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Juthani R, Das A, Doss K, Mandal J. Exploring the use of Congo red agar in improving the serotyping of non-serotypeable Shigella with In-silico evidence. Indian J Med Microbiol 2023; 44:100381. [PMID: 37356833 DOI: 10.1016/j.ijmmb.2023.100381] [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: 09/21/2022] [Revised: 12/27/2022] [Accepted: 04/26/2023] [Indexed: 06/27/2023]
Abstract
OBJECTIVES To assess if congo red could make non-serotypeable Shigella strains serotypeable and to employ molecular docking to determine the basis of the same phenomenon. METHODS We used 42 bacterial strains of non-serotypeable Shigella collected from 2012 to 2019 for this study. Each bacterial strain was freshly inoculated onto congo red agar and incubated at 37° C for 18-24 h. Bacterial colonies obtained were re-subjected to biochemical tests followed by serotyping and serogrouping. In-silico studies to investigate the interaction between MxiC protein of T3SS and O-antigen LPS with congo red were performed. RESULTS Of the total 42 non-serotypeable Shigella studied, (26/42)62% were capable of being serotyped following the use of congo red agar, 65% were Shigella flexneri, 19% were Shigella dysenteriae, while 2 strains (7%) each of Shigella boydii and Shigella sonnei were detected. We observed no change in their biochemical properties. The in-silico molecular docking studies revealed high binding affinity between congo red and the B-Chain of Mxi C. Out of the 5 chains of the O-Antigen, congo red showed robust binding with the B-chain with the involvement of a cluster of hydrophobic interactions between them. This may have a crucial role in the conversion of non-serotypeable strains to serotypeable strains on exposure to congo red as observed in our study. CONCLUSION Congo red agar as a medium converts a sizeable percentage of non-serotypeable Shigella strains to serotypeable Shigella strains.
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Affiliation(s)
- Ronit Juthani
- Jawaharlal Institute of Postgraduate Medical Institute and Research (JIPMER), Puducherry, India.
| | - Ankita Das
- Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Puducherry, India.
| | - Kamali Doss
- Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Puducherry, India.
| | - Jharna Mandal
- Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Institute and Research (JIPMER), Puducherry, India.
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2
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Navarrete KM, Bumba L, Prudnikova T, Malcova I, Allsop TR, Sebo P, Kamanova J. BopN is a Gatekeeper of the Bordetella Type III Secretion System. Microbiol Spectr 2023; 11:e0411222. [PMID: 37036369 PMCID: PMC10269732 DOI: 10.1128/spectrum.04112-22] [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: 10/11/2022] [Accepted: 03/17/2023] [Indexed: 04/11/2023] Open
Abstract
The classical Bordetella species infect the respiratory tract of mammals. While B. bronchiseptica causes rather chronic respiratory infections in a variety of mammals, the human-adapted species B. pertussis and B. parapertussisHU cause an acute respiratory disease known as whooping cough or pertussis. The virulence factors include a type III secretion system (T3SS) that translocates effectors BteA and BopN into host cells. However, the regulatory mechanisms underlying the secretion and translocation activity of T3SS in bordetellae are largely unknown. We have solved the crystal structure of BopN of B. pertussis and show that it is similar to the structures of gatekeepers that control access to the T3SS channel from the bacterial cytoplasm. We further found that BopN accumulates at the cell periphery at physiological concentrations of calcium ions (2 mM) that inhibit the secretion of BteA and BopN. Deletion of the bopN gene in B. bronchiseptica increased secretion of the BteA effector into calcium-rich medium but had no effect on secretion of the T3SS translocon components BopD and BopB. Moreover, the ΔbopN mutant secreted approximately 10-fold higher amounts of BteA into the medium of infected cells than the wild-type bacteria, but it translocated lower amounts of BteA into the host cell cytoplasm. These data demonstrate that BopN is a Bordetella T3SS gatekeeper required for regulated and targeted translocation of the BteA effector through the T3SS injectisome into host cells. IMPORTANCE The T3SS is utilized by many Gram-negative bacteria to deliver effector proteins from bacterial cytosol directly into infected host cell cytoplasm in a regulated and targeted manner. Pathogenic bordetellae use the T3SS to inject the BteA and BopN proteins into infected cells and upregulate the production of the anti-inflammatory cytokine interleukin-10 (IL-10) to evade host immunity. Previous studies proposed that BopN acted as an effector in host cells. In this study, we report that BopN is a T3SS gatekeeper that regulates the secretion and translocation activity of Bordetella T3SS.
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Affiliation(s)
- Kevin Munoz Navarrete
- Laboratory of Infection Biology, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Ladislav Bumba
- Laboratory of Molecular Biology of Bacterial Pathogens, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Tatyana Prudnikova
- Faculty of Science, University of South Bohemia in Ceske Budejovice, Ceske Budejovice, Czech Republic
| | - Ivana Malcova
- Laboratory of Infection Biology, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Tania Romero Allsop
- Laboratory of Infection Biology, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Peter Sebo
- Laboratory of Molecular Biology of Bacterial Pathogens, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Jana Kamanova
- Laboratory of Infection Biology, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
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Whelan R, McVicker G, Leo JC. Staying out or Going in? The Interplay between Type 3 and Type 5 Secretion Systems in Adhesion and Invasion of Enterobacterial Pathogens. Int J Mol Sci 2020; 21:E4102. [PMID: 32521829 PMCID: PMC7312957 DOI: 10.3390/ijms21114102] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 06/03/2020] [Accepted: 06/05/2020] [Indexed: 12/12/2022] Open
Abstract
Enteric pathogens rely on a variety of toxins, adhesins and other virulence factors to cause infections. Some of the best studied pathogens belong to the Enterobacterales order; these include enteropathogenic and enterohemorrhagic Escherichia coli, Shigella spp., and the enteropathogenic Yersiniae. The pathogenesis of these organisms involves two different secretion systems, a type 3 secretion system (T3SS) and type 5 secretion systems (T5SSs). The T3SS forms a syringe-like structure spanning both bacterial membranes and the host cell plasma membrane that translocates toxic effector proteins into the cytoplasm of the host cell. T5SSs are also known as autotransporters, and they export part of their own polypeptide to the bacterial cell surface where it exerts its function, such as adhesion to host cell receptors. During infection with these enteropathogens, the T3SS and T5SS act in concert to bring about rearrangements of the host cell cytoskeleton, either to invade the cell, confer intracellular motility, evade phagocytosis or produce novel structures to shelter the bacteria. Thus, in these bacteria, not only the T3SS effectors but also T5SS proteins could be considered "cytoskeletoxins" that bring about profound alterations in host cell cytoskeletal dynamics and lead to pathogenic outcomes.
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Affiliation(s)
| | | | - Jack C. Leo
- Antimicrobial Resistance, Omics and Microbiota Group, Department of Biosciences, Nottingham Trent University, Nottingham NG1 4FQ, UK; (R.W.); (G.M.)
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4
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El Hajjami N, Moussa S, Houssa J, Monteyne D, Perez-Morga D, Botteaux A. The inner-rod component of Shigella flexneri type 3 secretion system, MxiI, is involved in the transmission of the secretion activation signal by its interaction with MxiC. Microbiologyopen 2017; 7. [PMID: 29194994 PMCID: PMC5822323 DOI: 10.1002/mbo3.520] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 05/29/2017] [Accepted: 06/13/2017] [Indexed: 11/28/2022] Open
Abstract
The virulence of Shigella mainly resides in the use of a Type 3 Secretion System (T3SS) to inject several proteins inside the host cell. Three categories of proteins are hierarchically secreted: (1) the needle components (MxiH and MxiI), (2) the translocator proteins which form a pore (translocon) inside the host cell membrane, and (3) the effectors interfering with the host cell signaling pathways. In the absence of host cell contact, the T3SS is maintained in an “off” state by the presence of a tip complex. We have previously identified a gatekeeper protein, MxiC, which sequesters effectors inside the bacteria probably by interacting with MxiI, the inner‐rod component. Upon cell contact and translocon insertion, a signal is most likely transmitted from the top of the needle to the base, passing through the needle and allowing effectors release. However, the molecular mechanism underlying the transmission of the activation signal through the needle is still poorly understood. In this work, we investigate the role of MxiI in the activation of the T3SS by performing a mutational study. Interestingly we have shown that mutations of a single residue in MxiI (T82) induce an mxiC‐like phenotype and prevent the interaction with MxiC. Moreover, we have shown that the L26A mutation significantly reduces T3 secretion. The L26A mutation impairs the interaction between MxiI and Spa40, a keystone component of the switch between needle assembly and translocators secretion. The L26A mutation also sequesters MxiC. All these results highlight the crucial role of MxiI in regulating the secretion and transmitting the activation signal of the T3SS.
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Affiliation(s)
- Nargisse El Hajjami
- Laboratoire de Bactériologie Moléculaire, Faculté de Médecine, Université Libre de Bruxelles, Bruxelles, Belgium
| | - Simon Moussa
- Laboratoire de Bactériologie Moléculaire, Faculté de Médecine, Université Libre de Bruxelles, Bruxelles, Belgium
| | - Jonathan Houssa
- Laboratoire de Bactériologie Moléculaire, Faculté de Médecine, Université Libre de Bruxelles, Bruxelles, Belgium
| | - Daniel Monteyne
- Laboratoire de Parasitologie Moléculaire, Faculté des Sciences, Université Libre de Bruxelles, Charleroi, Belgium.,Center for Microscopy and Molecular Imaging-CMMI, Université Libre de Bruxelles, Gosselies, Belgium
| | - David Perez-Morga
- Laboratoire de Parasitologie Moléculaire, Faculté des Sciences, Université Libre de Bruxelles, Charleroi, Belgium
| | - Anne Botteaux
- Laboratoire de Bactériologie Moléculaire, Faculté de Médecine, Université Libre de Bruxelles, Bruxelles, Belgium
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5
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Francis MS, Amer AAA, Milton DL, Costa TRD. Site-Directed Mutagenesis and Its Application in Studying the Interactions of T3S Components. Methods Mol Biol 2017; 1531:11-31. [PMID: 27837478 DOI: 10.1007/978-1-4939-6649-3_2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Type III secretion systems are a prolific virulence determinant among Gram-negative bacteria. They are used to paralyze the host cell, which enables bacterial pathogens to establish often fatal infections-unless an effective therapeutic intervention is available. However, as a result of a catastrophic rise in infectious bacteria resistant to conventional antibiotics, these bacteria are again a leading cause of worldwide mortality. Hence, this report describes a pDM4-based site-directed mutagenesis strategy that is assisting in our foremost objective to better understand the fundamental workings of the T3SS, using Yersinia as a model pathogenic bacterium. Examples are given that clearly document how pDM4-mediated site-directed mutagenesis has been used to establish clean point mutations and in-frame deletion mutations that have been instrumental in identifying and understanding the molecular interactions between components of the Yersinia type III secretion system.
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Affiliation(s)
- Matthew S Francis
- Department of Molecular Biology, Umeå University, 6K och 6L, Sjukhusområdet, Umeå, 901 87, Sweden.
- Umeå Centre for Microbial Research, Umeå University, 6K och 6L, Sjukhusområdet, Umeå, 901 87, Sweden.
| | - Ayad A A Amer
- Department of Molecular Biology, Umeå University, 6K och 6L, Sjukhusområdet, Umeå, 901 87, Sweden
- Umeå Centre for Microbial Research, Umeå University, 6K och 6L, Sjukhusområdet, Umeå, 901 87, Sweden
- Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Debra L Milton
- Department of Molecular Biology, Umeå University, 6K och 6L, Sjukhusområdet, Umeå, 901 87, Sweden
- Umeå Centre for Microbial Research, Umeå University, 6K och 6L, Sjukhusområdet, Umeå, 901 87, Sweden
- Department of Biological and Environmental Sciences, Troy University, Troy, AL, USA
| | - Tiago R D Costa
- Department of Molecular Biology, Umeå University, 6K och 6L, Sjukhusområdet, Umeå, 901 87, Sweden
- Umeå Centre for Microbial Research, Umeå University, 6K och 6L, Sjukhusområdet, Umeå, 901 87, Sweden
- Institute of Structural and Molecular Biology, University College London and Birkbeck, Malet Street, London, UK
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Roehrich AD, Bordignon E, Mode S, Shen DK, Liu X, Pain M, Murillo I, Martinez-Argudo I, Sessions RB, Blocker AJ. Steps for Shigella Gatekeeper Protein MxiC Function in Hierarchical Type III Secretion Regulation. J Biol Chem 2016; 292:1705-1723. [PMID: 27974466 PMCID: PMC5290946 DOI: 10.1074/jbc.m116.746826] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 12/14/2016] [Indexed: 01/18/2023] Open
Abstract
Type III secretion systems are complex nanomachines used for injection of proteins from Gram-negative bacteria into eukaryotic cells. Although they are assembled when the environmental conditions are appropriate, they only start secreting upon contact with a host cell. Secretion is hierarchical. First, the pore-forming translocators are released. Second, effector proteins are injected. Hierarchy between these protein classes is mediated by a conserved gatekeeper protein, MxiC, in Shigella. As its molecular mechanism of action is still poorly understood, we used its structure to guide site-directed mutagenesis and to dissect its function. We identified mutants predominantly affecting all known features of MxiC regulation as follows: secretion of translocators, MxiC and/or effectors. Using molecular genetics, we then mapped at which point in the regulatory cascade the mutants were affected. Analysis of some of these mutants led us to a set of electron paramagnetic resonance experiments that provide evidence that MxiC interacts directly with IpaD. We suggest how this interaction regulates a switch in its conformation that is key to its functions.
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Affiliation(s)
- A Dorothea Roehrich
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Enrica Bordignon
- the Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | - Selma Mode
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Da-Kang Shen
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Xia Liu
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Maria Pain
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Isabel Murillo
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Isabel Martinez-Argudo
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom; the Área de Genética, Facultad de Ciencias Ambientales y Bioquímica, Universidad de Castilla-La Mancha, E-45071 Toledo, Spain
| | - Richard B Sessions
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Ariel J Blocker
- From the School of Cellular and Molecular Medicine and School of Biochemistry, Medical Sciences Building, Faculty of Medical and Veterinary Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom.
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7
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Abstract
Type III secretion systems (T3SSs) afford Gram-negative bacteria an intimate means of altering the biology of their eukaryotic hosts--the direct delivery of effector proteins from the bacterial cytoplasm to that of the eukaryote. This incredible biophysical feat is accomplished by nanosyringe "injectisomes," which form a conduit across the three plasma membranes, peptidoglycan layer, and extracellular space that form a barrier to the direct delivery of proteins from bacterium to host. The focus of this chapter is T3SS function at the structural level; we will summarize the core findings that have shaped our understanding of the structure and function of these systems and highlight recent developments in the field. In turn, we describe the T3SS secretory apparatus, consider its engagement with secretion substrates, and discuss the posttranslational regulation of secretory function. Lastly, we close with a discussion of the future prospects for the interrogation of structure-function relationships in the T3SS.
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8
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Gaytán MO, Martínez-Santos VI, Soto E, González-Pedrajo B. Type Three Secretion System in Attaching and Effacing Pathogens. Front Cell Infect Microbiol 2016; 6:129. [PMID: 27818950 PMCID: PMC5073101 DOI: 10.3389/fcimb.2016.00129] [Citation(s) in RCA: 117] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 09/27/2016] [Indexed: 02/06/2023] Open
Abstract
Enteropathogenic Escherichia coli and enterohemorrhagic E. coli are diarrheagenic bacterial human pathogens that cause severe gastroenteritis. These enteric pathotypes, together with the mouse pathogen Citrobacter rodentium, belong to the family of attaching and effacing pathogens that form a distinctive histological lesion in the intestinal epithelium. The virulence of these bacteria depends on a type III secretion system (T3SS), which mediates the translocation of effector proteins from the bacterial cytosol into the infected cells. The core architecture of the T3SS consists of a multi-ring basal body embedded in the bacterial membranes, a periplasmic inner rod, a transmembrane export apparatus in the inner membrane, and cytosolic components including an ATPase complex and the C-ring. In addition, two distinct hollow appendages are assembled on the extracellular face of the basal body creating a channel for protein secretion: an approximately 23 nm needle, and a filament that extends up to 600 nm. This filamentous structure allows these pathogens to get through the host cells mucus barrier. Upon contact with the target cell, a translocation pore is assembled in the host membrane through which the effector proteins are injected. Assembly of the T3SS is strictly regulated to ensure proper timing of substrate secretion. The different type III substrates coexist in the bacterial cytoplasm, and their hierarchical secretion is determined by specialized chaperones in coordination with two molecular switches and the so-called sorting platform. In this review, we present recent advances in the understanding of the T3SS in attaching and effacing pathogens.
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Affiliation(s)
- Meztlli O Gaytán
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México Ciudad de México, Mexico
| | - Verónica I Martínez-Santos
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México Ciudad de México, Mexico
| | - Eduardo Soto
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México Ciudad de México, Mexico
| | - Bertha González-Pedrajo
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México Ciudad de México, Mexico
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9
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Diepold A, Armitage JP. Type III secretion systems: the bacterial flagellum and the injectisome. Philos Trans R Soc Lond B Biol Sci 2016; 370:rstb.2015.0020. [PMID: 26370933 DOI: 10.1098/rstb.2015.0020] [Citation(s) in RCA: 139] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The flagellum and the injectisome are two of the most complex and fascinating bacterial nanomachines. At their core, they share a type III secretion system (T3SS), a transmembrane export complex that forms the extracellular appendages, the flagellar filament and the injectisome needle. Recent advances, combining structural biology, cryo-electron tomography, molecular genetics, in vivo imaging, bioinformatics and biophysics, have greatly increased our understanding of the T3SS, especially the structure of its transmembrane and cytosolic components, the transcriptional, post-transcriptional and functional regulation and the remarkable adaptivity of the system. This review aims to integrate these new findings into our current knowledge of the evolution, function, regulation and dynamics of the T3SS, and to highlight commonalities and differences between the two systems, as well as their potential applications.
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Affiliation(s)
- Andreas Diepold
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Judith P Armitage
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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10
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Shen DK, Blocker AJ. MxiA, MxiC and IpaD Regulate Substrate Selection and Secretion Mode in the T3SS of Shigella flexneri. PLoS One 2016; 11:e0155141. [PMID: 27171191 PMCID: PMC4865121 DOI: 10.1371/journal.pone.0155141] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 04/25/2016] [Indexed: 11/19/2022] Open
Abstract
Type III secretion systems (T3SSs) are central virulence devices for many Gram-negative bacterial pathogens of humans, animals & plants. Upon physical contact with eukaryotic host cells, they translocate virulence-mediating proteins, known as effectors, into them during infection. T3SSs are gated from the outside by host-cell contact and from the inside via two cytoplasmic negative regulators, MxiC and IpaD in Shigella flexneri, which together control the effector secretion hierarchy. Their absence leads to premature and increased secretion of effectors. Here, we investigated where and how these regulators act. We demonstrate that the T3SS inner membrane export apparatus protein MxiA plays a role in substrate selection. Indeed, using a genetic screen, we identified two amino acids located on the surface of MxiA's cytoplasmic region (MxiAC) which, when mutated, upregulate late effector expression and, in the case of MxiAI674V, also secretion. The cytoplasmic region of MxiA, but not MxiAN373D and MxiAI674V, interacts directly with the C-terminus of MxiC in a two-hybrid assay. Efficient T3S requires a cytoplasmic ATPase and the proton motive force (PMF), which is composed of the ΔΨ and the ΔpH. MxiA family proteins and their regulators are implicated in utilization of the PMF for protein export. However, our MxiA point mutants show similar PMF utilisation to wild-type, requiring primarily the ΔΨ. On the other hand, lack of MxiC or IpaD, renders the faster T3S seen increasingly dependent on the ΔpH. Therefore, MxiA, MxiC and IpaD act together to regulate substrate selection and secretion mode in the T3SS of Shigella flexneri.
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Affiliation(s)
- Da-Kang Shen
- School of Cellular & Molecular Medicine, Faculty of Biomedical Sciences, University of Bristol, Bristol, United Kingdom
| | - Ariel J. Blocker
- Schools of Cellular & Molecular Medicine and Biochemistry, Faculty of Biomedical Sciences, University of Bristol, Bristol, United Kingdom
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11
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Burkinshaw BJ, Souza SA, Strynadka NCJ. Structural analysis of SepL, an enteropathogenic Escherichia coli type III secretion-system gatekeeper protein. Acta Crystallogr F Struct Biol Commun 2015; 71:1300-8. [PMID: 26457522 PMCID: PMC4601595 DOI: 10.1107/s2053230x15016064] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2015] [Accepted: 08/27/2015] [Indexed: 12/26/2022] Open
Abstract
During infection, enteropathogenic Escherichia coli assembles a complex multi-protein type III secretion system that traverses the bacterial membranes and targets the host cell membrane to directly deliver virulence or effector proteins to the host cytoplasm. As this secretion system is composed of more than 20 proteins, many of which form oligomeric associations, its assembly must be tightly regulated. A protein called the gatekeeper, or SepL, ensures that the secretion of the translocon component, which inserts into the host membrane, occurs before the secretion of effectors. The crystal structure of the gatekeeper SepL was determined and compared with the structures of SepL homologues from other bacterial pathogens in order to identify SepL residues that may be critical for its role in type III secretion-system assembly.
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Affiliation(s)
- Brianne J. Burkinshaw
- Department of Biochemistry and Molecular Biology, University of British Columbia, Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
- Centre for Blood Research, Life Sciences Centre, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - Sergio A. Souza
- Department of Biochemistry and Molecular Biology, University of British Columbia, Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
- Centre for Blood Research, Life Sciences Centre, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - Natalie C. J. Strynadka
- Department of Biochemistry and Molecular Biology, University of British Columbia, Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
- Centre for Blood Research, Life Sciences Centre, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
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12
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Archuleta TL, Spiller BW. A gatekeeper chaperone complex directs translocator secretion during type three secretion. PLoS Pathog 2014; 10:e1004498. [PMID: 25375170 PMCID: PMC4222845 DOI: 10.1371/journal.ppat.1004498] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Accepted: 10/02/2014] [Indexed: 11/18/2022] Open
Abstract
Many Gram-negative bacteria use Type Three Secretion Systems (T3SS) to deliver effector proteins into host cells. These protein delivery machines are composed of cytosolic components that recognize substrates and generate the force needed for translocation, the secretion conduit, formed by a needle complex and associated membrane spanning basal body, and translocators that form the pore in the target cell. A defined order of secretion in which needle component proteins are secreted first, followed by translocators, and finally effectors, is necessary for this system to be effective. While the secreted effectors vary significantly between organisms, the ∼20 individual protein components that form the T3SS are conserved in many pathogenic bacteria. One such conserved protein, referred to as either a plug or gatekeeper, is necessary to prevent unregulated effector release and to allow efficient translocator secretion. The mechanism by which translocator secretion is promoted while effector release is inhibited by gatekeepers is unknown. We present the structure of the Chlamydial gatekeeper, CopN, bound to a translocator-specific chaperone. The structure identifies a previously unknown interface between gatekeepers and translocator chaperones and reveals that in the gatekeeper-chaperone complex the canonical translocator-binding groove is free to bind translocators. Structure-based mutagenesis of the homologous complex in Shigella reveals that the gatekeeper-chaperone-translocator complex is essential for translocator secretion and for the ordered secretion of translocators prior to effectors. Type Three Secretion Systems (T3SS) are essential virulence factors found in many pathogenic Gram-negative bacteria. These machines aid infection by delivering bacterial proteins into host cells where these proteins modulate host processes and help establish a niche for the bacteria. Protein delivery occurs in a highly regulated manner in which proteins involved in early steps in infection, or necessary to build the secretion conduit, are typically secreted before other substrates, a phenomenon termed secretion hierarchy. This study presents the structure of a molecular complex that physically links one class of early substrates, components of the secretion pore termed translocators, to a gatekeeper protein, a protein that has been implicated in the secretion hierarchy. Disruption of this interaction in Shigella disrupts the secretion of translocators, while supporting increased secretion of effectors, resulting in phenotypes indistinguishable from a gatekeeper deletion, and leading to the conclusion that a gatekeeper-chaperone-translocator complex is a critical component of the T3SS.
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Affiliation(s)
- Tara L. Archuleta
- Chemical and Physical Biology Program, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Benjamin W. Spiller
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- * E-mail:
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13
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Nawrotek A, Guimarães BG, Velours C, Subtil A, Knossow M, Gigant B. Biochemical and structural insights into microtubule perturbation by CopN from Chlamydia pneumoniae. J Biol Chem 2014; 289:25199-210. [PMID: 25056950 DOI: 10.1074/jbc.m114.568436] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Although the actin network is commonly hijacked by pathogens, there are few reports of parasites targeting microtubules. The proposed member of the LcrE protein family from some Chlamydia species (e.g. pCopN from C. pneumoniae) binds tubulin and inhibits microtubule assembly in vitro. From the pCopN structure and its similarity with that of MxiC from Shigella, we definitively confirm CopN as the Chlamydia homolog of the LcrE family of bacterial proteins involved in the regulation of type III secretion. We have also investigated the molecular basis for the pCopN effect on microtubules. We show that pCopN delays microtubule nucleation and acts as a pure tubulin-sequestering protein at steady state. It targets the β subunit interface involved in the tubulin longitudinal self-association in a way that inhibits nucleotide exchange. pCopN contains three repetitions of a helical motif flanked by disordered N- and C-terminal extensions. We have identified the pCopN minimal tubulin-binding region within the second and third repeats. Together with the intriguing observation that C. trachomatis CopN does not bind tubulin, our data support the notion that, in addition to the shared function of type III secretion regulation, these proteins have evolved different functions in the host cytosol. Our results provide a mechanistic framework for understanding the C. pneumoniae CopN-specific inhibition of microtubule assembly.
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Affiliation(s)
- Agata Nawrotek
- From the Laboratoire d'Enzymologie et Biochimie Structurales (LEBS), Centre de Recherche de Gif, CNRS, 91198 Gif sur Yvette, France
| | - Beatriz G Guimarães
- the Synchrotron SOLEIL, L'Orme de Merisiers, St Aubin, 91192 Gif sur Yvette, France, and
| | - Christophe Velours
- From the Laboratoire d'Enzymologie et Biochimie Structurales (LEBS), Centre de Recherche de Gif, CNRS, 91198 Gif sur Yvette, France
| | - Agathe Subtil
- the Institut Pasteur, Unité de Biologie des Interactions Cellulaires, 25 Rue du Docteur Roux, 75015 Paris, France
| | - Marcel Knossow
- From the Laboratoire d'Enzymologie et Biochimie Structurales (LEBS), Centre de Recherche de Gif, CNRS, 91198 Gif sur Yvette, France
| | - Benoît Gigant
- From the Laboratoire d'Enzymologie et Biochimie Structurales (LEBS), Centre de Recherche de Gif, CNRS, 91198 Gif sur Yvette, France,
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14
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Control of type III secretion activity and substrate specificity by the cytoplasmic regulator PcrG. Proc Natl Acad Sci U S A 2014; 111:E2027-36. [PMID: 24778208 DOI: 10.1073/pnas.1402658111] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Pathogenic Gram-negative bacteria use syringe-like type III secretion systems (T3SS) to inject effector proteins directly into targeted host cells. Effector secretion is triggered by host cell contact, and before contact is prevented by a set of conserved regulators. How these regulators interface with the T3SS apparatus to control secretion is unclear. We present evidence that the proton motive force (pmf) drives T3SS secretion in Pseudomonas aeruginosa, and that the cytoplasmic regulator PcrG interacts with distinct components of the T3SS apparatus to control two important aspects of effector secretion: (i) It coassembles with a second regulator (Pcr1) on the inner membrane T3SS component PcrD to prevent effectors from accessing the T3SS, and (ii) In conjunction with PscO, it controls protein secretion activity by modulating the ability of T3SS to convert pmf.
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15
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Burkinshaw BJ, Strynadka NCJ. Assembly and structure of the T3SS. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1649-63. [PMID: 24512838 DOI: 10.1016/j.bbamcr.2014.01.035] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 01/27/2014] [Accepted: 01/29/2014] [Indexed: 02/06/2023]
Abstract
The Type III Secretion System (T3SS) is a multi-mega Dalton apparatus assembled from more than twenty components and is found in many species of animal and plant bacterial pathogens. The T3SS creates a contiguous channel through the bacterial and host membranes, allowing injection of specialized bacterial effector proteins directly to the host cell. In this review, we discuss our current understanding of T3SS assembly and structure, as well as highlight structurally characterized Salmonella effectors. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
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Affiliation(s)
- Brianne J Burkinshaw
- Department of Biochemistry and Molecular Biology, Center for Blood Research, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Natalie C J Strynadka
- Department of Biochemistry and Molecular Biology, Center for Blood Research, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
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16
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Barison N, Gupta R, Kolbe M. A sophisticated multi-step secretion mechanism: how the type 3 secretion system is regulated. Cell Microbiol 2013; 15:1809-17. [PMID: 23927570 DOI: 10.1111/cmi.12178] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 07/31/2013] [Accepted: 08/01/2013] [Indexed: 11/28/2022]
Abstract
Many Gram-negative pathogens utilize type 3 secretion systems (T3SSs) for a successful infection. The T3SS is a large macromolecular complex which spans both bacterial membranes and delivers effector proteins into the host cell. The infection requires spatiotemporal control of diverse sets of secreted effectors and various mechanisms have evolved to regulate T3SS in response to external stimuli. This review will describe mechanisms that may control type 3 secretion, revealing a multi-step regulatory strategy. We then propose an updated model of T3SS that illustrates different stages of secretion and integrates the most recent structural and functional data.
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Affiliation(s)
- Nicola Barison
- Max-Planck-Institute for Infection Biology, Cellular Microbiology, Charitéplatz 1, 10117, Berlin, Germany
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17
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Cherradi Y, Schiavolin L, Moussa S, Meghraoui A, Meksem A, Biskri L, Azarkan M, Allaoui A, Botteaux A. Interplay between predicted inner-rod and gatekeeper in controlling substrate specificity of the type III secretion system. Mol Microbiol 2013; 87:1183-99. [PMID: 23336839 DOI: 10.1111/mmi.12158] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/15/2013] [Indexed: 11/30/2022]
Abstract
The type III secretion apparatus (T3SA) is a multi-protein complex central to the virulence of many Gram-negative pathogens. Currently, the mechanisms controlling the hierarchical addressing of needle subunits, translocators and effectors to the T3SA are still poorly understood. In Shigella, MxiC is known to sequester effectors within the cytoplasm prior to receiving the activation signal from the needle. However, molecules involved in linking the needle and MxiC are unknown. Here, we demonstrate a molecular interaction between MxiC and the predicted inner-rod component MxiI suggesting that this complex plugs the T3SA entry gate. Our results suggest that MxiI-MxiC complex dissociation facilitates the switch in secretion from translocators to effectors. We identified MxiC(F)(206)(S) variant, unable to interact with MxiI, which exhibits a constitutive secretion phenotype although it remains responsive to induction. Moreover, we identified the mxiI(Q67A) mutant that only secretes translocators, a phenotype that was suppressed by coexpression of the MxiC(F)(206)(S) variant. We demonstrated the interaction between MxiI and MxiC homologues in Yersinia and Salmonella. Lastly, we identified an interaction between MxiC and chaperone IpgC which contributes to understanding how translocators secretion is regulated. In summary, this study suggests the existence of a widely conserved T3S mechanism that regulates effectors secretion.
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Affiliation(s)
- Youness Cherradi
- Laboratoire de Bactériologie Moléculaire, Université Libre de Bruxelles, Route de Lennik, 808, 1070, Bruxelles, Belgium
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18
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Roehrich AD, Guillossou E, Blocker AJ, Martinez-Argudo I. Shigella IpaD has a dual role: signal transduction from the type III secretion system needle tip and intracellular secretion regulation. Mol Microbiol 2013; 87:690-706. [PMID: 23305090 PMCID: PMC3575693 DOI: 10.1111/mmi.12124] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/04/2012] [Indexed: 12/25/2022]
Abstract
Type III secretion systems (T3SSs) are protein injection devices essential for the interaction of many Gram-negative bacteria with eukaryotic cells. While Shigella assembles its T3SS when the environmental conditions are appropriate for invasion, secretion is only activated after physical contact with a host cell. First, the translocators are secreted to form a pore in the host cell membrane, followed by effectors which manipulate the host cell. Secretion activation is tightly controlled by conserved T3SS components: the needle tip proteins IpaD and IpaB, the needle itself and the intracellular gatekeeper protein MxiC. To further characterize the role of IpaD during activation, we combined random mutagenesis with a genetic screen to identify ipaD mutant strains unable to respond to host cell contact. Class II mutants have an overall defect in secretion induction. They map to IpaD's C-terminal helix and likely affect activation signal generation or transmission. The Class I mutant secretes translocators prematurely and is specifically defective in IpaD secretion upon activation. A phenotypically equivalent mutant was found in mxiC. We show that IpaD and MxiC act in the same intracellular pathway. In summary, we demonstrate that IpaD has a dual role and acts at two distinct locations during secretion activation.
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Affiliation(s)
- A Dorothea Roehrich
- School of Cellular & Molecular Medicine, University of Bristol, University Walk, Bristol BS8 1TD, UK
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19
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Kim JS, Jang JI, Eom JS, Oh CH, Kim HG, Kim BH, Bang IS, Bang SH, Park YK. Molecular characterization of the InvE regulator in the secretion of type III secretion translocases in Salmonella enterica serovar Typhimurium. MICROBIOLOGY-SGM 2013; 159:446-461. [PMID: 23288540 DOI: 10.1099/mic.0.061689-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The type III secretion systems (T3SSs) are exploited by many Gram-negative pathogenic bacteria to deliver a set of effector proteins into the host cytosol during cell entry. The T3SS of Salmonella enterica serovar Typhimurium is composed of more than 20 proteins that constitute the membrane-associated base, the needle and the tip complex at the distal end of the T3SS needle. Membrane docking and piercing between the T3SS and host cells is followed by the secretion of effector proteins. Therefore, a secretion hierarchy among the substrates of the T3SS is required. The secretion of the pore-forming translocase proteins SipB, SipC and SipD is controlled by the T3SS regulator protein, InvE. During an attempt to identify the regions of InvE that are involved in T3SS regulation, it was observed that the secretion of SipB, SipC and SipD was inhibited when the C-terminal 52 amino acids were removed from InvE. In addition, InvE derivatives lacking the N-terminal 30 and 100 residues were unable to secrete translocases into the culture medium. Interestingly, in the absence of the N-terminal 180 residues of InvE, SipD is unstable, resulting in the hypersecretion of SipB. We also found that both the type III secretion signals of SipB and SptP were functionally interchangeable with the first 30 amino acids of InvE, which could allow the secretion of a reporter protein. These results indicate that InvE may have two functional domains responsible for regulating the secretion of translocases: an N-terminal secretion signal and a C-terminal regulatory domain.
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Affiliation(s)
- Jin Seok Kim
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea
| | - Jung Im Jang
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea
| | - Jeong Seon Eom
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea
| | - Chang Heon Oh
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea
| | - Hyeon Guk Kim
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea
| | - Bae Hoon Kim
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea
| | - Iel Soo Bang
- Department of Microbiology and Immunology, Chosun University School of Dentistry, Gwang ju 501-759, Republic of Korea
| | - Seong Ho Bang
- Department of Biological Science, Hanseo University, Chungcheongnam-do 356-706, Republic of Korea
| | - Yong Keun Park
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea
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20
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Protein export according to schedule: architecture, assembly, and regulation of type III secretion systems from plant- and animal-pathogenic bacteria. Microbiol Mol Biol Rev 2012; 76:262-310. [PMID: 22688814 DOI: 10.1128/mmbr.05017-11] [Citation(s) in RCA: 304] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Flagellar and translocation-associated type III secretion (T3S) systems are present in most gram-negative plant- and animal-pathogenic bacteria and are often essential for bacterial motility or pathogenicity. The architectures of the complex membrane-spanning secretion apparatuses of both systems are similar, but they are associated with different extracellular appendages, including the flagellar hook and filament or the needle/pilus structures of translocation-associated T3S systems. The needle/pilus is connected to a bacterial translocon that is inserted into the host plasma membrane and mediates the transkingdom transport of bacterial effector proteins into eukaryotic cells. During the last 3 to 5 years, significant progress has been made in the characterization of membrane-associated core components and extracellular structures of T3S systems. Furthermore, transcriptional and posttranscriptional regulators that control T3S gene expression and substrate specificity have been described. Given the architecture of the T3S system, it is assumed that extracellular components of the secretion apparatus are secreted prior to effector proteins, suggesting that there is a hierarchy in T3S. The aim of this review is to summarize our current knowledge of T3S system components and associated control proteins from both plant- and animal-pathogenic bacteria.
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21
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Archuleta TL, Du Y, English CA, Lory S, Lesser C, Ohi MD, Ohi R, Spiller BW. The Chlamydia effector chlamydial outer protein N (CopN) sequesters tubulin and prevents microtubule assembly. J Biol Chem 2011; 286:33992-8. [PMID: 21841198 DOI: 10.1074/jbc.m111.258426] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Chlamydia species are obligate intracellular pathogens that utilize a type three secretion system to manipulate host cell processes. Genetic manipulations are currently not possible in Chlamydia, necessitating study of effector proteins in heterologous expression systems and severely complicating efforts to relate molecular strategies used by Chlamydia to the biochemical activities of effector proteins. CopN is a chlamydial type three secretion effector that is essential for virulence. Heterologous expression of CopN in cells results in loss of microtubule spindles and metaphase plate formation and causes mitotic arrest. CopN is a multidomain protein with similarity to type three secretion system "plug" proteins from other organisms but has functionally diverged such that it also functions as an effector protein. We show that CopN binds directly to αβ-tubulin but not to microtubules (MTs). Furthermore, CopN inhibits tubulin polymerization by sequestering free αβ-tubulin, similar to one of the mechanisms utilized by stathmin. Although CopN and stathmin share no detectable sequence identity, both influence MT formation by sequestration of αβ-tubulin. CopN displaces stathmin from preformed stathmin-tubulin complexes, indicating that the proteins bind overlapping sites on tubulin. CopN is the first bacterial effector shown to disrupt MT formation directly. This recognition affords a mechanistic understanding of a strategy Chlamydia species use to manipulate the host cell cycle.
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Affiliation(s)
- Tara L Archuleta
- Division of Chemical and Physical Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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22
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Osborne SE, Coombes BK. Expression and secretion hierarchy in the nonflagellar type III secretion system. Future Microbiol 2011; 6:193-202. [PMID: 21366419 DOI: 10.2217/fmb.10.172] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Type III secretion systems that deliver bacterial proteins into eukaryotic cells are the basis for both symbiotic and pathogenic relationships between many Gram-negative bacteria and their hosts. Exploration of the structure, function and assembly of this secretion system has greatly enhanced our knowledge of bacterial ecology in the context of infectious disease and has spawned new avenues in anti-infective research with a view towards inhibiting virulence functions. We outline advances in understanding type III secretion system function with specific focus on how assembly is hierarchically coordinated at the level of expression and how the type III secretion system mediates transitions in substrate specificity.
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Affiliation(s)
- Suzanne E Osborne
- Michael G DeGroote Institute for Infectious Disease Research & Department of Biochemistry & Biomedical Sciences, HSC-4H17, McMaster University, Hamilton, ON, Canada
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23
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Srikanth CV, Wall DM, Maldonado-Contreras A, Shi H, Zhou D, Demma Z, Mumy KL, McCormick BA. Salmonella pathogenesis and processing of secreted effectors by caspase-3. Science 2010; 330:390-393. [PMID: 20947770 DOI: 10.1126/science.1194598] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The enteric pathogen Salmonella enterica serovar Typhimurium causes food poisoning resulting in gastroenteritis. The S. Typhimurium effector Salmonella invasion protein A (SipA) promotes gastroenteritis by functional motifs that trigger either mechanisms of inflammation or bacterial entry. During infection of intestinal epithelial cells, SipA was found to be responsible for the early activation of caspase-3, an enzyme that is required for SipA cleavage at a specific recognition motif that divided the protein into its two functional domains and activated SipA in a manner necessary for pathogenicity. Other caspase-3 cleavage sites identified in S. Typhimurium appeared to be restricted to secreted effector proteins, which indicates that this may be a general strategy used by this pathogen for processing of its secreted effectors.
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Affiliation(s)
- C V Srikanth
- Department of Pediatric Gastroenterology and Nutrition, Harvard Medical School and Massachusetts General Hospital, Boston, MA 02129, USA.,Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA
| | - Daniel M Wall
- Department of Pediatric Gastroenterology and Nutrition, Harvard Medical School and Massachusetts General Hospital, Boston, MA 02129, USA.,Institute of Infection, Immunity & Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, G12 8QQ, UK
| | - Ana Maldonado-Contreras
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA
| | - Haining Shi
- Department of Pediatric Gastroenterology and Nutrition, Harvard Medical School and Massachusetts General Hospital, Boston, MA 02129, USA
| | - Daoguo Zhou
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907
| | - Zachary Demma
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA
| | - Karen L Mumy
- Department of Pediatric Gastroenterology and Nutrition, Harvard Medical School and Massachusetts General Hospital, Boston, MA 02129, USA.,Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA
| | - Beth A McCormick
- Department of Pediatric Gastroenterology and Nutrition, Harvard Medical School and Massachusetts General Hospital, Boston, MA 02129, USA.,Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA
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Peng J, Yang J, Jin Q. Research progress in Shigella in the postgenomic era. SCIENCE CHINA-LIFE SCIENCES 2010; 53:1284-90. [DOI: 10.1007/s11427-010-4089-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Accepted: 12/20/2009] [Indexed: 01/01/2023]
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25
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Martinez-Argudo I, Blocker AJ. The Shigella T3SS needle transmits a signal for MxiC release, which controls secretion of effectors. Mol Microbiol 2010. [PMID: 21143311 DOI: 10.1111/journal.1365-2958.2010.07413.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Type III secretion systems (T3SSs) are key determinants of virulence in many Gram-negative bacteria, including animal and plant pathogens. They inject 'effector' proteins through a 'needle' protruding from the bacterial surface directly into eukaryotic cells after assembly of a 'translocator' pore in the host plasma membrane. Secretion is a tightly regulated process, which is blocked until physical contact with a host cell takes place. Host cell sensing occurs through a distal needle 'tip complex' and translocators are secreted before effectors. MxiC, a Shigella T3SS substrate, prevents premature effector secretion. Here, we examine how the different parts of T3SSs work together to allow orderly secretion. We show that T3SS assembly and needle tip composition are not altered in an mxiC mutant. We find that MxiC not only represses effector secretion but that it is also required for translocator release. We provide genetic evidence that MxiC acts downstream of the tip complex and then the needle during secretion activation. Finally, we show that the needle controls MxiC release. Therefore, for the first time, our data allow us to propose a model of secretion activation that goes from the tip complex to cytoplasmic MxiC via the needle.
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26
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Martinez-Argudo I, Blocker AJ. The Shigella T3SS needle transmits a signal for MxiC release, which controls secretion of effectors. Mol Microbiol 2010; 78:1365-78. [PMID: 21143311 PMCID: PMC3020320 DOI: 10.1111/j.1365-2958.2010.07413.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Type III secretion systems (T3SSs) are key determinants of virulence in many Gram-negative bacteria, including animal and plant pathogens. They inject ‘effector’ proteins through a ‘needle’ protruding from the bacterial surface directly into eukaryotic cells after assembly of a ‘translocator’ pore in the host plasma membrane. Secretion is a tightly regulated process, which is blocked until physical contact with a host cell takes place. Host cell sensing occurs through a distal needle ‘tip complex’ and translocators are secreted before effectors. MxiC, a Shigella T3SS substrate, prevents premature effector secretion. Here, we examine how the different parts of T3SSs work together to allow orderly secretion. We show that T3SS assembly and needle tip composition are not altered in an mxiC mutant. We find that MxiC not only represses effector secretion but that it is also required for translocator release. We provide genetic evidence that MxiC acts downstream of the tip complex and then the needle during secretion activation. Finally, we show that the needle controls MxiC release. Therefore, for the first time, our data allow us to propose a model of secretion activation that goes from the tip complex to cytoplasmic MxiC via the needle.
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27
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Timing is everything: the regulation of type III secretion. Cell Mol Life Sci 2009; 67:1065-75. [PMID: 20043184 PMCID: PMC2835726 DOI: 10.1007/s00018-009-0230-0] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Revised: 11/23/2009] [Accepted: 12/08/2009] [Indexed: 12/19/2022]
Abstract
Type Three Secretion Systems (T3SSs) are essential virulence determinants of many Gram-negative bacteria. The T3SS is an injection device that can transfer bacterial virulence proteins directly into host cells. The apparatus is made up of a basal body that spans both bacterial membranes and an extracellular needle that possesses a channel that is thought to act as a conduit for protein secretion. Contact with a host-cell membrane triggers the insertion of a pore into the target membrane, and effectors are translocated through this pore into the host cell. To assemble a functional T3SS, specific substrates must be targeted to the apparatus in the correct order. Recently, there have been many developments in our structural and functional understanding of the proteins involved in the regulation of secretion. Here we review the current understanding of protein components of the system thought to be involved in switching between different stages of secretion.
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28
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Gazi AD, Charova SN, Panopoulos NJ, Kokkinidis M. Coiled-coils in type III secretion systems: structural flexibility, disorder and biological implications. Cell Microbiol 2009; 11:719-29. [PMID: 19215225 DOI: 10.1111/j.1462-5822.2009.01297.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recent structural studies and analyses of microbial genomes have consolidated the understanding of the structural and functional versatility of coiled-coil domains in proteins from bacterial type III secretion systems (T3SS). Such domains consist of two or more α-helices forming a bundle structure. The occurrence of coiled-coils in T3SS is considerably higher than the average predicted occurrence in prokaryotic proteomes. T3SS proteins comprising coiled-coil domains are frequently characterized by an increased structural flexibility, which may vary from localized structural disorder to the establishment of molten globule-like state. The propensity for coiled-coil formation and structural disorder are frequently essential requirements for various T3SS functions, including the establishment of protein-protein interaction networks and the polymerization of extracellular components of T3SS appendages. Possible correlations between the frequently observed N-terminal structural disorder of effectors and the T3SS secretion signal are discussed. The results for T3SS are also compared with other Gram-negative secretory systems.
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Affiliation(s)
- Anastasia D Gazi
- Institute of Molecular Biology and Biotechnology, Foundation of Research and Technology and Department of Biology, University of Crete, Vasilika Vouton, Heraklion, Crete, Greece
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29
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Botteaux A, Sory MP, Biskri L, Parsot C, Allaoui A. MxiC is secreted by and controls the substrate specificity of the Shigella flexneri type III secretion apparatus. Mol Microbiol 2008; 71:449-60. [PMID: 19017268 DOI: 10.1111/j.1365-2958.2008.06537.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Many gram-negative pathogenic bacteria use a type III secretion (T3S) system to interact with cells of their hosts. Mechanisms controlling the hierarchical addressing of needle subunits, translocators and effectors to the T3S apparatus (T3SA) are still poorly understood. We investigated the function of MxiC, the member of the YopN/InvE/SepL family in the Shigella flexneri T3S system. Inactivation of mxiC led specifically to a deregulated secretion of effectors (including IpaA, IpgD, IcsB, IpgB2, OspD1 and IpaHs), but not of translocators (IpaB and IpaC) and proteins controlling the T3SA structure or activity (Spa32 and IpaD). Expression of effector-encoding genes controlled by the activity of the T3SA and the transcription activator MxiE was increased in the mxiC mutant, as a consequence of the increased secretion of the MxiE anti-activator OspD1. MxiC is a T3SA substrate and its ability to be secreted is required for its function. By using co-purification assays, we found that MxiC can associate with the Spa47 ATPase, which suggests that MxiC might prevent secretion of effectors by blocking the T3SA from the inside. Although with a 10-fold reduced efficiency compared with the wild-type strain, the mxiC mutant was still able to enter epithelial cells.
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Affiliation(s)
- Anne Botteaux
- Laboratoire de Bactériologie Moléculaire, Faculté de Médecine, Université Libre de Bruxelles, Route de Lennik, 808, CP: 614b, 1070, Brussels, Belgium
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Deane JE, Graham SC, Mitchell EP, Flot D, Johnson S, Lea SM. Crystal structure of Spa40, the specificity switch for the Shigella flexneri type III secretion system. Mol Microbiol 2008; 69:267-76. [PMID: 18485071 PMCID: PMC2615192 DOI: 10.1111/j.1365-2958.2008.06293.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/08/2008] [Indexed: 12/17/2022]
Abstract
The pathogenic bacterium Shigella flexneri uses a type III secretion system to inject virulence factors from the bacterial cytosol directly into host cells. The machinery that identifies secretion substrates and controls the export of extracellular components and effector proteins consists of several inner-membrane and cytoplasmic proteins. One of the inner membrane components, Spa40, belongs to a family of proteins proposed to regulate the switching of substrate specificity of the export apparatus. We show that Spa40 is cleaved within the strictly conserved amino acid sequence NPTH and substitution of the proposed autocatalytic residue abolishes cleavage. Here we also report the crystal structure of the cytoplasmic complex Spa40(C) and compare it with the recent structures of the homologues from Escherichia coli and Salmonella typhimurium. These structures reveal the tight association of the cleaved fragments and show that the conserved NPTH sequence lies on a loop which, when cleaved, swings away from the catalytic N257 residue, resulting in different surface features in this region. This structural rearrangement suggests a mechanism by which non-cleaving forms of these proteins interfere with correct substrate switching of the apparatus.
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Affiliation(s)
- Janet E Deane
- Sir William Dunn School of Pathology, South Parks Rd, University of OxfordOX1 3RE, UK
| | - Stephen C Graham
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, Roosevelt Drive, University of OxfordOX3 7BN, UK
| | - Edward P Mitchell
- European Synchrotron Radiation Facility6 Rue Jules Horowitz, 38043 Grenoble, France
- EPSAM, Keele UniversityStafforshire, ST5 5BG, UK
| | - David Flot
- European Molecular Biology Laboratory6 Rue Jules Horowitz, 38042 Grenoble, France
| | - Steven Johnson
- Sir William Dunn School of Pathology, South Parks Rd, University of OxfordOX1 3RE, UK
| | - Susan M Lea
- Sir William Dunn School of Pathology, South Parks Rd, University of OxfordOX1 3RE, UK
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