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Li L, Yang B, Wang J, Wei Y, Xiang B, Liu Y, Wu P, Li W, Wang Y, Zhao X, Qin J, Liu M, Liu R, Ma G, Fu T, Wang M, Liu B. CobB-mediated deacetylation of the chaperone CesA regulates Escherichia coli O157:H7 virulence. Gut Microbes 2024; 16:2331435. [PMID: 38502202 PMCID: PMC10956630 DOI: 10.1080/19490976.2024.2331435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Accepted: 03/13/2024] [Indexed: 03/21/2024] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a common food-borne pathogen that can cause acute diseases. Lysine acetylation is a post-translational modification (PTM) that occurs in various prokaryotes and is regulated by CobB, the only deacetylase found in bacteria. Here, we demonstrated that CobB plays an important role in the virulence of EHEC O157:H7 and that deletion of cobB significantly decreased the intestinal colonization ability of bacteria. Using acetylation proteomic studies, we systematically identified several proteins that could be regulated by CobB in EHEC O157:H7. Among these CobB substrates, we found that acetylation at the K44 site of CesA, a chaperone for the type-III secretion system (T3SS) translocator protein EspA, weakens its binding to EspA, thereby reducing the stability of this virulence factor; this PTM ultimately attenuating the virulence of EHEC O157:H7. Furthermore, we showed that deacetylation of the K44 site, which is deacetylated by CobB, promotes the interaction between CesA and EspA, thereby increasing bacterial virulence in vitro and in animal experiments. In summary, we showed that acetylation influences the virulence of EHEC O157:H7, and uncovered the mechanism by which CobB contributes to bacterial virulence based on the regulation of CesA deacetylation.
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Affiliation(s)
- Linxing Li
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Bin Yang
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Jing Wang
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Yi Wei
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Binbin Xiang
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Yutao Liu
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Pan Wu
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Wanwu Li
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Yanling Wang
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Xinyu Zhao
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Jingliang Qin
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Miaomiao Liu
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Ruiying Liu
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Guozhen Ma
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Tian Fu
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
| | - Min Wang
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
- Key Laboratory of Molecular Microbiology and Technology, Nankai University, Ministry of Education, Tianjin, China
- Nankai International Advanced Research Institute, Nankai University, Shenzhen, China
| | - Bin Liu
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China
- Key Laboratory of Molecular Microbiology and Technology, Nankai University, Ministry of Education, Tianjin, China
- Nankai International Advanced Research Institute, Nankai University, Shenzhen, China
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2
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Sirisaengtaksin N, O'Donoghue EJ, Jabbari S, Roe AJ, Krachler AM. Bacterial outer membrane vesicles provide an alternative pathway for trafficking of Escherichia coli O157 type III secreted effectors to epithelial cells. mSphere 2023; 8:e0052023. [PMID: 37929984 PMCID: PMC10732017 DOI: 10.1128/msphere.00520-23] [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: 09/18/2023] [Accepted: 10/03/2023] [Indexed: 11/07/2023] Open
Abstract
IMPORTANCE Bacteria can package protein cargo into nanosized membrane blebs that are shed from the bacterial membrane and released into the environment. Here, we report that a type of pathogenic bacteria called enterohemorrhagic Escherichia coli O157 (EHEC) uses their membrane blebs (outer membrane vesicles) to package components of their type 3 secretion system and send them into host cells, where they can manipulate host signaling pathways including those involved in infection response, such as immunity. Usually, EHEC use a needle-like apparatus to inject these components into host cells, but packaging them into membrane blebs that get taken up by host cells is another way of delivery that can bypass the need for a functioning injection system.
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Affiliation(s)
- Natalie Sirisaengtaksin
- Department of Microbiology and Molecular Genetics, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Eloise J. O'Donoghue
- School of Biosciences, Institute of Microbiology and Infection, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - Sara Jabbari
- School of Mathematics, Institute of Microbiology and Infection, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - Andrew J. Roe
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Anne Marie Krachler
- Department of Microbiology and Molecular Genetics, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, Texas, USA
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3
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Guo EZ, Desrosiers DC, Zalesak J, Tolchard J, Berbon M, Habenstein B, Marlovits T, Loquet A, Galán JE. A polymorphic helix of a Salmonella needle protein relays signals defining distinct steps in type III secretion. PLoS Biol 2019; 17:e3000351. [PMID: 31260457 PMCID: PMC6625726 DOI: 10.1371/journal.pbio.3000351] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Revised: 07/12/2019] [Accepted: 06/18/2019] [Indexed: 12/22/2022] Open
Abstract
Type III protein-secretion machines are essential for the interactions of many pathogenic or symbiotic bacterial species with their respective eukaryotic hosts. The core component of these machines is the injectisome, a multiprotein complex that mediates the selection of substrates, their passage through the bacterial envelope, and ultimately their delivery into eukaryotic target cells. The injectisome is composed of a large cytoplasmic complex or sorting platform, a multiring base embedded in the bacterial envelope, and a needle-like filament that protrudes several nanometers from the bacterial surface and is capped at its distal end by the tip complex. A characteristic feature of these machines is that their activity is stimulated by contact with target host cells. The sensing of target cells, thought to be mediated by the distal tip of the needle filament, generates an activating signal that must be transduced to the secretion machine by the needle filament. Here, through a multidisciplinary approach, including solid-state NMR (SSNMR) and cryo electron microscopy (cryo-EM) analyses, we have identified critical residues of the needle filament protein of a Salmonella Typhimurium type III secretion system that are involved in the regulation of the activity of the secretion machine. We found that mutations in the needle filament protein result in various specific phenotypes associated with different steps in the type III secretion process. More specifically, these studies reveal an important role for a polymorphic helix of the needle filament protein and the residues that line the lumen of its central channel in the control of type III secretion.
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Affiliation(s)
- Emily Z. Guo
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Daniel C. Desrosiers
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Jan Zalesak
- Institute of Molecular Biotechnology (IMBA), Vienna Biocenter (VBC), Vienna, Austria
| | - James Tolchard
- Institute of Chemistry and Biology of Membranes and Nano-objects, CBMN-CNRS Université de Bordeaux, Pessac, France
| | - Mélanie Berbon
- Institute of Chemistry and Biology of Membranes and Nano-objects, CBMN-CNRS Université de Bordeaux, Pessac, France
| | - Birgit Habenstein
- Institute of Chemistry and Biology of Membranes and Nano-objects, CBMN-CNRS Université de Bordeaux, Pessac, France
| | - Thomas Marlovits
- Institute of Molecular Biotechnology (IMBA), Vienna Biocenter (VBC), Vienna, Austria
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria
- Center for Structural Systems Biology (CSSB), University Medical Center Hamburg-Eppendorf (UKE) and German Electron Synchrotron Centre (DESY), Hamburg, Germany
| | - Antoine Loquet
- Institute of Chemistry and Biology of Membranes and Nano-objects, CBMN-CNRS Université de Bordeaux, Pessac, France
| | - Jorge E. Galán
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America
- * E-mail:
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Slater SL, Sågfors AM, Pollard DJ, Ruano-Gallego D, Frankel G. The Type III Secretion System of Pathogenic Escherichia coli. Curr Top Microbiol Immunol 2019; 416:51-72. [PMID: 30088147 DOI: 10.1007/82_2018_116] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Infection with enteropathogenic and enterohaemorrhagic Escherichia coli (EPEC and EHEC), enteroinvasive E. coli (EIEC) and Shigella relies on the elaboration of a type III secretion system (T3SS). Few strains also encode a second T3SS, named ETT2. Through the integration of coordinated intracellular and extracellular cues, the modular T3SS is assembled within the bacterial cell wall, as well as the plasma membrane of the host cell. As such, the T3SS serves as a conduit, allowing the chaperone-regulated translocation of effector proteins directly into the host cytosol to subvert eukaryotic cell processes. Recent technological advances revealed high structural resolution of the T3SS apparatus and how it could be exploited to treat enteric disease. This chapter summarises the current knowledge of the structure and function of the E. coli T3SSs.
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Affiliation(s)
- Sabrina L Slater
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
| | - Agnes M Sågfors
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
| | - Dominic J Pollard
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
| | - David Ruano-Gallego
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
| | - Gad Frankel
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK.
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5
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Abstract
Type III secretion systems (T3SSs) are protein transport nanomachines that are found in Gram-negative bacterial pathogens and symbionts. Resembling molecular syringes, T3SSs form channels that cross the bacterial envelope and the host cell membrane, which enable bacteria to inject numerous effector proteins into the host cell cytoplasm and establish trans-kingdom interactions with diverse hosts. Recent advances in cryo-electron microscopy and integrative imaging have provided unprecedented views of the architecture and structure of T3SSs. Furthermore, genetic and molecular analyses have elucidated the functions of many effectors and key regulators of T3SS assembly and secretion hierarchy, which is the sequential order by which the protein substrates are secreted. As essential virulence factors, T3SSs are attractive targets for vaccines and therapeutics. This Review summarizes our current knowledge of the structure and function of this important protein secretion machinery. A greater understanding of T3SSs should aid mechanism-based drug design and facilitate their manipulation for biotechnological applications.
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A Novel Mechanism for Protein Delivery by the Type 3 Secretion System for Extracellularly Secreted Proteins. mBio 2017; 8:mBio.00184-17. [PMID: 28351918 PMCID: PMC5371411 DOI: 10.1128/mbio.00184-17] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
The type 3 secretion system (T3SS) is essential for bacterial virulence through delivering effector proteins directly into the host cytosol. Here, we identified an alternative delivery mechanism of virulence factors mediated by the T3SS, which consists of the association of extracellularly secreted proteins from bacteria with the T3SS to gain access to the host cytosol. Both EspC, a protein secreted as an enteropathogenic Escherichia coli (EPEC) autotransporter, and YopH, a protein detected on the surface of Yersinia, require a functional T3SS for host cell internalization; here we provide biophysical and molecular evidence to support the concept of the EspC translocation mechanism, which requires (i) an interaction between EspA and an EspC middle segment, (ii) an EspC translocation motif (21 residues that are shared with the YopH translocation motif), (iii) increases in the association and dissociation rates of EspC mediated by EspA interacting with EspD, and (iv) an interaction of EspC with the EspD/EspB translocon pore. Interestingly, this novel mechanism does not exclude the injection model (i.e., EspF) operating through the T3SS conduit; therefore, T3SS can be functioning as an internal conduit or as an external railway, which can be used to reach the translocator pore, and this mechanism appears to be conserved among different T3SS-dependent pathogens. The type 3 secretion system is essential for injection of virulence factors, which are delivered directly into the cytosol of the host cells for usurping and subverting host processes. Recent studies have shown that these effectors proteins indeed travel inside an “injectisome” conduit through a single step of translocation by connecting the bacterium and host cell cytoplasms. However, all findings are not compatible with this model. For example, both YopH, a protein detected on the surface of Yersinia, and EspC, an autotransporter protein secreted by enteropathogenic E. coli, require a functional T3SS for host cell translocation. Both proteins have an intermediate extracellular step before their T3SS-dependent translocation. Here, we show an alternative delivery mechanism for these extracellularly secreted virulence factors that are then incorporated into the T3SS to enter the cells; this novel mechanism coexists with but diverges from the canonical injection model that involves the passage of the protein inside the injectisome.
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7
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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: 115] [Impact Index Per Article: 14.4] [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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8
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The Locus of Enterocyte Effacement and Associated Virulence Factors of Enterohemorrhagic Escherichia coli. Microbiol Spectr 2016; 2:EHEC-0007-2013. [PMID: 26104209 DOI: 10.1128/microbiolspec.ehec-0007-2013] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A subset of Shiga toxin-producing Escherichia coli strains, termed enterohemorrhagic E. coli (EHEC), is defined in part by the ability to produce attaching and effacing (A/E) lesions on intestinal epithelia. Such lesions are characterized by intimate bacterial attachment to the apical surface of enterocytes, cytoskeletal rearrangements beneath adherent bacteria, and destruction of proximal microvilli. A/E lesion formation requires the locus of enterocyte effacement (LEE), which encodes a Type III secretion system that injects bacterial proteins into host cells. The translocated proteins, termed effectors, subvert a plethora of cellular pathways to the benefit of the pathogen, for example, by recruiting cytoskeletal proteins, disrupting epithelial barrier integrity, and interfering with the induction of inflammation, phagocytosis, and apoptosis. The LEE and selected effectors play pivotal roles in intestinal persistence and virulence of EHEC, and it is becoming clear that effectors may act in redundant, synergistic, and antagonistic ways during infection. Vaccines that target the function of the Type III secretion system limit colonization of reservoir hosts by EHEC and may thus aid control of zoonotic infections. Here we review the features and functions of the LEE-encoded Type III secretion system and associated effectors of E. coli O157:H7 and other Shiga toxin-producing E. coli strains.
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Ruano-Gallego D, Álvarez B, Fernández LÁ. Engineering the Controlled Assembly of Filamentous Injectisomes in E. coli K-12 for Protein Translocation into Mammalian Cells. ACS Synth Biol 2015; 4:1030-41. [PMID: 26017572 PMCID: PMC4603727 DOI: 10.1021/acssynbio.5b00080] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
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Bacterial pathogens containing type
III protein secretion systems
(T3SS) assemble large needle-like protein complexes in the bacterial
envelope, called injectisomes, for translocation of protein effectors
into host cells. The application of these “molecular syringes”
for the injection of proteins into mammalian cells is hindered by
their structural and genomic complexity, requiring multiple polypeptides
encoded along with effectors in various transcriptional units (TUs)
with intricate regulation. In this work, we have rationally designed
the controlled expression of the filamentous injectisomes found in
enteropathogenic Escherichia coli (EPEC) in the nonpathogenic strain E. coli K-12. All structural components of EPEC injectisomes, encoded in
a genomic island called the locus of enterocyte effacement
(LEE), were engineered in five TUs (eLEEs) excluding effectors, promoters
and transcriptional regulators. These eLEEs were placed under the
control of the IPTG-inducible promoter Ptac and integrated into specific
chromosomal sites of E. coli K-12 using a marker-less
strategy. The resulting strain, named synthetic injector E.
coli (SIEC), assembles filamentous injectisomes similar to
those in EPEC. SIEC injectisomes form pores in the host plasma membrane
and are able to translocate T3-substrate proteins (e.g., translocated intimin receptor, Tir) into the cytoplasm of HeLa
cells reproducing the phenotypes of intimate attachment and polymerization
of actin-pedestals elicited by EPEC bacteria. Hence, SIEC strain allows
the controlled expression of functional filamentous injectisomes for
efficient translocation of proteins with T3S-signals into mammalian
cells.
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Affiliation(s)
- David Ruano-Gallego
- Department of Microbial Biotechnology,
Centro Nacional de Biotecnología, Consejo Superior de Investigaciones
Científicas (CSIC), Campus UAM Cantoblanco, 28049 Madrid, Spain
| | - Beatriz Álvarez
- Department of Microbial Biotechnology,
Centro Nacional de Biotecnología, Consejo Superior de Investigaciones
Científicas (CSIC), Campus UAM Cantoblanco, 28049 Madrid, Spain
| | - Luis Ángel Fernández
- Department of Microbial Biotechnology,
Centro Nacional de Biotecnología, Consejo Superior de Investigaciones
Científicas (CSIC), Campus UAM Cantoblanco, 28049 Madrid, Spain
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Galán JE, Lara-Tejero M, Marlovits TC, Wagner S. Bacterial type III secretion systems: specialized nanomachines for protein delivery into target cells. Annu Rev Microbiol 2014; 68:415-38. [PMID: 25002086 DOI: 10.1146/annurev-micro-092412-155725] [Citation(s) in RCA: 367] [Impact Index Per Article: 36.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
One of the most exciting developments in the field of bacterial pathogenesis in recent years is the discovery that many pathogens utilize complex nanomachines to deliver bacterially encoded effector proteins into target eukaryotic cells. These effector proteins modulate a variety of cellular functions for the pathogen's benefit. One of these protein-delivery machines is the type III secretion system (T3SS). T3SSs are widespread in nature and are encoded not only by bacteria pathogenic to vertebrates or plants but also by bacteria that are symbiotic to plants or insects. A central component of T3SSs is the needle complex, a supramolecular structure that mediates the passage of the secreted proteins across the bacterial envelope. Working in conjunction with several cytoplasmic components, the needle complex engages specific substrates in sequential order, moves them across the bacterial envelope, and ultimately delivers them into eukaryotic cells. The central role of T3SSs in pathogenesis makes them great targets for novel antimicrobial strategies.
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Affiliation(s)
- Jorge E Galán
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut 06536;
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11
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EscO, a functional and structural analog of the flagellar FliJ protein, is a positive regulator of EscN ATPase activity of the enteropathogenic Escherichia coli injectisome. J Bacteriol 2014; 196:2227-41. [PMID: 24706741 DOI: 10.1128/jb.01551-14] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Type III secretion systems (T3SSs) are multiprotein molecular devices used by many Gram-negative bacterial pathogens to translocate effector proteins into eukaryotic cells. A T3SS is also used for protein export in flagellar assembly, which promotes bacterial motility. The two systems are evolutionarily related, possessing highly conserved components in their export apparatuses. Enteropathogenic Escherichia coli (EPEC) employs a T3SS, encoded by genes in the locus of enterocyte effacement (LEE) pathogenicity island, to colonize the human intestine and cause diarrheal disease. In the present work, we investigated the role of the LEE-encoded EscO protein (previously Orf15 or EscA) in T3SS biogenesis. We show that EscO shares similar properties with the flagellar FliJ and the Yersinia YscO protein families. Our findings demonstrate that EscO is essential for secretion of all categories of T3SS substrates. Consistent with its central role in protein secretion, it was found to interact with the ATPase EscN and its negative regulator, EscL, of the export apparatus. Moreover, we show that EscO stimulates EscN enzymatic activity; however, it is unable to upregulate ATP hydrolysis in the presence of EscL. Remarkably, EscO partially restored the swimming defect of a Salmonella flagellar fliJ mutant and was able to stimulate the ATPase activity of FliI. Overall, our data indicate that EscO is the virulence counterpart of the flagellar FliJ protein.
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12
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Structure of a type III secretion needle at 7-Å resolution provides insights into its assembly and signaling mechanisms. Proc Natl Acad Sci U S A 2012; 109:4461-6. [PMID: 22388746 DOI: 10.1073/pnas.1116126109] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Type III secretion systems of Gram-negative bacteria form injection devices that deliver effector proteins into eukaryotic cells during infection. They span both bacterial membranes and the extracellular space to connect with the host cell plasma membrane. Their extracellular portion is a needle-like, hollow tube that serves as a secretion conduit for effector proteins. The needle of Shigella flexneri is approximately 50-nm long and 7-nm thick and is made by the helical assembly of one protein, MxiH. We provide a 7-Å resolution 3D image reconstruction of the Shigella needle by electron cryomicroscopy, which resolves α-helices and a β-hairpin that has never been observed in the crystal and solution structures of needle proteins, including MxiH. An atomic model of the needle based on the 3D-density map, in comparison with that of the bacterial-flagellar filament, provides insights into how such a thin tubular structure is stably assembled by intricate intermolecular interactions. The map also illuminates how the needle-length control protein functions as a ruler within the central channel during export of MxiH for assembly at the distal end of the needle, and how the secretion-activation signal may be transduced through a conformational change of the needle upon host-cell contact.
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13
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Sato H, Frank DW. Multi-Functional Characteristics of the Pseudomonas aeruginosa Type III Needle-Tip Protein, PcrV; Comparison to Orthologs in other Gram-negative Bacteria. Front Microbiol 2011; 2:142. [PMID: 21772833 PMCID: PMC3131520 DOI: 10.3389/fmicb.2011.00142] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2011] [Accepted: 06/15/2011] [Indexed: 01/02/2023] Open
Abstract
Pseudomonas aeruginosa possesses a type III secretion system (T3SS) to intoxicate host cells and evade innate immunity. This virulence-related machinery consists of a molecular syringe and needle assembled on the bacterial surface, which allows delivery of T3 effector proteins into infected cells. To accomplish a one-step effector translocation, a tip protein is required at the top end of the T3 needle structure. Strains lacking expression of the functional tip protein fail to intoxicate host cells. P. aeruginosa encodes a T3S that is highly homologous to the proteins encoded by Yersinia spp. The needle-tip proteins of Yersinia, LcrV, and P. aeruginosa, PcrV, share 37% identity and 65% similarity. Other known tip proteins are AcrV (Aeromonas), IpaD (Shigella), SipD (Salmonella), BipD (Burkholderia), EspA (EPEC, EHEC), Bsp22 (Bordetella), with additional proteins identified from various Gram-negative species, such as Vibrio and Bordetella. The tip proteins can serve as a protective antigen or may be critical for sensing host cells and evading innate immune responses. Recognition of the host microenvironment transcriptionally activates synthesis of T3SS components. The machinery appears to be mechanically controlled by the assemblage of specific junctions within the apparatus. These junctions include the tip and base of the T3 apparatus, the needle proteins and components within the bacterial cytoplasm. The tip proteins likely have chaperone functions for translocon proteins, allowing the proper assembly of translocation channels in the host membrane and completing vectorial delivery of effector proteins into the host cytoplasm. Multi-functional features of the needle-tip proteins appear to be intricately controlled. In this review, we highlight the functional aspects and complex controls of T3 needle-tip proteins with particular emphasis on PcrV and LcrV.
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Affiliation(s)
- Hiromi Sato
- Center for Infectious Disease Research, Medical College of Wisconsin Milwaukee, WI, USA
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14
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Humphries RM, Armstrong GD. Sticky situation: localized adherence of enteropathogenic Escherichia coli to the small intestine epithelium. Future Microbiol 2011; 5:1645-61. [PMID: 21133687 DOI: 10.2217/fmb.10.124] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Enteropathogenic Escherichia coli (EPEC) primarily cause gastrointestinal illness in neonates. They accomplish this by a complex coordinated multistage strategy, whereby the organisms colonize the epithelial lining of the small intestine. This process can be divided into four stages: first, localized, nonintimate adherence; second, type III secretion-mediated injection of effector proteins, third effacement of microvilli and, finally, intimate adherence. In this article, we review the history and current state of knowledge, as well as present potential future directions for further investigating the fascinating processes by which EPEC and related organisms colonize the human intestine and cause disease.
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Affiliation(s)
- Romney M Humphries
- University of Calgary, Department of Microbiology and Infectious Diseases, Calgary, Alberta, Canada
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15
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Misyurina O, Asper DJ, Deng W, Finlay BB, Rogan D, Potter AA. The role of Tir, EspA, and NleB in the colonization of cattle by Shiga toxin producingEscherichia coliO26:H11. Can J Microbiol 2010; 56:739-47. [DOI: 10.1139/w10-059] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Shiga toxin producing Escherichia coli (STEC) O26:H11 is an enteric pathogen capable of causing severe hemorrhagic colitis that can lead to hemolytic uremic syndrome. This organism is able to colonize cattle and human intestinal epithelial cells by secreting effectors via a type III secretion system (T3SS). In this investigation, we examined the role of 2 effectors, Tir and NleB, and the structural translocator component EspA in the adherence of STEC to epithelial cells and in the colonization of cattle. Isogenic deletion mutants were constructed and using microscopy and flow cytometry compared to the wild-type strain in their ability to adhere to HEp-2 cells. A competitive assay was also used to measure the capacity of the mutants to colonize the intestinal tract of cattle, where both the mutant and the parental strains were introduced orally at the same time. Genomic DNA was extracted from enriched fecal samples collected at various time points, and quantitative real-time PCR was used to quantify bacteria. A significant reduction in fecal shedding was observed, and adherence to HEp-2 cells was decreased for the tir and espA mutants. Deletion of the nleB gene did not have a significant effect on the adherence of HEp-2 cells; however, in an in vivo model, it strongly reduced the ability of STEC O26:H11 to colonize the bovine intestinal tract.
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Affiliation(s)
- Olga Misyurina
- Vaccine and Infectious Disease Organization, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK S7N 5E3, Canada
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, BC V6T 1Z4, Canada
- Bioniche Life Sciences, 231 Dundas Street East, Belleville, ON K8N 1E2, Canada
| | - David J. Asper
- Vaccine and Infectious Disease Organization, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK S7N 5E3, Canada
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, BC V6T 1Z4, Canada
- Bioniche Life Sciences, 231 Dundas Street East, Belleville, ON K8N 1E2, Canada
| | - Wanyin Deng
- Vaccine and Infectious Disease Organization, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK S7N 5E3, Canada
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, BC V6T 1Z4, Canada
- Bioniche Life Sciences, 231 Dundas Street East, Belleville, ON K8N 1E2, Canada
| | - B. Brett Finlay
- Vaccine and Infectious Disease Organization, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK S7N 5E3, Canada
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, BC V6T 1Z4, Canada
- Bioniche Life Sciences, 231 Dundas Street East, Belleville, ON K8N 1E2, Canada
| | - Dragan Rogan
- Vaccine and Infectious Disease Organization, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK S7N 5E3, Canada
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, BC V6T 1Z4, Canada
- Bioniche Life Sciences, 231 Dundas Street East, Belleville, ON K8N 1E2, Canada
| | - Andrew A. Potter
- Vaccine and Infectious Disease Organization, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK S7N 5E3, Canada
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, BC V6T 1Z4, Canada
- Bioniche Life Sciences, 231 Dundas Street East, Belleville, ON K8N 1E2, Canada
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16
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N-terminal type III secretion signal of enteropathogenic Escherichia coli translocator proteins. J Bacteriol 2010; 192:3534-9. [PMID: 20400543 DOI: 10.1128/jb.00046-10] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
We report that the N terminus of the type III secretion system translocator proteins EspB, EspD, and EspA mediate protein secretion and translocation from wild-type enteropathogenic Escherichia coli and hypersecretion from sepL and sepD mutants. EspA containing the translocation signal of Map and Tir containing the secretion signal of EspA are biologically active.
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17
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Schüller S, Phillips AD. Microaerobic conditions enhance type III secretion and adherence of enterohaemorrhagic Escherichia coli to polarized human intestinal epithelial cells. Environ Microbiol 2010; 12:2426-35. [PMID: 20406285 PMCID: PMC4966633 DOI: 10.1111/j.1462-2920.2010.02216.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Advances in the understanding of the pathogenesis of enterohaemorrhagic Escherichia coli (EHEC) have greatly benefited from the use of human epithelial cell lines under aerobic conditions. However, in the target site of EHEC infection, the human intestine, conditions are microaerobic. In our study we used polarized human colon carcinoma cells in a vertical diffusion chamber system to investigate the influence of reduced apical oxygen levels on EHEC colonization. While apical microaerobiosis did not affect cell integrity and barrier function, numbers of adherent bacteria were significantly increased under low compared with high apical oxygen concentrations. In addition, expression and translocation of EHEC type III secreted (T3S) effector proteins was considerably enhanced under microaerobic conditions and dependent on the presence of host cells. Increased colonization was mainly mediated via EspA as adherence levels of an isogenic deletion mutant were not influenced by low oxygen levels. Other potential adherence factors (E. coli common pilus and flagella) were only minimally expressed under high and low oxygen levels. Addition of nitrate and trimethylamine N-oxide as terminal electron acceptors for anaerobic respiration failed to further increase bacterial colonization or T3S under microaerobiosis. This study indicates that EHEC T3S and colonization are enhanced by the microaerobic environment in the gut and therefore might be underestimated in conventional aerobic cell culture systems.
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Affiliation(s)
- Stephanie Schüller
- Centre for Paediatric Gastroenterology, UCL Medical School, Royal Free Campus, London, UK.
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18
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Enninga J, Rosenshine I. Imaging the assembly, structure and activity of type III secretion systems. Cell Microbiol 2009; 11:1462-70. [PMID: 19622097 DOI: 10.1111/j.1462-5822.2009.01360.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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19
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Saier MH, Ma CH, Rodgers L, Tamang DG, Yen MR. Protein secretion and membrane insertion systems in bacteria and eukaryotic organelles. ADVANCES IN APPLIED MICROBIOLOGY 2009; 65:141-97. [PMID: 19026865 DOI: 10.1016/s0065-2164(08)00606-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Milton H Saier
- Division of Biological Sciences, University of California at San Diego, La Jolla, California 92093-0116, USA
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20
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The two-component system QseEF and the membrane protein QseG link adrenergic and stress sensing to bacterial pathogenesis. Proc Natl Acad Sci U S A 2009; 106:5889-94. [PMID: 19289831 DOI: 10.1073/pnas.0811409106] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Bacterial pathogens sense host cues to activate expression of virulence genes. Most of these signals are sensed through histidine kinases (HKs), which comprise the main sensory mechanism in bacteria. The host stress hormones epinephrine (Epi) and norepinephrine are sensed through the QseC HK, which initiates a complex signaling cascade to regulate virulence gene expression in enterohemorrhagic Escherichia coli (EHEC). Epi signaling through QseC activates expression of the genes encoding the QseEF 2-component system. QseE is an HK, and QseF is a response regulator. Here, we show that QseE is a second bacterial adrenergic receptor that gauges the stress signals Epi, sulfate, and phosphate. The qseEF genes are organized within an unusual operonic structure, in that a gene is encoded between qseE and qseF. This gene was renamed qseG, and it was shown to encode an outer membrane (OM) protein. EHEC uses a type III secretion system (TTSS) to translocate effector proteins to the epithelial cells that rearrange the host cytoskeleton to form pedestal-like structures that cup the bacterium. QseE, QseG, and QseF are necessary for pedestal formation. Although QseE and QseF are involved in the transcriptional control of genes necessary for pedestal formation, QseG is necessary for translocation of effectors into epithelial cells. QseG is an OM protein necessary for translocation of TTSS effectors that also works in conjunction with a 2-component signaling system that senses host stress signals.
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21
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Architectures and biogenesis of non-flagellar protein appendages in Gram-negative bacteria. EMBO J 2009; 27:2271-80. [PMID: 18668121 PMCID: PMC2500206 DOI: 10.1038/emboj.2008.155] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2008] [Accepted: 07/07/2008] [Indexed: 11/22/2022] Open
Abstract
Bacteria commonly expose non-flagellar proteinaceous appendages on their outer surfaces. These extracellular structures, called pili or fimbriae, are employed in attachment and invasion, biofilm formation, cell motility or protein and DNA transport across membranes. Over the past 15 years, the power of molecular and structural techniques has revolutionalized our understanding of the biogenesis, structure, function and mode of action of these bacterial organelles. Here, we review the five known classes of Gram-negative non-flagellar appendages from a biosynthetic and structural point of view.
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Badea L, Beatson SA, Kaparakis M, Ferrero RL, Hartland EL. Secretion of flagellin by the LEE-encoded type III secretion system of enteropathogenic Escherichia coli. BMC Microbiol 2009; 9:30. [PMID: 19200386 PMCID: PMC2647546 DOI: 10.1186/1471-2180-9-30] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Accepted: 02/06/2009] [Indexed: 12/29/2022] Open
Abstract
Background Enteropathogenic Escherichia coli (EPEC) is an attaching and effacing (A/E) pathogen that possesses a type III secretion system (T3SS) encoded within the locus of enterocyte effacement (LEE). The LEE is essential for A/E lesion formation and directs the secretion and translocation of multiple LEE-encoded and non-LEE encoded effector proteins into the cytosol of infected cells. In this study we used proteomics to compare proteins exported to the culture supernatant by wild type EPEC E2348/69, a ΔespADB mutant and a ΔescF T3SS mutant. Results We observed that flagellin was consistently and strongly present in the secretome of wild type EPEC and the ΔespADB mutant but present only weakly in the secretome of the ΔescF mutant. Given the ancestral relationship between the flagella export apparatus and virulence associated T3SSs, we investigated whether FliC could utilise the LEE-encoded T3SS for export. In the absence of a functional flagella export apparatus, we showed that FliC could be secreted by the LEE-encoded T3SS and stimulate (Toll-like receptor 5) TLR5 signalling but could not confer motility. Conclusion Since the secretion of FliC during A/E lesion formation would presumably be disadvantageous for the pathogen, we propose that virulence associated T3SSs and flagella T3SSs have evolved through a system of chaperones and complex regulatory pathways to be functional at different times to ensure that FliC secretion does not occur during T3SS effector translocation.
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Affiliation(s)
- Luminita Badea
- Department of Microbiology, Monash University, Melbourne, Victoria, Australia.
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23
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Wagner S, Sorg I, Degiacomi M, Journet L, Peraro MD, Cornelis GR. The helical content of the YscP molecular ruler determines the length of theYersiniainjectisome. Mol Microbiol 2009; 71:692-701. [DOI: 10.1111/j.1365-2958.2008.06556.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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24
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Wiesand U, Sorg I, Amstutz M, Wagner S, van den Heuvel J, Lührs T, Cornelis GR, Heinz DW. Structure of the Type III Secretion Recognition Protein YscU from Yersinia enterocolitica. J Mol Biol 2009; 385:854-66. [DOI: 10.1016/j.jmb.2008.10.034] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Revised: 10/06/2008] [Accepted: 10/08/2008] [Indexed: 12/30/2022]
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25
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Lodato PB, Kaper JB. Post-transcriptional processing of the LEE4 operon in enterohaemorrhagic Escherichia coli. Mol Microbiol 2008; 71:273-90. [PMID: 19019141 DOI: 10.1111/j.1365-2958.2008.06530.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Enterohaemorrhagic Escherichia coli (EHEC) employs a type III secretion system (T3SS) to export translocator and effector proteins required for mucosal colonization. The T3SS is encoded in a pathogenicity island called the locus of enterocyte effacement (LEE) that is organized in five major operons, LEE1 to LEE5. LEE4 encodes a regulator of secretion (SepL), translocators (EspA, D and B), two chaperones (CesD2 and L0017), a T3SS component (EscF) and an effector protein (EspF). It was originally proposed that the esp transcript is transcribed from a promoter located at the end of sepL but other authors suggested that this transcript is the result of a post-transcriptional processing event. In this study, we established that the espADB mRNA is generated by post-transcriptional processing at the end of the sepL coding sequence. RNase E is the endonuclease involved in the cleavage, but the interaction of this enzyme with other proteins through its C-terminal half is dispensable. A putative transcription termination event in the cesD2 coding region would generate the 3' end of the transcript. Similar to what has been described for other processed transcripts, the cleavage of LEE4 seems a mechanism to differentially regulate SepL and Esp protein production.
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Affiliation(s)
- Patricia B Lodato
- Center for Vaccine Development and Department of Microbiology and Immunology, University of Maryland School of Medicine, 685 W. Baltimore St, Baltimore, MD 21201, USA
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26
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Abstract
Recent work by several groups has significantly expanded our knowledge of the structure, regulation of assembly, and function of components of the extracellular portion of the type III secretion system (T3SS) of Gram-negative bacteria. This perspective presents a structure-informed analysis of functional data and discusses three nonmutually exclusive models of how a key aspect of T3SS biology, the sensing of host cells, may be performed.
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27
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Shaw RK, Berger CN, Feys B, Knutton S, Pallen MJ, Frankel G. Enterohemorrhagic Escherichia coli exploits EspA filaments for attachment to salad leaves. Appl Environ Microbiol 2008; 74:2908-14. [PMID: 18310437 PMCID: PMC2394865 DOI: 10.1128/aem.02704-07] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Accepted: 02/14/2008] [Indexed: 12/29/2022] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) strains are important food-borne pathogens that use a filamentous type III secretion system (fT3SS) for colonization of the gut epithelium. In this study we have shown that EHEC O157 and O26 strains use the fT3SS apparatus for attachment to leaves. Leaf attachment was independent of effector protein translocation.
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Affiliation(s)
- Robert K Shaw
- Division of Immunity and Infection, School of Medicine, University of Birmingham, Birmingham, United Kingdom
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28
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Hoare A, Timms P, Bavoil PM, Wilson DP. Spatial constraints within the chlamydial host cell inclusion predict interrupted development and persistence. BMC Microbiol 2008; 8:5. [PMID: 18182115 PMCID: PMC2254404 DOI: 10.1186/1471-2180-8-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2007] [Accepted: 01/09/2008] [Indexed: 11/10/2022] Open
Abstract
Background The chlamydial developmental cycle involves the alternation between the metabolically inert elementary body (EB) and the replicating reticulate body (RB). The triggers that mediate the interchange between these particle types are unknown and yet this is crucial for understanding basic Chlamydia biology. Presentation of the hypothesis We have proposed a hypothesis to explain key chlamydial developmental events whereby RBs are replicating strictly whilst in contact with the host cell membrane-derived inclusion via type three secretion (T3S) injectisomes. As the inclusion expands, the contact between each RB and the inclusion membrane decreases, eventually reaching a threshold, beyond which T3S is inactivated upon detachment and this is the signal for RB-to-EB differentiation. Testing the hypothesis We explore this hypothesis through the development of a detailed mathematical model. The model uses knowledge and data of the biological system wherever available and simulates the chlamydial developmental cycle under the assumptions of the hypothesis in order to predict various outcomes and implications under a number of scenarios. Implications of the hypothesis We show that the concept of in vitro persistent infection is not only consistent with the hypothesis but in fact an implication of it. We show that increasing the RB radius, and/or the maximum length of T3S needles mediating contact between RBs and the inclusion membrane, and/or the number of inclusions per infected cell, will contribute to the development of persistent infection. The RB radius is the most important determinant of whether persistent infection would ensue, and subsequently, the magnitude of the EB yield. We determine relationships between the length of the T3S needle and the RB radius within an inclusion, and between the RB radius and the number of inclusions per host cell to predict whether persistent infection or normal development would occur within a host cell. These results are all testable experimentally and could lead to significantly greater understanding of one of the most crucial steps in chlamydial development.
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Affiliation(s)
- Alexander Hoare
- National Centre in HIV Epidemiology and Clinical Research, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia.
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29
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Identification of amino acid residues within the N-terminal domain of EspA that play a role in EspA filament biogenesis and function. J Bacteriol 2008; 190:2221-6. [PMID: 18178741 DOI: 10.1128/jb.01753-07] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Enteropathogenic Escherichia coli employs a filamentous type III secretion system, made by homopolymerization of the translocator protein EspA. In this study, we have shown that the N-terminal region of EspA has a role in EspA's protein stability, interaction with the CesAB chaperone, and filament biogenesis and function.
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30
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Sorg I, Wagner S, Amstutz M, Müller SA, Broz P, Lussi Y, Engel A, Cornelis GR. YscU recognizes translocators as export substrates of the Yersinia injectisome. EMBO J 2007; 26:3015-24. [PMID: 17510628 PMCID: PMC1894769 DOI: 10.1038/sj.emboj.7601731] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2007] [Accepted: 04/27/2007] [Indexed: 12/28/2022] Open
Abstract
YscU is an essential component of the export apparatus of the Yersinia injectisome. It consists of an N-terminal transmembrane domain and a long cytoplasmic C-terminal domain, which undergoes auto-cleavage at a NPTH site. Substitutions N263A and P264A prevented cleavage of YscU and abolished export of LcrV, YopB and YopD but not of Yop effectors. As a consequence, yscU(N263A) mutant bacteria made needles without the LcrV tip complex and they could not form translocation pores. The graft of the export signal of the effector YopE, at the N-terminus of LcrV, restored LcrV export and assembly of the tip complex. Thus, YscU cleavage is required to acquire the conformation allowing recognition of translocators, which represent an individual category of substrates in the hierarchy of export. In addition, yscU(N263A) mutant bacteria exported reduced amounts of the YscP ruler and made longer needles. Increasing YscP export resulted in needles with normal size, depending on the length of the ruler. Hence, the effect of the yscU(N263A) mutation on needle length was the consequence of a reduced YscP export.
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Affiliation(s)
- Isabel Sorg
- Biozentrum der Universität Basel, Basel, Switzerland
| | | | | | - Shirley A Müller
- Biozentrum der Universität Basel, Basel, Switzerland
- ME Müller Institute for Structural Biology, Basel, Switzerland
| | - Petr Broz
- Biozentrum der Universität Basel, Basel, Switzerland
| | - Yvonne Lussi
- Biozentrum der Universität Basel, Basel, Switzerland
| | - Andreas Engel
- Biozentrum der Universität Basel, Basel, Switzerland
- ME Müller Institute for Structural Biology, Basel, Switzerland
| | - Guy R Cornelis
- Biozentrum der Universität Basel, Basel, Switzerland
- Biozentrum, Universität Basel, Infection Biology, Klingelbergstrasse 50-70, Basel, CH 4056, Switzerland. Tel.: +41 61 267 21 10; Fax: +41 61 267 21 18; E-mail:
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31
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Galán JE, Wolf-Watz H. Protein delivery into eukaryotic cells by type III secretion machines. Nature 2007; 444:567-73. [PMID: 17136086 DOI: 10.1038/nature05272] [Citation(s) in RCA: 757] [Impact Index Per Article: 44.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Bacteria that have sustained long-standing close associations with eukaryotic hosts have evolved specific adaptations to survive and replicate in this environment. Perhaps one of the most remarkable of those adaptations is the type III secretion system (T3SS)--a bacterial organelle that has specifically evolved to deliver bacterial proteins into eukaryotic cells. Although originally identified in a handful of pathogenic bacteria, T3SSs are encoded by a large number of bacterial species that are symbiotic or pathogenic for humans, other animals including insects or nematodes, and plants. The study of these systems is leading to unique insights into not only organelle assembly and protein secretion but also mechanisms of symbiosis and pathogenesis.
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Affiliation(s)
- Jorge E Galán
- Section of Microbial Pathogenesis, Yale University School of Medicine, Boyer Center for Molecular Medicine, New Haven, Connecticut 0636, USA.
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32
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Abstract
The type III secretion injectisome is a complex nanomachine that allows bacteria to deliver protein effectors across eukaryotic cellular membranes. In recent years, significant progress has been made in our understanding of its structure, assembly and mode of operation. The principal structural components of the injectisome, from the base located in the bacterial cytosol to the tip of the needle protruding from the cell surface, have been investigated in detail. The structures of several constituent proteins were solved at the atomic level and important insights into the assembly process have been gained. However, despite the ongoing concerted efforts of molecular and structural biologists, the role of many of the constituent components of this nanomachine remain unknown.
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Affiliation(s)
- Guy R Cornelis
- Biozentrum der Universität Basel, Klingelbergstrasse 50, CH-4056, Basel, Switzerland.
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33
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Davis AJ, Mecsas J. Mutations in the Yersinia pseudotuberculosis type III secretion system needle protein, YscF, that specifically abrogate effector translocation into host cells. J Bacteriol 2006; 189:83-97. [PMID: 17071752 PMCID: PMC1797200 DOI: 10.1128/jb.01396-06] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The trafficking of effectors, termed Yops, from Yersinia spp. into host cells is a multistep process that requires the type III secretion system (TTSS). The TTSS has three main structural parts: a base, a needle, and a translocon, which work together to ensure the polarized movement of Yops directly from the bacterial cytosol into the host cell cytosol. To understand the interactions that take place at the interface between the tip of the TTSS needle and the translocon, we developed a screen to identify mutations in the needle protein YscF that separated its function in secretion from its role in translocation. We identified 25 translocation-defective (TD) yscF mutants, which fall into five phenotypic classes. Some classes exhibit aberrant needle structure and/or reduced levels of Yop secretion, consistent with known functions for YscF. Strikingly, two yscF TD classes formed needles and secreted Yops normally but displayed distinct translocation defects. Class I yscF TD mutants showed diminished pore formation, suggesting incomplete pore insertion and/or assembly. Class II yscF TD mutants formed pores but showed nonpolar translocation, suggesting unstable needle-translocon interactions. These results indicate that YscF functions in Yop secretion and translocation can be genetically separated. Furthermore, the identification of YscF residues that are required for the assembly of the translocon and/or productive interactions with the translocon has allowed us to initiate the mapping of the needle-translocon interface.
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Affiliation(s)
- Alison J Davis
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Ave., Boston, MA 02111, USA
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34
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Abstract
In the recent Dover trial, and elsewhere, the 'Intelligent Design' movement has championed the bacterial flagellum as an irreducibly complex system that, it is claimed, could not have evolved through natural selection. Here we explore the arguments in favour of viewing bacterial flagella as evolved, rather than designed, entities. We dismiss the need for any great conceptual leaps in creating a model of flagellar evolution and speculate as to how an experimental programme focused on this topic might look.
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Affiliation(s)
- Mark J Pallen
- Division of Immunity & Infection, Medical School, University of Birmingham, Birmingham, B15 2TT UK.
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35
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Sorg JA, Miller NC, Schneewind O. Substrate recognition of type III secretion machines--testing the RNA signal hypothesis. Cell Microbiol 2006; 7:1217-25. [PMID: 16098210 DOI: 10.1111/j.1462-5822.2005.00563.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Secretion by the type III pathway of Gram-negative microbes transports polypeptides into the extracellular medium or into the cytoplasm of host cells during infection. In pathogenic Yersinia spp., type III machines recognize 14 different Yop protein substrates via discrete signals genetically encoded in 7-15 codons at the 5' portion of yop genes. Although the signals necessary and sufficient for substrate recognition of Yop proteins have been mapped, a clear mechanism on how proteins are recognized by the machinery and then initiated into the transport pathway has not yet emerged. As synonymous substitutions, mutations that alter mRNA sequence but not codon specificity, affect the function of some secretion signals, recent work with several different microbes tested the hypothesis of an RNA-encoded secretion signal for polypeptides that travel the type III pathway. This review summarizes experimental observations and mechanistic models for substrate recognition in this field.
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Affiliation(s)
- Joseph A Sorg
- Department of Microbiology, University of Chicago, Chicago, IL 60637, USA
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36
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Abstract
Enterohemorrhagic Escherichia coli (EHEC) was first recognized as a cause of human disease in 1983 and is associated with diarrhea and hemorrhagic colitis, which may be complicated by life-threatening renal and neurological sequelae. EHEC are defined by their ability to produce one or more Shiga-like toxins (Stx), which mediate the systemic complications of EHEC infections, and to induce characteristic attaching and effacing lesions on intestinal epithelia, a phenotype that depends on the locus of enterocyte effacement. Acquisition of Stx-encoding bacteriophages by enteropathogenic E. coli is believed to have contributed to the evolution of EHEC, and consequently some virulence factors are conserved in both pathotypes. A key requirement for E. coli to colonize the intestines and produce disease is the ability to adhere to epithelial cells lining the gastrointestinal tract. Here, we review knowledge of the adhesins produced by EHEC and other Stx-producing E. coli, with emphasis on genetic, structural, and mechanistic aspects and their contribution to pathogenesis.
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Affiliation(s)
- Mark P Stevens
- Division of Microbiology, Institute for Animal Health, Compton Laboratory, Berkshire RG20 7NN, United Kingdom
| | - Timothy S Wallis
- Division of Microbiology, Institute for Animal Health, Compton Laboratory, Berkshire RG20 7NN, United Kingdom
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37
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Kenjale R, Wilson J, Zenk SF, Saurya S, Picking WL, Picking WD, Blocker A. The needle component of the type III secreton of Shigella regulates the activity of the secretion apparatus. J Biol Chem 2005; 280:42929-37. [PMID: 16227202 DOI: 10.1074/jbc.m508377200] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Gram-negative bacteria commonly interact with eukaryotic host cells by using type III secretion systems (TTSSs or secretons). TTSSs serve to transfer bacterial proteins into host cells. Two translocators, IpaB and IpaC, are first inserted with the aid of IpaD by Shigella into the host cell membrane. Then at least two supplementary effectors of cell invasion, IpaA and IpgD, are transferred into the host cytoplasm. How TTSSs are induced to secrete is unknown, but their activation appears to require direct contact of the external distal tip of the apparatus with the host cell. The extracellular domain of the TTSS is a hollow needle protruding 60 nm beyond the bacterial surface. The monomeric unit of the Shigella flexneri needle, MxiH, forms a superhelical assembly. To probe the role of the needle in the activation of the TTSS for secretion, we examined the structure-function relationship of MxiH by mutagenesis. Most point mutations led to normal needle assembly, but some led to polymerization or possible length control defects. In other mutants, secretion was constitutively turned "on." In a further set, it was "constitutively on" but experimentally "uninducible." Finally, upon induction of secretion, some mutants released only the translocators and not the effectors. Most types of mutants were defective in interactions with host cells. Together, these data indicate that the needle directly controls the activity of the TTSS and suggest that it may be used to "sense" host cells.
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Affiliation(s)
- Roma Kenjale
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
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38
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Crepin VF, Shaw R, Knutton S, Frankel G. Molecular basis of antigenic polymorphism of EspA filaments: development of a peptide display technology. J Mol Biol 2005; 350:42-52. [PMID: 15921692 DOI: 10.1016/j.jmb.2005.04.060] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2005] [Revised: 04/26/2005] [Accepted: 04/26/2005] [Indexed: 12/23/2022]
Abstract
Like many Gram-negative pathogens, enteropathogenic (EPEC) and enterohaemorrhagic Escherichia coli (EHEC) use a macromolecular type III secretion system (TTSS) to inject effector proteins into eukaryotic host cells. The membrane-associated needle complex (NC) of the TTSS, which shows broad similarity to the flagellar basal body, is conserved amongst bacterial pathogens. However, the extracellular part of the TTSS of EPEC and EHEC is unique, in that it has a hollow, approximately 12 nm in diameter, filamentous extension to the NC. EspA filaments are homo-polymers made of the translocator protein EspA. The three-dimensional structure of EspA filaments is comparable to that of flagella; the helical symmetry and packing of the subunits forming both filamentous structures are very similar. Like flagella, EspA filaments show antigenic polymorphism as EspA from different EPEC and EHEC clones show no immunological cross-reactivity. In this study, we determined the molecular basis of the antigenic polymorphism of EspA filaments and identified a surface-exposed hypervariable domain that contains the immunodominant EspA epitope. By exchanging the hypervariable domains of EspA(EPEC) and EspA(EHEC) we swapped the antigenic specificity of the EspA filaments. As for the flagellin D3 domain, which is known to tolerate insertions of natural and artificial amino acid sequences, we have inserted short peptides into the surface-exposed, hypervariable domain of EspA. We demonstrated that the inserted peptides are presented on the surface of the recombinant EspA filaments forming a new immunodominant epitope. Accordingly, EspA filaments have a potential to be developed into a novel epitope display system.
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Affiliation(s)
- Valérie F Crepin
- Centre for Molecular Microbiology and Infection, Flowers Building, Imperial College London, London SW7 2AZ, UK
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Garmendia J, Frankel G, Crepin VF. Enteropathogenic and enterohemorrhagic Escherichia coli infections: translocation, translocation, translocation. Infect Immun 2005; 73:2573-85. [PMID: 15845459 PMCID: PMC1087358 DOI: 10.1128/iai.73.5.2573-2585.2005] [Citation(s) in RCA: 300] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Affiliation(s)
- Junkal Garmendia
- CMMI, Flowers Building, Imperial College London, London SW7 2AZ, United Kingdom
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