1
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Godlee C, Holden DW. Transmembrane substrates of type three secretion system injectisomes. MICROBIOLOGY (READING, ENGLAND) 2023; 169:001292. [PMID: 36748571 PMCID: PMC9993115 DOI: 10.1099/mic.0.001292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The type three secretion system injectisome of Gram-negative bacterial pathogens injects virulence proteins, called effectors, into host cells. Effectors of mammalian pathogens carry out a range of functions enabling bacterial invasion, replication, immune suppression and transmission. The injectisome secretes two translocon proteins that insert into host cell membranes to form a translocon pore, through which effectors are delivered. A subset of effectors also integrate into infected cell membranes, enabling a unique range of biochemical functions. Both translocon proteins and transmembrane effectors avoid cytoplasmic aggregation and integration into the bacterial inner membrane. Translocated transmembrane effectors locate and integrate into the appropriate host membrane. In this review, we focus on transmembrane translocon proteins and effectors of bacterial pathogens of mammals. We discuss what is known about the mechanisms underlying their membrane integration, as well as the functions conferred by the position of injectisome effectors within membranes.
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Affiliation(s)
- Camilla Godlee
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Road, London SW7 2AZ, UK
- Present address: Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, UK
- *Correspondence: Camilla Godlee, ;
| | - David W. Holden
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Road, London SW7 2AZ, UK
- *Correspondence: David W. Holden,
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2
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Song Y, Xu G, Li C, Li Z, Lu C, Shen Y. Structural optimization of natural product fusaric acid to discover novel T3SS inhibitors of Salmonella. Biochem Biophys Res Commun 2021; 582:72-76. [PMID: 34695753 DOI: 10.1016/j.bbrc.2021.10.035] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 10/14/2021] [Indexed: 11/17/2022]
Abstract
Type III secretion system (T3SS) plays a critical role in host cell invasion and pathogenesis of Salmonella. We recently identified the mycotoxin fusaric acid (FA) as a T3SS inhibitor of Salmonella. Herein, twenty-two diphenylsulfane derivatives were designed and synthesized using FA as a lead compound through scaffold hopping. Among them, SL-8 and SL-19 possessing strong anti-T3SS and anti-invasion activity were identified as T3SS inhibitors with improvement in potency as compared to FA. The inhibitory mechanisms on SPI-1 did not depend on the HilD-HilC-RtsA-HilA or PhoP-PhoQ pathway or the assembly of T3SS needle complex. Accordingly, we proposed that the inhibitory effects of SL-8 and SL-19 on SPI-1 probably influence the formation of SicA/InvF-effector complex or other related proteins.
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Affiliation(s)
- Yuliang Song
- Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, 250012, China
| | - Guangsen Xu
- Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, 250012, China
| | - Chaoqun Li
- Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, 250012, China
| | - Zhiying Li
- Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, 250012, China
| | - Chunhua Lu
- Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, 250012, China.
| | - Yuemao Shen
- Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, 250012, China
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3
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Abstract
Quorum sensing (QS) is one of the most studied cell-cell communication mechanisms in fungi. Research in the last 20 years has explored various fungal QS systems that are involved in a wide range of biological processes, especially eukaryote- or fungus-specific behaviors, mirroring the significant contribution of QS regulation to fungal biology and evolution. Based on recent progress, we summarize in this review fungal QS regulation, with an emphasis on its functional role in behaviors unique to fungi or eukaryotes. We suggest that using fungi as genetically amenable eukaryotic model systems to address why and how QS regulation is integrated into eukaryotic reproductive strategies and molecular or cellular processes could be an important direction for QS research. Expected final online publication date for the Annual Review of Microbiology, Volume 75 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Xiuyun Tian
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; .,University of Chinese Academy of Sciences, Beijing 100039, China
| | - Hao Ding
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; .,University of Chinese Academy of Sciences, Beijing 100039, China
| | - Weixin Ke
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; .,University of Chinese Academy of Sciences, Beijing 100039, China
| | - Linqi Wang
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; .,University of Chinese Academy of Sciences, Beijing 100039, China
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4
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Bernal I, Römermann J, Flacht L, Lunelli M, Uetrecht C, Kolbe M. Structural analysis of ligand-bound states of the Salmonella type III secretion system ATPase InvC. Protein Sci 2019; 28:1888-1901. [PMID: 31393998 PMCID: PMC6739812 DOI: 10.1002/pro.3704] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 08/02/2019] [Accepted: 08/06/2019] [Indexed: 12/21/2022]
Abstract
Translocation of virulence effector proteins through the type III secretion system (T3SS) is essential for the virulence of many medically relevant Gram‐negative bacteria. The T3SS ATPases are conserved components that specifically recognize chaperone–effector complexes and energize effector secretion through the system. It is thought that functional T3SS ATPases assemble into a cylindrical structure maintained by their N‐terminal domains. Using size‐exclusion chromatography coupled to multi‐angle light scattering and native mass spectrometry, we show that in the absence of the N‐terminal oligomerization domain the Salmonella T3SS ATPase InvC can form monomers and dimers in solution. We also present for the first time a 2.05 å resolution crystal structure of InvC lacking the oligomerization domain (InvCΔ79) and map the amino acids suggested for ATPase intersubunit interaction, binding to other T3SS proteins and chaperone–effector recognition. Furthermore, we validate the InvC ATP‐binding site by co‐crystallization of InvCΔ79 with ATPγS (2.65 å) and ADP (2.80 å). Upon ATP‐analogue recognition, these structures reveal remodeling of the ATP‐binding site and conformational changes of two loops located outside of the catalytic site. Both loops face the central pore of the predicted InvC cylinder and are essential for the function of the T3SS ATPase. Our results present a fine functional and structural correlation of InvC and provide further details of the homo‐oligomerization process and ATP‐dependent conformational changes underlying the T3SS ATPase activity. PDB Code(s): 6RAE, 6RAD and 6SDX
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Affiliation(s)
- Ivonne Bernal
- Department of Structural Infection Biology, Center for Structural Systems Biology (CSSB), Helmholtz-Center for Infection Research (HZI), Hamburg, Germany
| | - Jonas Römermann
- Department of Structural Infection Biology, Center for Structural Systems Biology (CSSB), Helmholtz-Center for Infection Research (HZI), Hamburg, Germany
| | - Lara Flacht
- Department of Structural Infection Biology, Center for Structural Systems Biology (CSSB), Helmholtz-Center for Infection Research (HZI), Hamburg, Germany.,Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany
| | - Michele Lunelli
- Department of Structural Infection Biology, Center for Structural Systems Biology (CSSB), Helmholtz-Center for Infection Research (HZI), Hamburg, Germany
| | - Charlotte Uetrecht
- Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany.,European XFEL GmbH, Schenefeld, Germany
| | - Michael Kolbe
- Department of Structural Infection Biology, Center for Structural Systems Biology (CSSB), Helmholtz-Center for Infection Research (HZI), Hamburg, Germany.,MIN-Faculty University Hamburg, Hamburg, Germany
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5
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Patel S, Wall DM, Castillo A, McCormick BA. Caspase-3 cleavage of Salmonella type III secreted effector protein SifA is required for localization of functional domains and bacterial dissemination. Gut Microbes 2019; 10:172-187. [PMID: 30727836 PMCID: PMC6546311 DOI: 10.1080/19490976.2018.1506668] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
SifA is a bi-functional Type III Secretion System (T3SS) effector protein that plays an important role in Salmonella virulence. The N-terminal domain of SifA binds SifA-Kinesin-Interacting-Protein (SKIP), and via an interaction with kinesin, forms tubular membrane extensions called Sif filaments (Sifs) that emanate from the Salmonella Containing Vacuole (SCV). The C-terminal domain of SifA harbors a WxxxE motif that functions to mimic active host cell GTPases. Taken together, SifA functions in inducing endosomal tubulation in order to maintain the integrity of the SCV and promote bacterial dissemination. Since SifA performs multiple, unrelated functions, the objective of this study was to determine how each functional domain of SifA becomes processed. Our work demonstrates that a linker region containing a caspase-3 cleavage motif separates the two functional domains of SifA. To test the hypothesis that processing of SifA by caspase-3 at this particular site is required for function and proper localization of the effector protein domains, we developed two tracking methods to analyze the intracellular localization of SifA. We first adapted a fluorescent tag called phiLOV that allowed for type-III secretion system (T3SS) mediated delivery of SifA and observation of its intracellular colocalization with caspase-3. Additionally, we created a dual-tagging strategy that permitted tracking of each of the SifA functional domains following caspase-3 cleavage to different subcellular locations. The results of this study reveal that caspase-3 cleavage of SifA is required for the proper localization of functional domains and bacterial dissemination. Considering the importance of these events in Salmonella pathogenesis, we conclude that caspase-3 cleavage of effector proteins is a more broadly applicable effector processing mechanism utilized by Salmonella to invade and persist during infection.
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Affiliation(s)
- Samir Patel
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA, USA,CONTACT Beth McCormick Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, 368 Plantation Street AS8-2011, Worcester, MA 01605, USA
| | - Daniel M. Wall
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Antonio Castillo
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA, USA
| | - Beth A. McCormick
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA, USA
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6
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Abstract
Many bacteria have evolved specialized nanomachines with the remarkable ability to inject multiple bacterially encoded effector proteins into eukaryotic or prokaryotic cells. Known as type III, type IV, and type VI secretion systems, these machines play a central role in the pathogenic or symbiotic interactions between multiple bacteria and their eukaryotic hosts, or in the establishment of bacterial communities in a diversity of environments. Here we focus on recent progress elucidating the structure and assembly pathways of these machines. As many of the interactions shaped by these machines are of medical importance, they provide an opportunity to develop novel therapeutic approaches to combat important human diseases.
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Affiliation(s)
- Jorge E Galán
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06536, USA.
| | - Gabriel Waksman
- Institute of Structural and Molecular Biology, Birkbeck, Malet Street, London WC1E 7HX, UK; Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK.
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7
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Godiee C, Cerny O, Durkin CH, Hoiden DW. SrcA is a chaperone for the Salmonella SPI-2 type three secretion system effector SteD. MICROBIOLOGY (READING, ENGLAND) 2019; 165:15-25. [PMID: 30457515 PMCID: PMC7614968 DOI: 10.1099/mic.0.000732] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Effector proteins of type three secretion systems (T3SS) often require cytosolic chaperones for their stabilization, to interact with the secretion machinery and to enable effector delivery into host cells. We found that deletion of srcA, previously shown to encode a chaperone for the Salmonella pathogenicity island 2 (SPI-2) T3SS effectors SseL and PipB2, prevented the reduction of mature Major Histocompatibility Complex class II (mMHCII) from the surface of antigen-presenting cells during Salmonella infection. This activity was shown previously to be caused by the SPI-2 T3SS effector SteD. Since srcA and steD are located in the same operon on the Salmonella chromosome, this suggested that the srcA phenotype might be due to an indirect effect on SteD. We found that SrcA is not translocated by the SPI-2 T3SS but interacts directly and forms a stable complex with SteD in bacteria with a 2 : 1 stoichiometry. We found that SrcA was not required for SPI-2 T3SS-dependent, neutral pH-induced secretion of either SseL or PipB2 but was essential for secretion of SteD. SrcA therefore functions as a chaperone for SteD, explaining its requirement for the reduction in surface levels of mMHCII.
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Affiliation(s)
- Camilla Godiee
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, SW7 2AZ, UK
| | - Ondrej Cerny
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, SW7 2AZ, UK
| | - Charlotte H. Durkin
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, SW7 2AZ, UK
| | - David W. Hoiden
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, SW7 2AZ, UK
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8
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Molecular basis for CesT recognition of type III secretion effectors in enteropathogenic Escherichia coli. PLoS Pathog 2018; 14:e1007224. [PMID: 30118511 PMCID: PMC6114900 DOI: 10.1371/journal.ppat.1007224] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 08/29/2018] [Accepted: 07/17/2018] [Indexed: 11/19/2022] Open
Abstract
Enteropathogenic Escherichia coli (EPEC) use a needle-like injection apparatus known as the type III secretion system (T3SS) to deliver protein effectors into host cells. Effector translocation is highly stratified in EPEC with the translocated intimin receptor (Tir) being the first effector delivered into the host. CesT is a multi-cargo chaperone that is required for the secretion of Tir and at least 9 other effectors. However, the structural and mechanistic basis for differential effector recognition by CesT remains unclear. Here, we delineated the minimal CesT-binding region on Tir to residues 35–77 and determined the 2.74 Å structure of CesT bound to an N-terminal fragment of Tir. Our structure revealed that the CesT-binding region in the N-terminus of Tir contains an additional conserved sequence, distinct from the known chaperone-binding β-motif, that we termed the CesT-extension motif because it extends the β-sheet core of CesT. This motif is also present in the C-terminus of Tir that we confirmed to be a unique second CesT-binding region. Point mutations that disrupt CesT-binding to the N- or C-terminus of Tir revealed that the newly identified carboxy-terminal CesT-binding region was required for efficient Tir translocation into HeLa cells and pedestal formation. Furthermore, the CesT-extension motif was identified in the N-terminal region of NleH1, NleH2, and EspZ, and mutations that disrupt this motif reduced translocation of these effectors, and in some cases, overall effector stability, thus validating the universality of this CesT-extension motif. The presence of two CesT-binding regions in Tir, along with the presence of the CesT-extension motif in other highly translocated effectors, may contribute to differential cargo recognition by CesT. Enteropathogenic Escherichia coli injects effector proteins into host cells using a type III secretion system (T3SS). The translocated intimin receptor (Tir) is the first effector delivered into host cells and imparts efficient secretion of other effectors. However, the mechanism for Tir-dependent modulation of the T3SS is poorly understood. We provide evidence that the multi-cargo chaperone CesT binds to two regions in Tir at the N- and C-terminus through a specific recognition motif, and show that CesT binding to the Tir C-terminus is important for host translocation. Furthermore we show that the CesT-specific motif is conserved in a subset of highly translocated effectors. This study highlights the multi-faceted role that T3SS chaperones play in effector secretion dynamics.
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Hobbs CK, Porter VL, Stow MLS, Siame BA, Tsang HH, Leung KY. Computational approach to predict species-specific type III secretion system (T3SS) effectors using single and multiple genomes. BMC Genomics 2016; 17:1048. [PMID: 27993130 PMCID: PMC5168842 DOI: 10.1186/s12864-016-3363-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 12/01/2016] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Many gram-negative bacteria use type III secretion systems (T3SSs) to translocate effector proteins into host cells. T3SS effectors can give some bacteria a competitive edge over others within the same environment and can help bacteria to invade the host cells and allow them to multiply rapidly within the host. Therefore, developing efficient methods to identify effectors scattered in bacterial genomes can lead to a better understanding of host-pathogen interactions and ultimately to important medical and biotechnological applications. RESULTS We used 21 genomic and proteomic attributes to create a precise and reliable T3SS effector prediction method called Genome Search for Effectors Tool (GenSET). Five machine learning algorithms were trained on effectors selected from different organisms and a trained (voting) algorithm was then applied to identify other effectors present in the genome testing sets from the same (GenSET Phase 1) or different (GenSET Phase 2) organism. Although a select group of attributes that included the codon adaptation index, probability of expression in inclusion bodies, N-terminal disorder, and G + C content (filtered) were better at discriminating between positive and negative sets, algorithm performance was better when all 21 attributes (unfiltered) were used. Performance scores (sensitivity, specificity and area under the curve) from GenSET Phase 1 were better than those reported for six published methods. More importantly, GenSET Phase 1 ranked more known effectors (70.3%) in the top 40 ranked proteins and predicted 10-80% more effectors than three available programs in three of the four organisms tested. GenSET Phase 2 predicted 43.8% effectors in the top 40 ranked proteins when tested on four related or unrelated organisms. The lower prediction rates from GenSET Phase 2 may be due to the presence of different translocation signals in effectors from different T3SS families. CONCLUSIONS The species-specific GenSET Phase 1 method offers an alternative approach to T3SS effector prediction that can be used with other published programs to improve effector predictions. Additionally, our approach can be applied to predict effectors of other secretion systems as long as these effectors have translocation signals embedded in their sequences.
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Affiliation(s)
- Christopher K Hobbs
- Applied Research Laboratory, Faculty of Natural and Applied Sciences, Trinity Western University, 7600 Glover Road, Langley, BC, Canada, V2Y 1Y1
| | - Vanessa L Porter
- Department of Biology, Faculty of Natural and Applied Sciences, Trinity Western University, 7600 Glover Road, Langley, BC, Canada, V2Y 1Y1
| | - Maxwell L S Stow
- Applied Research Laboratory, Faculty of Natural and Applied Sciences, Trinity Western University, 7600 Glover Road, Langley, BC, Canada, V2Y 1Y1
| | - Bupe A Siame
- Department of Biology, Faculty of Natural and Applied Sciences, Trinity Western University, 7600 Glover Road, Langley, BC, Canada, V2Y 1Y1
| | - Herbert H Tsang
- Applied Research Laboratory, Faculty of Natural and Applied Sciences, Trinity Western University, 7600 Glover Road, Langley, BC, Canada, V2Y 1Y1.
| | - Ka Yin Leung
- Department of Biology, Faculty of Natural and Applied Sciences, Trinity Western University, 7600 Glover Road, Langley, BC, Canada, V2Y 1Y1. .,State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China.
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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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11
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Runkel S, Wells HC, Rowley G. Living with Stress: A Lesson from the Enteric Pathogen Salmonella enterica. ADVANCES IN APPLIED MICROBIOLOGY 2016; 83:87-144. [PMID: 23651595 DOI: 10.1016/b978-0-12-407678-5.00003-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The ability to sense and respond to the environment is essential for the survival of all living organisms. Bacterial pathogens such as Salmonella enterica are of particular interest due to their ability to sense and adapt to the diverse range of conditions they encounter, both in vivo and in environmental reservoirs. During this cycling from host to non-host environments, Salmonella encounter a variety of environmental insults ranging from temperature fluctuations, nutrient availability and changes in osmolarity, to the presence of antimicrobial peptides and reactive oxygen/nitrogen species. Such fluctuating conditions impact on various areas of bacterial physiology including virulence, growth and antimicrobial resistance. A key component of the success of any bacterial pathogen is the ability to recognize and mount a suitable response to the discrete chemical and physical stresses elicited by the host. Such responses occur through a coordinated and complex programme of gene expression and protein activity, involving a range of transcriptional regulators, sigma factors and two component regulatory systems. This review briefly outlines the various stresses encountered throughout the Salmonella life cycle and the repertoire of regulatory responses with which Salmonella counters. In particular, how these Gram-negative bacteria are able to alleviate disruption in periplasmic envelope homeostasis through a group of stress responses, known collectively as the Envelope Stress Responses, alongside the mechanisms used to overcome nitrosative stress, will be examined in more detail.
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Affiliation(s)
- Sebastian Runkel
- School of Biological Sciences, University of East Anglia, Norwich, UK
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12
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Structural Features Reminiscent of ATP-Driven Protein Translocases Are Essential for the Function of a Type III Secretion-Associated ATPase. J Bacteriol 2015; 197:3007-14. [PMID: 26170413 DOI: 10.1128/jb.00434-15] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 07/03/2015] [Indexed: 01/04/2023] Open
Abstract
UNLABELLED Many bacterial pathogens and symbionts utilize type III secretion systems to interact with their hosts. These machines have evolved to deliver bacterial effector proteins into eukaryotic target cells to modulate a variety of cellular functions. One of the most conserved components of these systems is an ATPase, which plays an essential role in the recognition and unfolding of proteins destined for secretion by the type III pathway. Here we show that structural features reminiscent of other ATP-driven protein translocases are essential for the function of InvC, the ATPase associated with a Salmonella enterica serovar Typhimurium type III secretion system. Mutational and functional analyses showed that a two-helix-finger motif and a conserved loop located at the entrance of and within the predicted pore formed by the hexameric ATPase are essential for InvC function. These findings provide mechanistic insight into the function of this highly conserved component of type III secretion machines. IMPORTANCE Type III secretion machines are essential for the virulence or symbiotic relationships of many bacteria. These machines have evolved to deliver bacterial effector proteins into host cells to modulate cellular functions, thus facilitating bacterial colonization and replication. An essential component of these machines is a highly conserved ATPase, which is necessary for the recognition and secretion of proteins destined to be delivered by the type III secretion pathway. Using modeling and structure and function analyses, we have identified structural features of one of these ATPases from Salmonella enterica serovar Typhimurium that help to explain important aspects of its function.
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13
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Roblin P, Dewitte F, Villeret V, Biondi EG, Bompard C. A Salmonella type three secretion effector/chaperone complex adopts a hexameric ring-like structure. J Bacteriol 2015; 197:688-98. [PMID: 25404693 PMCID: PMC4334183 DOI: 10.1128/jb.02294-14] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 11/10/2014] [Indexed: 11/20/2022] Open
Abstract
Many bacterial pathogens use type three secretion systems (T3SS) to inject virulence factors, named effectors, directly into the cytoplasm of target eukaryotic cells. Most of the T3SS components are conserved among plant and animal pathogens, suggesting a common mechanism of recognition and secretion of effectors. However, no common motif has yet been identified for effectors allowing T3SS recognition. In this work, we performed a biochemical and structural characterization of the Salmonella SopB/SigE chaperone/effector complex by small-angle X-ray scattering (SAXS). Our results showed that the SopB/SigE complex is assembled in dynamic homohexameric-ring-shaped structures with an internal tunnel. In this ring, the chaperone maintains a disordered N-terminal end of SopB molecules, in a good position to be reached and processed by the T3SS. This ring dimensionally fits the ring-organized molecules of the injectisome, including ATPase hexameric rings; this organization suggests that this structural feature is important for ATPase recognition by T3SS. Our work constitutes the first evidence of the oligomerization of an effector, analogous to the organization of the secretion machinery, obtained in solution. As effectors share neither sequence nor structural identity, the quaternary oligomeric structure could constitute a strategy evolved to promote the specificity and efficiency of T3SS recognition.
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Affiliation(s)
- Pierre Roblin
- INRA Biopolymères, Interactions et Assemblages, Nantes, France Synchrotron SOLEIL, Gif sur Yvette, France
| | - Frédérique Dewitte
- Unité de Glycobiologie Structurale et Fonctionnelle, CNRS UMR8576, Université Lille Nord de France, Villeneuve d'Ascq, France
| | - Vincent Villeret
- Unité de Glycobiologie Structurale et Fonctionnelle, CNRS UMR8576, Université Lille Nord de France, Villeneuve d'Ascq, France
| | - Emanuele G Biondi
- Unité de Glycobiologie Structurale et Fonctionnelle, CNRS UMR8576, Université Lille Nord de France, Villeneuve d'Ascq, France
| | - Coralie Bompard
- Unité de Glycobiologie Structurale et Fonctionnelle, CNRS UMR8576, Université Lille Nord de France, Villeneuve d'Ascq, France
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14
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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: 360] [Impact Index Per Article: 36.0] [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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15
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Roblin P, Lebrun P, Rucktooa P, Dewitte F, Lens Z, Receveur-Brechot V, Raussens V, Villeret V, Bompard C. The structural organization of the N-terminus domain of SopB, a virulence factor of Salmonella, depends on the nature of its protein partners. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:2564-72. [PMID: 24075929 DOI: 10.1016/j.bbapap.2013.09.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Revised: 09/03/2013] [Accepted: 09/18/2013] [Indexed: 01/17/2023]
Abstract
The TTSS is used by Salmonella and many bacterial pathogens to inject virulence factors directly into the cytoplasm of target eukaryotic cells. Once translocated these so-called effector proteins hijack a vast array of crucial cellular functions to the benefit of the bacteria. In the bacterial cytoplasm, some effectors are stabilized and maintained in a secretion competent state by interaction with specific type III chaperones. In this work we studied the conformation of the Chaperone Binding Domain of the effector named Salmonella Outer protein B (SopB) alone and in complex with its cognate chaperone SigE by a combination of biochemical, biophysical and structural approaches. Our results show that the N-terminus part of SopB is mainly composed by α-helices and unfolded regions whose organization/stabilization depends on their interaction with the different partners. This suggests that the partially unfolded state of this N-terminal region, which confers the adaptability of the effector to bind very different partners during the infection cycle, allows the bacteria to modulate numerous host cells functions limiting the number of translocated effectors.
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Affiliation(s)
- Pierre Roblin
- INRA Biopolymères, Interactions et Assemblages, Rue de la Geraudière, 44316 Nantes, France; Synchrotron SOLEIL, L'orme des Merisiers, Saint Aubin, BP 48, 91192 Gif sur Yvette Cedex, France.
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16
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Vujanac M, Stebbins CE. Context-dependent protein folding of a virulence peptide in the bacterial and host environments: structure of an SycH-YopH chaperone-effector complex. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2013; 69:546-54. [PMID: 23519663 DOI: 10.1107/s0907444912051086] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 12/17/2012] [Indexed: 12/17/2022]
Abstract
Yersinia pestis injects numerous bacterial proteins into host cells through an organic nanomachine called the type 3 secretion system. One such substrate is the tyrosine phosphatase YopH, which requires an interaction with a cognate chaperone in order to be effectively injected. Here, the first crystal structure of a SycH-YopH complex is reported, determined to 1.9 Å resolution. The structure reveals the presence of (i) a nonglobular polypeptide in YopH, (ii) a so-called β-motif in YopH and (iii) a conserved hydrophobic patch in SycH that recognizes the β-motif. Biochemical studies establish that the β-motif is critical to the stability of this complex. Finally, since previous work has shown that the N-terminal portion of YopH adopts a globular fold that is functional in the host cell, aspects of how this polypeptide adopts radically different folds in the host and in the bacterial environments are analysed.
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Affiliation(s)
- Milos Vujanac
- Laboratory of Structural Microbiology, The Rockefeller University, New York, NY 10065, USA
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17
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Structure of the HopA1(21-102)-ShcA chaperone-effector complex of Pseudomonas syringae reveals conservation of a virulence factor binding motif from animal to plant pathogens. J Bacteriol 2012. [PMID: 23204470 DOI: 10.1128/jb.01621-12] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas syringae injects numerous bacterial proteins into host plant cells through a type 3 secretion system (T3SS). One of the first such bacterial effectors discovered, HopA1, is a protein that has unknown functions in the host cell but possesses close homologs that trigger the plant hypersensitive response in resistant strains. Like the virulence factors in many bacterial pathogens of animals, HopA1 depends upon a cognate chaperone in order to be effectively translocated by the P. syringae T3SS. Herein, we report the crystal structure of a complex of HopA1(21-102) with its chaperone, ShcA, determined to 1.56-Å resolution. The structure reveals that three key features of the chaperone-effector interactions found in animal pathogens are preserved in the Gram-negative pathogens of plants, namely, (i) the interaction of the chaperone with a nonglobular polypeptide of the effector, (ii) an interaction centered on the so-called β-motif, and (iii) the presence of a conserved hydrophobic patch in the chaperone that recognizes the β-motif. Structure-based mutagenesis and biochemical studies have established that the β-motif is critical for the stability of this complex. Overall, these results show that the β-motif interactions are broadly conserved in bacterial pathogens utilizing T3SSs, spanning an interkingdom host range.
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Structural basis for type VI secretion effector recognition by a cognate immunity protein. PLoS Pathog 2012; 8:e1002613. [PMID: 22511866 PMCID: PMC3325213 DOI: 10.1371/journal.ppat.1002613] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2011] [Accepted: 02/14/2012] [Indexed: 11/29/2022] Open
Abstract
The type VI secretion system (T6SS) has emerged as an important mediator of interbacterial interactions. A T6SS from Pseudomonas aeruginosa targets at least three effector proteins, type VI secretion exported 1–3 (Tse1–3), to recipient Gram-negative cells. The Tse2 protein is a cytoplasmic effector that acts as a potent inhibitor of target cell proliferation, thus providing a pronounced fitness advantage for P. aeruginosa donor cells. P. aeruginosa utilizes a dedicated immunity protein, type VI secretion immunity 2 (Tsi2), to protect against endogenous and intercellularly-transferred Tse2. Here we show that Tse2 delivered by the T6SS efficiently induces quiescence, not death, within recipient cells. We demonstrate that despite direct interaction of Tsi2 and Tse2 in the cytoplasm, Tsi2 is dispensable for targeting the toxin to the secretory apparatus. To gain insights into the molecular basis of Tse2 immunity, we solved the 1.00 Å X-ray crystal structure of Tsi2. The structure shows that Tsi2 assembles as a dimer that does not resemble previously characterized immunity or antitoxin proteins. A genetic screen for Tsi2 mutants deficient in Tse2 interaction revealed an acidic patch distal to the Tsi2 homodimer interface that mediates toxin interaction and immunity. Consistent with this finding, we observed that destabilization of the Tsi2 dimer does not impact Tse2 interaction. The molecular insights into Tsi2 structure and function garnered from this study shed light on the mechanisms of T6 effector secretion, and indicate that the Tse2–Tsi2 effector–immunity pair has features distinguishing it from previously characterized toxin–immunity and toxin–antitoxin systems. Bacterial species have been at war with each other for over a billion years. During this period they have evolved many pathways for besting the competition; one of the most recent of these to be described is the type VI secretion system (T6SS). The T6SS of Pseudomonas aeruginosa is a complex machine that the bacterium uses to intoxicate neighboring cells. Among the toxins this system delivers is type VI secretion exported 2 (Tse2). In addition to acting on competing organisms, this toxin can act on P. aeruginosa; thus, the organism synthesizes a protein, type VI secretion immunity 2 (Tsi2), which neutralizes the toxin. In this paper we dissect the function and structure of Tsi2. We show that although Tsi2 interacts with and stabilizes Tse2 inside the bacterium, the toxin does not require the immunity protein to reach the secretion apparatus. Our structure of Tsi2 shows that the protein adopts a dimeric configuration; however, we find that its dimerization is not required for Tse2 interaction. Instead, our findings indicate that Tse2 interacts with an acidic surface of Tsi2 that is opposite the homodimer interface. Our results provide key molecular insights into the process of T6 toxin secretion and immunity.
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Aguilera L, Ferreira E, Giménez R, Fernández FJ, Taulés M, Aguilar J, Vega MC, Badia J, Baldomà L. Secretion of the housekeeping protein glyceraldehyde-3-phosphate dehydrogenase by the LEE-encoded type III secretion system in enteropathogenic Escherichia coli. Int J Biochem Cell Biol 2012; 44:955-62. [PMID: 22433988 DOI: 10.1016/j.biocel.2012.03.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Revised: 03/02/2012] [Accepted: 03/02/2012] [Indexed: 01/14/2023]
Abstract
Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a multifunctional housekeeping protein secreted by pathogens and involved in adhesion and/or virulence. Previously we reported that enterohemorrhagic (EHEC) and enteropathogenic (EPEC) Escherichia coli secrete GAPDH into the culture medium. This bacterial protein binds human plasminogen and fibrinogen and remains associated with Caco-2 cells upon infection. In these pathogens, GAPDH secretion is not linked to outer membrane vesicles and depends on growth conditions, although the secretion mechanism is still unknown. EPEC is an attaching and effacing pathogen able to secrete and translocate multiple effector proteins into infected cells through a type III secretion system (T3SS). The secretion process is often dependent on a bacterial chaperone. The chaperone CesT displays broad substrate specificity and plays a central role in the recruitment of multiple type III effectors to the T3SS apparatus. Here we provide genetic evidences on GAPDH secretion through T3SS by EPEC grown in DMEM. Secretion of GAPDH is increased in ΔsepD mutants and abolished in mutants defective in the type III ATPase EscN. Complementation with escN gene restores GAPDH secretion. In addition, we prove by means of pull down experiments, overlay immunoblotting and biolayer interferometry a novel interaction between GAPDH and the chaperone CesT. This interaction, which is strong and slow dissociating, may stabilize a population of GAPDH molecules in a secretion competent-state and target them to the type III secretion apparatus. This is the first description of CesT interaction with a housekeeping protein and its export through T3SS.
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Affiliation(s)
- Laura Aguilera
- Departament de Bioquímica i Biología Molecular, Institut de Biomedicina de la Universitat de Barcelona (IBUB), Facultat de Farmàcia, Universitat de Barcelona, 08028 Barcelona, Spain
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20
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Zheng Z, Ma D, Yahr TL, Chen L. The transiently ordered regions in intrinsically disordered ExsE are correlated with structural elements involved in chaperone binding. Biochem Biophys Res Commun 2011; 417:129-34. [PMID: 22138394 DOI: 10.1016/j.bbrc.2011.11.070] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Accepted: 11/15/2011] [Indexed: 01/05/2023]
Abstract
Many Gram-negative bacteria utilize a type III secretion system (T3SS) to deliver protein effectors to target host cells. Transcriptional control of T3SS gene expression is generally coupled to secretion through the release of a regulatory protein. T3SS gene expression in Pseudomonas aeruginosa is regulated by extracellular secretion of ExsE. ExsE is a small 81 residue protein that appears to lack a stable structural core as indicated by previous studies. In this study, we employed various NMR methods to characterize the structure of ExsE alone and when bound to its secretion chaperone ExsC. We found that ExsE is largely unfolded throughout the polypeptide chain, belonging to a class of proteins that are intrinsically disordered. The unfolded, extended conformation of ExsE may expedite efficient secretion through the narrow path of the T3SS secretion channel to activate gene expression in a timely manner. We also found that the structurally flexible ExsE samples through conformations with localized structurally ordered regions. Importantly, these transiently ordered elements are related to the secondary structures involved in binding ExsC based on a prior crystal structure of the ExsC-ExsE complex. These findings support the notion that preexisting structured elements facilitate binding of intrinsically disordered proteins to their targets.
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Affiliation(s)
- Zhida Zheng
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405, USA
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21
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Salmonella effector proteins and host-cell responses. Cell Mol Life Sci 2011; 68:3687-97. [PMID: 21984608 DOI: 10.1007/s00018-011-0841-0] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Revised: 09/07/2011] [Accepted: 09/07/2011] [Indexed: 10/17/2022]
Abstract
Acute gastroenteritis caused by Salmonella enterica serovar typhimurium is a significant public health problem. This pathogen has very sophisticated molecular machinery encoded by the two pathogenicity islands, namely Salmonella Pathogenicity Island 1 and 2 (SPI-1 and SPI-2). Remarkably, both SPI-1 and SPI-2 are very tightly regulated in terms of timing of expression and spatial localization of the encoded effectors during the infection process within the host cell. This regulation is governed at several levels, including transcription and translation, and by post-translational modifications. In the context of a finely tuned regulatory system, we will highlight how these effector proteins co-opt host signaling pathways that control the ability of the organism to infect and survive within the host, as well as elicit host pro-inflammatory responses.
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22
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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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23
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24
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Structural Insights on Two Hypothetical Secretion Chaperones from Xanthomonas axonopodis pv. citri. Protein J 2011; 30:324-33. [DOI: 10.1007/s10930-011-9335-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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25
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Hallstrom K, McCormick BA. Salmonella Interaction with and Passage through the Intestinal Mucosa: Through the Lens of the Organism. Front Microbiol 2011; 2:88. [PMID: 21747800 PMCID: PMC3128981 DOI: 10.3389/fmicb.2011.00088] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Accepted: 04/13/2011] [Indexed: 01/13/2023] Open
Abstract
Salmonella enterica serotypes are invasive enteric pathogens spread through fecal contamination of food and water sources, and represent a constant public health threat around the world. The symptoms associated with salmonellosis and typhoid disease are largely due to the host response to invading Salmonella, and to the mechanisms these bacteria employ to survive in the presence of, and invade through the intestinal mucosal epithelia. Surmounting this barrier is required for survival within the host, as well as for further dissemination throughout the body, and subsequent systemic disease. In this review, we highlight some of the major hurdles Salmonella must overcome upon encountering the intestinal mucosal epithelial barrier, and examine how these bacteria surmount and exploit host defense mechanisms.
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Affiliation(s)
- Kelly Hallstrom
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School Worcester, MA, USA
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26
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Cooper CA, Zhang K, Andres SN, Fang Y, Kaniuk NA, Hannemann M, Brumell JH, Foster LJ, Junop MS, Coombes BK. Structural and biochemical characterization of SrcA, a multi-cargo type III secretion chaperone in Salmonella required for pathogenic association with a host. PLoS Pathog 2010; 6:e1000751. [PMID: 20140193 PMCID: PMC2816692 DOI: 10.1371/journal.ppat.1000751] [Citation(s) in RCA: 35] [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: 08/31/2009] [Accepted: 01/06/2010] [Indexed: 02/02/2023] Open
Abstract
Many Gram-negative bacteria colonize and exploit host niches using a protein apparatus called a type III secretion system (T3SS) that translocates bacterial effector proteins into host cells where their functions are essential for pathogenesis. A suite of T3SS-associated chaperone proteins bind cargo in the bacterial cytosol, establishing protein interaction networks needed for effector translocation into host cells. In Salmonella enterica serovar Typhimurium, a T3SS encoded in a large genomic island (SPI-2) is required for intracellular infection, but the chaperone complement required for effector translocation by this system is not known. Using a reverse genetics approach, we identified a multi-cargo secretion chaperone that is functionally integrated with the SPI-2-encoded T3SS and required for systemic infection in mice. Crystallographic analysis of SrcA at a resolution of 2.5 Å revealed a dimer similar to the CesT chaperone from enteropathogenic E. coli but lacking a 17-amino acid extension at the carboxyl terminus. Further biochemical and quantitative proteomics data revealed three protein interactions with SrcA, including two effector cargos (SseL and PipB2) and the type III-associated ATPase, SsaN, that increases the efficiency of effector translocation. Using competitive infections in mice we show that SrcA increases bacterial fitness during host infection, highlighting the in vivo importance of effector chaperones for the SPI-2 T3SS. Systemic typhoid fever caused by Salmonella enterica serovar Typhi leads to high mortality in the developing world and can be linked with chronic, persistent infections in survivors. To cause disease, Salmonella uses a specialized secretion device called a type III secretion system to disarm cells of the immune system and replicate within them. The assembly and function of this secretion system requires a set of chaperone proteins to direct the process, but the chaperone proteins themselves have remained elusive. Here, we found a new chaperone protein, called SrcA, which is required for proper function of the type III secretion system. Using a bacterial mutant lacking the srcA gene, we found that this chaperone was needed for Salmonella to compete against wild type cells during systemic disease because it controls secretion of at least 2 key proteins involved in immune escape and cell-to-cell transmission. This chaperone is present in all types of virulent Salmonella, but not in Salmonella that don't cause human infections, providing new insights into the pathogenic nature of this organism.
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Affiliation(s)
- Colin A. Cooper
- Michael G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry & Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Kun Zhang
- Michael G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry & Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Sara N. Andres
- Michael G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry & Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Yuan Fang
- Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Natalia A. Kaniuk
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Mandy Hannemann
- Michael G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry & Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - John H. Brumell
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Molecular Genetics and the Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Leonard J. Foster
- Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Murray S. Junop
- Michael G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry & Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Brian K. Coombes
- Michael G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry & Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- * E-mail:
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Tan YW, Yu HB, Sivaraman J, Leung KY, Mok YK. Mapping of the chaperone AcrH binding regions of translocators AopB and AopD and characterization of oligomeric and metastable AcrH-AopB-AopD complexes in the type III secretion system of Aeromonas hydrophila. Protein Sci 2009; 18:1724-34. [PMID: 19530229 DOI: 10.1002/pro.187] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
In the type III secretion system (T3SS) of Aeromonas hydrophila, AcrH acts as a chaperone for translocators AopB and AopD. AcrH forms a stable 1:1 monomeric complex with AopD, whereas the 1:1 AcrH-AopB complex exists mainly as a metastable oligomeric form and only in minor amounts as a stable monomeric form. Limited protease digestion shows that these complexes contain highly exposed regions, thus allowing mapping of intact functional chaperone binding regions of AopB and AopD. AopD uses the transmembrane domain (DF1, residues 16-147) and the C-terminal amphipathic helical domain (DF2, residues 242-296) whereas AopB uses a discrete region containing the transmembrane domain and the putative N-terminal coiled coil domain (BF1, residues 33-264). Oligomerization of the AcrH-AopB complex is mainly through the C-terminal coiled coil domain of AopB, which is dispensable for chaperone binding. The three proteins, AcrH, AopB, and AopD, can be coexpressed to form an oligomeric and metastable complex. These three proteins are also oligomerized mainly through the C-terminal domain of AopB. Formation of such an oligomeric and metastable complex may be important for the proper formation of translocon of correct topology and stoichiometry on the host membrane.
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Affiliation(s)
- Yih Wan Tan
- Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore
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28
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Salmonella enterica serovar typhimurium pathogenicity island 1-encoded type III secretion system translocases mediate intimate attachment to nonphagocytic cells. Infect Immun 2009; 77:2635-42. [PMID: 19364837 DOI: 10.1128/iai.00077-09] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Delivery of bacterial proteins into mammalian cells by type III secretion systems (TTSS) is thought to require the intimate association of bacteria with target cells. The molecular bases of this intimate association appear to be different in different bacteria involving TTSS components, as well as surface determinants not associated with TTSS. We show here that the protein translocases SipB, SipC, and SipD of the Salmonella enterica serovar Typhimurium pathogenicity island 1 (SPI-1)-encoded TTSS are required for the intimate association of these bacteria with mammalian cells. S. Typhimurium mutant strains lacking any of the translocases were defective for intimate attachment. Immunofluorescence microscopy showed that SipD is present on the bacterial surface prior to bacterial contact with host cells. In contrast, SipB and SipC were detected on the bacterial surface only subsequent to bacterial contact with the target cell. We conclude that the coordinated deployment and interaction between the protein translocases mediate the SPI-1 TTSS-dependent intimate association of S. Typhimurium with host cells.
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Essential role of the SycP chaperone in type III secretion of the YspP effector. J Bacteriol 2008; 191:1703-15. [PMID: 19114483 PMCID: PMC2648209 DOI: 10.1128/jb.01021-08] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The Ysa type III secretion (T3S) system enhances gastrointestinal infection by Yersinia enterocolitica bv. 1B. One effector protein targeted into host cells is YspP, a protein tyrosine phosphatase. It was determined in this study that the secretion of YspP requires a chaperone, SycP. Genetic analysis showed that deletion of sycP completely abolished the secretion of YspP without affecting the secretion of other Ysps by the Ysa T3S system. Analysis of the secretion and translocation signals of YspP defined the first 73 amino acids to form the minimal region of YspP necessary to promote secretion and translocation by the Ysa T3S system. Function of the YspP secretion/translocation signals was dependent on SycP. Curiously, when YspP was constitutively expressed in Y. enterocolitica bv. 1B, it was recognized and secreted by the Ysc T3S system and the flagellar T3S system. In these cases, the first 21 amino acids were sufficient to promote secretion, and while SycP did enhance secretion, it was not essential. However, neither the Ysc T3S system nor the flagellar T3S system translocated YspP into mammalian cells. This supports a model where SycP confers secretion/translocation specificities for YspP by the Ysa T3S system. A series of biochemical approaches further established that SycP specifically interacts with YspP and protected YspP degradation in the cell prior to secretion. Collectively, the evidence suggests that YspP secretion by the Ysa T3S system is a posttranslational event.
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30
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Gébus C, Caroline G, Faudry E, Eric F, Bohn YST, Elsen S, Sylvie E, Attree I. Oligomerization of PcrV and LcrV, protective antigens of Pseudomonas aeruginosa and Yersinia pestis. J Biol Chem 2008; 283:23940-9. [PMID: 18583342 DOI: 10.1074/jbc.m803146200] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Protective antigens of Pseudomonas aeruginosa (PcrV) and Yersinia pestis (LcrV) are key elements of specialized machinery, the type III secretion system (T3SS), which enables the injection of effector molecules into eukaryotic cells. Being positioned at the injectisome extremity, V proteins participate in the translocation process across the host cell plasma membrane. In this study, we demonstrate the assembly of V proteins into oligomeric doughnut-like complexes upon controlled refolding of the proteins in vitro. The oligomeric nature of refolded PcrV was revealed by size exclusion chromatography, native gel electrophoresis, and native mass spectrometry, which ascertain the capacity of the protein to multimerize into higher-order species. Furthermore, transmission electron microscopy performed on oligomers of both PcrV and LcrV revealed the presence of distinct structures with approximate internal and external diameters of 3-4 and 8-10 nm, respectively. The C-terminal helix, alpha12, of PcrV and notably the hydrophobic residues Val(255), Leu(262), and Leu(276) located within this helix, were shown to be crucial for oligomerization. Moreover, the corresponding mutant proteins produced in P. aeruginosa were found to be non-functional in in vivo type III-dependent cytotoxicity assays by directly affecting the correct assembly of PopB/D translocon within the host cell membranes. The detailed understanding of structure-function relationships of T3SS needle tip proteins will be of value in further developments of new vaccines and antimicrobials.
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Affiliation(s)
- Caroline Gébus
- Laboratoire de Biochimie et Biophysique des Systèmes Intégrés (Unité mixte de recherche 5092), CNRS, Université Joseph Fourier, Commissariat à l'Energie Atomique, DSV, iRTSV, 17 rue des Martyrs, Grenoble, France
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Mazhab-Jafari MT, Das R, Fotheringham SA, SilDas S, Chowdhury S, Melacini G. Understanding cAMP-dependent allostery by NMR spectroscopy: comparative analysis of the EPAC1 cAMP-binding domain in its apo and cAMP-bound states. J Am Chem Soc 2007; 129:14482-92. [PMID: 17973384 DOI: 10.1021/ja0753703] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
cAMP (adenosine 3',5'-cyclic monophosphate) is a ubiquitous second messenger that activates a multitude of essential cellular responses. Two key receptors for cAMP in eukaryotes are protein kinase A (PKA) and the exchange protein directly activated by cAMP (EPAC), which is a recently discovered guanine nucleotide exchange factor (GEF) for the small GTPases Rap1 and Rap2. Previous attempts to investigate the mechanism of allosteric activation of eukaryotic cAMP-binding domains (CBDs) at atomic or residue resolution have been hampered by the instability of the apo form, which requires the use of mixed apo/holo systems, that have provided only a partial picture of the CBD apo state and of the allosteric networks controlled by cAMP. Here, we show that, unlike other eukaryotic CBDs, both apo and cAMP-bound states of the EPAC1 CBD are stable under our experimental conditions, providing a unique opportunity to define at an unprecedented level of detail the allosteric interactions linking two critical functional sites of this CBD. These are the phosphate binding cassette (PBC), where cAMP binds, and the N-terminal helical bundle (NTHB), which is the site of the inhibitory interactions between the regulatory and catalytic regions of EPAC. Specifically, the combined analysis of the cAMP-dependent changes in chemical shifts, 2 degrees structure probabilities, hydrogen/hydrogen exchange (H/H) and hydrogen/deuterium exchange (H/D) protection factors reveals that the long-range communication between the PBC and the NTHB is implemented by two distinct intramolecular cAMP-signaling pathways, respectively, mediated by the beta2-beta3 loop and the alpha6 helix. Docking of cAMP into the PBC perturbs the NTHB inner core packing and the helical probabilities of selected NTHB residues. The proposed model is consistent with the allosteric role previously hypothesized for L273 and F300 based on site-directed mutagenesis; however, our data show that such a contact is part of a significantly more extended allosteric network that, unlike PKA, involves a tight coupling between the alpha- and beta-subdomains of the EPAC CBD. The proposed mechanism of allosteric activation will serve as a basis to understand agonism and antagonism in the EPAC system and provides also a general paradigm for how small ligands control protein-protein interfaces.
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Affiliation(s)
- Mohammad T Mazhab-Jafari
- Department of Chemistry, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1, Canada
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Faudry E, Job V, Dessen A, Attree I, Forge V. Type III secretion system translocator has a molten globule conformation both in its free and chaperone-bound forms. FEBS J 2007; 274:3601-3610. [PMID: 17578515 DOI: 10.1111/j.1742-4658.2007.05893.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Type III secretion systems of Gram-negative pathogenic bacteria allow the injection of effector proteins into the cytosol of host eukaryotic cells. Crossing of the eukaryotic plasma membrane is facilitated by a translocon, an oligomeric structure made up of two bacterial proteins inserted into the host membrane during infection. In Pseudomonas aeruginosa, a major human opportunistic pathogen, these proteins are PopB and PopD. Their interactions with their common chaperone PcrH in the cytosol of the bacteria are essential for the proper function of the injection system. The interaction region between PopD and PcrH was identified using limited proteolysis, revealing that the putative PopD transmembrane fragment is buried within the PopD/PcrH complex. In addition, structural features of PopD and PcrH, either individually or within the binary complex, were characterized using spectroscopic methods and 1D NMR. Whereas PcrH possesses the characteristics of a folded protein, PopD is in a molten globule state either alone or in the PopD/PcrH complex. The molten globule state is known to enable the membrane insertion of translocation/pore-forming domains of bacterial toxins. Therefore, within the bacterial cytoplasm, PopD is preserved in a state that is favorable to secretion and insertion into cell membranes.
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Affiliation(s)
- Eric Faudry
- CEA Grenoble, DSV-iRTSV, Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, UMR5092 (CNRS, CEA, Université Joseph Fourier), Grenoble, France Institut de Biologie Structurale Jean-Pierre Ebel, UMR5075 (CNRS, CEA, Université Joseph Fourier), Grenoble, France CEA Grenoble, DSV-iRTSV, Laboratoire de Chimie et Biologie des Métaux, UMR5249 (CNRS, CEA, Université Joseph Fourier), Grenoble, France
| | - Viviana Job
- CEA Grenoble, DSV-iRTSV, Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, UMR5092 (CNRS, CEA, Université Joseph Fourier), Grenoble, France Institut de Biologie Structurale Jean-Pierre Ebel, UMR5075 (CNRS, CEA, Université Joseph Fourier), Grenoble, France CEA Grenoble, DSV-iRTSV, Laboratoire de Chimie et Biologie des Métaux, UMR5249 (CNRS, CEA, Université Joseph Fourier), Grenoble, France
| | - Andréa Dessen
- CEA Grenoble, DSV-iRTSV, Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, UMR5092 (CNRS, CEA, Université Joseph Fourier), Grenoble, France Institut de Biologie Structurale Jean-Pierre Ebel, UMR5075 (CNRS, CEA, Université Joseph Fourier), Grenoble, France CEA Grenoble, DSV-iRTSV, Laboratoire de Chimie et Biologie des Métaux, UMR5249 (CNRS, CEA, Université Joseph Fourier), Grenoble, France
| | - Ina Attree
- CEA Grenoble, DSV-iRTSV, Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, UMR5092 (CNRS, CEA, Université Joseph Fourier), Grenoble, France Institut de Biologie Structurale Jean-Pierre Ebel, UMR5075 (CNRS, CEA, Université Joseph Fourier), Grenoble, France CEA Grenoble, DSV-iRTSV, Laboratoire de Chimie et Biologie des Métaux, UMR5249 (CNRS, CEA, Université Joseph Fourier), Grenoble, France
| | - Vincent Forge
- CEA Grenoble, DSV-iRTSV, Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, UMR5092 (CNRS, CEA, Université Joseph Fourier), Grenoble, France Institut de Biologie Structurale Jean-Pierre Ebel, UMR5075 (CNRS, CEA, Université Joseph Fourier), Grenoble, France CEA Grenoble, DSV-iRTSV, Laboratoire de Chimie et Biologie des Métaux, UMR5249 (CNRS, CEA, Université Joseph Fourier), Grenoble, France
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Roe AJ, Tysall L, Dransfield T, Wang D, Fraser-Pitt D, Mahajan A, Constandinou C, Inglis N, Downing A, Talbot R, Smith DGE, Gally DL. Analysis of the expression, regulation and export of NleA-E in Escherichia coli O157 : H7. MICROBIOLOGY (READING, ENGLAND) 2007; 153:1350-1360. [PMID: 17464049 DOI: 10.1099/mic.0.2006/003707-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Previous work has shown that locus of enterocyte effacement (LEE)-encoded effector proteins such as Tir and Map can be exported via the type III secretion system (T3SS) of Escherichia coli O157 : H7. Additionally, a family of non-LEE-encoded (Nle) effector proteins has been shown to be secreted from Citrobacter rodentium, homologues of which are located on the E. coli O157 chromosome. While NleA has been shown to be secreted from pathogenic E. coli, the secretion of other Nle effector proteins has only been detected under induced conditions, or using a mutated T3SS. This study aimed to determine: (1) which nle genes are expressed in E. coli O157 : H7 under secretion-permissive conditions; (2) if Nle proteins are secreted from wild-type E. coli O157 : H7 under secretion-permissive conditions; and (3) if nle gene expression is regulated co-ordinately with other LEE-encoded effectors. Using data generated from a combination of transcriptome arrays, reporter fusions and proteomics, it was demonstrated that only nleA is expressed co-ordinately with the LEE. Secretion and expression of NleA were regulated directly or indirectly by ler, a key activator of the LEE. MS confirmed the secretion of NleA into the culture supernatant, while NleB-F were not detected.
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Affiliation(s)
- Andrew J Roe
- Zoonotic and Animal Pathogens Research Laboratory, Centre for Infectious Disease, The Chancellor's Building, 49 Little France Crescent, Edinburgh EH16 4SB, UK
| | - Luke Tysall
- Zoonotic and Animal Pathogens Research Laboratory, Centre for Infectious Disease, The Chancellor's Building, 49 Little France Crescent, Edinburgh EH16 4SB, UK
| | - Tracy Dransfield
- Zoonotic and Animal Pathogens Research Laboratory, Centre for Infectious Disease, The Chancellor's Building, 49 Little France Crescent, Edinburgh EH16 4SB, UK
| | - Dai Wang
- Zoonotic and Animal Pathogens Research Laboratory, Centre for Infectious Disease, The Chancellor's Building, 49 Little France Crescent, Edinburgh EH16 4SB, UK
| | - Douglas Fraser-Pitt
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian EH26 0PZ, UK
| | - Arvind Mahajan
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian EH26 0PZ, UK
- Zoonotic and Animal Pathogens Research Laboratory, Centre for Infectious Disease, The Chancellor's Building, 49 Little France Crescent, Edinburgh EH16 4SB, UK
| | | | - Neil Inglis
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian EH26 0PZ, UK
| | - Alison Downing
- Roslin Institute, Roslin BioCentre, Midlothian EH25 9PS, UK
| | - Richard Talbot
- Roslin Institute, Roslin BioCentre, Midlothian EH25 9PS, UK
| | - David G E Smith
- Institute for Comparative Medicine, University of Glasgow, Glasgow G61 1QH, UK
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian EH26 0PZ, UK
| | - David L Gally
- Zoonotic and Animal Pathogens Research Laboratory, Centre for Infectious Disease, The Chancellor's Building, 49 Little France Crescent, Edinburgh EH16 4SB, UK
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Cunliffe JM, Sunahara RK, Kennedy RT. Detection of adenylyl cyclase activity using a fluorescent ATP substrate and capillary electrophoresis. Anal Chem 2007; 78:1731-8. [PMID: 16536404 DOI: 10.1021/ac0521201] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A capillary electrophoresis laser-induced fluorescence (CE-LIF) assay was developed for detection of adenylyl cyclase (AC) activity using BODIPY FL ATP (BATP) as substrate. In the assay, BATP was incubated with AC and the resulting mixture of BATP and enzyme product (BODIPY cyclic AMP, BcAMP) separated in 5 min by CE-LIF. Substrate depletion and product accumulation were simultaneously monitored during the course of the reaction. The rate of product formation depended upon the presence of AC activators forskolin or Galpha(s)-GTPgammaS as evidenced by a more rapid BATP turnover to BcAMP compared to basal levels. The CE-LIF assay detected EC50 values for forskolin and Galpha(s)-GTPgammaS of 27 +/- 6 microM and 317 +/- 56 nM, respectively. These EC50 values compared well to those previously reported using [alpha-32P]ATP as substrate. When AC was concurrently activated with 2.5 microM forskolin and 25 nM Galpha(s)-GTPgammaS, the amount of BcAMP formed was 3.4 times higher than the additive amounts of each activator alone indicating a positively cooperative activation by these compounds in agreement with previous assays using radiolabeled substrate. Inhibition of AC activity was also demonstrated using the AC inhibitor 2'-(or-3')-O-(N-methylanthraniloyl) guanosine 5'-triphosphate with an IC50 of 9 +/- 6 nM. The use of a fluorescent substrate combined with CE separation has enabled development of a rapid and robust method for detection of AC activity that is an attractive alternative to the AC assay using radioactive nucleotide and column chromatography. In addition, the assay has potential for high-throughput screening of drugs that act at AC.
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Affiliation(s)
- Jennifer M Cunliffe
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
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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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36
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Chen LM, Briones G, Donis RO, Galán JE. Optimization of the delivery of heterologous proteins by the Salmonella enterica serovar Typhimurium type III secretion system for vaccine development. Infect Immun 2006; 74:5826-33. [PMID: 16988261 PMCID: PMC1594939 DOI: 10.1128/iai.00375-06] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Type III protein secretion systems, which are organelles with the capacity to deliver bacterial proteins into host cells, have been adapted to deliver heterologous antigens for vaccine development. A limitation of these antigen delivery systems is that some proteins are not amenable to secretion through this pathway. We show here that proteins from the simian and human immunodeficiency viruses that are not permissive for secretion through a Salmonella enterica serovar Typhimurium type III secretion system can be modified to travel this secretion pathway by introduction of discrete mutations. Proteins optimized for secretion were presented more efficiently via the major histocompatibility complex class I pathway and were able to induce a better immune response.
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Affiliation(s)
- Li-Mei Chen
- Section of Microbial Pathogenesis, School of Medicine, Yale University, New Haven, CT 06536, USA
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37
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Knodler LA, Bertero M, Yip C, Strynadka NCJ, Steele-Mortimer O. Structure-based mutagenesis of SigE verifies the importance of hydrophobic and electrostatic residues in type III chaperone function. Mol Microbiol 2006; 62:928-40. [PMID: 17038123 DOI: 10.1111/j.1365-2958.2006.05418.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Despite sharing little sequence identity, most type III chaperones display a similar homodimeric structure characterized by negative charges distributed broadly over their entire surface, interspersed with hydrophobic patches. Here we have used SigE from Salmonella as a model for class IA type III chaperones to investigate the role of these surface-exposed residues in chaperone function. SigE is essential for the stability, secretion and translocation of its cognate effector, SopB (SigD). We analysed the effect of mutating nine conserved hydrophobic and electronegative surface-exposed amino acids of SigE on SopB binding, stability, secretion and translocation. Six of these mutations affected some aspect of SigE function (Leu14, Asp20, Leu22, Leu23, Ile25 and Asp51) and three were without effect (Leu54, Glu92 and Glu99). Our results highlight that both hydrophobic and electronegative surfaces are required for the function of SigE and provide an important basis for the prediction of side-chain requirements for other chaperone-effector pairs.
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Affiliation(s)
- Leigh A Knodler
- Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, NIAID, NIH, Hamilton, MT 59840, USA.
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38
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Aldridge PD, Karlinsey JE, Aldridge C, Birchall C, Thompson D, Yagasaki J, Hughes KT. The flagellar-specific transcription factor, sigma28, is the Type III secretion chaperone for the flagellar-specific anti-sigma28 factor FlgM. Genes Dev 2006; 20:2315-26. [PMID: 16912280 PMCID: PMC1553213 DOI: 10.1101/gad.380406] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The sigma(28) protein is a member of the bacterial sigma(70)-family of transcription factors that directs RNA polymerase to flagellar late (class 3) promoters. The sigma(28) protein is regulated in response to flagellar assembly by the anti-sigma(28) factor FlgM. FlgM inhibits sigma(28)-dependent transcription of genes whose products are needed late in assembly until the flagellar basal motor structure, the hook-basal body (HBB), is constructed. A second function for the sigma(28) transcription factor has been discovered: sigma(28) facilitates the secretion of FlgM through the HBB, acting as the FlgM Type III secretion chaperone. Transcription-specific mutants in sigma(28) were isolated that remained competent for FlgM-facilitated secretion separating the transcription and secretion-facilitation activities of sigma (28). Conversely, we also describe the isolation of mutants in sigma(28) that are specific for FlgM-facilitated secretion. The data demonstrate that sigma(28) is the Type III secretion chaperone for its own anti-sigma factor FlgM. Thus, a novel role for a sigma(70)-family transcription factor is described.
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Affiliation(s)
- Phillip D Aldridge
- Institute for Cell and Molecular Biosciences, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK.
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39
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Scholten A, Poh MK, van Veen TAB, van Breukelen B, Vos MA, Heck AJR. Analysis of the cGMP/cAMP interactome using a chemical proteomics approach in mammalian heart tissue validates sphingosine kinase type 1-interacting protein as a genuine and highly abundant AKAP. J Proteome Res 2006; 5:1435-47. [PMID: 16739995 DOI: 10.1021/pr0600529] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The cyclic nucleotide monophosphates cAMP and cGMP play an essential role in many signaling pathways. To analyze which proteins do interact with these second messenger molecules, we developed a chemical proteomics approach using cAMP and cGMP immobilized onto agarose beads, via flexible linkers in the 2- and 8-position of the nucleotide. Optimization of the affinity pull-down procedures in lysates of HEK293 cells revealed that a large variety of proteins could be pulled down specifically. Identification of these proteins by mass spectrometry showed that many of these proteins were indeed genuine cAMP or cGMP binding proteins. However, additionally many of the pulled-down proteins were more abundant AMP/ADP/ATP, GMP/GDP/GTP, or general DNA/RNA binding proteins. Therefore, a sequential elution protocol was developed, eluting proteins from the beads using solutions containing ADP, GDP, cGMP, and/or cAMP, respectively. Using this protocol, we were able to sequentially and selectively elute ADP, GDP, and DNA binding proteins. The fraction left on the beads was further enriched, for cAMP/cGMP binding proteins. Transferring this protocol to the analysis of the cGMP/cAMP "interactome" in rat heart ventricular tissue enabled the specific pull-down of known cAMP/cGMP binding proteins such as cAMP and cGMP dependent protein kinases PKA and PKG, several phosphodiesterases and 6 AKAPs, that interact with PKA. Among the latter class of proteins was the highly abundant sphingosine kinase type1-interating protein (SKIP), recently proposed to be a potential AKAP. Further bioinformatics analysis endorses that SKIP is indeed a genuine PKA interacting protein, which is highly abundant in heart ventricular tissue.
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Affiliation(s)
- Arjen Scholten
- Department of Biomolecular Mass Spectrometry, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands
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Lilic M, Vujanac M, Stebbins CE. A common structural motif in the binding of virulence factors to bacterial secretion chaperones. Mol Cell 2006; 21:653-64. [PMID: 16507363 DOI: 10.1016/j.molcel.2006.01.026] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2005] [Revised: 09/30/2005] [Accepted: 01/19/2006] [Indexed: 12/16/2022]
Abstract
Salmonella invasion protein A (SipA) is translocated into host cells by a type III secretion system (T3SS) and comprises two regions: one domain binds its cognate type III secretion chaperone, InvB, in the bacterium to facilitate translocation, while a second domain functions in the host cell, contributing to bacterial uptake by polymerizing actin. We present here the crystal structures of the SipA chaperone binding domain (CBD) alone and in complex with InvB. The SipA CBD is found to consist of a nonglobular polypeptide as well as a large globular domain, both of which are necessary for binding to InvB. We also identify a structural motif that may direct virulence factors to their cognate chaperones in a diverse range of pathogenic bacteria. Disruption of this structural motif leads to a destabilization of several chaperone-substrate complexes from different species, as well as an impairment of secretion in Salmonella.
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Affiliation(s)
- Mirjana Lilic
- Laboratory of Structural Microbiology, The Rockefeller University, New York, New York 10021, USA
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41
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Briones G, Hofreuter D, Galán JE. Cre reporter system to monitor the translocation of type III secreted proteins into host cells. Infect Immun 2006; 74:1084-90. [PMID: 16428755 PMCID: PMC1360346 DOI: 10.1128/iai.74.2.1084-1090.2006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Central to the study of type III secretion systems is the availability of reporter systems to monitor bacterial protein translocation into host cells. We report here the development of a bacteriophage P1 Cre recombinase-based system to monitor the translocation of bacterial proteins into mammalian cells. Bacteriophage P1 Cre recombinase fused to the secretion and translocation signals of Salmonella enterica serovar Typhimurium of the type III secreted protein SopE was secreted in a type III secretion system-dependent fashion. More importantly, the SopE-Cre chimera was translocated into host cells via the type III secretion system and activated the expression of luciferase and green fluorescent protein reporters of Cre recombinase activity.
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Affiliation(s)
- Gabriel Briones
- Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06536, USA
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Abstract
Bacterial pathogens achieve the internalization of a multitude of virulence factors into eukaryotic cells. Some secrete extracellular toxins which bring about their own entry, usually by hijacking cell surface receptors and endocytic pathways. Others possess specialized secretion and translocation systems to directly inject bacterial proteins into the host cytosol. Recent advances in the structural biology of these virulence factors has begun to reveal at the molecular level how these bacterial proteins are delivered and modulate host activities ranging from cytoskeletal structure to cell cycle progression.
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Affiliation(s)
- C Erec Stebbins
- Laboratory of Structural Microbiology, Rockefeller University, New York, NY 10021, USA.
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Bröms JE, Edqvist PJ, Carlsson KE, Forsberg A, Francis MS. Mapping of a YscY binding domain within the LcrH chaperone that is required for regulation of Yersinia type III secretion. J Bacteriol 2005; 187:7738-52. [PMID: 16267298 PMCID: PMC1280294 DOI: 10.1128/jb.187.22.7738-7752.2005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Type III secretion systems are used by many animal and plant interacting bacteria to colonize their host. These systems are often composed of at least 40 genes, making their temporal and spatial regulation very complex. Some type III chaperones of the translocator class are important regulatory molecules, such as the LcrH chaperone of Yersinia pseudotuberculosis. In contrast, the highly homologous PcrH chaperone has no regulatory effect in native Pseudomonas aeruginosa or when produced in Yersinia. In this study, we used LcrH-PcrH chaperone hybrids to identify a discrete region in the N terminus of LcrH that is necessary for YscY binding and regulatory control of the Yersinia type III secretion machinery. PcrH was unable to bind YscY and the homologue Pcr4 of P. aeruginosa. YscY and Pcr4 were both essential for type III secretion and reciprocally bound to both substrates YscX of Yersinia and Pcr3 of P. aeruginosa. Still, Pcr4 was unable to complement a DeltayscY null mutant defective for type III secretion and yop-regulatory control in Yersinia, despite the ability of YscY to function in P. aeruginosa. Taken together, we conclude that the cross-talk between the LcrH and YscY components represents a strategic regulatory pathway specific to Yersinia type III secretion.
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Affiliation(s)
- Jeanette E Bröms
- Department of Medical Countermeasures, Swedish Defence Research Agency, Umeå
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44
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Akeda Y, Galán JE. Chaperone release and unfolding of substrates in type III secretion. Nature 2005; 437:911-5. [PMID: 16208377 DOI: 10.1038/nature03992] [Citation(s) in RCA: 336] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2005] [Accepted: 07/01/2005] [Indexed: 01/18/2023]
Abstract
Type III protein secretion systems are essential virulence factors of many bacteria pathogenic to humans, animals and plants. These systems mediate the transfer of bacterial virulence proteins directly into the host cell cytoplasm. Proteins are thought to travel this pathway in a largely unfolded manner, and a family of customized cytoplasmic chaperones, which specifically bind cognate secreted proteins, are essential for secretion. Here we show that InvC, an ATPase associated with a Salmonella enterica type III secretion system, has a critical function in substrate recognition. Furthermore, InvC induces chaperone release from and unfolding of the cognate secreted protein in an ATP-dependent manner. Our results show a similarity between the mechanisms of substrate recognition by type III protein secretion systems and AAA + ATPase disassembly machines.
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Affiliation(s)
- Yukihiro Akeda
- Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut 06536, USA
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Saouros S, Edwards-Jones B, Reiss M, Sawmynaden K, Cota E, Simpson P, Dowse TJ, Jäkle U, Ramboarina S, Shivarattan T, Matthews S, Soldati-Favre D. A novel galectin-like domain from Toxoplasma gondii micronemal protein 1 assists the folding, assembly, and transport of a cell adhesion complex. J Biol Chem 2005; 280:38583-91. [PMID: 16166092 DOI: 10.1074/jbc.c500365200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Immediately prior to invasion Toxoplasma gondii tachyzoites release a large number of micronemal proteins (TgMICs) that participate in host cell attachment and penetration. The TgMIC4-MIC1-MIC6 complex was the first to be identified in T. gondii and has been recently shown to be critical in invasion. This study establishes that the N-terminal thrombospondin type I repeat-like domains (TSR1-like) from TgMIC1 function as an independent adhesin as well as promoting association with TgMIC4. Using the newly solved three-dimensional structure of the C-terminal domain of TgMIC1 we have identified a novel Galectin-like fold that does not possess carbohydrate binding properties and redefines the architecture of TgMIC1. Instead, the TgMIC1 Galectin-like domain interacts and stabilizes TgMIC6, which provides the basis for a highly specific quality control mechanism for successful exit from the early secretory compartments and for subsequent trafficking of the complex to the micronemes.
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Affiliation(s)
- Savvas Saouros
- Department of Biological Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
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Thomas NA, Deng W, Puente JL, Frey EA, Yip CK, Strynadka NCJ, Finlay BB. CesT is a multi-effector chaperone and recruitment factor required for the efficient type III secretion of both LEE- and non-LEE-encoded effectors of enteropathogenicEscherichia coli. Mol Microbiol 2005; 57:1762-79. [PMID: 16135239 DOI: 10.1111/j.1365-2958.2005.04802.x] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Enteropathogenic Escherichia coli (EPEC) is an intestinal attaching and effacing pathogen that utilizes a type III secretion system (T3SS) for the delivery of effectors into host cells. The chaperone CesT has been shown to bind and stabilize the type III translocated effectors Tir and Map in the bacterial cytoplasm prior to their delivery into host cells. In this study we demonstrate a role for CesT in effector recruitment to the membrane embedded T3SS. CesT-mediated effector recruitment was dependent on the presence of the T3SS membrane-associated ATPase EscN. EPEC DeltacesT carrying a C-terminal CesT variant, CesT(E142G), exhibited normal cytoplasmic Tir stability function, but was less efficient in secreting Tir, further implicating CesT in type III secretion. In vivo co-immunoprecipitation studies using CesT-FLAG containing EPEC lysates demonstrated that CesT interacts with Tir and EscN, consistent with the notion of CesT recruiting Tir to the T3SS. CesT was also shown to be required for the efficient secretion of several type III effectors encoded within and outside the locus of enterocyte effacement (LEE) in addition to Tir and Map. Furthermore, a CesT affinity column was shown to specifically retain multiple effector proteins from EPEC culture supernatants. These findings indicate that CesT is centrally involved in recruiting multiple type III effectors to the T3SS via EscN for efficient secretion, and functionally redefine the role of CesT in multiple type III effector interactions.
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Affiliation(s)
- Nikhil A Thomas
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
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Wulf J, Pascuzzi PE, Fahmy A, Martin GB, Nicholson LK. The solution structure of type III effector protein AvrPto reveals conformational and dynamic features important for plant pathogenesis. Structure 2005; 12:1257-68. [PMID: 15242602 DOI: 10.1016/j.str.2004.04.017] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2004] [Revised: 04/28/2004] [Accepted: 04/28/2004] [Indexed: 12/01/2022]
Abstract
Pseudomonas syringae pv. tomato, the causative agent of bacterial speck disease of tomato, uses a type III secretion system (TTSS) to deliver effector proteins into the host cell. In resistant plants, the bacterial effector protein AvrPto physically interacts with the host Pto kinase and elicits antibacterial defense responses. In susceptible plants, which lack the Pto kinase, AvrPto acts as a virulence factor to promote bacterial growth. The solution structure of AvrPto reveals a functional core consisting of a three-helix bundle motif flanked by disordered N- and C-terminal tails. Residues required for Pto binding lie in a 19 residue Omega loop. Modeling suggests a hydrophobic patch involving the activation loop of Pto forms a contact surface with the AvrPto Omega loop and that helix packing mediates interactions between AvrPto and putative virulence targets Api2 and Api3. The AvrPto structure has a low stability that may facilitate chaperone-independent secretion by the TTSS.
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Affiliation(s)
- Jennifer Wulf
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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Sander P, Rezwan M, Walker B, Rampini SK, Kroppenstedt RM, Ehlers S, Keller C, Keeble JR, Hagemeier M, Colston MJ, Springer B, Böttger EC. Lipoprotein processing is required for virulence of Mycobacterium tuberculosis. Mol Microbiol 2005; 52:1543-52. [PMID: 15186407 DOI: 10.1111/j.1365-2958.2004.04041.x] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Lipoproteins are a subgroup of secreted bacterial proteins characterized by a lipidated N-terminus, processing of which is mediated by the consecutive activity of prolipoprotein diacylglyceryl transferase (Lgt) and lipoprotein signal peptidase (LspA). The study of LspA function has been limited mainly to non-pathogenic microorganisms. To study a potential role for LspA in the pathogenesis of bacterial infections, we have disrupted lspA by allelic replacement in Mycobacterium tuberculosis, one of the world's most devastating pathogens. Despite the presence of an impermeable lipid outer layer, it was found that LspA was dispensable for growth under in vitro culture conditions. In contrast, the mutant was markedly attenuated in virulence models of tuberculosis. Our findings establish lipoprotein metabolism as a major virulence determinant of tuberculosis and define a role for lipoprotein processing in bacterial pathogenesis. In addition, these results hint at a promising new target for therapeutic intervention, as a highly specific inhibitor of bacterial lipoprotein signal peptidases is available.
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Affiliation(s)
- P Sander
- Institut für Medizinische Mikrobiologie, Universität Zürich, Gloriastrasse 30/32, CH-8028 Zürich, Schweiz.
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Abstract
The type III secretion system (TTSS) of gram-negative bacteria is responsible for delivering bacterial proteins, termed effectors, from the bacterial cytosol directly into the interior of host cells. The TTSS is expressed predominantly by pathogenic bacteria and is usually used to introduce deleterious effectors into host cells. While biochemical activities of effectors vary widely, the TTSS apparatus used to deliver these effectors is conserved and shows functional complementarity for secretion and translocation. This review focuses on proteins that constitute the TTSS apparatus and on mechanisms that guide effectors to the TTSS apparatus for transport. The TTSS apparatus includes predicted integral inner membrane proteins that are conserved widely across TTSSs and in the basal body of the bacterial flagellum. It also includes proteins that are specific to the TTSS and contribute to ring-like structures in the inner membrane and includes secretin family members that form ring-like structures in the outer membrane. Most prominently situated on these coaxial, membrane-embedded rings is a needle-like or pilus-like structure that is implicated as a conduit for effector translocation into host cells. A short region of mRNA sequence or protein sequence in effectors acts as a signal sequence, directing proteins for transport through the TTSS. Additionally, a number of effectors require the action of specific TTSS chaperones for efficient and physiologically meaningful translocation into host cells. Numerous models explaining how effectors are transported into host cells have been proposed, but understanding of this process is incomplete and this topic remains an active area of inquiry.
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Affiliation(s)
- Partho Ghosh
- Department of Chemistry & Biochemistry, University of California-San Diego, La Jolla, CA 92093-0314, USA.
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Brüssow H, Canchaya C, Hardt WD. Phages and the evolution of bacterial pathogens: from genomic rearrangements to lysogenic conversion. Microbiol Mol Biol Rev 2004; 68:560-602, table of contents. [PMID: 15353570 PMCID: PMC515249 DOI: 10.1128/mmbr.68.3.560-602.2004] [Citation(s) in RCA: 1071] [Impact Index Per Article: 53.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Comparative genomics demonstrated that the chromosomes from bacteria and their viruses (bacteriophages) are coevolving. This process is most evident for bacterial pathogens where the majority contain prophages or phage remnants integrated into the bacterial DNA. Many prophages from bacterial pathogens encode virulence factors. Two situations can be distinguished: Vibrio cholerae, Shiga toxin-producing Escherichia coli, Corynebacterium diphtheriae, and Clostridium botulinum depend on a specific prophage-encoded toxin for causing a specific disease, whereas Staphylococcus aureus, Streptococcus pyogenes, and Salmonella enterica serovar Typhimurium harbor a multitude of prophages and each phage-encoded virulence or fitness factor makes an incremental contribution to the fitness of the lysogen. These prophages behave like "swarms" of related prophages. Prophage diversification seems to be fueled by the frequent transfer of phage material by recombination with superinfecting phages, resident prophages, or occasional acquisition of other mobile DNA elements or bacterial chromosomal genes. Prophages also contribute to the diversification of the bacterial genome architecture. In many cases, they actually represent a large fraction of the strain-specific DNA sequences. In addition, they can serve as anchoring points for genome inversions. The current review presents the available genomics and biological data on prophages from bacterial pathogens in an evolutionary framework.
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Affiliation(s)
- Harald Brüssow
- Nestlé, Research Center, Vers-chez-les-Blanc, CH-1000 Lausanne, Switzerland.
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