1
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Luo G, Ming T, Yang L, He L, Tao T, Wang Y. Modulators targeting protein-protein interactions in Mycobacterium tuberculosis. Microbiol Res 2024; 284:127675. [PMID: 38636239 DOI: 10.1016/j.micres.2024.127675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 03/03/2024] [Accepted: 03/04/2024] [Indexed: 04/20/2024]
Abstract
Tuberculosis (TB) is a chronic infectious disease caused by Mycobacterium tuberculosis (M. tuberculosis), mainly transmitted through droplets to infect the lungs, and seriously affecting patients' health and quality of life. Clinically, anti-TB drugs often entail side effects and lack efficacy against resistant strains. Thus, the exploration and development of novel targeted anti-TB medications are imperative. Currently, protein-protein interactions (PPIs) offer novel avenues for anti-TB drug development, and the study of targeted modulators of PPIs in M. tuberculosis has become a prominent research focus. Furthermore, a comprehensive PPI network has been constructed using computational methods and bioinformatics tools. This network allows for a more in-depth analysis of the structural biology of PPIs and furnishes essential insights for the development of targeted small-molecule modulators. Furthermore, this article provides a detailed overview of the research progress and regulatory mechanisms of PPI modulators in M. tuberculosis, the causative agent of TB. Additionally, it summarizes potential targets for anti-TB drugs and discusses the prospects of existing PPI modulators.
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Affiliation(s)
- Guofeng Luo
- School of Medical and Life Sciences, Chengdu University of Traditional Chinese Medicine, Chengdu 611137, China
| | - Tianqi Ming
- State Key Laboratory of Southwestern Chinese Medicine Resources, Department of Pharmacology, Chengdu University of Traditional Chinese Medicine, Chengdu 611137, China
| | - Luchuan Yang
- Institute of traditional Chinese medicine, Sichuan College of traditional Chinese Medicine (Sichuan Second Hospital of TCM), Chengdu 610031, China
| | - Lei He
- Institute of traditional Chinese medicine, Sichuan College of traditional Chinese Medicine (Sichuan Second Hospital of TCM), Chengdu 610031, China
| | - Tao Tao
- Institute of traditional Chinese medicine, Sichuan College of traditional Chinese Medicine (Sichuan Second Hospital of TCM), Chengdu 610031, China
| | - Yanmei Wang
- Institute of traditional Chinese medicine, Sichuan College of traditional Chinese Medicine (Sichuan Second Hospital of TCM), Chengdu 610031, China.
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2
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Garrett SR, Higginson AB, Palmer T. Multiple variants of the type VII secretion system in Gram-positive bacteria. MICROLIFE 2024; 5:uqae013. [PMID: 38957458 PMCID: PMC11217815 DOI: 10.1093/femsml/uqae013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 05/08/2024] [Accepted: 06/04/2024] [Indexed: 07/04/2024]
Abstract
Type VII secretion systems (T7SS) are found in bacteria across the Bacillota and Actinomycetota phyla and have been well described in Staphylococcus aureus, Bacillus subtilis, and pathogenic mycobacteria. The T7SS from Actinomycetota and Bacillota share two common components, a membrane-bound EccC/EssC ATPase and EsxA, a small helical hairpin protein of the WXG100 family. However, they also have additional phylum-specific components, and as a result they are termed the T7SSa (Actinomycetota) and T7SSb (Bacillota), respectively. Here, we identify additional organizations of the T7SS across these two phyla and describe eight additional T7SS subtypes, which we have named T7SSc-T7SSj. T7SSd is found exclusively in Actinomycetota including the Olselnella and Bifodobacterium genus, whereas the other seven are found only in Bacillota. All of the novel subtypes contain the canonical ATPase (TsxC) and the WXG100-family protein (TsxA). Most of them also contain a small ubiquitin-related protein, TsxB, related to the T7SSb EsaB/YukD component. Protein kinases, phosphatases, and forkhead-associated (FHA) proteins are often encoded in the novel T7SS gene clusters. Candidate substrates of these novel T7SS subtypes include LXG-domain and RHS proteins. Predicted substrates are frequently encoded alongside genes for additional small WXG100-related proteins that we speculate serve as cosecretion partners. Collectively our findings reveal unexpected diversity in the T7SS in Gram-positive bacteria.
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Affiliation(s)
- Stephen R Garrett
- Newcastle University Biosciences Institute, Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, United Kingdom
| | - Andrew B Higginson
- Newcastle University Biosciences Institute, Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, United Kingdom
| | - Tracy Palmer
- Newcastle University Biosciences Institute, Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, United Kingdom
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3
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Boardman ER, Palmer T, Alcock F. Interbacterial competition mediated by the type VIIb secretion system. MICROBIOLOGY (READING, ENGLAND) 2023; 169:001420. [PMID: 38116759 PMCID: PMC10765036 DOI: 10.1099/mic.0.001420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 12/06/2023] [Indexed: 12/21/2023]
Abstract
Successful occupancy of a given niche requires the colonising bacteria to interact extensively with the biotic and abiotic environment, including other resident microbes. Bacteria have evolved a range of protein secretion machines for this purpose with eleven such systems identified to date. The type VIIb secretion system (T7SSb) is utilised by Bacillota to secrete a range of protein substrates, including antibacterial toxins targeting closely related strains, and the system as a whole has been implicated in a range of activities such as iron acquisition, intercellular signalling, host colonisation and virulence. This review covers the components and secretion mechanism of the T7SSb, the substrates of these systems and their roles in Gram-positive bacteria, with a focus on interbacterial competition.
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Affiliation(s)
- Eleanor R. Boardman
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Tracy Palmer
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Felicity Alcock
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
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4
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Bunduc CM, Ding Y, Kuijl C, Marlovits TC, Bitter W, Houben ENG. Reconstitution of a minimal ESX-5 type VII secretion system suggests a role for PPE proteins in the outer membrane transport of proteins. mSphere 2023; 8:e0040223. [PMID: 37747201 PMCID: PMC10597459 DOI: 10.1128/msphere.00402-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 08/03/2023] [Indexed: 09/26/2023] Open
Abstract
Mycobacteria utilize type VII secretion systems (T7SSs) to secrete proteins across their highly hydrophobic and diderm cell envelope. Pathogenic mycobacteria have up to five different T7SSs, called ESX-1 to ESX-5, which are crucial for growth and virulence. Here, we use a functionally reconstituted ESX-5 system in the avirulent species Mycobacterium smegmatis that lacks ESX-5, to define the role of each esx-5 gene in system functionality. By creating an array of gene deletions and assessing protein levels of components and membrane complex assembly, we observed that only the five components of the inner membrane complex are required for its assembly. However, in addition to these five core components, active secretion also depends on both the Esx and PE/PPE substrates. Tagging the PPE substrates followed by subcellular fractionation, surface labeling and membrane extraction showed that these proteins localize to the mycobacterial outer membrane. This indicates that they could play a role in secretion across this enigmatic outer barrier. These results provide the first full overview of the role of each esx-5 gene in T7SS functionality. IMPORTANCE Pathogenic mycobacteria, such as the notorious Mycobacterium tuberculosis, are highly successful as pathogens, in part due to their specific and diderm cell envelope, with a mycolic acid-containing outer membrane. The architecture of this highly impermeable membrane is little understood and the proteins that populate it even less so. To transport proteins across their cell envelope, mycobacteria employ a specialized transport pathway called type VII secretion. While recent studies have elucidated the type VII secretion membrane channel that mediates transport across the inner membrane, the identity of the outer membrane channel remains a black box. Here, we show evidence that specific substrates of the type VII pathway could form these channels. Elucidating the pathway and mechanism of protein secretion through the mycobacterial outer membrane will allow its exploitation for the development of novel mycobacterial therapeutics.
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Affiliation(s)
- C. M. Bunduc
- Molecular Microbiology Section, Amsterdam Institute for Life and Environment (A-Life), Vrije Universiteit, Amsterdam, The Netherlands
- Centre for Structural Systems Biology, Notkestraße, Hamburg, Germany
- Institute of Structural and Systems Biology, University Medical Center Hamburg-Eppendorf, Notkestraße, Hamburg, Germany
- German Electron Synchrotron Centre, Notkestraße, Hamburg, Germany
| | - Y. Ding
- Molecular Microbiology Section, Amsterdam Institute for Life and Environment (A-Life), Vrije Universiteit, Amsterdam, The Netherlands
| | - C. Kuijl
- Department of Medical Microbiology and Infection Control, Amsterdam UMC, Amsterdam, The Netherlands
| | - T. C. Marlovits
- Centre for Structural Systems Biology, Notkestraße, Hamburg, Germany
- Institute of Structural and Systems Biology, University Medical Center Hamburg-Eppendorf, Notkestraße, Hamburg, Germany
- German Electron Synchrotron Centre, Notkestraße, Hamburg, Germany
| | - W. Bitter
- Molecular Microbiology Section, Amsterdam Institute for Life and Environment (A-Life), Vrije Universiteit, Amsterdam, The Netherlands
- Department of Medical Microbiology and Infection Control, Amsterdam UMC, Amsterdam, The Netherlands
| | - E. N. G. Houben
- Molecular Microbiology Section, Amsterdam Institute for Life and Environment (A-Life), Vrije Universiteit, Amsterdam, The Netherlands
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5
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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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6
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D'Souza C, Kishore U, Tsolaki AG. The PE-PPE Family of Mycobacterium tuberculosis: Proteins in Disguise. Immunobiology 2023; 228:152321. [PMID: 36805109 DOI: 10.1016/j.imbio.2022.152321] [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: 06/28/2022] [Revised: 12/22/2022] [Accepted: 12/27/2022] [Indexed: 12/31/2022]
Abstract
Mycobacterium tuberculosis has thrived in parallel with humans for millennia, and despite our efforts, M. tuberculosis continues to plague us, currently infecting a third of the world's population. The success of M. tuberculosis has recently been attributed, in part, to the PE-PPE family; a unique collection of 168 proteins fundamentally involved in the pathogenesis of M. tuberculosis. The PE-PPE family proteins have been at the forefront of intense research efforts since their discovery in 1998 and whilst our knowledge and understanding has significantly advanced over the last two decades, many important questions remain to be elucidated. This review consolidates and examines the vast body of existing literature regarding the PE-PPE family proteins, with respect to the latest developments in elucidating their evolution, structure, subcellular localisation, function, and immunogenicity. This review also highlights significant inconsistencies and contradictions within the field. Additionally, possible explanations for these knowledge gaps are explored. Lastly, this review poses many important questions, which need to be addressed to complete our understanding of the PE-PPE family, as well as highlighting the challenges associated with studying this enigmatic family of proteins. Further research into the PE-PPE family, together with technological advancements in genomics and proteomics, will undoubtedly improve our understanding of the pathogenesis of M. tuberculosis, as well as identify key targets/candidates for the development of novel drugs, diagnostics, and vaccines.
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Affiliation(s)
- Christopher D'Souza
- Biosciences, Department of Life Sciences, College of Health, Medicine and Life Sciences, Brunel University London, Uxbridge UB8 3PH, United Kingdom
| | - Uday Kishore
- Department of Veterinary Medicine, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Anthony G Tsolaki
- Biosciences, Department of Life Sciences, College of Health, Medicine and Life Sciences, Brunel University London, Uxbridge UB8 3PH, United Kingdom.
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7
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The ESX-1 Substrate PPE68 Has a Key Function in ESX-1-Mediated Secretion in Mycobacterium marinum. mBio 2022; 13:e0281922. [PMID: 36409073 PMCID: PMC9765416 DOI: 10.1128/mbio.02819-22] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Mycobacteria use specialized type VII secretion systems (T7SSs) to secrete proteins across their diderm cell envelope. One of the T7SS subtypes, named ESX-1, is a major virulence determinant in pathogenic species such as Mycobacterium tuberculosis and the fish pathogen Mycobacterium marinum. ESX-1 secretes a variety of substrates, called Esx, PE, PPE, and Esp proteins, at least some of which are folded heterodimers. Investigation into the functions of these substrates is problematic, because of the intricate network of codependent secretion between several ESX-1 substrates. Here, we describe the ESX-1 substrate PPE68 as essential for secretion of the highly immunogenic substrates EsxA and EspE via the ESX-1 system in M. marinum. While secreted PPE68 is processed on the cell surface, the majority of cell-associated PPE68 of M. marinum and M. tuberculosis is present in a cytosolic complex with its PE partner and the EspG1 chaperone. Interfering with the binding of EspG1 to PPE68 blocked its export and the secretion of EsxA and EspE. In contrast, esxA was not required for the secretion of PPE68, revealing a hierarchy in codependent secretion. Remarkably, the final 10 residues of PPE68, a negatively charged domain, seem essential for EspE secretion, but not for the secretion of EsxA and of PPE68 itself. This indicates that distinctive domains of PPE68 are involved in secretion of the different ESX-1 substrates. Based on these findings, we propose a mechanistic model for the central role of PPE68 in ESX-1-mediated secretion and substrate codependence. IMPORTANCE Pathogenic mycobacteria, such Mycobacterium tuberculosis and Mycobacterium marinum, use a type VII secretion system (T7SS) subtype, called ESX-1, to mediate intracellular survival via phagosomal rupture and subsequent translocation of the mycobacterium to the host cytosol. Identifying the ESX-1 substrate that is responsible for this process is problematic because of the intricate network of codependent secretion between ESX-1 substrates. Here, we show the central role of the ESX-1 substrate PPE68 for the secretion of ESX-1 substrates in Mycobacterium marinum. Unravelling the mechanism of codependent secretion will aid the functional understanding of T7SSs and will allow the analysis of the individual roles of ESX-1 substrates in the virulence caused by the significant human pathogen Mycobacterium tuberculosis.
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8
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Rivera-Calzada A, Famelis N, Llorca O, Geibel S. Type VII secretion systems: structure, functions and transport models. Nat Rev Microbiol 2021; 19:567-584. [PMID: 34040228 DOI: 10.1038/s41579-021-00560-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/09/2021] [Indexed: 02/07/2023]
Abstract
Type VII secretion systems (T7SSs) have a key role in the secretion of effector proteins in non-pathogenic mycobacteria and pathogenic mycobacteria such as Mycobacterium tuberculosis, the main causative agent of tuberculosis. Tuberculosis-causing mycobacteria, still accounting for 1.4 million deaths annually, rely on paralogous T7SSs to survive in the host and efficiently evade its immune response. Although it is still unknown how effector proteins of T7SSs cross the outer membrane of the diderm mycobacterial cell envelope, recent advances in the structural characterization of these secretion systems have revealed the intricate network of interactions of conserved components in the plasma membrane. This structural information, added to recent advances in the molecular biology and regulation of mycobacterial T7SSs as well as progress in our understanding of their secreted effector proteins, is shedding light on the inner working of the T7SS machinery. In this Review, we highlight the implications of these studies and the derived transport models, which provide new scenarios for targeting the deathly human pathogen M. tuberculosis.
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Affiliation(s)
- Angel Rivera-Calzada
- Structural Biology Programme, Spanish National Cancer Research Centre (CNIO), Madrid, Spain.
| | - Nikolaos Famelis
- Institute for Molecular Infection Biology, Julius-Maximilian University of Würzburg, Würzburg, Germany.,Rudolf Virchow Center for Integrative and Translational Biomedicine, Julius-Maximilian University of Würzburg, Würzburg, Germany
| | - Oscar Llorca
- Structural Biology Programme, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | - Sebastian Geibel
- Institute for Molecular Infection Biology, Julius-Maximilian University of Würzburg, Würzburg, Germany. .,Rudolf Virchow Center for Integrative and Translational Biomedicine, Julius-Maximilian University of Würzburg, Würzburg, Germany.
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9
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Abstract
The type VII protein secretion system (T7SS) of Staphylococcus aureus is encoded at the ess locus. T7 substrate recognition and protein transport are mediated by EssC, a membrane-bound multidomain ATPase. Four EssC sequence variants have been identified across S. aureus strains, each accompanied by a specific suite of substrate proteins. The ess genes are upregulated during persistent infection, and the secretion system contributes to virulence in disease models. It also plays a key role in intraspecies competition, secreting nuclease and membrane-depolarizing toxins that inhibit the growth of strains lacking neutralizing immunity proteins. A genomic survey indicates that the T7SS is widely conserved across staphylococci and is encoded in clusters that contain diverse arrays of toxin and immunity genes. The presence of genomic islands encoding multiple immunity proteins in species such as Staphylococcus warneri that lack the T7SS points to a major role for the secretion system in bacterial antagonism. Expected final online publication date for the Annual Review of Microbiology, Volume 75 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Lisa Bowman
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, United Kingdom; ,
| | - Tracy Palmer
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, United Kingdom; ,
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10
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Gijsbers A, Vinciauskaite V, Siroy A, Gao Y, Tria G, Mathew A, Sánchez-Puig N, López-Iglesias C, Peters PJ, Ravelli RBG. Priming mycobacterial ESX-secreted protein B to form a channel-like structure. Curr Res Struct Biol 2021; 3:153-164. [PMID: 34337436 PMCID: PMC8313811 DOI: 10.1016/j.crstbi.2021.06.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 05/20/2021] [Accepted: 06/17/2021] [Indexed: 01/24/2023] Open
Abstract
ESX-1 is a major virulence factor of Mycobacterium tuberculosis, a secretion machinery directly involved in the survival of the microorganism from the immune system defence. It disrupts the phagosome membrane of the host cell through a contact-dependent mechanism. Recently, the structure of the inner-membrane core complex of the homologous ESX-3 and ESX-5 was resolved; however, the elements involved in the secretion through the outer membrane or those acting on the host cell membrane are unknown. Protein substrates might form this missing element. Here, we describe the oligomerisation process of the ESX-1 substrate EspB, which occurs upon cleavage of its C-terminal region and is favoured by an acidic environment. Cryo-electron microscopy data shows that quaternary structure of EspB is conserved across slow growing species, but not in the fast growing M. smegmatis. EspB assembles into a channel with dimensions and characteristics suitable for the transit of ESX-1 substrates, as shown by the presence of another EspB trapped within. Our results provide insight into the structure and assembly of EspB, and suggests a possible function as a structural element of ESX-1.
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Affiliation(s)
- Abril Gijsbers
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Universiteitssingel 50, 6229 ER, Maastricht, the Netherlands
| | - Vanesa Vinciauskaite
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Universiteitssingel 50, 6229 ER, Maastricht, the Netherlands
| | - Axel Siroy
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Universiteitssingel 50, 6229 ER, Maastricht, the Netherlands
| | - Ye Gao
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Universiteitssingel 50, 6229 ER, Maastricht, the Netherlands
| | - Giancarlo Tria
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Universiteitssingel 50, 6229 ER, Maastricht, the Netherlands
| | - Anjusha Mathew
- Division of Imaging Mass Spectrometry, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Universiteitssingel 50, 6229 ER, Maastricht, the Netherlands
| | - Nuria Sánchez-Puig
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Universiteitssingel 50, 6229 ER, Maastricht, the Netherlands
- Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Ciudad de México, 04510, Mexico
| | - Carmen López-Iglesias
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Universiteitssingel 50, 6229 ER, Maastricht, the Netherlands
| | - Peter J Peters
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Universiteitssingel 50, 6229 ER, Maastricht, the Netherlands
| | - Raimond B G Ravelli
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Universiteitssingel 50, 6229 ER, Maastricht, the Netherlands
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11
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Tran HKR, Grebenc DW, Klein TA, Whitney JC. Bacterial type VII secretion: An important player in host-microbe and microbe-microbe interactions. Mol Microbiol 2021; 115:478-489. [PMID: 33410158 DOI: 10.1111/mmi.14680] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Revised: 01/03/2021] [Accepted: 01/04/2021] [Indexed: 12/19/2022]
Abstract
Type VII secretion systems (T7SSs) are poorly understood protein export apparatuses found in mycobacteria and many species of Gram-positive bacteria. To date, this pathway has predominantly been studied in Mycobacterium tuberculosis, where it has been shown to play an essential role in virulence; however, much less studied is an evolutionarily divergent subfamily of T7SSs referred to as the T7SSb. The T7SSb is found in the major Gram-positive phylum Firmicutes where it was recently shown to target both eukaryotic and prokaryotic cells, suggesting a dual role for this pathway in host-microbe and microbe-microbe interactions. In this review, we compare the current understanding of the molecular architectures and substrate repertoires of the well-studied mycobacterial T7SSa systems to that of recently characterized T7SSb pathways and highlight how these differences may explain the observed biological functions of this understudied protein export machine.
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Affiliation(s)
- Hiu-Ki R Tran
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada.,Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada
| | - Dirk W Grebenc
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada.,Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada
| | - Timothy A Klein
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada.,Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada
| | - John C Whitney
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada.,Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada.,David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, ON, Canada
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12
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Modeling Tubercular ESX-1 Secretion Using Mycobacterium marinum. Microbiol Mol Biol Rev 2020; 84:84/4/e00082-19. [DOI: 10.1128/mmbr.00082-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Pathogenic mycobacteria cause chronic and acute diseases ranging from human tuberculosis (TB) to nontubercular infections.
Mycobacterium tuberculosis
causes both acute and chronic human tuberculosis. Environmentally acquired nontubercular mycobacteria (NTM) cause chronic disease in humans and animals. Not surprisingly, NTM and
M. tuberculosis
often use shared molecular mechanisms to survive within the host. The ESX-1 system is a specialized secretion system that is essential for virulence and is functionally conserved between
M. tuberculosis
and
Mycobacterium marinum
.
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13
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Qu Z, Zhou J, Zhou Y, Xie Y, Jiang Y, Wu J, Luo Z, Liu G, Yin L, Zhang XL. Mycobacterial EST12 activates a RACK1-NLRP3-gasdermin D pyroptosis-IL-1β immune pathway. SCIENCE ADVANCES 2020; 6:6/43/eaba4733. [PMID: 33097533 PMCID: PMC7608829 DOI: 10.1126/sciadv.aba4733] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 09/11/2020] [Indexed: 05/28/2023]
Abstract
Pyroptosis, an inflammatory form of programmed cell death, has been implicated in eliminating pathogenic infections. However, macrophage pyroptosis-related proteins from Mycobacterium tuberculosis (M.tb) have largely gone unexplored. Here, we identified a cell pyroptosis-inducing protein, Rv1579c, named EST12, secreted from the M.tb H37Rv region of difference 3. EST12 binds to the receptor for activated C kinase 1 (RACK1) in macrophages, and the EST12-RACK1 complex recruits the deubiquitinase UCHL5 to promote the K48-linked deubiquitination of NLRP3, subsequently leading to an NLRP3 inflammasome caspase-1/11-pyroptosis gasdermin D-interleukin-1β immune process. Analysis of the crystal structure of EST12 reveals that the amino acid Y80 acts as a critical binding site for RACK1. An EST12-deficient strain (H37RvΔEST12) displayed higher susceptibility to M.tb infection in vitro and in vivo. These results provide the first proof that RACK1 acts as an endogenous host sensor for pathogens and that EST12-RACK1-induced pyroptosis plays a pivotal role in M.tb-induced immunity.
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Affiliation(s)
- Zilu Qu
- Hubei Province Key Laboratory of Allergy and Immunology, Department of Immunology of School of Basic Medical Sciences and Department of Allergy of Zhongnan Hospital, Wuhan University, Wuhan 430071, China
| | - Jin Zhou
- State Key Laboratory of Virology, Department of Biochemistry and Molecular Biology, College of Life Sciences, Wuhan University, Wuhan 430077, China
| | - Yidan Zhou
- Department of Microbiology, School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, Champaign, IL, USA
| | - Yan Xie
- Hubei Province Key Laboratory of Allergy and Immunology, Department of Immunology of School of Basic Medical Sciences and Department of Allergy of Zhongnan Hospital, Wuhan University, Wuhan 430071, China
| | - Yanjing Jiang
- State Key Laboratory of Virology, Department of Biochemistry and Molecular Biology, College of Life Sciences, Wuhan University, Wuhan 430077, China
| | - Jian Wu
- Hubei Province Key Laboratory of Allergy and Immunology, Department of Immunology of School of Basic Medical Sciences and Department of Allergy of Zhongnan Hospital, Wuhan University, Wuhan 430071, China
| | - Zuoqin Luo
- State Key Laboratory of Virology, Department of Biochemistry and Molecular Biology, College of Life Sciences, Wuhan University, Wuhan 430077, China
| | - Guanghui Liu
- Hubei Province Key Laboratory of Allergy and Immunology, Department of Immunology of School of Basic Medical Sciences and Department of Allergy of Zhongnan Hospital, Wuhan University, Wuhan 430071, China
| | - Lei Yin
- State Key Laboratory of Virology, Department of Biochemistry and Molecular Biology, College of Life Sciences, Wuhan University, Wuhan 430077, China.
| | - Xiao-Lian Zhang
- Hubei Province Key Laboratory of Allergy and Immunology, Department of Immunology of School of Basic Medical Sciences and Department of Allergy of Zhongnan Hospital, Wuhan University, Wuhan 430071, China.
- State Key Laboratory of Virology, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan 430071, China
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14
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Bunduc CM, Bitter W, Houben E. Structure and Function of the Mycobacterial Type VII Secretion Systems. Annu Rev Microbiol 2020; 74:315-335. [DOI: 10.1146/annurev-micro-012420-081657] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Bacteria have evolved intricate secretion machineries for the successful delivery of large molecules across their cell envelopes. Such specialized secretion systems allow a variety of bacteria to thrive in specific host environments. In mycobacteria, type VII secretion systems (T7SSs) are dedicated protein transport machineries that fulfill diverse and crucial roles, ranging from metabolite uptake to immune evasion and subversion to conjugation. Since the discovery of mycobacterial T7SSs about 15 y ago, genetic, structural, and functional studies have provided insight into the roles and functioning of these secretion machineries. Here, we focus on recent advances in the elucidation of the structure and mechanism of mycobacterial T7SSs in protein secretion. As many of these systems are essential for mycobacterial growth or virulence, they provide opportunities for the development of novel therapies to combat a number of relevant mycobacterial diseases.
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Affiliation(s)
- Catalin M. Bunduc
- Section of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences, Vrije Universiteit Amsterdam, 1081 HZ Amsterdam, The Netherlands
| | - W. Bitter
- Section of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences, Vrije Universiteit Amsterdam, 1081 HZ Amsterdam, The Netherlands
- Department of Medical Microbiology and Infection Control, Amsterdam Infection and Immunity Institute, Amsterdam University Medical Centers, 1007 MB Amsterdam, The Netherlands
| | - E.N.G. Houben
- Section of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences, Vrije Universiteit Amsterdam, 1081 HZ Amsterdam, The Netherlands
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15
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Crosskey TD, Beckham KS, Wilmanns M. The ATPases of the mycobacterial type VII secretion system: Structural and mechanistic insights into secretion. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2020; 152:25-34. [DOI: 10.1016/j.pbiomolbio.2019.11.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 11/08/2019] [Accepted: 11/22/2019] [Indexed: 12/12/2022]
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16
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Damen MPM, Phan TH, Ummels R, Rubio-Canalejas A, Bitter W, Houben ENG. Modification of a PE/PPE substrate pair reroutes an Esx substrate pair from the mycobacterial ESX-1 type VII secretion system to the ESX-5 system. J Biol Chem 2020; 295:5960-5969. [PMID: 32184351 DOI: 10.1074/jbc.ra119.011682] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 03/13/2020] [Indexed: 01/20/2023] Open
Abstract
Bacterial type VII secretion systems secrete a wide range of extracellular proteins that play important roles in bacterial viability and in interactions of pathogenic mycobacteria with their hosts. Mycobacterial type VII secretion systems consist of five subtypes, ESX-1-5, and have four substrate classes, namely, Esx, PE, PPE, and Esp proteins. At least some of these substrates are secreted as heterodimers. Each ESX system mediates the secretion of a specific set of Esx, PE, and PPE proteins, raising the question of how these substrates are recognized in a system-specific fashion. For the PE/PPE heterodimers, it has been shown that they interact with their cognate EspG chaperone and that this chaperone determines the designated secretion pathway. However, both structural and pulldown analyses have suggested that EspG cannot interact with the Esx proteins. Therefore, the determining factor for system specificity of the Esx proteins remains unknown. Here, we investigated the secretion specificity of the ESX-1 substrate pair EsxB_1/EsxA_1 in Mycobacterium marinum Although this substrate pair was hardly secreted when homologously expressed, it was secreted when co-expressed together with the PE35/PPE68_1 pair, indicating that this pair could stimulate secretion of the EsxB_1/EsxA_1 pair. Surprisingly, co-expression of EsxB_1/EsxA_1 with a modified PE35/PPE68_1 version that carried the EspG5 chaperone-binding domain, previously shown to redirect this substrate pair to the ESX-5 system, also resulted in redirection and co-secretion of the Esx pair via ESX-5. Our results suggest a secretion model in which PE35/PPE68_1 determines the system-specific secretion of EsxB_1/EsxA_1.
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Affiliation(s)
- Merel P M Damen
- Section Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
| | - Trang H Phan
- Section Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
| | - Roy Ummels
- Department of Medical Microbiology and Infection Control, Amsterdam Infection & Immunity Institute, Amsterdam University Medical Centers, 1081 HV Amsterdam, The Netherlands
| | - Alba Rubio-Canalejas
- Section Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
| | - Wilbert Bitter
- Department of Medical Microbiology and Infection Control, Amsterdam Infection & Immunity Institute, Amsterdam University Medical Centers, 1081 HV Amsterdam, The Netherlands
| | - Edith N G Houben
- Section Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands.
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17
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Bunduc CM, Ummels R, Bitter W, Houben ENG. Species-specific secretion of ESX-5 type VII substrates is determined by the linker 2 of EccC 5. Mol Microbiol 2020; 114:66-76. [PMID: 32096294 PMCID: PMC7384006 DOI: 10.1111/mmi.14496] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 02/21/2020] [Indexed: 12/20/2022]
Abstract
Mycobacteria use type VII secretion systems (T7SSs) to translocate a wide range of proteins across their diderm cell envelope. These systems, also called ESX systems, are crucial for the viability and/or virulence of mycobacterial pathogens, including Mycobacterium tuberculosis and the fish pathogen Mycobacterium marinum. We have previously shown that the M. tuberculosis ESX-5 system is unable to fully complement secretion in an M. marinum esx-5 mutant, suggesting species specificity in secretion. In this study, we elaborated on this observation and established that the membrane ATPase EccC5 , possessing four (putative) nucleotide-binding domains (NBDs), is responsible for this. By creating M. marinum-M. tuberculosis EccC5 chimeras, we observed both in M. marinum and in M. tuberculosis that secretion specificity of PE_PGRS proteins depends on the presence of the cognate linker 2 domain of EccC5 . This region connects NBD1 and NBD2 of EccC5 and is responsible for keeping NBD1 in an inhibited state. Notably, the ESX-5 substrate EsxN, predicted to bind to NBD3 on EccC5 , showed a distinct secretion profile. These results indicate that linker 2 is involved in species-specific substrate recognition and might therefore be an additional substrate recognition site of EccC5 .
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Affiliation(s)
- Catalin M Bunduc
- Section Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Roy Ummels
- Department of Medical Microbiology and Infection Control, Amsterdam Infection & Immunity Institute, Amsterdam UMC, Amsterdam, The Netherlands
| | - Wilbert Bitter
- Section Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.,Department of Medical Microbiology and Infection Control, Amsterdam Infection & Immunity Institute, Amsterdam UMC, Amsterdam, The Netherlands
| | - Edith N G Houben
- Section Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
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18
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Ates LS. New insights into the mycobacterial PE and PPE proteins provide a framework for future research. Mol Microbiol 2020; 113:4-21. [PMID: 31661176 PMCID: PMC7028111 DOI: 10.1111/mmi.14409] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/25/2019] [Indexed: 12/30/2022]
Abstract
The PE and PPE proteins of Mycobacterium tuberculosis have been studied with great interest since their discovery. Named after the conserved proline (P) and glutamic acid (E) residues in their N-terminal domains, these proteins are postulated to perform wide-ranging roles in virulence and immune modulation. However, technical challenges in studying these proteins and their encoding genes have hampered the elucidation of molecular mechanisms and leave many open questions regarding the biological functions mediated by these proteins. Here, I review the shared and unique characteristics of PE and PPE proteins from a molecular perspective linking this information to their functions in mycobacterial virulence. I discuss how the different subgroups (PE_PGRS, PPE-PPW, PPE-SVP and PPE-MPTR) are defined and why this classification of paramount importance to understand the PE and PPE proteins as individuals and or groups. The goal of this MicroReview is to summarize and structure the existing information on this gene family into a simplified framework of thinking about PE and PPE proteins and genes. Thereby, I hope to provide helpful starting points in studying these genes and proteins for researchers with different backgrounds. This has particular implications for the design and monitoring of novel vaccine candidates and in understanding the evolution of the M. tuberculosis complex.
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Affiliation(s)
- Louis S. Ates
- Department of Experimental ImmunologyAmsterdam Infection & Immunity InstituteAmsterdam UMCUniversity of AmsterdamMeibergdreef 9Amsterdamthe Netherlands
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19
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Phan TH, Houben ENG. Bacterial secretion chaperones: the mycobacterial type VII case. FEMS Microbiol Lett 2019; 365:5067300. [PMID: 30085058 PMCID: PMC6109436 DOI: 10.1093/femsle/fny197] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 08/04/2018] [Indexed: 12/13/2022] Open
Abstract
Chaperones are central players in maintaining the proteostasis in all living cells. Besides highly conserved generic chaperones that assist protein folding and assembly in the cytosol, additional more specific chaperones have evolved to ensure the successful trafficking of proteins with extra-cytoplasmic locations. Associated with the distinctive secretion systems present in bacteria, different dedicated chaperones have been described that not only keep secretory proteins in a translocation competent state, but often are also involved in substrate targeting to the specific translocation channel. Recently, a new class of such chaperones has been identified that are involved in the specific recognition of substrates transported via the type VII secretion pathway in mycobacteria. In this minireview, we provide an overview of the different bacterial chaperones with a focus on their roles in protein secretion and will discuss in detail the roles of mycobacterial type VII secretion chaperones in substrate recognition and targeting.
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Affiliation(s)
- Trang H Phan
- Section Molecular Microbiology, Amsterdam Institute for Molecules, Medicines and Systems, Vrije Universiteit, Amsterdam, The Netherlands
| | - Edith N G Houben
- Section Molecular Microbiology, Amsterdam Institute for Molecules, Medicines and Systems, Vrije Universiteit, Amsterdam, The Netherlands
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20
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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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21
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van Winden VJC, Houben ENG, Braunstein M. Protein Export into and across the Atypical Diderm Cell Envelope of Mycobacteria. Microbiol Spectr 2019; 7:10.1128/microbiolspec.gpp3-0043-2018. [PMID: 31400094 PMCID: PMC10957183 DOI: 10.1128/microbiolspec.gpp3-0043-2018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Indexed: 02/07/2023] Open
Abstract
Mycobacteria, including the infamous pathogen Mycobacterium tuberculosis, are high-GC Gram-positive bacteria with a distinctive cell envelope. Although there is a typical inner membrane, the mycobacterial cell envelope is unusual in having its peptidoglycan layer connected to a polymer of arabinogalactan, which in turn is covalently attached to long-chain mycolic acids that help form a highly impermeable mycobacterial outer membrane. This complex double-membrane, or diderm, cell envelope imparts mycobacteria with unique requirements for protein export into and across the cell envelope for secretion into the extracellular environment. In this article, we review the four protein export pathways known to exist in mycobacteria: two conserved systems that exist in all types of bacteria (the Sec and Tat pathways) and two specialized systems that exist in mycobacteria, corynebacteria, and a subset of low-GC Gram-positive bacteria (the SecA2 and type VII secretion pathways). We describe the progress made over the past 15 years in understanding each of these mycobacterial export pathways, and we highlight the need for research to understand the specific steps of protein export across the mycobacterial outer membrane.
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Affiliation(s)
- Vincent J C van Winden
- Department of Medical Microbiology and Infection Control, Amsterdam UMC, Vrije Universiteit, Amsterdam, The Netherlands
| | - Edith N G Houben
- Section of Molecular Microbiology, Amsterdam Institute for Molecules, Medicines, and Systems, Vrije Universiteit, Amsterdam, The Netherlands
| | - Miriam Braunstein
- Department of Microbiology and Immunology, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599
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22
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A New ESX-1 Substrate in Mycobacterium marinum That Is Required for Hemolysis but Not Host Cell Lysis. J Bacteriol 2019; 201:JB.00760-18. [PMID: 30833360 DOI: 10.1128/jb.00760-18] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 02/28/2019] [Indexed: 02/07/2023] Open
Abstract
The ESX-1 (ESAT-6 system 1) secretion system plays a conserved role in the virulence of diverse mycobacterial pathogens, including the human pathogen Mycobacterium tuberculosis and M. marinum, an environmental mycobacterial species. The ESX-1 system promotes the secretion of protein virulence factors to the extracytoplasmic environment. The secretion of these proteins triggers the host response by lysing the phagosome during macrophage infection. Using proteomic analyses of the M. marinum secretome in the presence and absence of a functional ESX-1 system, we and others have hypothesized that MMAR_2894, a PE family protein, is a potential ESX-1 substrate in M. marinum We used genetic and quantitative proteomic approaches to determine if MMAR_2894 is secreted by the ESX-1 system, and we defined the requirement of MMAR_2894 for ESX-1-mediated secretion and virulence. We show that MMAR_2894 is secreted by the ESX-1 system in M. marinum and is itself required for the optimal secretion of the known ESX-1 substrates in M. marinum Moreover, we found that MMAR_2894 was differentially required for hemolysis and cytolysis of macrophages, two lytic activities ascribed to the M. marinum ESX-1 system.IMPORTANCE Both Mycobacterium tuberculosis, the cause of human tuberculosis (TB), and Mycobacterium marinum, a pathogen of ectotherms, use the ESX-1 secretion system to cause disease. There are many established similarities between the ESX-1 systems in M. tuberculosis and in M. marinum Yet the two bacteria infect different hosts, hinting at species-specific functions of the ESX-1 system. Our findings demonstrate that MMAR_2894 is a PE protein secreted by the ESX-1 system of M. marinum We show that MMAR_2894 is required for the optimal secretion of mycobacterial proteins required for disease. Because the MMAR_2894 gene is not conserved in M. tuberculosis, our findings demonstrate that MMAR_2894 may contribute to a species-specific function of the ESX-1 system in M. marinum, providing new insight into how the M. marinum and M. tuberculosis systems differ.
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23
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Tuukkanen AT, Freire D, Chan S, Arbing MA, Reed RW, Evans TJ, Zenkeviciutė G, Kim J, Kahng S, Sawaya MR, Chaton CT, Wilmanns M, Eisenberg D, Parret AHA, Korotkov KV. Structural Variability of EspG Chaperones from Mycobacterial ESX-1, ESX-3, and ESX-5 Type VII Secretion Systems. J Mol Biol 2018; 431:289-307. [PMID: 30419243 DOI: 10.1016/j.jmb.2018.11.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 08/28/2018] [Accepted: 11/06/2018] [Indexed: 10/27/2022]
Abstract
Type VII secretion systems (ESX) are responsible for transport of multiple proteins in mycobacteria. How different ESX systems achieve specific secretion of cognate substrates remains elusive. In the ESX systems, the cytoplasmic chaperone EspG forms complexes with heterodimeric PE-PPE substrates that are secreted from the cells or remain associated with the cell surface. Here we report the crystal structure of the EspG1 chaperone from the ESX-1 system determined using a fusion strategy with T4 lysozyme. EspG1 adopts a quasi 2-fold symmetric structure that consists of a central β-sheet and two α-helical bundles. In addition, we describe the structures of EspG3 chaperones from four different crystal forms. Alternate conformations of the putative PE-PPE binding site are revealed by comparison of the available EspG3 structures. Analysis of EspG1, EspG3, and EspG5 chaperones using small-angle X-ray scattering reveals that EspG1 and EspG3 chaperones form dimers in solution, which we observed in several of our crystal forms. Finally, we propose a model of the ESX-3 specific EspG3-PE5-PPE4 complex based on the small-angle X-ray scattering analysis.
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Affiliation(s)
- Anne T Tuukkanen
- European Molecular Biology Laboratory, Hamburg Unit, Hamburg 22607, Germany
| | - Diana Freire
- European Molecular Biology Laboratory, Hamburg Unit, Hamburg 22607, Germany
| | - Sum Chan
- UCLA-DOE Institute, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Mark A Arbing
- UCLA-DOE Institute, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Robert W Reed
- Department of Molecular & Cellular Biochemistry, and Center for Structural Biology, University of Kentucky, Lexington, KY 40536, USA
| | - Timothy J Evans
- Department of Molecular & Cellular Biochemistry, and Center for Structural Biology, University of Kentucky, Lexington, KY 40536, USA
| | | | - Jennifer Kim
- UCLA-DOE Institute, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Sara Kahng
- UCLA-DOE Institute, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Michael R Sawaya
- UCLA-DOE Institute, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Catherine T Chaton
- Department of Molecular & Cellular Biochemistry, and Center for Structural Biology, University of Kentucky, Lexington, KY 40536, USA
| | - Matthias Wilmanns
- European Molecular Biology Laboratory, Hamburg Unit, Hamburg 22607, Germany
| | - David Eisenberg
- UCLA-DOE Institute, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Annabel H A Parret
- European Molecular Biology Laboratory, Hamburg Unit, Hamburg 22607, Germany.
| | - Konstantin V Korotkov
- Department of Molecular & Cellular Biochemistry, and Center for Structural Biology, University of Kentucky, Lexington, KY 40536, USA.
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24
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Phan TH, van Leeuwen LM, Kuijl C, Ummels R, van Stempvoort G, Rubio-Canalejas A, Piersma SR, Jiménez CR, van der Sar AM, Houben ENG, Bitter W. EspH is a hypervirulence factor for Mycobacterium marinum and essential for the secretion of the ESX-1 substrates EspE and EspF. PLoS Pathog 2018; 14:e1007247. [PMID: 30102741 PMCID: PMC6107294 DOI: 10.1371/journal.ppat.1007247] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 08/23/2018] [Accepted: 07/26/2018] [Indexed: 12/31/2022] Open
Abstract
The pathogen Mycobacterium tuberculosis employs a range of ESX-1 substrates to manipulate the host and build a successful infection. Although the importance of ESX-1 secretion in virulence is well established, the characterization of its individual components and the role of individual substrates is far from complete. Here, we describe the functional characterization of the Mycobacterium marinum accessory ESX-1 proteins EccA1, EspG1 and EspH, i.e. proteins that are neither substrates nor structural components. Proteomic analysis revealed that EspG1 is crucial for ESX-1 secretion, since all detectable ESX-1 substrates were absent from the cell surface and culture supernatant in an espG1 mutant. Deletion of eccA1 resulted in minor secretion defects, but interestingly, the severity of these secretion defects was dependent on the culture conditions. Finally, espH deletion showed a partial secretion defect; whereas several ESX-1 substrates were secreted in normal amounts, secretion of EsxA and EsxB was diminished and secretion of EspE and EspF was fully blocked. Interaction studies showed that EspH binds EspE and therefore could function as a specific chaperone for this substrate. Despite the observed differences in secretion, hemolytic activity was lost in all M. marinum mutants, implying that hemolytic activity is not strictly correlated with EsxA secretion. Surprisingly, while EspH is essential for successful infection of phagocytic host cells, deletion of espH resulted in a significantly increased virulence phenotype in zebrafish larvae, linked to poor granuloma formation and extracellular outgrowth. Together, these data show that different sets of ESX-1 substrates play different roles at various steps of the infection cycle of M. marinum. M. tuberculosis is a facultative intracellular pathogen that has an intimate relationship with host macrophages. Proteins secreted by the ESX-1 secretion system play an important role in this interaction, for instance by orchestrating the escape from the phagosome into the cytosol of the macrophage. However, the exact role of the ESX-1 substrates is unknown, due to their complicated interdependency for secretion. Here, we study the function of ESX-1 accessory proteins EccA1, EspG1 and EspH in ESX-1 secretion in Mycobacterium marium, the causative agent of fish tuberculosis. We found that these proteins affect the secretion of different substrate classes, which offers an approach to study the roles of these substrate groups. An espG1 deletion broadly aborts ESX-1 secretion and thus resulted in severe attenuation in a zebrafish model for tuberculosis, whereas EccA1 is only crucial under specific growth conditions. The most surprising results were obtained for EspH. This protein seems to function as a molecular chaperone for EspE and is as such involved in the secretion of a small subset of ESX-1 substrates. Disruption of espH showed a dual character: whereas this gene is essential for the successful infection of macrophages, deletion of espH resulted in significantly increased virulence in zebrafish larvae. These data convincingly show that different subsets of ESX-1 substrates play different roles at various steps in the mycobacterial infection cycle.
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Affiliation(s)
- Trang H. Phan
- Section Molecular Microbiology, Amsterdam Institute of Molecules, Medicines & Systems, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Lisanne M. van Leeuwen
- Department of Medical Microbiology and Infection Control, Amsterdam University Medical Centers, Amsterdam, the Netherlands
| | - Coen Kuijl
- Department of Medical Microbiology and Infection Control, Amsterdam University Medical Centers, Amsterdam, the Netherlands
| | - Roy Ummels
- Department of Medical Microbiology and Infection Control, Amsterdam University Medical Centers, Amsterdam, the Netherlands
| | - Gunny van Stempvoort
- Department of Medical Microbiology and Infection Control, Amsterdam University Medical Centers, Amsterdam, the Netherlands
| | - Alba Rubio-Canalejas
- Section Molecular Microbiology, Amsterdam Institute of Molecules, Medicines & Systems, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Sander R. Piersma
- Department of Medical Oncology, OncoProteomics Laboratory, Amsterdam University Medical Centers, Amsterdam, the Netherlands
| | - Connie R. Jiménez
- Department of Medical Oncology, OncoProteomics Laboratory, Amsterdam University Medical Centers, Amsterdam, the Netherlands
| | - Astrid M. van der Sar
- Department of Medical Microbiology and Infection Control, Amsterdam University Medical Centers, Amsterdam, the Netherlands
| | - Edith N. G. Houben
- Section Molecular Microbiology, Amsterdam Institute of Molecules, Medicines & Systems, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Wilbert Bitter
- Section Molecular Microbiology, Amsterdam Institute of Molecules, Medicines & Systems, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
- Department of Medical Microbiology and Infection Control, Amsterdam University Medical Centers, Amsterdam, the Netherlands
- * E-mail:
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25
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Esx Paralogs Are Functionally Equivalent to ESX-1 Proteins but Are Dispensable for Virulence in Mycobacterium marinum. J Bacteriol 2018; 200:JB.00726-17. [PMID: 29555701 DOI: 10.1128/jb.00726-17] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 03/11/2018] [Indexed: 12/20/2022] Open
Abstract
Mycobacterium marinum is a nontuberculous pathogen of poikilothermic fish and an opportunistic human pathogen. Like tuberculous mycobacteria, the M. marinum M strain requires the ESX-1 (ESAT-6 system 1) secretion system for virulence in host cells. EsxB and EsxA, two major virulence factors exported by the ESX-1 system, are encoded by the esxBA genes within the ESX-1 locus. Deletion of the esxBA genes abrogates ESX-1 export and attenuates M. marinum in ex vivo and in vivo models of infection. Interestingly, there are several duplications of the esxB and esxA genes (esxB_1, esxB_2, esxA_1, esxA_2, and esxA_3) in the M. marinum M genome located outside the ESX-1 locus. We sought to understand if this region, known as ESX-6, contributes to ESX-1-mediated virulence. We found that deletion of the esxB_1 gene alone or the entire ESX-6 locus did not impact ESX-1 export or function, supporting the idea that the esxBA genes present at the ESX-1 locus are the primary contributors to ESX-1-mediated virulence. Nevertheless, overexpression of the esxB_1 locus complemented ESX-1 function in the ΔesxBA strain, signifying that the two loci are functionally equivalent. Our findings raise questions about why duplicate versions of the esxBA genes are maintained in the M. marinum M genome and how these proteins, which are functionally equivalent to virulence factors, contribute to mycobacterial biology.IMPORTANCEMycobacterium tuberculosis is the causative agent of the human disease tuberculosis (TB). There are 10.4 million cases and 1.7 million TB-associated deaths annually, making TB a leading cause of death globally. Nontuberculous mycobacteria (NTM) cause chronic human infections that are acquired from the environment. Despite differences in disease etiology, both tuberculous and NTM pathogens use the ESX-1 secretion system to cause disease. The nontubercular mycobacterial species, Mycobacterium marinum, has additional copies of specific ESX-1 genes. Our findings demonstrate that the duplicated genes do not contribute to virulence but can substitute for virulence factors in M. marinum These findings suggest that the duplicated genes may play a specific role in NTM biology.
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Jäger F, Kneuper H, Palmer T. EssC is a specificity determinant for Staphylococcus aureus type VII secretion. MICROBIOLOGY-SGM 2018; 164:816-820. [PMID: 29620499 PMCID: PMC5994694 DOI: 10.1099/mic.0.000650] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The type VII protein secretion system (T7SS) is found in actinobacteria and firmicutes, and plays important roles in virulence and interbacterial competition. A membrane-bound ATPase protein, EssC in Staphylococcus aureus, lies at the heart of the secretion machinery. The EssC protein from S. aureus strains can be grouped into four variants (EssC1-EssC4) that display sequence variability in the C-terminal region. Here we show that the EssC2, EssC3 and EssC4 variants can be produced in a strain deleted for essC1, and that they are able to mediate secretion of EsxA, an essential component of the secretion apparatus. They are, however, unable to support secretion of the substrate protein EsxC, which is only encoded in essC1-specific strains. This finding indicates that EssC is a specificity determinant for T7 protein secretion. Our results support a model in which the C-terminal domain of EssC interacts with substrate proteins, whereas EsxA interacts elsewhere.
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Affiliation(s)
- Franziska Jäger
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, UK
| | - Holger Kneuper
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, UK
| | - Tracy Palmer
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, UK
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Boot M, van Winden VJC, Sparrius M, van de Weerd R, Speer A, Ummels R, Rustad T, Sherman DR, Bitter W. Cell envelope stress in mycobacteria is regulated by the novel signal transduction ATPase IniR in response to trehalose. PLoS Genet 2017; 13:e1007131. [PMID: 29281637 PMCID: PMC5760070 DOI: 10.1371/journal.pgen.1007131] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 01/09/2018] [Accepted: 11/28/2017] [Indexed: 12/20/2022] Open
Abstract
The cell envelope of mycobacteria is a highly unique and complex structure that is functionally equivalent to that of Gram-negative bacteria to protect the bacterial cell. Defects in the integrity or assembly of this cell envelope must be sensed to allow the induction of stress response systems. The promoter that is specifically and most strongly induced upon exposure to ethambutol and isoniazid, first line drugs that affect cell envelope biogenesis, is the iniBAC promoter. In this study, we set out to identify the regulator of the iniBAC operon in Mycobacterium marinum using an unbiased transposon mutagenesis screen in a constitutively iniBAC-expressing mutant background. We obtained multiple mutants in the mce1 locus as well as mutants in an uncharacterized putative transcriptional regulator (MMAR_0612). This latter gene was shown to function as the iniBAC regulator, as overexpression resulted in constitutive iniBAC induction, whereas a knockout mutant was unable to respond to the presence of ethambutol and isoniazid. Experiments with the M. tuberculosis homologue (Rv0339c) showed identical results. RNAseq experiments showed that this regulatory gene was exclusively involved in the regulation of the iniBAC operon. We therefore propose to name this dedicated regulator iniBAC Regulator (IniR). IniR belongs to the family of signal transduction ATPases with numerous domains, including a putative sugar-binding domain. Upon testing different sugars, we identified trehalose as an activator and metabolic cue for iniBAC activation, which could also explain the effect of the mce1 mutations. In conclusion, cell envelope stress in mycobacteria is regulated by IniR in a cascade that includes trehalose.
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Affiliation(s)
- Maikel Boot
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
| | - Vincent J. C. van Winden
- 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
| | - Robert van de Weerd
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
| | - Alexander Speer
- 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
| | - Tige Rustad
- Center for Infectious Disease, Seattle, Washington, United States of America
| | - David R. Sherman
- Center for Infectious Disease, Seattle, Washington, United States of America
| | - Wilbert Bitter
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
- Department of Molecular Microbiology, VU University, Amsterdam, the Netherlands
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