaohui Li
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Liu Chen
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Jingjing Liao
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Jiechen Hui
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Weihui Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, Nanning, China
| | - Zheng-Guo He
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China; State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, Nanning, China.
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12
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Guo Q, Bi J, Wang H, Zhang X. Mycobacterium tuberculosis ESX-1-secreted substrate protein EspC promotes mycobacterial survival through endoplasmic reticulum stress-mediated apoptosis. Emerg Microbes Infect 2020; 10:19-36. [PMID: 33290182 PMCID: PMC7832037 DOI: 10.1080/22221751.2020.1861913] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
EsxA, secreted by the ESAT-6 secretion system 1 (ESX-1) secretion system, is considered the major Mycobacterium tuberculosis (Mtb) virulence determinant. However, the roles of the individual ESX-1 substrates, such as EspC, remain unclear due to their interdependency for secretion with EsxA. Here, we validated that EspC triggered ER stress-mediated apoptosis in macrophages. The EspC-mediated ER stress was involved in pro-inflammatory cytokines generation, intracellular Ca2+ release, and reactive oxygen species accumulation. Mitochondrial transmembrane potential dissipation and mitochondrial outer membrane permeabilization occurred in EspC-treated macrophages, causing apoptosis. Furthermore, ER stress-mediated apoptosis was effectively induced in EspC-overexpressing Mycobacterium smegmatis-infected macrophages and mice. EspC overexpression caused a significant increase in bacterial survival in the macrophages, spleens, and lungs, and accelerated mouse death was observed. Moreover, the increased viability of bacteria in the macrophages was significantly reduced by pretreatment with the apoptosis inhibitor. Overall, our results revealed that EspC is an essential ESX-1 protein for Mtb–host interactions and EspC-induced ER stress-mediated apoptosis may be employed by Mtb to establish and spread infection. Given the critical roles of the ESX systems in Mtb pathogenesis and immunity, our findings offer new perspectives on the complex host-pathogen interactions and mechanisms underlying ESX-1-mediated pathogenesis.
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Affiliation(s)
- Qinglong Guo
- State Key Laboratory of Genetic Engineering, School of Life Science, Fudan University, Shanghai, People's Republic of China.,National Clinical Research Center for Infectious Disease (Tuberculosis), Shenzhen Third People's Hospital, South University of Science and Technology of China, Shenzhen, People's Republic of China
| | - Jing Bi
- State Key Laboratory of Genetic Engineering, School of Life Science, Fudan University, Shanghai, People's Republic of China.,Key Laboratory of Medical Molecular Virology, Ministry of Education and Health, School of Basic Medical Sciences, Fudan University, Shanghai, People's Republic of China
| | - Honghai Wang
- State Key Laboratory of Genetic Engineering, School of Life Science, Fudan University, Shanghai, People's Republic of China
| | - Xuelian Zhang
- State Key Laboratory of Genetic Engineering, School of Life Science, Fudan University, Shanghai, People's Republic of China.,Shanghai Engineering Research Center of Industrial Microorganisms, Fudan University, Shanghai, People's Republic of China
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13
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Cui Z, Dang G, Song N, Cui Y, Li Z, Zang X, Liu H, Wang Z, Liu S. Rv3091, An Extracellular Patatin-Like Phospholipase in Mycobacterium tuberculosis, Prolongs Intracellular Survival of Recombinant Mycolicibacterium smegmatis by Mediating Phagosomal Escape. Front Microbiol 2020; 11:2204. [PMID: 33042041 PMCID: PMC7517356 DOI: 10.3389/fmicb.2020.532371] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 08/19/2020] [Indexed: 12/02/2022] Open
Abstract
Patatin-like phospholipases (PLPs) are important virulence factors of many pathogens. However, there are no prevailing studies regarding PLPs as a virulence factor of Mycobacterium tuberculosis (Mtb). Analysis of Rv3091, a putative protein of Mtb, shows that it belongs to the PLPs family. Here, we cloned and expressed the rv3091 gene in Mycobacterium smegmatis and, subsequently, conducted protein purification and characterization. We show that it possesses phospholipase A1, phospholipase A2, and lipase activity. We confirm the putative active site residues, namely, Ser214 and Asp407, using site directed mutagenesis. The Rv3091 is an extracellular protein that alters the colony morphology of M. smegmatis. The presence of Rv3091 enhances the intracellular survival capability of M. smegmatis in murine peritoneal macrophages. Additionally, it promotes M. smegmatis phagosomal escape from macrophages. Moreover, Rv3091 significantly increased the survival of M. smegmatis and aggravated lesions in C57BL/6 J murine lungs in vivo. Taken together, our results indicate that Rv3091 as an extracellular PLP that is critical to the pathogenicity of mycobacterium as it allows mycobacterium to utilize phospholipids for its growth and provides resistance to phagosome killing, resulting in its enhanced intracellular survival.
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Affiliation(s)
- Ziyin Cui
- State Key Laboratory of Veterinary Biotechnology, Division of Bacterial Diseases, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Guanghui Dang
- State Key Laboratory of Veterinary Biotechnology, Division of Bacterial Diseases, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Ningning Song
- State Key Laboratory of Veterinary Biotechnology, Division of Bacterial Diseases, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Yingying Cui
- State Key Laboratory of Veterinary Biotechnology, Division of Bacterial Diseases, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Zhe Li
- State Key Laboratory of Veterinary Biotechnology, Division of Bacterial Diseases, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Xinxin Zang
- State Key Laboratory of Veterinary Biotechnology, Division of Bacterial Diseases, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Hongxiu Liu
- State Key Laboratory of Veterinary Biotechnology, Division of Bacterial Diseases, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Zhongxing Wang
- State Key Laboratory of Veterinary Biotechnology, Division of Bacterial Diseases, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Siguo Liu
- State Key Laboratory of Veterinary Biotechnology, Division of Bacterial Diseases, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
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14
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Discovery of ANTAR-RNAs and their Mechanism of Action in Mycobacteria. J Mol Biol 2020; 432:4032-4048. [PMID: 32422150 DOI: 10.1016/j.jmb.2020.05.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 05/07/2020] [Accepted: 05/07/2020] [Indexed: 02/07/2023]
Abstract
Non-coding RNAs play pivotal roles in bacterial signaling. However, RNAs from certain phyla (specially high-GC actinobacteria) still remain elusive. Here, by re-engineering the existing genome-wide search approach, we discover a family of structurally conserved RNAs that are present ubiquitously across actinobacteria, including mycobacteria. In vitro analysis shows that RNAs belonging to this family bind response-regulator proteins that contain the widely prevalent ANTAR domain. The Mycobacterium tuberculosis ANTAR protein gets phosphorylated by a histidine kinase and interacts with RNA only in its phosphorylated state. These newly identified RNAs reside only in certain transcripts and typically overlap with the ribosome-binding site, regulating translation of these transcripts. In this way, the RNAs directly link signaling pathways to translational control, thus expanding the mechanistic tool kit available for ANTAR-based control of gene expression. In mycobacteria, we find that RNAs targeted by ANTAR proteins majorly encode enzymes of lipid metabolism and associated redox pathways. This now allows us to identify the key genes that mediate ANTAR-dependent control of lipid metabolism. Our study establishes the identity and wide prevalence of ANTAR-target RNAs in mycobacteria, bringing RNA-mediated regulation in these bacteria to the center stage.
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15
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Kurniawati S, Mertaniasih NM, Ato M, Tamura T, Soedarsono S, Aulanni'am A, Mori S, Maeda Y, Mukai T. Cloning and Protein Expression of eccB5 Gene in ESX-5 System from Mycobacterium tuberculosis. Biores Open Access 2020; 9:86-93. [PMID: 32257624 PMCID: PMC7133456 DOI: 10.1089/biores.2019.0019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Mycobacterium tuberculosis (M. tuberculosis) is the causative agent of tuberculosis in human. One of the major M. tuberculosis virulence factors is early secretory antigenic target of 6-kDa (ESAT-6), and EccB5 protein encoded by eccB5 is one of its components. EccB5 protein is a transmembrane protein in ESX-5 system. The aim of this study is to explore the characteristics of wild-type EccB5 and its mutant form N426I. We expressed the EccB5 protein by cloning the mutant and wild-type eccB5 gene in Escherichia coli (E. coli). We compared the protein structure of wild type and mutant form of EccB5 and found changes in structure around Asn426 (loop structure) in wild type and around Ile426 (β-strand) in the mutant. The truncated recombinant protein of EccB5 was successfully cloned and expressed using plasmid pCold I in E. coli DH5α and E. coli strain Rosetta-gami B (DE3) and purified as a 38.6 kDa protein by using the affinity column. There was no detectable adenosine triphosphatase activity in truncated forms of EccB5 and its mutant. In conclusion, our study reveals successful cloning and protein expression of truncated form of eccB5 gene of M. tuberculosis. EccB5 protein in ESX-5 system may be an important membrane component involved in the transport machinery of type VII secretion system, which is essential for growth and virulence.
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Affiliation(s)
- Siti Kurniawati
- Faculty of Medicine, Universitas Airlangga, Surabaya, Indonesia
| | - Ni Made Mertaniasih
- Department of Clinical Microbiology, Faculty of Medicine, Universitas Airlangga, Surabaya, Indonesia
| | - Manabu Ato
- Department of Mycobacteriology, Leprosy Research Center, National Institute of Infectious Diseases, Tokyo, Japan
| | - Toshiki Tamura
- Department of Mycobacteriology, Leprosy Research Center, National Institute of Infectious Diseases, Tokyo, Japan
| | - Soedarsono Soedarsono
- Department of Pulmonology and Respiratory Medicine, Faculty of Medicine, Universitas Airlangga, Surabaya, Indonesia
| | - Aulanni'am Aulanni'am
- Department of Biochemistry, Faculty of Veterinary Medicine, Brawijaya University, Malang, Indonesia
| | - Shigetarou Mori
- Department of Bacteriology II, National Institute of Infectious Diseases, Tokyo, Japan
| | - Yumi Maeda
- Department of Mycobacteriology, Leprosy Research Center, National Institute of Infectious Diseases, Tokyo, Japan
| | - Tetsu Mukai
- Department of Mycobacteriology, Leprosy Research Center, National Institute of Infectious Diseases, Tokyo, Japan
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16
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Polarly Localized EccE 1 Is Required for ESX-1 Function and Stabilization of ESX-1 Membrane Proteins in Mycobacterium tuberculosis. J Bacteriol 2020; 202:JB.00662-19. [PMID: 31843799 DOI: 10.1128/jb.00662-19] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 12/11/2019] [Indexed: 12/15/2022] Open
Abstract
Mycobacterium tuberculosis is a slow-growing intracellular bacterium with the ability to induce host cell death and persist indefinitely in the human body. This pathogen uses the specialized ESX-1 secretion system to secrete virulence factors and potent immunogenic effectors required for disease progression. ESX-1 is a multisubunit apparatus with a membrane complex that is predicted to form a channel in the cytoplasmic membrane. In M. tuberculosis this complex is composed of five membrane proteins: EccB1, EccCa1, EccCb1, EccD1, and EccE1 In this study, we have characterized the membrane component EccE1 and found that deletion of eccE 1 lowers the levels of EccB1, EccCa1, and EccD1, thereby abolishing ESX-1 secretion and attenuating M. tuberculosis ex vivo Surprisingly, secretion of EspB was not affected by loss of EccE1 Furthermore, EccE1 was found to be a membrane- and cell wall-associated protein that needs the presence of other ESX-1 components to assemble into a stable complex at the poles of M. tuberculosis Overall, this investigation provides new insights into the role of EccE1 and its localization in M. tuberculosis IMPORTANCE Tuberculosis (TB), the world's leading cause of death of humans from an infectious disease, is caused by the intracellular bacterium Mycobacterium tuberculosis The development of successful strategies to control TB requires better understanding of the complex interactions between the pathogen and the human host. We investigated the contribution of EccE1, a membrane protein, to the function of the ESX-1 secretion system, the major virulence determinant of M. tuberculosis By combining genetic analysis of selected mutants with eukaryotic cell biology and proteomics, we demonstrate that EccE1 is critical for ESX-1 function, secretion of effector proteins, and pathogenesis. Our research improves knowledge of the molecular basis of M. tuberculosis virulence and enhances our understanding of pathogenesis.
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17
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Vaziri F, Brosch R. ESX/Type VII Secretion Systems-An Important Way Out for Mycobacterial Proteins. Microbiol Spectr 2019; 7:10.1128/microbiolspec.psib-0029-2019. [PMID: 31298207 PMCID: PMC10957191 DOI: 10.1128/microbiolspec.psib-0029-2019] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Indexed: 11/20/2022] Open
Abstract
The causative agent of human tuberculosis, Mycobacterium tuberculosis, has a complex lipid-rich diderm envelope, which acts as a major barrier protecting the bacterium against the hostile environment inside the host cells. For the transfer of diverse molecules across this complex cell envelope, M. tuberculosis has a series of general and specialized protein secretion systems, characterized by the SecA general secretion pathway, the twin-arginine translocation pathway, and five specific ESX type VII secretion systems. In this review, we focus on the latter systems, known as ESX-1 to ESX-5, which were first discovered almost 20 years ago during the in silico analysis of the genome sequence of M. tuberculosis H37Rv. Since then, these systems have been the subject of highly dynamic research due to their involvement in several key biological processes and host-pathogen interactions of the tubercle bacilli.
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Affiliation(s)
- Farzam Vaziri
- Institut Pasteur, Unit for Integrated Mycobacterial Pathogenomics, UMR3525 CNRS, 75015 Paris, France
- Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, 13164 Tehran, Iran
- Microbiology Research Center, Pasteur Institute of Iran, 13164 Tehran, Iran
| | - Roland Brosch
- Institut Pasteur, Unit for Integrated Mycobacterial Pathogenomics, UMR3525 CNRS, 75015 Paris, France
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18
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PE17 protein from Mycobacterium tuberculosis enhances Mycobacterium smegmatis survival in macrophages and pathogenicity in mice. Microb Pathog 2019; 126:63-73. [DOI: 10.1016/j.micpath.2018.10.030] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 10/22/2018] [Accepted: 10/22/2018] [Indexed: 01/26/2023]
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19
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Kurniawati S, Soedarsono S, Aulanni'am A, Mertaniasih NM. SINGLE NUCLEOTIDE POLYMORPHISM OF ECCB5 GENE OF MYCOBACTERIUM TUBERCULOSIS COMPLEX ISOLATES FROM SUSPECTED PULMONARY TB PATIENTS IN SURABAYA INDONESIA. Afr J Infect Dis 2018; 12:37-42. [PMID: 30109284 PMCID: PMC6085738 DOI: 10.21010/ajid.v12i2.6] [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: 04/18/2017] [Revised: 08/31/2017] [Accepted: 09/07/2017] [Indexed: 12/29/2022] Open
Abstract
Background: Mycobacterium tuberculosis Complex (MTBC) is a group of Mycobacterium that causes tuberculosis (TB). TB is an infectious disease that remains a global health problem. Indonesia is one of the five countries in the world where TB is the most prevalent and became the country with tle second largest rate of TB in 2014 and 2015. MTBC has high pathogenicity that can cause infections in animals and humans. The most common route of transmission is via airborne droplet nuclei and contact with animals or humans infected with TB. MTBC has many virulence factors. One of these factors is EccB5 that is encoded by eccB5 gene. EccB5 is a transmembrane protein-conserved membrane protein and could play a role in inducing damage in host cells, macrophage infection, and may correlate with active disease. The characterization of eccB5 gene needs to be studied to determine the nucleotide sequences, which may be associated with active disease. The aim of this research was to analyze the nuclotide sequences of eccB5 gene of MTBC from suspected pulmonary tuberculosis patients, SNPs of eccB5 gene and possible correlation with the disease, especially in Indonesia. Materials and Methods: Samples were collected from the Tuberculosis Laboratory, Clinical Microbiology of Dr. Soetomo Hospital Surabaya Indonesia. DNA extraction used boiling extraction method and continued nucleic acid amplification using PCR techniques. Primer pairs used eccB5 SK.. The positivity of DNA specific revealed amplicon in 1592 bp. PCR product was sequenced by 1st Base (First BASE Laboratories Sdn Bhd, Selangor, Malaysia). The sequence analysis used Genetyx-Win version 10.0 (Genetyx Corporation, Tokyo, Japan). Results: Total isolates of Mycobacterium spp. were 28 and those that showed positive MTBC were 24 isolates and 4 nontuberculosis mycobacteria (NTM) using immunochromatographic test (ICT). The amount of homology from MTBC using blast NCBI was 99%-100%. Two SNPs were found in position c.1277 which revealed replacement of amino acid in 426 of codon position. Conclusion: The sequence of eccB5 gene of MTBC showed high significant homology, while proposed non-synoymous single nucleotide polymorphisms (nsSNP) may associated with clinical outcomes.
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Affiliation(s)
- Siti Kurniawati
- Magister of Tropical Medicine, Faculty of Medicine, Universitas Airlangga, Surabaya Indonesia
| | - Soedarsono Soedarsono
- Department of Pulmonology and Respiratory Medicine, Faculty of Medicine, Universitas Airlangga, Surabaya, Indonesia
| | - Aulanni'am Aulanni'am
- Department of Biochemistry, Faculty of Veterinary Medicine, Brawijaya University, Malang, Indonesia
| | - Ni Made Mertaniasih
- Department of Clinical Microbiology, Faculty of Medicine, Universitas Airlangga, Surabaya, Indonesia.,Laboratory of Tuberculosis, Institute Tropical Diseases, Universitas Airlangga, Surabaya, Indonesia
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20
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Mycobacterium tuberculosis Pst/SenX3-RegX3 Regulates Membrane Vesicle Production Independently of ESX-5 Activity. mBio 2018; 9:mBio.00778-18. [PMID: 29895636 PMCID: PMC6016242 DOI: 10.1128/mbio.00778-18] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Mycobacterium tuberculosis releases membrane vesicles (MV) that modulate host immune responses and aid in iron acquisition, although they may have additional unappreciated functions. MV production appears to be a regulated process, but virR remains the only characterized genetic regulator of vesiculogenesis. Here, we present data supporting a role for the M. tuberculosis Pst/SenX3-RegX3 signal transduction system in regulating MV production. Deletion of pstA1, which encodes a transmembrane component of the phosphate-specific transport (Pst) system, causes constitutive activation of the SenX3-RegX3 two-component system, leading to increased protein secretion via the specialized ESX-5 type VII secretion system. Using proteomic mass spectrometry, we identified several additional proteins hyper-secreted by the ΔpstA1 mutant, including LpqH, an MV-associated lipoprotein. Nanoparticle tracking analysis revealed a 15-fold increase in MV production by the ΔpstA1 mutant. Both hyper-secretion of LpqH and increased MV release required RegX3 but were independent of VirR, suggesting that Pst/SenX3-RegX3 controls MV release by a novel mechanism. Prior proteomic analysis identified ESX-5 substrates associated with MV. We therefore hypothesized that MV release requires ESX-5 activity. We constructed strains that conditionally express eccD5, which encodes the predicted ESX-5 transmembrane channel. Upon EccD5 depletion, we observed reduced secretion of the ESX-5 substrates EsxN and PPE41, but MV release was unaffected. Our data suggest that ESX-5 does not affect vesicle production and imply that further characterization of the Pst/SenX3-RegX3 regulon might reveal novel mechanisms of M. tuberculosis vesicle biogenesis. In Gram-negative bacteria, MV derived from the outer membrane have diverse functions in bacterial physiology and pathogenesis, and several factors regulating their production have been identified. Though Gram-positive bacteria and mycobacteria that lack an outer membrane also produce vesicles with described roles in pathogenesis, the mechanisms of MV biogenesis in these organisms remain poorly characterized. Defining mechanisms of MV biogenesis might yield significant insights into the importance of MV production during infection. In M. tuberculosis, only a single genetic element, virR, is known to regulate MV production. Our work reveals that the Pst/SenX3-RegX3 signal transduction system is a novel regulator of MV biogenesis that controls MV production by a mechanism that is independent of both VirR and activation of the specialized ESX-5 protein secretion system. Understanding which genes in the RegX3 regulon cause increased MV production might reveal novel molecular mechanisms of MV release.
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21
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The C-terminus of the ESAT6-like secretion system virulence factor EsxC mediates divalent cation-dependent homodimerization. Toxicon 2018; 146:129-137. [PMID: 29499245 DOI: 10.1016/j.toxicon.2018.02.047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 01/29/2018] [Accepted: 02/26/2018] [Indexed: 11/21/2022]
Abstract
The human pathogen Staphylococcus aureus encodes the ESAT6-like Secretion System (ESS). The ESS pathway secretes pathogenic substrates such as EsxA, EsxB, EsxC, EsxD and EssD that mediate staphylococcal establishment in persistent abscess lesions. The biochemical behavior of these substrates is not fully understood. EsxC is species-specific lysine-rich homodimer that lacks recognizable topogenic sequence. Studies have shown that EsxC is required for the secretion of other substrates, thereby revealing its biomedical importance. Here, EsxC self-association was investigated in the presence of several metal ion chelators. Results show that EsxC homodimerization is abolished in the presence of EDTA and EGTA, suggesting a role for calcium in mediating EsxC self-association. Complementation experiments confirm that EsxC homodimerization is calcium-dependent. N- and C-terminal truncations of EsxC were constructed, followed by bacterial two-hybrid screening. Results show that EsxC self-association is mediated by its C-terminal domain. Affinity purification of recombinant EsxC to apparent homogeneity, followed by chemical crosslinking and SDS-PAGE led to the detection of the monomeric and dimeric forms of the protein. In contrast and when a purified EsxC variant lacking the C-terminus was subjected to similar conditions, only the monomeric form was observed. These in vivo and in vitro data highlight the contribution of the C-terminus of the virulence factor EsxC to self-association, and document a previously unreported role for calcium in mediating protein-protein interactions in this pathogenic secretion system.
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22
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Seveau S, Turner J, Gavrilin MA, Torrelles JB, Hall-Stoodley L, Yount JS, Amer AO. Checks and Balances between Autophagy and Inflammasomes during Infection. J Mol Biol 2017; 430:174-192. [PMID: 29162504 DOI: 10.1016/j.jmb.2017.11.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Revised: 11/05/2017] [Accepted: 11/09/2017] [Indexed: 12/24/2022]
Abstract
Autophagy and inflammasome complex assembly are physiological processes that control homeostasis, inflammation, and immunity. Autophagy is a ubiquitous pathway that degrades cytosolic macromolecules or organelles, as well as intracellular pathogens. Inflammasomes are multi-protein complexes that assemble in the cytosol of cells upon detection of pathogen- or danger-associated molecular patterns. A critical outcome of inflammasome assembly is the activation of the cysteine protease caspase-1, which activates the pro-inflammatory cytokine precursors pro-IL-1β and pro-IL-18. Studies on chronic inflammatory diseases, heart diseases, Alzheimer's disease, and multiple sclerosis revealed that autophagy and inflammasomes intersect and regulate each other. In the context of infectious diseases, however, less is known about the interplay between autophagy and inflammasome assembly, although it is becoming evident that pathogens have evolved multiple strategies to inhibit and/or subvert these pathways and to take advantage of their intricate crosstalk. An improved appreciation of these pathways and their subversion by diverse pathogens is expected to help in the design of anti-infective therapeutic interventions.
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Affiliation(s)
- Stephanie Seveau
- Department of Microbial Infection and Immunity, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA; Infectious Diseases Institute, The Ohio State University, Columbus, OH, USA.
| | - Joanne Turner
- Texas Biomedical Research Institute, San Antonio, TX 78227, USA
| | - Mikhail A Gavrilin
- Infectious Diseases Institute, The Ohio State University, Columbus, OH, USA; Department of Internal Medicine, College of Medicine, The Ohio State University, Columbus, OH, USA
| | | | - Luanne Hall-Stoodley
- Department of Microbial Infection and Immunity, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA; Infectious Diseases Institute, The Ohio State University, Columbus, OH, USA
| | - Jacob S Yount
- Department of Microbial Infection and Immunity, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA; Infectious Diseases Institute, The Ohio State University, Columbus, OH, USA
| | - Amal O Amer
- Department of Microbial Infection and Immunity, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA; Infectious Diseases Institute, The Ohio State University, Columbus, OH, USA
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23
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Protein Secretion in Gram-Positive Bacteria: From Multiple Pathways to Biotechnology. Curr Top Microbiol Immunol 2017; 404:267-308. [PMID: 27885530 DOI: 10.1007/82_2016_49] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A number of Gram-positive bacteria are important players in industry as producers of a diverse array of economically interesting metabolites and proteins. As discussed in this overview, several Gram-positive bacteria are valuable hosts for the production of heterologous proteins. In contrast to Gram-negative bacteria, proteins secreted by Gram-positive bacteria are released into the culture medium where conditions for correct folding are more appropriate, thus facilitating the isolation and purification of active proteins. Although seven different protein secretion pathways have been identified in Gram-positive bacteria, the majority of heterologous proteins are produced via the general secretion or Sec pathway. Not all proteins are equally well secreted, because heterologous protein production often faces bottlenecks including hampered secretion, susceptibility to proteases, secretion stress, and metabolic burden. These bottlenecks are associated with reduced yields leading to non-marketable products. In this chapter, besides a general overview of the different protein secretion pathways, possible hurdles that may hinder efficient protein secretion are described and attempts to improve yield are discussed including modification of components of the Sec pathway. Attention is also paid to omics-based approaches that may offer a more rational approach to optimize production of heterologous proteins.
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24
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Snyder DT, Hedges JF, Jutila MA. Getting "Inside" Type I IFNs: Type I IFNs in Intracellular Bacterial Infections. J Immunol Res 2017; 2017:9361802. [PMID: 28529959 PMCID: PMC5424489 DOI: 10.1155/2017/9361802] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2017] [Revised: 03/20/2017] [Accepted: 03/27/2017] [Indexed: 12/23/2022] Open
Abstract
Type I interferons represent a unique and complex group of cytokines, serving many purposes during innate and adaptive immunity. Discovered in the context of viral infections, type I IFNs are now known to have myriad effects in infectious and autoimmune disease settings. Type I IFN signaling during bacterial infections is dependent on many factors including whether the infecting bacterium is intracellular or extracellular, as different signaling pathways are activated. As such, the repercussions of type I IFN induction can positively or negatively impact the disease outcome. This review focuses on type I IFN induction and downstream consequences during infection with the following intracellular bacteria: Chlamydia trachomatis, Listeria monocytogenes, Mycobacterium tuberculosis, Salmonella enterica serovar Typhimurium, Francisella tularensis, Brucella abortus, Legionella pneumophila, and Coxiella burnetii. Intracellular bacterial infections are unique because the bacteria must avoid, circumvent, and even co-opt microbial "sensing" mechanisms in order to reside and replicate within a host cell. Furthermore, life inside a host cell makes intracellular bacteria more difficult to target with antibiotics. Because type I IFNs are important immune effectors, modulating this pathway may improve disease outcomes. But first, it is critical to understand the context-dependent effects of the type I IFN pathway in intracellular bacterial infections.
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Affiliation(s)
- Deann T. Snyder
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT, USA
| | - Jodi F. Hedges
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT, USA
| | - Mark A. Jutila
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT, USA
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25
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Gray TA, Clark RR, Boucher N, Lapierre P, Smith C, Derbyshire KM. Intercellular communication and conjugation are mediated by ESX secretion systems in mycobacteria. Science 2017; 354:347-350. [PMID: 27846571 DOI: 10.1126/science.aag0828] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 08/31/2016] [Indexed: 11/02/2022]
Abstract
Communal bacterial processes require intercellular communication mediated by secretion systems to coordinate appropriate molecular responses. Intercellular communication has not been described previously in mycobacteria. Here we show that the ESX secretion-system family member ESX-4 is essential for conjugal recipient activity in Mycobacterium smegmatis Transcription of esx4 genes in the recipient requires coculture with a donor strain and a functional ESX-1 apparatus in the recipient. Conversely, mutation of the donor ESX-1 apparatus amplifies the esx4 transcriptional response in the recipient. The effect of ESX-1 on esx4 transcription correlates with conjugal DNA transfer efficiencies. Our data show that intercellular communication via ESX-1 controls the expression of its evolutionary progenitor, ESX-4, to promote conjugation between mycobacteria.
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Affiliation(s)
- Todd A Gray
- Wadsworth Center, New York State Department of Health, P.O. Box 22002, Albany, NY 12201-2002, USA. .,Department of Biomedical Sciences, University at Albany, State University of New York, Albany, NY 12201-02002, USA
| | - Ryan R Clark
- Wadsworth Center, New York State Department of Health, P.O. Box 22002, Albany, NY 12201-2002, USA
| | - Nathalie Boucher
- Wadsworth Center, New York State Department of Health, P.O. Box 22002, Albany, NY 12201-2002, USA
| | - Pascal Lapierre
- Wadsworth Center, New York State Department of Health, P.O. Box 22002, Albany, NY 12201-2002, USA
| | - Carol Smith
- Wadsworth Center, New York State Department of Health, P.O. Box 22002, Albany, NY 12201-2002, USA
| | - Keith M Derbyshire
- Wadsworth Center, New York State Department of Health, P.O. Box 22002, Albany, NY 12201-2002, USA. .,Department of Biomedical Sciences, University at Albany, State University of New York, Albany, NY 12201-02002, USA
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Unnikrishnan M, Constantinidou C, Palmer T, Pallen MJ. The Enigmatic Esx Proteins: Looking Beyond Mycobacteria. Trends Microbiol 2017; 25:192-204. [DOI: 10.1016/j.tim.2016.11.004] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 10/20/2016] [Accepted: 11/04/2016] [Indexed: 01/17/2023]
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EssD, a Nuclease Effector of the Staphylococcus aureus ESS Pathway. J Bacteriol 2016; 199:JB.00528-16. [PMID: 27795323 DOI: 10.1128/jb.00528-16] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 10/04/2016] [Indexed: 02/07/2023] Open
Abstract
Specialized secretion systems of bacteria evolved for selective advantage, either killing microbial competitors or implementing effector functions during parasitism. Earlier work characterized the ESAT-6 secretion system (ESS) of Staphylococcus aureus and demonstrated its contribution to persistent staphylococcal infection of vertebrate hosts. Here, we identify a novel secreted effector of the ESS pathway, EssD, that functions as a nuclease and cleaves DNA but not RNA. EssI, a protein of the DUF600 family, binds EssD to block its nuclease activity in the staphylococcal cytoplasm. An essD knockout mutant or a variant lacking nuclease activity, essDL546P, elicited a diminished interleukin-12 (IL-12) cytokine response following bloodstream infection of mice, suggesting that the effector function of EssD stimulates immune signaling to support the pathogenesis of S. aureus infections. IMPORTANCE Bacterial type VII or ESAT-6-like secretion systems (ESS) may have evolved to modulate host immune responses during infection, thereby contributing to the pathogenesis of important diseases such as tuberculosis and methicillin-resistant S. aureus (MRSA) infection. The molecular mechanisms whereby type VII secretion systems achieve their goals are not fully elucidated as secreted effectors with biochemical functions have heretofore not been identified. We show here that MRSA infection relies on the secretion of a nuclease effector that cleaves DNA and contributes to the stimulation of IL-12 signaling during infection. These results identify a biological mechanism for the contribution of the ESS pathway toward the establishment of MRSA disease.
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Lou Y, Rybniker J, Sala C, Cole ST. EspC forms a filamentous structure in the cell envelope ofMycobacterium tuberculosisand impacts ESX-1 secretion. Mol Microbiol 2016; 103:26-38. [DOI: 10.1111/mmi.13575] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/07/2016] [Indexed: 11/28/2022]
Affiliation(s)
- Ye Lou
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL); Lausanne CH-1015 Switzerland
| | - Jan Rybniker
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL); Lausanne CH-1015 Switzerland
- 1st Department of Internal Medicine; University of Cologne; Cologne D-50937 Germany
| | - Claudia Sala
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL); Lausanne CH-1015 Switzerland
| | - Stewart T. Cole
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL); Lausanne CH-1015 Switzerland
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Mycosins Are Required for the Stabilization of the ESX-1 and ESX-5 Type VII Secretion Membrane Complexes. mBio 2016; 7:mBio.01471-16. [PMID: 27795391 PMCID: PMC5082899 DOI: 10.1128/mbio.01471-16] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Pathogenic mycobacteria contain up to five type VII secretion (T7S) systems, ESX-1 to ESX-5. One of the conserved T7S components is the serine protease mycosin (MycP). Strikingly, whereas MycP is essential for secretion, the protease activity of MycP1 in Mycobacterium tuberculosis has been shown to be dispensable for secretion. The essential role of MycP therefore remains unclear. Here we show that MycP1 and MycP5 of M. marinum have similar phenotypes, confirming that MycP has a second unknown function that is essential for its T7S system. To investigate whether this role is related to proper functioning of the T7S membrane complex, we first analyzed the composition of the ESX-1 membrane complex and showed that this complex consists of EccBCDE1, similarly to what was previously shown for ESX-5. Surprisingly, while mycosins are not an integral part of these purified core complexes, we noticed that the stability of both the ESX-1 complex and the ESX-5 complex is compromised in the absence of their MycP subunit. Additional interaction studies showed that, although mycosins are not part of the central ESX membrane complex, they loosely associate with this complex. We hypothesize that this MycP association with the core membrane complex is crucial for the integrity and functioning of the T7S machinery. Among the major virulence factors of pathogenic mycobacteria are the type VII secretion (T7S) systems. Three of these systems, ESX-1, ESX-3, and ESX-5, have been shown to be crucial for virulence or viability. Here we describe the function of mycosin proteases, which are conserved components within these systems. We show that MycP1 and MycP5 have a second, proteolytic-independent function which is essential for the T7S system. We additionally found that this second essential role is related to the stabilization and proper functioning of their respective ESX membrane core complexes. Finally, we found that this is mediated by a loose association of MycP with the complex. Understanding the essential role of mycosins in type VII secretion systems, which play central roles in the virulence and viability of pathogenic mycobacteria, may provide new intervention strategies to treat tuberculosis.
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Yi N, Jung BG, Wang X, Vankayalapati R, Samten B. The early secreted antigenic target of 6 kD of Mycobacterium tuberculosis inhibits the proliferation and differentiation of human peripheral blood CD34 + cells. Tuberculosis (Edinb) 2016; 101S:S28-S34. [PMID: 27745787 DOI: 10.1016/j.tube.2016.09.018] [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] [Indexed: 12/30/2022]
Abstract
Abnormalities in hematopoiesis are common in tuberculosis patients and highly prevalent in AIDS patients with tuberculosis coinfection. To explore the potential role of the early secreted antigenic target of 6-kD (ESAT-6) of Mycobacterium tuberculosis (Mtb) in abnormal hematopoiesis in tuberculosis, we studied the effect of ESAT-6 on proliferation and differentiation of in vitro-expanded CD34+ cells isolated from the peripheral blood of the healthy donors. ESAT-6 but not control protein antigen 85A (Ag85A) of Mtb inhibited the proliferation of CD34+ cell derived peripheral blood stem/progenitor cells (PBSPC) in a dose dependent manner when determined by MTT-assay. ESAT-6 but not Ag85A reduced the number of colony forming cells (CFC) of PBSPC by 60-90% as determined by CFC assay by incubation of CD34+ cells in a semi-solid cellulose media in the presence of cytokine cocktail for two weeks. ESAT-6 but not Ag85A increased the percentages of the Annexin-V positive cells and enhanced the cleavage of caspase-3 in PBSPC in a time and dose dependent manner as determined by flow cytometry and Western blot analysis, respectively. ESAT-6 also inhibited murine bone marrow derived non-adherent cell proliferation in response to granulocyte-macrophage colony stimulating factor treatment. We conclude that ESAT-6, an essential virulence factor of Mtb, may contribute to the abnormal hematopoiesis of tuberculosis patients by inhibiting the proliferation and differentiation of hematopoietic cells via apoptosis.
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Affiliation(s)
- Na Yi
- The Department of Pulmonary Immunology, University of Texas Health Science Center at Tyler, 11937 US HWY 271, Tyler, TX 75708-3154, USA
| | - Bock-Gie Jung
- The Department of Pulmonary Immunology, University of Texas Health Science Center at Tyler, 11937 US HWY 271, Tyler, TX 75708-3154, USA
| | - Xisheng Wang
- The Department of Pulmonary Immunology, University of Texas Health Science Center at Tyler, 11937 US HWY 271, Tyler, TX 75708-3154, USA
| | - RamaKrishna Vankayalapati
- The Department of Pulmonary Immunology, University of Texas Health Science Center at Tyler, 11937 US HWY 271, Tyler, TX 75708-3154, USA
| | - Buka Samten
- The Department of Pulmonary Immunology, University of Texas Health Science Center at Tyler, 11937 US HWY 271, Tyler, TX 75708-3154, USA.
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Inflammasome Activation and Function During Infection with Mycobacterium Tuberculosis. Curr Top Microbiol Immunol 2016; 397:183-97. [DOI: 10.1007/978-3-319-41171-2_9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Russell DG. The ins and outs of the Mycobacterium tuberculosis-containing vacuole. Cell Microbiol 2016; 18:1065-9. [PMID: 27247149 DOI: 10.1111/cmi.12623] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 05/17/2016] [Accepted: 05/25/2016] [Indexed: 12/16/2022]
Abstract
The past few years have seen publication of reports from several groups documenting the escape of Mycobacterium tuberculosis (Mtb) from its intracellular vacuole to access the cytosol. The major questions addressed in these publications are the mechanism(s) underlying this process, the frequency of its occurrence and, most importantly, the biological significance of this phenomenon to bacterial survival, growth and virulence. I believe that the first two questions are moving towards resolution, but questions relating to biological context have yet to be answered fully. In this viewpoint article, I will try to convince the readers why escape from the vacuole in no way diminishes the significance of Mtb's intravacuolar survival mechanisms and why, as a lab, we continue to focus the majority of our efforts on the 'bug in the bag'.
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Affiliation(s)
- David G Russell
- Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY, 14853, USA
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Benard EL, Rougeot J, Racz PI, Spaink HP, Meijer AH. Transcriptomic Approaches in the Zebrafish Model for Tuberculosis-Insights Into Host- and Pathogen-specific Determinants of the Innate Immune Response. ADVANCES IN GENETICS 2016; 95:217-51. [PMID: 27503359 DOI: 10.1016/bs.adgen.2016.04.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Mycobacterium marinum infection in zebrafish has become a well-established model of tuberculosis. Both embryonic and adult zebrafish infection studies have contributed to our knowledge of the development and function of tuberculous granulomas, which are typical of mycobacterial pathogenesis. In this review we discuss how transcriptome profiling studies have helped to characterize this infection process. We illustrate this using new RNA sequencing (RNA-Seq) data that reveals three main phases in the host response to M. marinum during the early stages of granuloma development in zebrafish embryos and larvae. The early phase shows induction of complement and transcription factors, followed by a relatively minor induction of pro-inflammatory cytokines within hours following phagocytosis of M. marinum. A minimal response is observed in the mid-phase, between 6 hours and 1day post infection, when the tissue dissemination of M. marinum begins. During subsequent larval development the granulomas expand and a late-phase response is apparent, which is characterized by progressively increasing induction of complement, transcription factors, pro-inflammatory cytokines, matrix metalloproteinases, and other defense and inflammation-related gene groups. This late-phase response shares common components with the strong and acute host transcriptome response that has previously been reported for Salmonella typhimurium infection in zebrafish embryos. In contrast, the early/mid-phase response to M. marinum infection, characterized by suppressed pro-inflammatory signaling, is strikingly different from the acute response to S. typhimurium infection. Furthermore, M. marinum infection shows a collective and strongly fluctuating regulation of lipoproteins, while S. typhimurium infection has pronounced effects on amino acid metabolism and glycolysis.
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Affiliation(s)
- E L Benard
- Institute of Biology, Leiden University, Leiden, The Netherlands
| | - J Rougeot
- Institute of Biology, Leiden University, Leiden, The Netherlands
| | - P I Racz
- Institute of Biology, Leiden University, Leiden, The Netherlands
| | - H P Spaink
- Institute of Biology, Leiden University, Leiden, The Netherlands
| | - A H Meijer
- Institute of Biology, Leiden University, Leiden, The Netherlands
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Chenge J, Kavanagh ME, Driscoll MD, McLean KJ, Young DB, Cortes T, Matak-Vinkovic D, Levy CW, Rigby SEJ, Leys D, Abell C, Munro AW. Structural characterization of CYP144A1 - a cytochrome P450 enzyme expressed from alternative transcripts in Mycobacterium tuberculosis. Sci Rep 2016; 6:26628. [PMID: 27225995 PMCID: PMC4880925 DOI: 10.1038/srep26628] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 04/25/2016] [Indexed: 12/03/2022] Open
Abstract
Mycobacterium tuberculosis (Mtb) causes the disease tuberculosis (TB). The virulent Mtb H37Rv strain encodes 20 cytochrome P450 (CYP) enzymes, many of which are implicated in Mtb survival and pathogenicity in the human host. Bioinformatics analysis revealed that CYP144A1 is retained exclusively within the Mycobacterium genus, particularly in species causing human and animal disease. Transcriptomic annotation revealed two possible CYP144A1 start codons, leading to expression of (i) a “full-length” 434 amino acid version (CYP144A1-FLV) and (ii) a “truncated” 404 amino acid version (CYP144A1-TRV). Computational analysis predicted that the extended N-terminal region of CYP144A1-FLV is largely unstructured. CYP144A1 FLV and TRV forms were purified in heme-bound states. Mass spectrometry confirmed production of intact, His6-tagged forms of CYP144A1-FLV and -TRV, with EPR demonstrating cysteine thiolate coordination of heme iron in both cases. Hydrodynamic analysis indicated that both CYP144A1 forms are monomeric. CYP144A1-TRV was crystallized and the first structure of a CYP144 family P450 protein determined. CYP144A1-TRV has an open structure primed for substrate binding, with a large active site cavity. Our data provide the first evidence that Mtb produces two different forms of CYP144A1 from alternative transcripts, with CYP144A1-TRV generated from a leaderless transcript lacking a 5′-untranslated region and Shine-Dalgarno ribosome binding site.
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Affiliation(s)
- Jude Chenge
- Manchester Institute of Biotechnology, Centre for Synthetic Biology of Fine and Specialty Chemicals (SYNBIOCHEM), Faculty of Life Sciences, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - Madeline E Kavanagh
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Max D Driscoll
- Manchester Institute of Biotechnology, Centre for Synthetic Biology of Fine and Specialty Chemicals (SYNBIOCHEM), Faculty of Life Sciences, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - Kirsty J McLean
- Manchester Institute of Biotechnology, Centre for Synthetic Biology of Fine and Specialty Chemicals (SYNBIOCHEM), Faculty of Life Sciences, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - Douglas B Young
- Centre for Molecular Microbiology and Infection, Imperial College London, London, United Kingdom
| | - Teresa Cortes
- Department of Pathogen Molecular Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom
| | - Dijana Matak-Vinkovic
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Colin W Levy
- Manchester Institute of Biotechnology, Centre for Synthetic Biology of Fine and Specialty Chemicals (SYNBIOCHEM), Faculty of Life Sciences, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - Stephen E J Rigby
- Manchester Institute of Biotechnology, Centre for Synthetic Biology of Fine and Specialty Chemicals (SYNBIOCHEM), Faculty of Life Sciences, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - David Leys
- Manchester Institute of Biotechnology, Centre for Synthetic Biology of Fine and Specialty Chemicals (SYNBIOCHEM), Faculty of Life Sciences, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - Chris Abell
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Andrew W Munro
- Manchester Institute of Biotechnology, Centre for Synthetic Biology of Fine and Specialty Chemicals (SYNBIOCHEM), Faculty of Life Sciences, The University of Manchester, Manchester M1 7DN, United Kingdom
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Phosphate responsive regulation provides insights for ESX-5 function in Mycobacterium tuberculosis. Curr Genet 2016; 62:759-763. [PMID: 27105642 DOI: 10.1007/s00294-016-0604-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 04/08/2016] [Accepted: 04/11/2016] [Indexed: 10/21/2022]
Abstract
Pathogenic microbes commonly respond to environmental cues in the host by activating specialized protein secretion systems. Mycobacterium tuberculosis uses the specialized Type VII ESX protein secretion systems to transport a subset of effector proteins. The ESX-5 secretion system is involved in virulence, but both the mechanism of regulation and activating signal were unknown. Our work, reviewed here, has established that the phosphate sensing Pst/SenX3-RegX3 system directly activates ESX-5 secretion in response to phosphate limitation, a relevant environmental signal likely encountered by M. tuberculosis in the host. This review focuses on how elucidation of the ESX-5 regulatory network provides insight into its biological roles, which may include both phosphate acquisition and pathogenesis.
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Elliott SR, Tischler AD. Phosphate starvation: a novel signal that triggers ESX-5 secretion in Mycobacterium tuberculosis. Mol Microbiol 2016; 100:510-26. [PMID: 26800324 DOI: 10.1111/mmi.13332] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/18/2016] [Indexed: 12/13/2022]
Abstract
Mycobacterium tuberculosis uses the Type VII ESX secretion systems to transport proteins across its complex cell wall. ESX-5 has been implicated in M. tuberculosis virulence, but the regulatory mechanisms controlling ESX-5 secretion were unknown. Here we uncover a link between ESX-5 and the Pst/SenX3-RegX3 system that controls gene expression in response to phosphate availability. The DNA-binding response regulator RegX3 is normally activated by phosphate limitation. Deletion of pstA1, which encodes a Pst phosphate uptake system component, causes constitutive activation of RegX3. A ΔpstA1 mutant exhibited RegX3-dependent overexpression of esx-5 genes and hyper-secretion of the ESX-5 substrates EsxN and PPE41 when the bacteria were grown in phosphate-rich medium. In wild-type M. tuberculosis, phosphate limitation activated esx-5 transcription and secretion of both EsxN and PPE41, and this response required RegX3. Electrophoretic mobility shift assays revealed that RegX3 binds directly to a promoter within the esx-5 locus. Remarkably, phosphate limitation also induced secretion of EsxB, an effector of the virulence-associated ESX-1 secretion system, though this induction was RegX3 independent. Our work demonstrates that the Pst/SenX3-RegX3 system directly regulates ESX-5 secretion at the transcriptional level in response to phosphate availability and defines phosphate limitation as an environmental signal that activates ESX-5 secretion.
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Affiliation(s)
- Sarah R Elliott
- Department of Microbiology and Immunology, Minneapolis, MN, 55455, USA
| | - Anna D Tischler
- Department of Microbiology and Immunology, Minneapolis, MN, 55455, USA.,Center for Infectious Diseases and Microbiology Translational Research, University of Minnesota Twin Cities, Minneapolis, MN, 55455, USA
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Tufariello JM, Chapman JR, Kerantzas CA, Wong KW, Vilchèze C, Jones CM, Cole LE, Tinaztepe E, Thompson V, Fenyö D, Niederweis M, Ueberheide B, Philips JA, Jacobs WR. Separable roles for Mycobacterium tuberculosis ESX-3 effectors in iron acquisition and virulence. Proc Natl Acad Sci U S A 2016; 113:E348-57. [PMID: 26729876 PMCID: PMC4725510 DOI: 10.1073/pnas.1523321113] [Citation(s) in RCA: 132] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Mycobacterium tuberculosis (Mtb) encodes five type VII secretion systems (T7SS), designated ESX-1-ESX-5, that are critical for growth and pathogenesis. The best characterized is ESX-1, which profoundly impacts host cell interactions. In contrast, the ESX-3 T7SS is implicated in metal homeostasis, but efforts to define its function have been limited by an inability to recover deletion mutants. We overcame this impediment using medium supplemented with various iron complexes to recover mutants with deletions encompassing select genes within esx-3 or the entire operon. The esx-3 mutants were defective in uptake of siderophore-bound iron and dramatically accumulated cell-associated mycobactin siderophores. Proteomic analyses of culture filtrate revealed that secretion of EsxG and EsxH was codependent and that EsxG-EsxH also facilitated secretion of several members of the proline-glutamic acid (PE) and proline-proline-glutamic acid (PPE) protein families (named for conserved PE and PPE N-terminal motifs). Substrates that depended on EsxG-EsxH for secretion included PE5, encoded within the esx-3 locus, and the evolutionarily related PE15-PPE20 encoded outside the esx-3 locus. In vivo characterization of the mutants unexpectedly showed that the ESX-3 secretion system plays both iron-dependent and -independent roles in Mtb pathogenesis. PE5-PPE4 was found to be critical for the siderophore-mediated iron-acquisition functions of ESX-3. The importance of this iron-acquisition function was dependent upon host genotype, suggesting a role for ESX-3 secretion in counteracting host defense mechanisms that restrict iron availability. Further, we demonstrate that the ESX-3 T7SS secretes certain effectors that are important for iron uptake while additional secreted effectors modulate virulence in an iron-independent fashion.
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Affiliation(s)
- JoAnn M Tufariello
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461; Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Jessica R Chapman
- Office of Collaborative Science, New York University School of Medicine, New York, NY 10016
| | - Christopher A Kerantzas
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Ka-Wing Wong
- Shanghai Public Health Clinical Center, Key Laboratory of Medical Molecular Virology of the Ministry of Education/Health, School of Basic Medical Sciences, Fudan University, Shanghai 201508, China
| | - Catherine Vilchèze
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461; Howard Hughes Medical Institute, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Christopher M Jones
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Laura E Cole
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Emir Tinaztepe
- Division of Infectious Diseases, Department of Medicine, New York University School of Medicine, New York, NY 10016
| | - Victor Thompson
- Division of Infectious Diseases, Department of Medicine, New York University School of Medicine, New York, NY 10016
| | - David Fenyö
- Laboratory of Computational Proteomics, Center for Health Informatics and Bioinformatics, New York University School of Medicine, New York, NY 10016; Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016
| | - Michael Niederweis
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Beatrix Ueberheide
- Office of Collaborative Science, New York University School of Medicine, New York, NY 10016; Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016
| | - Jennifer A Philips
- Division of Infectious Diseases, Department of Medicine, New York University School of Medicine, New York, NY 10016;
| | - William R Jacobs
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461; Howard Hughes Medical Institute, Albert Einstein College of Medicine, Bronx, NY 10461;
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Majlessi L, Prados-Rosales R, Casadevall A, Brosch R. Release of mycobacterial antigens. Immunol Rev 2015; 264:25-45. [PMID: 25703550 DOI: 10.1111/imr.12251] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Mycobacterium tuberculosis has evolved from a Mycobacterium canettii-like progenitor pool into one of the most successful and widespread human pathogens. The pathogenicity of M. tuberculosis is linked to its ability to secrete/export/release selected mycobacterial proteins, and it is also established that active release of mycobacterial antigens is a prerequisite for strong immune recognition. Recent research has enabled mycobacterial secretion systems and vesicle-based release of mycobacterial antigens to be elucidated, which together with host-related specificities constitute key variables that determine the outcome of infection. Here, we discuss recently discovered, novel aspects on the nature and the regulation of antigen release of the tuberculosis agent with particular emphasis on the biological characterization of mycobacteria-specific ESX/type VII secretion systems and their secreted proteins, belonging to the Esx, PE, and PPE categories. The importance of specific mycobacterial antigen release is probably best exemplified by the striking differences observed between the cellular events during infection with the ESX-1-deficient, attenuated Mycobacterium bovis BCG compared to the virulent M. tuberculosis, which are clearly important for design of more specific diagnostics and more efficient vaccines.
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Affiliation(s)
- Laleh Majlessi
- Institut Pasteur, Unit for Integrated Mycobacterial Pathogenomics, Paris, France
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The Complete Genome Sequence of the Emerging Pathogen Mycobacterium haemophilum Explains Its Unique Culture Requirements. mBio 2015; 6:e01313-15. [PMID: 26578674 PMCID: PMC4659460 DOI: 10.1128/mbio.01313-15] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
UNLABELLED Mycobacterium haemophilum is an emerging pathogen associated with a variety of clinical syndromes, most commonly skin infections in immunocompromised individuals. M. haemophilum exhibits a unique requirement for iron supplementation to support its growth in culture, but the basis for this property and how it may shape pathogenesis is unclear. Using a combination of Illumina, PacBio, and Sanger sequencing, the complete genome sequence of M. haemophilum was determined. Guided by this sequence, experiments were performed to define the basis for the unique growth requirements of M. haemophilum. We found that M. haemophilum, unlike many other mycobacteria, is unable to synthesize iron-binding siderophores known as mycobactins or to utilize ferri-mycobactins to support growth. These differences correlate with the absence of genes associated with mycobactin synthesis, secretion, and uptake. In agreement with the ability of heme to promote growth, we identified genes encoding heme uptake machinery. Consistent with its propensity to infect the skin, we show at the whole-genome level the genetic closeness of M. haemophilum with Mycobacterium leprae, an organism which cannot be cultivated in vitro, and we identify genes uniquely shared by these organisms. Finally, we identify means to express foreign genes in M. haemophilum. These data explain the unique culture requirements for this important pathogen, provide a foundation upon which the genome sequence can be exploited to improve diagnostics and therapeutics, and suggest use of M. haemophilum as a tool to elucidate functions of genes shared with M. leprae. IMPORTANCE Mycobacterium haemophilum is an emerging pathogen with an unknown natural reservoir that exhibits unique requirements for iron supplementation to grow in vitro. Understanding the basis for this iron requirement is important because it is fundamental to isolation of the organism from clinical samples and environmental sources. Defining the molecular basis for M. haemophilium's growth requirements will also shed new light on mycobacterial strategies to acquire iron and can be exploited to define how differences in such strategies influence pathogenesis. Here, through a combination of sequencing and experimental approaches, we explain the basis for the iron requirement. We further demonstrate the genetic closeness of M. haemophilum and Mycobacterium leprae, the causative agent of leprosy which cannot be cultured in vitro, and we demonstrate methods to genetically manipulate M. haemophilum. These findings pave the way for the use of M. haemophilum as a model to elucidate functions of genes shared with M. leprae.
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40
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Zhang XL, Li DF, Fleming J, Wang LW, Zhou Y, Wang DC, Zhang XE, Bi LJ. Core component EccB1 of the Mycobacterium tuberculosis type VII secretion system is a periplasmic ATPase. FASEB J 2015; 29:4804-14. [PMID: 26396239 DOI: 10.1096/fj.15-270843] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 07/27/2015] [Indexed: 11/11/2022]
Abstract
Pathogenic mycobacteria transport virulence factors across their complex cell wall via a type VII secretion system (T7SS)/early secreted antigenic target-6 of kDa secretion system (ESX). ESX conserved component (Ecc) B, a core component of the T7SS architecture, is predicted to be a membrane bound protein, but little is known about its structure and function. Here, we characterize EccB1, showing that it is an ATPase with no sequence or structural homology to other ATPases located in the cell envelope of Mycobacterium tuberculosis H37Rv. We obtained the crystal structure of an EccB1-ΔN72 truncated transmembrane helix and performed modeling and ATP docking studies, showing that EccB1 likely exists as a hexamer. Sequence alignment and ATPase activity determination of EccB1 homologues indicated the presence of 3 conserved motifs in the N- and C-terminals of EccB1-ΔN72 that assemble together between 2 membrane proximal domains of the EccB1-ΔN72 monomer. Models of the EccB1 hexamer show that 2 of the conserved motifs are involved in ATPase activity and form an ATP binding pocket located on the surface of 2 adjacent molecules. Our results suggest that EccB may act as the energy provider in the transport of T7SS virulence factors and may be involved in the formation of a channel across the mycomembrane.
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Affiliation(s)
- Xiao-Li Zhang
- *State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China; National Laboratory of Biomacromolecules and Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; and Graduate School, Chinese Academy of Sciences, Beijing, China
| | - De-Feng Li
- *State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China; National Laboratory of Biomacromolecules and Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; and Graduate School, Chinese Academy of Sciences, Beijing, China
| | - Joy Fleming
- *State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China; National Laboratory of Biomacromolecules and Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; and Graduate School, Chinese Academy of Sciences, Beijing, China
| | - Li-Wei Wang
- *State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China; National Laboratory of Biomacromolecules and Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; and Graduate School, Chinese Academy of Sciences, Beijing, China
| | - Ying Zhou
- *State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China; National Laboratory of Biomacromolecules and Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; and Graduate School, Chinese Academy of Sciences, Beijing, China
| | - Da-Cheng Wang
- *State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China; National Laboratory of Biomacromolecules and Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; and Graduate School, Chinese Academy of Sciences, Beijing, China
| | - Xian-En Zhang
- *State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China; National Laboratory of Biomacromolecules and Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; and Graduate School, Chinese Academy of Sciences, Beijing, China
| | - Li-Jun Bi
- *State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China; National Laboratory of Biomacromolecules and Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; and Graduate School, Chinese Academy of Sciences, Beijing, China
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Ahmed A, Das A, Mukhopadhyay S. Immunoregulatory functions and expression patterns of PE/PPE family members: Roles in pathogenicity and impact on anti-tuberculosis vaccine and drug design. IUBMB Life 2015; 67:414-27. [DOI: 10.1002/iub.1387] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 04/29/2015] [Indexed: 01/27/2023]
Affiliation(s)
- Asma Ahmed
- Laboratory of Molecular Cell Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD); Hyderabad, Telengana India
| | - Arghya Das
- Laboratory of Molecular Cell Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD); Hyderabad, Telengana India
- Manipal University; Manipal Karnataka India
| | - Sangita Mukhopadhyay
- Laboratory of Molecular Cell Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD); Hyderabad, Telengana India
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Rybniker J, Chen JM, Sala C, Hartkoorn RC, Vocat A, Benjak A, Boy-Röttger S, Zhang M, Székely R, Greff Z, Orfi L, Szabadkai I, Pató J, Kéri G, Cole ST. Anticytolytic screen identifies inhibitors of mycobacterial virulence protein secretion. Cell Host Microbe 2015; 16:538-48. [PMID: 25299337 DOI: 10.1016/j.chom.2014.09.008] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 08/20/2014] [Accepted: 09/17/2014] [Indexed: 11/18/2022]
Abstract
Mycobacterium tuberculosis (Mtb) requires protein secretion systems like ESX-1 for intracellular survival and virulence. The major virulence determinant and ESX-1 substrate, EsxA, arrests phagosome maturation and lyses cell membranes, resulting in tissue damage and necrosis that promotes pathogen spread. To identify inhibitors of Mtb protein secretion, we developed a fibroblast survival assay exploiting this phenotype and selected molecules that protect host cells from Mtb-induced lysis without being bactericidal in vitro. Hit compounds blocked EsxA secretion and promoted phagosome maturation in macrophages, thus reducing bacterial loads. Target identification studies led to the discovery of BTP15, a benzothiophene inhibitor of the histidine kinase MprB that indirectly regulates ESX-1, and BBH7, a benzyloxybenzylidene-hydrazine compound. BBH7 affects Mtb metal-ion homeostasis and revealed zinc stress as an activating signal for EsxA secretion. This screening approach extends the target spectrum of small molecule libraries and will help tackle the mounting problem of antibiotic-resistant mycobacteria.
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Affiliation(s)
- Jan Rybniker
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland; 1(st) Department of Internal Medicine, University of Cologne, 50937 Cologne, Germany
| | - Jeffrey M Chen
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Claudia Sala
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Ruben C Hartkoorn
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Anthony Vocat
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Andrej Benjak
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Stefanie Boy-Röttger
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Ming Zhang
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Rita Székely
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Zoltán Greff
- Vichem Chemie Research Ltd., Herman Otto u. 15, 1022 Budapest, Hungary
| | - László Orfi
- Vichem Chemie Research Ltd., Herman Otto u. 15, 1022 Budapest, Hungary; Department of Pharmaceutical Chemistry, Semmelweis University, Hőgyes Endre u. 9, 1092 Budapest, Hungary
| | - István Szabadkai
- Vichem Chemie Research Ltd., Herman Otto u. 15, 1022 Budapest, Hungary
| | - János Pató
- Vichem Chemie Research Ltd., Herman Otto u. 15, 1022 Budapest, Hungary
| | - György Kéri
- Vichem Chemie Research Ltd., Herman Otto u. 15, 1022 Budapest, Hungary; MTA-SE Pathobiochemistry Research Group, Department of Medical Chemistry, Semmelweis University, 1094 Budapest, Hungary
| | - Stewart T Cole
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.
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Bitter W, Kuijl C. Targeting bacterial virulence: the coming out of type VII secretion inhibitors. Cell Host Microbe 2015; 16:430-2. [PMID: 25299328 DOI: 10.1016/j.chom.2014.09.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Type VII (ESX) secretion systems of pathogenic mycobacteria, such as Mycobacterium tuberculosis, are crucial for intracellular survival, host cell lysis, and the subsequent cell-to-cell spread. In this issue of Cell Host & Microbe, Rybniker et al. (2014) have used these characteristics to identify two classes of type VII secretion inhibitors.
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Affiliation(s)
- Wilbert Bitter
- Department of Medical Microbiology, VU University Medical Center, 1081 BT Amsterdam, the Netherlands; Molecular Microbiology, VU University, 1081 HV Amsterdam, The Netherlands.
| | - Coen Kuijl
- Department of Medical Microbiology, VU University Medical Center, 1081 BT Amsterdam, the Netherlands
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Wassermann R, Gulen MF, Sala C, Perin SG, Lou Y, Rybniker J, Schmid-Burgk JL, Schmidt T, Hornung V, Cole ST, Ablasser A. Mycobacterium tuberculosis Differentially Activates cGAS- and Inflammasome-Dependent Intracellular Immune Responses through ESX-1. Cell Host Microbe 2015; 17:799-810. [PMID: 26048138 DOI: 10.1016/j.chom.2015.05.003] [Citation(s) in RCA: 287] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 03/02/2015] [Accepted: 04/15/2015] [Indexed: 12/21/2022]
Abstract
Cytosolic detection of microbial products is essential for the initiation of an innate immune response against intracellular pathogens such as Mycobacterium tuberculosis (Mtb). During Mtb infection of macrophages, activation of cytosolic surveillance pathways is dependent on the mycobacterial ESX-1 secretion system and leads to type I interferon (IFN) and interleukin-1β (IL-1β) production. Whereas the inflammasome regulates IL-1β secretion, the receptor(s) responsible for the activation of type I IFNs has remained elusive. We demonstrate that the cytosolic DNA sensor cyclic GMP-AMP synthase (cGAS) is essential for initiating an IFN response to Mtb infection. cGAS associates with Mtb DNA in the cytosol to stimulate cyclic GAMP (cGAMP) synthesis. Notably, activation of cGAS-dependent cytosolic host responses can be uncoupled from inflammasome activation by modulating the secretion of ESX-1 substrates. Our findings identify cGAS as an innate sensor of Mtb and provide insight into how ESX-1 controls the activation of specific intracellular recognition pathways.
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Affiliation(s)
- Ruth Wassermann
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Muhammet F Gulen
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Claudia Sala
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Sonia Garcia Perin
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Ye Lou
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Jan Rybniker
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland; First Department of Internal Medicine, University of Cologne, 50937 Cologne, Germany
| | - Jonathan L Schmid-Burgk
- Institute for Molecular Medicine, University Hospital, University of Bonn, 53127 Bonn, Germany
| | - Tobias Schmidt
- Institute for Molecular Medicine, University Hospital, University of Bonn, 53127 Bonn, Germany
| | - Veit Hornung
- Institute for Molecular Medicine, University Hospital, University of Bonn, 53127 Bonn, Germany
| | - Stewart T Cole
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.
| | - Andrea Ablasser
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.
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Mendum TA, Wu H, Kierzek AM, Stewart GR. Lipid metabolism and Type VII secretion systems dominate the genome scale virulence profile of Mycobacterium tuberculosis in human dendritic cells. BMC Genomics 2015; 16:372. [PMID: 25956932 PMCID: PMC4425887 DOI: 10.1186/s12864-015-1569-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 04/23/2015] [Indexed: 12/20/2022] Open
Abstract
Background Mycobacterium tuberculosis continues to kill more people than any other bacterium. Although its archetypal host cell is the macrophage, it also enters, and survives within, dendritic cells (DCs). By modulating the behaviour of the DC, M. tuberculosis is able to manipulate the host’s immune response and establish an infection. To identify the M. tuberculosis genes required for survival within DCs we infected primary human DCs with an M. tuberculosis transposon library and identified mutations with a reduced ability to survive. Results Parallel sequencing of the transposon inserts of the surviving mutants identified a large number of genes as being required for optimal intracellular fitness in DCs. Loci whose mutation attenuated intracellular survival included those involved in synthesising cell wall lipids, not only the well-established virulence factors, pDIM and cord factor, but also sulfolipids and PGL, which have not previously been identified as having a direct virulence role in cells. Other attenuated loci included the secretion systems ESX-1, ESX-2 and ESX-4, alongside many PPE genes, implicating a role for ESX-5. In contrast the canonical ESAT-6 family of ESX substrates did not have intra-DC fitness costs suggesting an alternative ESX-1 associated virulence mechanism. With the aid of a gene-nutrient interaction model, metabolic processes such as cholesterol side chain catabolism, nitrate reductase and cysteine-methionine metabolism were also identified as important for survival in DCs. Conclusion We conclude that many of the virulence factors required for survival in DC are shared with macrophages, but that survival in DCs also requires several additional functions, such as cysteine-methionine metabolism, PGLs, sulfolipids, ESX systems and PPE genes. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1569-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Tom A Mendum
- Department of Microbial and Cellular Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, UK.
| | - Huihai Wu
- Department of Microbial and Cellular Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, UK.
| | - Andrzej M Kierzek
- Department of Microbial and Cellular Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, UK.
| | - Graham R Stewart
- Department of Microbial and Cellular Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, UK.
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Ates LS, Ummels R, Commandeur S, van der Weerd R, Sparrius M, Weerdenburg E, Alber M, Kalscheuer R, Piersma SR, Abdallah AM, Abd El Ghany M, Abdel-Haleem AM, Pain A, Jiménez CR, Bitter W, Houben EN. Essential Role of the ESX-5 Secretion System in Outer Membrane Permeability of Pathogenic Mycobacteria. PLoS Genet 2015; 11:e1005190. [PMID: 25938982 PMCID: PMC4418733 DOI: 10.1371/journal.pgen.1005190] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 04/02/2015] [Indexed: 12/03/2022] Open
Abstract
Mycobacteria possess different type VII secretion (T7S) systems to secrete proteins across their unusual cell envelope. One of these systems, ESX-5, is only present in slow-growing mycobacteria and responsible for the secretion of multiple substrates. However, the role of ESX-5 substrates in growth and/or virulence is largely unknown. In this study, we show that esx-5 is essential for growth of both Mycobacterium marinum and Mycobacterium bovis. Remarkably, this essentiality can be rescued by increasing the permeability of the outer membrane, either by altering its lipid composition or by the introduction of the heterologous porin MspA. Mutagenesis of the first nucleotide-binding domain of the membrane ATPase EccC5 prevented both ESX-5-dependent secretion and bacterial growth, but did not affect ESX-5 complex assembly. This suggests that the rescuing effect is not due to pores formed by the ESX-5 membrane complex, but caused by ESX-5 activity. Subsequent proteomic analysis to identify crucial ESX-5 substrates confirmed that all detectable PE and PPE proteins in the cell surface and cell envelope fractions were routed through ESX-5. Additionally, saturated transposon-directed insertion-site sequencing (TraDIS) was applied to both wild-type M. marinum cells and cells expressing mspA to identify genes that are not essential anymore in the presence of MspA. This analysis confirmed the importance of esx-5, but we could not identify essential ESX-5 substrates, indicating that multiple of these substrates are together responsible for the essentiality. Finally, examination of phenotypes on defined carbon sources revealed that an esx-5 mutant is strongly impaired in the uptake and utilization of hydrophobic carbon sources. Based on these data, we propose a model in which the ESX-5 system is responsible for the transport of cell envelope proteins that are required for nutrient uptake. These proteins might in this way compensate for the lack of MspA-like porins in slow-growing mycobacteria.
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Affiliation(s)
- Louis S. Ates
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
| | - Roy Ummels
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
| | - Susanna Commandeur
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
| | - Robert van der Weerd
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
| | - Marion Sparrius
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
| | - Eveline Weerdenburg
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
| | - Marina Alber
- Institute for Medical Microbiology and Hospital Hygiene, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Rainer Kalscheuer
- Institute for Medical Microbiology and Hospital Hygiene, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Sander R. Piersma
- Department of Medical Oncology, OncoProteomics Laboratory, VU University Medical Center, Amsterdam, the Netherlands
| | - Abdallah M. Abdallah
- Biological and Environmental Sciences and Engineering (BESE) division, King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
| | - Moataz Abd El Ghany
- Biological and Environmental Sciences and Engineering (BESE) division, King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
| | - Alyaa M. Abdel-Haleem
- Biological and Environmental Sciences and Engineering (BESE) division, King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
| | - Arnab Pain
- Biological and Environmental Sciences and Engineering (BESE) division, King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
| | - Connie R. Jiménez
- Department of Medical Oncology, OncoProteomics Laboratory, VU University Medical Center, Amsterdam, the Netherlands
| | - Wilbert Bitter
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
- Section Molecular Microbiology, Amsterdam Institute of Molecules, Medicine & Systems, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Edith N.G. Houben
- Section Molecular Microbiology, Amsterdam Institute of Molecules, Medicine & Systems, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
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Abstract
PURPOSE OF REVIEW Chronic infections of the small intestine cause significant morbidity and mortality globally. This review focuses on the recent advances in the field of our understanding of selected intestinal infections. RECENT FINDINGS Primary and secondary immunodeficiency increase the susceptibility to many chronic intestinal infections. Endoscopy and intestinal biopsies are central to establishing a diagnosis of these conditions. Tuberculosis (TB) remains a major global health challenge. Emerging therapeutic agents to counteract multidrug-resistant strains have shown clinical efficacy, but concerns regarding mortality remain. PCR-based diagnostic TB tests have the potential to reduce diagnostic delays, but remain to be validated for intestinal infections. Adjunctive diagnostic imaging modalities can differentiate infections from Crohn's disease with increasing accuracy. Whipple's disease remains rare, but there have been substantial advances in our understanding of the causative organism Tropheryma whipplei. Extended treatment with broad-spectrum antibiotics is effective in most cases. The narrow therapeutic window and limited armamentarium for treating invasive filamentous fungal infections contribute to their significant morbidity and high rates of mortality. SUMMARY The speed and accuracy of diagnosing chronic intestinal infections have improved with recent imaging and laboratory methodologies. Significant research opportunities remain for clinicians and scientists to improve the diagnostic accuracy and clinical outcomes of chronic intestinal infections.
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Affiliation(s)
- Billy Bourke
- aNational Centre for Paediatric Gastroenterology, Our Lady's Children's Hospital bNational Children's Research Centre, Crumlin, Dublin cUCD School of Medicine and Medical Science dConway Institute, University College Dublin, Belfield, Dublin, Ireland
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Genome-wide transposon mutagenesis indicates that Mycobacterium marinum customizes its virulence mechanisms for survival and replication in different hosts. Infect Immun 2015; 83:1778-88. [PMID: 25690095 DOI: 10.1128/iai.03050-14] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 02/05/2015] [Indexed: 11/20/2022] Open
Abstract
The interaction of environmental bacteria with unicellular eukaryotes is generally considered a major driving force for the evolution of intracellular pathogens, allowing them to survive and replicate in phagocytic cells of vertebrate hosts. To test this hypothesis on a genome-wide level, we determined for the intracellular pathogen Mycobacterium marinum whether it uses conserved strategies to exploit host cells from both protozoan and vertebrate origin. Using transposon-directed insertion site sequencing (TraDIS), we determined differences in genetic requirements for survival and replication in phagocytic cells of organisms from different kingdoms. In line with the general hypothesis, we identified a number of general virulence mechanisms, including the type VII protein secretion system ESX-1, biosynthesis of polyketide lipids, and utilization of sterols. However, we were also able to show that M. marinum contains an even larger set of host-specific virulence determinants, including proteins involved in the modification of surface glycolipids and, surprisingly, the auxiliary proteins of the ESX-1 system. Several of these factors were in fact counterproductive in other hosts. Therefore, M. marinum contains different sets of virulence factors that are tailored for specific hosts. Our data imply that although amoebae could function as a training ground for intracellular pathogens, they do not fully prepare pathogens for crossing species barriers.
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49
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van Leeuwen LM, van der Sar AM, Bitter W. Animal models of tuberculosis: zebrafish. Cold Spring Harb Perspect Med 2014; 5:a018580. [PMID: 25414379 DOI: 10.1101/cshperspect.a018580] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Over the past decade the zebrafish (Danio rerio) has become an attractive new vertebrate model organism for studying mycobacterial pathogenesis. The combination of medium-throughput screening and real-time in vivo visualization has allowed new ways to dissect host pathogenic interaction in a vertebrate host. Furthermore, genetic screens on the host and bacterial sides have elucidated new mechanisms involved in the initiation of granuloma formation and the importance of a balanced immune response for control of mycobacterial pathogens. This article will highlight the unique features of the zebrafish-Mycobacterium marinum infection model and its added value for tuberculosis research.
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Affiliation(s)
- Lisanne M van Leeuwen
- Department of Pediatric Infectious Diseases and Immunology, VU University Medical Center, 1081 HV Amsterdam, The Netherlands Department of Medical Microbiology and Infection control, VU University Medical Center, 1081 BT Amsterdam, The Netherlands
| | - Astrid M van der Sar
- Department of Pediatric Infectious Diseases and Immunology, VU University Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Wilbert Bitter
- Department of Pediatric Infectious Diseases and Immunology, VU University Medical Center, 1081 HV Amsterdam, The Netherlands Department of Molecular Microbiology, VU University, 1081 HV Amsterdam, The Netherlands
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50
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Impact of protein domains on PE_PGRS30 polar localization in Mycobacteria. PLoS One 2014; 9:e112482. [PMID: 25390359 PMCID: PMC4229189 DOI: 10.1371/journal.pone.0112482] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 10/06/2014] [Indexed: 12/03/2022] Open
Abstract
PE_PGRS proteins are unique to the Mycobacterium tuberculosis complex and a number of other pathogenic mycobacteria. PE_PGRS30, which is required for the full virulence of M. tuberculosis (Mtb), has three main domains, i.e. an N-terminal PE domain, repetitive PGRS domain and the unique C-terminal domain. To investigate the role of these domains, we expressed a GFP-tagged PE_PGRS30 protein and a series of its functional deletion mutants in different mycobacterial species (Mtb, Mycobacterium bovis BCG and Mycobacterium smegmatis) and analysed protein localization by confocal microscopy. We show that PE_PGRS30 localizes at the mycobacterial cell poles in Mtb and M. bovis BCG but not in M. smegmatis and that the PGRS domain of the protein strongly contributes to protein cellular localization in Mtb. Immunofluorescence studies further showed that the unique C-terminal domain of PE_PGRS30 is not available on the surface, except when the PGRS domain is missing. Immunoblot demonstrated that the PGRS domain is required to maintain the protein strongly associated with the non-soluble cellular fraction. These results suggest that the repetitive GGA-GGN repeats of the PGRS domain contain specific sequences that contribute to protein cellular localization and that polar localization might be a key step in the PE_PGRS30-dependent virulence mechanism.
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