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Zhao Z, Hu Y, Hu Y, White AP, Wang Y. Features and algorithms: facilitating investigation of secreted effectors in Gram-negative bacteria. Trends Microbiol 2023; 31:1162-1178. [PMID: 37349207 DOI: 10.1016/j.tim.2023.05.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 05/22/2023] [Accepted: 05/22/2023] [Indexed: 06/24/2023]
Abstract
Gram-negative bacteria deliver effector proteins through type III, IV, or VI secretion systems (T3SSs, T4SSs, and T6SSs) into host cells, causing infections and diseases. In general, effector proteins for each of these distinct secretion systems lack homology and are difficult to identify. Sequence analysis has disclosed many common features, helping us to understand the evolution, function, and secretion mechanisms of the effectors. In combination with various algorithms, the known common features have facilitated accurate prediction of new effectors. Ensemblers or integrated pipelines achieve a better prediction of performance, which combines multiple computational models or modules with multidimensional features. Natural language processing (NLP) models also show the merits, which could enable discovery of novel features and, in turn, facilitate more precise effector prediction, extending our knowledge about each secretion mechanism.
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Affiliation(s)
- Ziyi Zhao
- Youth Innovation Team of Medical Bioinformatics, Shenzhen University Medical School, Shenzhen 518060, China
| | - Yixue Hu
- Youth Innovation Team of Medical Bioinformatics, Shenzhen University Medical School, Shenzhen 518060, China
| | - Yueming Hu
- Department of Bioinformatics, College of Life Sciences, Zhejiang University, Hangzhou, China
| | - Aaron P White
- Vaccine and Infectious Disease Organization (VIDO), University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Yejun Wang
- Youth Innovation Team of Medical Bioinformatics, Shenzhen University Medical School, Shenzhen 518060, China; Department of Cell Biology and Genetics, College of Basic Medicine, Shenzhen University Medical School, Shenzhen 518060, China.
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2
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Manera K, Kamal F, Burkinshaw B, Dong TG. Essential functions of chaperones and adaptors of protein secretion systems in Gram-negative bacteria. FEBS J 2021; 289:4704-4717. [PMID: 34092034 DOI: 10.1111/febs.16056] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 05/18/2021] [Accepted: 06/04/2021] [Indexed: 01/02/2023]
Abstract
Equipped with a plethora of secreted toxic effectors, protein secretion systems are essential for bacteria to interact with and manipulate their neighboring environment to survive in host microbiota and other highly competitive communities. While effectors have received spotlight attention in secretion system studies, many require accessory chaperone and adaptor proteins for proper folding/unfolding and stability throughout the secretion process. Here, we review the functions of chaperones and adaptors of three protein secretions systems, type 3 secretion system (T3SS), type 4 secretion system (T4SS), and type 6 secretion system (T6SS), which are employed by many Gram-negative bacterial pathogens to deliver toxins to bacterial, plant, and mammalian host cells through direct contact. Since chaperone and adaptor functions of the T3SS and the T4SS are relatively well studied, we discuss in detail the methods of chaperone-facilitated effector secretion by the T6SS and highlight commonalities between the effector chaperone/adaptor proteins of these diverse secretion systems. While the chaperones and adaptors are generally referred to as accessory proteins as they are not directly involved in toxicities to target cells, they are nonetheless vital for the biological functions of the secretion systems. Future research on biochemical and structural properties of these chaperones will not only elucidate the mechanisms of chaperone-effector binding and release process but also facilitate custom design of cargo effectors to be translocated by these widespread secretion systems for biotechnological applications.
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Affiliation(s)
- Kevin Manera
- Department of Ecosystem and Public Health, University of Calgary, Canada
| | - Fatima Kamal
- Department of Ecosystem and Public Health, University of Calgary, Canada
| | | | - Tao G Dong
- Department of Ecosystem and Public Health, University of Calgary, Canada.,State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, China
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3
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Hajra D, Nair AV, Chakravortty D. An elegant nano-injection machinery for sabotaging the host: Role of Type III secretion system in virulence of different human and animal pathogenic bacteria. Phys Life Rev 2021; 38:25-54. [PMID: 34090822 DOI: 10.1016/j.plrev.2021.05.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Accepted: 05/23/2021] [Indexed: 01/22/2023]
Abstract
Various Gram-negative bacteria possess a specialized membrane-bound protein secretion system known as the Type III secretion system (T3SS), which transports the bacterial effector proteins into the host cytosol thereby helping in bacterial pathogenesis. The T3SS has a special needle-like translocon that can sense the contact with the host cell membrane and translocate effectors. The export apparatus of T3SS recognizes these effector proteins bound to chaperones and translocates them into the host cell. Once in the host cell cytoplasm, these effector proteins result in modulation of the host system and promote bacterial localization and infection. Using molecular biology, bioinformatics, genetic techniques, electron microscopic studies, and mathematical modeling, the structure and function of the T3SS and the corresponding effector proteins in various bacteria have been studied. The strategies used by different human pathogenic bacteria to modulate the host system and thereby enhance their virulence mechanism using T3SS have also been well studied. Here we review the history, evolution, and general structure of the T3SS, highlighting the details of its comparison with the flagellar export machinery. Also, this article provides mechanistic details about the common role of T3SS in subversion and manipulation of host cellular processes. Additionally, this review describes specific T3SS apparatus and the role of their specific effectors in bacterial pathogenesis by considering several human and animal pathogenic bacteria.
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Affiliation(s)
- Dipasree Hajra
- Department of Microbiology & Cell Biology, Indian Institute of Science, India
| | - Abhilash Vijay Nair
- Department of Microbiology & Cell Biology, Indian Institute of Science, India
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4
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Computational prediction of secreted proteins in gram-negative bacteria. Comput Struct Biotechnol J 2021; 19:1806-1828. [PMID: 33897982 PMCID: PMC8047123 DOI: 10.1016/j.csbj.2021.03.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 03/18/2021] [Accepted: 03/18/2021] [Indexed: 12/29/2022] Open
Abstract
Gram-negative bacteria harness multiple protein secretion systems and secrete a large proportion of the proteome. Proteins can be exported to periplasmic space, integrated into membrane, transported into extracellular milieu, or translocated into cytoplasm of contacting cells. It is important for accurate, genome-wide annotation of the secreted proteins and their secretion pathways. In this review, we systematically classified the secreted proteins according to the types of secretion systems in Gram-negative bacteria, summarized the known features of these proteins, and reviewed the algorithms and tools for their prediction.
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5
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Serapio-Palacios A, Finlay BB. Dynamics of expression, secretion and translocation of type III effectors during enteropathogenic Escherichia coli infection. Curr Opin Microbiol 2020; 54:67-76. [PMID: 32058947 DOI: 10.1016/j.mib.2019.12.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 12/30/2019] [Indexed: 12/14/2022]
Abstract
Enteropathogenic Escherichia coli (EPEC) is an important cause of infant diarrhea and mortality worldwide. The locus of enterocyte effacement (LEE) pathogenicity island in the EPEC genome encodes a type 3 secretion system (T3SS). This nanomachine directly injects a sophisticated arsenal of effectors into host cells, which is critical for EPEC pathogenesis. To colonize the gut mucosa, EPEC alters its gene expression in response to host environmental signals. Regulation of the LEE has been studied extensively, revealing key mechanisms of transcriptional regulation, and more recently at the posttranscriptional and posttranslational levels. Moreover, the T3SS assembly and secretion is a highly coordinated process that ensures hierarchical delivery of effectors upon cell contact. EPEC effectors and virulence factors not only manipulate host cellular processes, but also modulate effector translocation by controlling T3SS formation. In this review, we focus on the regulation of EPEC virulence genes and modulation of effector secretion and translocation.
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Affiliation(s)
| | - Barton Brett Finlay
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada; Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada; Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada.
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6
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Miller BK, Hughes R, Ligon LS, Rigel NW, Malik S, Anjuwon-Foster BR, Sacchettini JC, Braunstein M. Mycobacterium tuberculosis SatS is a chaperone for the SecA2 protein export pathway. eLife 2019; 8:e40063. [PMID: 30604681 PMCID: PMC6333443 DOI: 10.7554/elife.40063] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 12/31/2018] [Indexed: 11/13/2022] Open
Abstract
The SecA2 protein export system is critical for the virulence of Mycobacterium tuberculosis. However, the mechanism of this export pathway remains unclear. Through a screen for suppressors of a secA2 mutant, we identified a new player in the mycobacterial SecA2 pathway that we named SatS for SecA2 (two) Suppressor. In M. tuberculosis, SatS is required for the export of a subset of SecA2 substrates and for growth in macrophages. We further identify a role for SatS as a protein export chaperone. SatS exhibits multiple properties of a chaperone, including the ability to bind to and protect substrates from aggregation. Our structural studies of SatS reveal a distinct combination of a new fold and hydrophobic grooves resembling preprotein-binding sites of the SecB chaperone. These results are significant in better defining a molecular pathway for M. tuberculosis pathogenesis and in expanding our appreciation of the diversity among chaperones and protein export systems.
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Affiliation(s)
- Brittany K Miller
- Department of Microbiology and ImmunologyUniversity of North Carolina at Chapel HillNorth CarolinaUnited States
| | - Ryan Hughes
- Department of Biochemistry and BiophysicsTexas A&M UniversityCollege StationUnited States
| | - Lauren S Ligon
- Department of Microbiology and ImmunologyUniversity of North Carolina at Chapel HillNorth CarolinaUnited States
| | - Nathan W Rigel
- Department of Microbiology and ImmunologyUniversity of North Carolina at Chapel HillNorth CarolinaUnited States
| | - Seidu Malik
- Department of Microbiology and ImmunologyUniversity of North Carolina at Chapel HillNorth CarolinaUnited States
| | - Brandon R Anjuwon-Foster
- Department of Microbiology and ImmunologyUniversity of North Carolina at Chapel HillNorth CarolinaUnited States
| | - James C Sacchettini
- Department of Biochemistry and BiophysicsTexas A&M UniversityCollege StationUnited States
| | - Miriam Braunstein
- Department of Microbiology and ImmunologyUniversity of North Carolina at Chapel HillNorth CarolinaUnited States
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7
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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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8
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Cossé MM, Barta ML, Fisher DJ, Oesterlin LK, Niragire B, Perrinet S, Millot GA, Hefty PS, Subtil A. The Loss of Expression of a Single Type 3 Effector (CT622) Strongly Reduces Chlamydia trachomatis Infectivity and Growth. Front Cell Infect Microbiol 2018; 8:145. [PMID: 29868501 PMCID: PMC5962693 DOI: 10.3389/fcimb.2018.00145] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Accepted: 04/20/2018] [Indexed: 12/20/2022] Open
Abstract
Invasion of epithelial cells by the obligate intracellular bacterium Chlamydia trachomatis results in its enclosure inside a membrane-bound compartment termed an inclusion. The bacterium quickly begins manipulating interactions between host intracellular trafficking and the inclusion interface, diverging from the endocytic pathway and escaping lysosomal fusion. We have identified a previously uncharacterized protein, CT622, unique to the Chlamydiaceae, in the absence of which most bacteria failed to establish a successful infection. CT622 is abundant in the infectious form of the bacteria, in which it associates with CT635, a putative novel chaperone protein. We show that CT622 is translocated into the host cytoplasm via type three secretion throughout the developmental cycle of the bacteria. Two separate domains of roughly equal size have been identified within CT622 and a 1.9 Å crystal structure of the C-terminal domain has been determined. Genetic disruption of ct622 expression resulted in a strong bacterial growth defect, which was due to deficiencies in proliferation and in the generation of infectious bacteria. Our results converge to identify CT622 as a secreted protein that plays multiple and crucial roles in the initiation and support of the C. trachomatis growth cycle. They reveal that genetic disruption of a single effector can deeply affect bacterial fitness.
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Affiliation(s)
- Mathilde M Cossé
- Unité de Biologie Cellulaire de l'Infection Microbienne, Institut Pasteur, Paris, France.,Centre National de la Recherche Scientifique UMR3691, Paris, France.,Collège Doctoral, Sorbonne Université, Paris, France
| | - Michael L Barta
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS, United States
| | - Derek J Fisher
- Department of Microbiology, Southern Illinois University, Carbondale, IL, United States
| | - Lena K Oesterlin
- Institut Curie, PSL Research University, Centre National de la Recherche Scientifique UMR 144, Molecular Mechanisms of Intracellular Transport, Paris, France
| | - Béatrice Niragire
- Unité de Biologie Cellulaire de l'Infection Microbienne, Institut Pasteur, Paris, France.,Centre National de la Recherche Scientifique UMR3691, Paris, France
| | - Stéphanie Perrinet
- Unité de Biologie Cellulaire de l'Infection Microbienne, Institut Pasteur, Paris, France.,Centre National de la Recherche Scientifique UMR3691, Paris, France
| | - Gaël A Millot
- Institut Pasteur-Bioinformatics and Biostatistics Hub-C3BI, USR3756 IP Centre National de la Recherche Scientifique, Paris, France
| | - P Scott Hefty
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS, United States
| | - Agathe Subtil
- Unité de Biologie Cellulaire de l'Infection Microbienne, Institut Pasteur, Paris, France.,Centre National de la Recherche Scientifique UMR3691, Paris, France
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9
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Runte CS, Jain U, Getz LJ, Secord S, Kuwae A, Abe A, LeBlanc JJ, Stadnyk AW, Kaper JB, Hansen AM, Thomas NA. Tandem tyrosine phosphosites in the Enteropathogenic Escherichia coli chaperone CesT are required for differential type III effector translocation and virulence. Mol Microbiol 2018; 108:536-550. [PMID: 29509331 DOI: 10.1111/mmi.13948] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/05/2018] [Indexed: 11/29/2022]
Abstract
Enteropathogenic Escherichia coli (EPEC) use a type 3 secretion system (T3SS) for injection of effectors into host cells and intestinal colonization. Here, we demonstrate that the multicargo chaperone CesT has two strictly conserved tyrosine phosphosites, Y152 and Y153 that regulate differential effector secretion in EPEC. Conservative substitution of both tyrosine residues to phenylalanine strongly attenuated EPEC type 3 effector injection into host cells, and limited Tir effector mediated intimate adherence during infection. EPEC expressing a CesT Y152F variant were deficient for NleA effector expression and exhibited significantly reduced translocation of NleA into host cells during infection. Other effectors were observed to be dependent on CesT Y152 for maximal translocation efficiency. Unexpectedly, EPEC expressing a CesT Y153F variant exhibited significantly enhanced effector translocation of many CesT-interacting effectors, further implicating phosphosites Y152 and Y153 in CesT functionality. A mouse infection model of intestinal disease using Citrobacter rodentium revealed that CesT tyrosine substitution variants displayed delayed colonization and were more rapidly cleared from the intestine. These data demonstrate genetically separable functions for tandem tyrosine phosphosites within CesT. Therefore, CesT via its C-terminal tyrosine phosphosites, has relevant roles beyond typical type III secretion chaperones that interact and stabilize effector proteins.
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Affiliation(s)
- Cameron S Runte
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Umang Jain
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Landon J Getz
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Sabrina Secord
- Department of Pediatrics, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Asaomi Kuwae
- Laboratory of Bacterial Infection, Graduate School of Infection Control Sciences, Kitasato University, Tokyo, Japan
| | - Akio Abe
- Laboratory of Bacterial Infection, Graduate School of Infection Control Sciences, Kitasato University, Tokyo, Japan
| | - Jason J LeBlanc
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Medicine, Division of Infectious Diseases, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Andrew W Stadnyk
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Pediatrics, Dalhousie University, Halifax, Nova Scotia, Canada
| | - James B Kaper
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Anne-Marie Hansen
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Nikhil A Thomas
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Medicine, Division of Infectious Diseases, Dalhousie University, Halifax, Nova Scotia, Canada
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10
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Castiblanco LF, Triplett LR, Sundin GW. Regulation of Effector Delivery by Type III Secretion Chaperone Proteins in Erwinia amylovora. Front Microbiol 2018; 9:146. [PMID: 29472907 PMCID: PMC5809446 DOI: 10.3389/fmicb.2018.00146] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 01/23/2018] [Indexed: 11/16/2022] Open
Abstract
Type III secretion (TTS) chaperones are critical for the delivery of many effector proteins from Gram-negative bacterial pathogens into host cells, functioning in the stabilization and hierarchical delivery of the effectors to the type III secretion system (TTSS). The plant pathogen Erwinia amylovora secretes at least four TTS effector proteins: DspE, Eop1, Eop3, and Eop4. DspE specifically interacts with the TTS chaperone protein DspF, which stabilizes the effector protein in the cytoplasm and promotes its efficient translocation through the TTSS. However, the role of E. amylovora chaperones in regulating the delivery of other secreted effectors is unknown. In this study, we identified functional interactions between the effector proteins DspE, Eop1, and Eop3 with the TTS chaperones DspF, Esc1 and Esc3 in yeast. Using site-directed mutagenesis, secretion, and translocation assays, we demonstrated that the three TTS chaperones have additive roles for the secretion and translocation of DspE into plant cells whereas DspF negatively affects the translocation of Eop1 and Eop3. Collectively, these results indicate that TTS chaperone proteins exhibit a cooperative behavior to orchestrate the effector secretion and translocation dynamics in E. amylovora.
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Affiliation(s)
- Luisa F Castiblanco
- Department of Plant, Soil and Microbial Sciences, Center for Microbial Pathogenesis, Michigan State University, East Lansing, MI, United States
| | - Lindsay R Triplett
- Department of Plant Pathology and Ecology, The Connecticut Agricultural Experiment Station, New Haven, CT, United States
| | - George W Sundin
- Department of Plant, Soil and Microbial Sciences, Center for Microbial Pathogenesis, Michigan State University, East Lansing, MI, United States
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11
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Scheibner F, Hartmann N, Hausner J, Lorenz C, Hoffmeister AK, Büttner D. The Type III Secretion Chaperone HpaB Controls the Translocation of Effector and Noneffector Proteins From Xanthomonas campestris pv. vesicatoria. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2018; 31:61-74. [PMID: 28771395 DOI: 10.1094/mpmi-06-17-0138-r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Pathogenicity of the gram-negative bacterium Xanthomonas campestris pv. vesicatoria depends on a type III secretion (T3S) system, which translocates effector proteins into plant cells. Effector proteins contain N-terminal T3S and translocation signals and interact with the T3S chaperone HpaB, which presumably escorts effectors to the secretion apparatus. The molecular mechanisms underlying the recognition of effectors by the T3S system are not yet understood. In the present study, we analyzed T3S and translocation signals in the type III effectors XopE2 and XopJ from X. campestris pv. vesicatoria. Both effectors contain minimal translocation signals, which are only recognized in the absence of HpaB. Additional N-terminal signals promote translocation of XopE2 and XopJ in the wild-type strain. The results of translocation and interaction studies revealed that the interaction of XopE2 and XopJ with HpaB and a predicted cytoplasmic substrate docking site of the T3S system is not sufficient for translocation. In agreement with this finding, we show that the presence of an artificial HpaB-binding site does not promote translocation of the noneffector XopA in the wild-type strain. Our data, therefore, suggest that the T3S chaperone HpaB not only acts as an escort protein but also controls the recognition of translocation signals.
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Affiliation(s)
- Felix Scheibner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany
| | - Nadine Hartmann
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany
| | - Jens Hausner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany
| | - Christian Lorenz
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany
| | - Anne-Katrin Hoffmeister
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany
| | - Daniela Büttner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany
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12
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Abstract
Type III secretion systems (T3SSs) are protein transport nanomachines that are found in Gram-negative bacterial pathogens and symbionts. Resembling molecular syringes, T3SSs form channels that cross the bacterial envelope and the host cell membrane, which enable bacteria to inject numerous effector proteins into the host cell cytoplasm and establish trans-kingdom interactions with diverse hosts. Recent advances in cryo-electron microscopy and integrative imaging have provided unprecedented views of the architecture and structure of T3SSs. Furthermore, genetic and molecular analyses have elucidated the functions of many effectors and key regulators of T3SS assembly and secretion hierarchy, which is the sequential order by which the protein substrates are secreted. As essential virulence factors, T3SSs are attractive targets for vaccines and therapeutics. This Review summarizes our current knowledge of the structure and function of this important protein secretion machinery. A greater understanding of T3SSs should aid mechanism-based drug design and facilitate their manipulation for biotechnological applications.
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13
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Kinoshita M, Nakanishi Y, Furukawa Y, Namba K, Imada K, Minamino T. Rearrangements of α-helical structures of FlgN chaperone control the binding affinity for its cognate substrates during flagellar type III export. Mol Microbiol 2016; 101:656-70. [PMID: 27178222 DOI: 10.1111/mmi.13415] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/05/2016] [Indexed: 11/29/2022]
Abstract
The bacterial flagellar type III export chaperones not only act as bodyguards to protect their cognate substrates from aggregation and proteolysis in the cytoplasm but also ensure the order of export through their interactions with an export gate protein FlhA. FlgN chaperone binds to FlgK and FlgL with nanomolar affinity and transfers them to FlhA for their efficient and rapid transport for the formation of the hook-filament junction zone. However, it remains unknown how FlgN releases FlgK and FlgL at the FlhA export gate platform in a timely manner. Here, we have solved the crystal structure of Salmonella FlgN at 2.3 Å resolution and carried out structure-based functional analyses. FlgN consists of three α helices, α1, α2 and α3. Helix α1 adopts two distinct, extended and bent conformations through the conformational change of N-loop between α1 and α2. The N-loop deletion not only increases the probability of FlgN dimer formation but also abolish the interaction between FlgN and FlgK. Highly conserved Asn-92, Asn-95 and Ile-103 residues in helix α3 are involved in the strong interaction with FlgK. We propose that the N-loop coordinates helical rearrangements of FlgN with the association and dissociation of its cognate substrates during their export.
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Affiliation(s)
- Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan.,Department of Macromolecular Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka, 560-0043, Japan
| | - Yuki Nakanishi
- Department of Macromolecular Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka, 560-0043, Japan
| | - Yukio Furukawa
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan.,Quantitative Biology Center, Riken, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Katsumi Imada
- Department of Macromolecular Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka, 560-0043, Japan
| | - Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
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14
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Lo Presti L, López Díaz C, Turrà D, Di Pietro A, Hampel M, Heimel K, Kahmann R. A conserved co-chaperone is required for virulence in fungal plant pathogens. THE NEW PHYTOLOGIST 2016; 209:1135-1148. [PMID: 26487566 DOI: 10.1111/nph.13703] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Accepted: 09/04/2015] [Indexed: 06/05/2023]
Abstract
The maize pathogenic fungus Ustilago maydis experiences endoplasmic reticulum (ER) stress during plant colonization and relies on the unfolded protein response (UPR) to cope with this stress. We identified the U. maydis co-chaperone, designated Dnj1, as part of this conserved cellular response to ER stress. ∆dnj1 cells are sensitive to the ER stressor tunicamycin and display a severe virulence defect in maize infection assays. A dnj1 mutant allele unable to stimulate the ATPase activity of chaperones phenocopies the null allele. A Dnj1-mCherry fusion protein localizes in the ER and interacts with the luminal chaperone Bip1. The Fusarium oxysporum Dnj1 ortholog contributes to the virulence of this fungal pathogen in tomato plants. Unlike the human ortholog, F. oxysporum Dnj1 partially rescues the virulence defect of the Ustilago dnj1 mutant. By enabling the fungus to restore ER homeostasis and maintain a high secretory activity, Dnj1 contributes to the establishment of a compatible interaction with the host. Dnj1 orthologs are present in many filamentous fungi, but are absent in budding and fission yeasts. We postulate a conserved and essential role during virulence for this class of co-chaperones.
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Affiliation(s)
- Libera Lo Presti
- Max Planck Institute for Terrestrial Microbiology, Karl-von Frisch-Strasse 10, 35043, Marburg, Germany
| | - Cristina López Díaz
- Departamento de Genética, Campus de Excelencia Internacional Agroalimentario ceiA3, Universidad de Córdoba, 14071, Cordoba, Spain
| | - David Turrà
- Departamento de Genética, Campus de Excelencia Internacional Agroalimentario ceiA3, Universidad de Córdoba, 14071, Cordoba, Spain
| | - Antonio Di Pietro
- Departamento de Genética, Campus de Excelencia Internacional Agroalimentario ceiA3, Universidad de Córdoba, 14071, Cordoba, Spain
| | - Martin Hampel
- Department of Molecular Microbiology and Genetics, Georg-August-Universität Göttingen, Grisebachstraße 8, 37077, Göttingen, Germany
| | - Kai Heimel
- Department of Molecular Microbiology and Genetics, Georg-August-Universität Göttingen, Grisebachstraße 8, 37077, Göttingen, Germany
| | - Regine Kahmann
- Max Planck Institute for Terrestrial Microbiology, Karl-von Frisch-Strasse 10, 35043, Marburg, Germany
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15
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Lonjon F, Turner M, Henry C, Rengel D, Lohou D, van de Kerkhove Q, Cazalé AC, Peeters N, Genin S, Vailleau F. Comparative Secretome Analysis of Ralstonia solanacearum Type 3 Secretion-Associated Mutants Reveals a Fine Control of Effector Delivery, Essential for Bacterial Pathogenicity. Mol Cell Proteomics 2015; 15:598-613. [PMID: 26637540 DOI: 10.1074/mcp.m115.051078] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Indexed: 12/21/2022] Open
Abstract
Ralstonia solanacearum, the causal agent of bacterial wilt, exerts its pathogenicity through more than a hundred secreted proteins, many of them depending directly on the functionality of a type 3 secretion system. To date, only few type 3 effectors have been identified as required for bacterial pathogenicity, notably because of redundancy among the large R. solanacearum effector repertoire. In order to identify groups of effectors collectively promoting disease on susceptible hosts, we investigated the role of putative post-translational regulators in the control of type 3 secretion. A shotgun secretome analysis with label-free quantification using tandem mass spectrometry was performed on the R. solanacearum GMI1000 strain. There were 228 proteins identified, among which a large proportion of type 3 effectors, called Rip (Ralstonia injected proteins). Thanks to this proteomic approach, RipBJ was identified as a new effector specifically secreted through type 3 secretion system and translocated into plant cells. A focused Rip secretome analysis using hpa (hypersensitive response and pathogenicity associated) mutants revealed a fine secretion regulation and specific subsets of Rips with different secretion patterns. We showed that a set of Rips (RipF1, RipW, RipX, RipAB, and RipAM) are secreted in an Hpa-independent manner. We hypothesize that these Rips could be preferentially involved in the first stages of type 3 secretion. In addition, the secretion of about thirty other Rips is controlled by HpaB and HpaG. HpaB, a candidate chaperone was shown to positively control secretion of numerous Rips, whereas HpaG was shown to act as a negative regulator of secretion. To evaluate the impact of altered type 3 effectors secretion on plant pathogenesis, the hpa mutants were assayed on several host plants. HpaB was required for bacterial pathogenicity on multiple hosts whereas HpaG was found to be specifically required for full R. solanacearum pathogenicity on the legume plant Medicago truncatula.
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Affiliation(s)
- Fabien Lonjon
- From the ‡INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, F-31326, France; §CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, F-31326, France
| | - Marie Turner
- From the ‡INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, F-31326, France; §CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, F-31326, France
| | - Céline Henry
- ¶PAPPSO, Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France
| | - David Rengel
- From the ‡INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, F-31326, France; §CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, F-31326, France
| | - David Lohou
- From the ‡INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, F-31326, France; §CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, F-31326, France
| | - Quitterie van de Kerkhove
- From the ‡INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, F-31326, France; §CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, F-31326, France
| | - Anne-Claire Cazalé
- From the ‡INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, F-31326, France; §CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, F-31326, France
| | - Nemo Peeters
- From the ‡INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, F-31326, France; §CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, F-31326, France
| | - Stéphane Genin
- From the ‡INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, F-31326, France; §CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, F-31326, France
| | - Fabienne Vailleau
- From the ‡INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, F-31326, France; §CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, F-31326, France; ‖Université de Toulouse; INP; ENSAT; 18 chemin de Borde Rouge, Castanet Tolosan, 31326, France
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16
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Eichinger V, Nussbaumer T, Platzer A, Jehl MA, Arnold R, Rattei T. EffectiveDB--updates and novel features for a better annotation of bacterial secreted proteins and Type III, IV, VI secretion systems. Nucleic Acids Res 2015; 44:D669-74. [PMID: 26590402 PMCID: PMC4702896 DOI: 10.1093/nar/gkv1269] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Accepted: 11/03/2015] [Indexed: 11/17/2022] Open
Abstract
Protein secretion systems play a key role in the interaction of bacteria and hosts. EffectiveDB (http://effectivedb.org) contains pre-calculated predictions of bacterial secreted proteins and of intact secretion systems. Here we describe a major update of the database, which was previously featured in the NAR Database Issue. EffectiveDB bundles various tools to recognize Type III secretion signals, conserved binding sites of Type III chaperones, Type IV secretion peptides, eukaryotic-like domains and subcellular targeting signals in the host. Beyond the analysis of arbitrary protein sequence collections, the new release of EffectiveDB also provides a ‘genome-mode’, in which protein sequences from nearly complete genomes or metagenomic bins can be screened for the presence of three important secretion systems (Type III, IV, VI). EffectiveDB contains pre-calculated predictions for currently 1677 bacterial genomes from the EggNOG 4.0 database and for additional bacterial genomes from NCBI RefSeq. The new, user-friendly and informative web portal offers a submission tool for running the EffectiveDB prediction tools on user-provided data.
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Affiliation(s)
- Valerie Eichinger
- Division of Computational System Biology, Department of Microbiology and Ecosystem Science, University of Vienna, 1090 Vienna, Austria
| | - Thomas Nussbaumer
- Division of Computational System Biology, Department of Microbiology and Ecosystem Science, University of Vienna, 1090 Vienna, Austria
| | - Alexander Platzer
- Division of Computational System Biology, Department of Microbiology and Ecosystem Science, University of Vienna, 1090 Vienna, Austria
| | - Marc-André Jehl
- Division of Computational System Biology, Department of Microbiology and Ecosystem Science, University of Vienna, 1090 Vienna, Austria
| | - Roland Arnold
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada
| | - Thomas Rattei
- Division of Computational System Biology, Department of Microbiology and Ecosystem Science, University of Vienna, 1090 Vienna, Austria
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17
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Jiménez-Guerrero I, Pérez-Montaño F, Medina C, Ollero FJ, López-Baena FJ. NopC Is a Rhizobium-Specific Type 3 Secretion System Effector Secreted by Sinorhizobium (Ensifer) fredii HH103. PLoS One 2015; 10:e0142866. [PMID: 26569401 PMCID: PMC4646503 DOI: 10.1371/journal.pone.0142866] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 10/27/2015] [Indexed: 12/19/2022] Open
Abstract
Sinorhizobium (Ensifer) fredii HH103 is a broad host-range nitrogen-fixing bacterium able to nodulate many legumes, including soybean. In several rhizobia, root nodulation is influenced by proteins secreted through the type 3 secretion system (T3SS). This specialized secretion apparatus is a common virulence mechanism of many plant and animal pathogenic bacteria that delivers proteins, called effectors, directly into the eukaryotic host cells where they interfere with signal transduction pathways and promote infection by suppressing host defenses. In rhizobia, secreted proteins, called nodulation outer proteins (Nops), are involved in host-range determination and symbiotic efficiency. S. fredii HH103 secretes at least eight Nops through the T3SS. Interestingly, there are Rhizobium-specific Nops, such as NopC, which do not have homologues in pathogenic bacteria. In this work we studied the S. fredii HH103 nopC gene and confirmed that its expression was regulated in a flavonoid-, NodD1- and TtsI-dependent manner. Besides, in vivo bioluminescent studies indicated that the S. fredii HH103 T3SS was expressed in young soybean nodules and adenylate cyclase assays confirmed that NopC was delivered directly into soybean root cells by means of the T3SS machinery. Finally, nodulation assays showed that NopC exerted a positive effect on symbiosis with Glycine max cv. Williams 82 and Vigna unguiculata. All these results indicate that NopC can be considered a Rhizobium-specific effector secreted by S. fredii HH103.
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Affiliation(s)
- Irene Jiménez-Guerrero
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | | | - Carlos Medina
- Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide, Consejo Superior de Investigaciones Científicas, Junta de Andalucía, Sevilla, Spain
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18
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Dai W, Li Z. Conserved type III secretion system exerts important roles in Chlamydia trachomatis. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2014; 7:5404-5414. [PMID: 25337183 PMCID: PMC4203154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 08/23/2014] [Indexed: 06/04/2023]
Abstract
Upon infection, Chlamydiae alter host cellular functions in a variety of ways. Chlamydial infection prevents host cell apoptosis, induces re-organization of the actin cytoskeleton and alters host cellular signaling mechanisms. Chlamydia is among the many pathogenic Gram-negative bacteria that employ the type III secretion system (T3SS) to overcome host defenses and exploit available resources. T3SS are used by many Gram-negative bacterial pathogens to manipulate eukaryotic host cells through the delivery of effector proteins into their cytosol and membranes. T3SS is an evolutionarily refined, virulence determinant of Gram-negative bacteria where more than 20 proteins form an apparatus, generally termed injectisome, to achieve the vectorial secretion and translocation of anti-host effector proteins. This review describes challenges and recent advances that have revealed how Chlamydia trachomatis utilizes diversification to produce a conserved T3SS that exerts an important role in Chlamydia trachomatis.
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Affiliation(s)
- Wenting Dai
- Pathogenic Biology Institute, School of Medicine, University of South China Hengyang City, Hunan Province, P. R. China
| | - Zhongyu Li
- Pathogenic Biology Institute, School of Medicine, University of South China Hengyang City, Hunan Province, P. R. China
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19
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Turco MM, Sousa MC. The structure and specificity of the type III secretion system effector NleC suggest a DNA mimicry mechanism of substrate recognition. Biochemistry 2014; 53:5131-9. [PMID: 25040221 PMCID: PMC4131895 DOI: 10.1021/bi500593e] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
![]()
Many pathogenic bacteria utilize
the type III secretion system
(T3SS) to translocate effector proteins directly into host cells,
facilitating colonization. In enterohemmorhagic Escherichia
coli (EHEC), a subset of T3SS effectors is essential for
suppression of the inflammatory response in hosts, including humans.
Identified as a zinc protease that cleaves NF-κB transcription
factors, NleC is one such effector. Here, we investigate NleC substrate
specificity, showing that four residues around the cleavage site in
the DNA-binding loop of the NF-κB subunit RelA strongly influence
the cleavage rate. Class I NF-κB subunit p50 is cleaved at a
reduced rate consistent with conservation of only three of these four
residues. However, peptides containing 10 residues on each side of
the scissile bond were not efficiently cleaved by NleC, indicating
that elements distal from the cleavage site are also important for
substrate recognition. We present the crystal structure of NleC and
show that it mimics DNA structurally and electrostatically. Consistent
with this model, mutation of phosphate-mimicking residues in NleC
reduces the level of RelA cleavage. We propose that global recognition
of NF-κB subunits by DNA mimicry combined with a high sequence
selectivity for the cleavage site results in exquisite NleC substrate
specificity. The structure also shows that despite undetectable similarity
of its sequence to those of other Zn2+ proteases beyond
its conserved HExxH Zn2+-binding motif, NleC is a member
of the Zincin protease superfamily, albeit divergent from its structural
homologues. In particular, NleC displays a modified Ψ-loop motif
that may be important for folding and refolding requirements implicit
in T3SS translocation.
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Affiliation(s)
- Michelle Marian Turco
- Department of Chemistry and Biochemistry, University of Colorado at Boulder , Boulder, Colorado 80309-0596, United States
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20
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Galán JE, Lara-Tejero M, Marlovits TC, Wagner S. Bacterial type III secretion systems: specialized nanomachines for protein delivery into target cells. Annu Rev Microbiol 2014; 68:415-38. [PMID: 25002086 DOI: 10.1146/annurev-micro-092412-155725] [Citation(s) in RCA: 367] [Impact Index Per Article: 36.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
One of the most exciting developments in the field of bacterial pathogenesis in recent years is the discovery that many pathogens utilize complex nanomachines to deliver bacterially encoded effector proteins into target eukaryotic cells. These effector proteins modulate a variety of cellular functions for the pathogen's benefit. One of these protein-delivery machines is the type III secretion system (T3SS). T3SSs are widespread in nature and are encoded not only by bacteria pathogenic to vertebrates or plants but also by bacteria that are symbiotic to plants or insects. A central component of T3SSs is the needle complex, a supramolecular structure that mediates the passage of the secreted proteins across the bacterial envelope. Working in conjunction with several cytoplasmic components, the needle complex engages specific substrates in sequential order, moves them across the bacterial envelope, and ultimately delivers them into eukaryotic cells. The central role of T3SSs in pathogenesis makes them great targets for novel antimicrobial strategies.
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Affiliation(s)
- Jorge E Galán
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut 06536;
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21
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Waddell B, Southward CM, McKenna N, DeVinney R. Identification of VPA0451 as the specific chaperone for theVibrio parahaemolyticuschromosome 1 type III-secreted effector VPA0450. FEMS Microbiol Lett 2014; 353:141-50. [DOI: 10.1111/1574-6968.12416] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 03/04/2014] [Indexed: 11/30/2022] Open
Affiliation(s)
- Barbara Waddell
- Department of Microbiology, Immunology and Infectious Diseases; Snyder Institute for Chronic Diseases; University of Calgary; Calgary AB Canada
| | - Carolyn M. Southward
- Department of Microbiology, Immunology and Infectious Diseases; Snyder Institute for Chronic Diseases; University of Calgary; Calgary AB Canada
| | - Neil McKenna
- Department of Microbiology, Immunology and Infectious Diseases; Snyder Institute for Chronic Diseases; University of Calgary; Calgary AB Canada
| | - Rebekah DeVinney
- Department of Microbiology, Immunology and Infectious Diseases; Snyder Institute for Chronic Diseases; University of Calgary; Calgary AB Canada
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22
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Chen YS, Bastidas RJ, Saka HA, Carpenter VK, Richards KL, Plano GV, Valdivia RH. The Chlamydia trachomatis type III secretion chaperone Slc1 engages multiple early effectors, including TepP, a tyrosine-phosphorylated protein required for the recruitment of CrkI-II to nascent inclusions and innate immune signaling. PLoS Pathog 2014; 10:e1003954. [PMID: 24586162 PMCID: PMC3930595 DOI: 10.1371/journal.ppat.1003954] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 01/10/2014] [Indexed: 02/06/2023] Open
Abstract
Chlamydia trachomatis, the causative agent of trachoma and sexually transmitted infections, employs a type III secretion (T3S) system to deliver effector proteins into host epithelial cells to establish a replicative vacuole. Aside from the phosphoprotein TARP, a Chlamydia effector that promotes actin re-arrangements, very few factors mediating bacterial entry and early inclusion establishment have been characterized. Like many T3S effectors, TARP requires a chaperone (Slc1) for efficient translocation into host cells. In this study, we defined proteins that associate with Slc1 in invasive C. trachomatis elementary bodies (EB) by immunoprecipitation coupled with mass spectrometry. We identified Ct875, a new Slc1 client protein and T3S effector, which we renamed TepP (Translocated early phosphoprotein). We provide evidence that T3S effectors form large molecular weight complexes with Scl1 in vitro and that Slc1 enhances their T3S-dependent secretion in a heterologous Yersinia T3S system. We demonstrate that TepP is translocated early during bacterial entry into epithelial cells and is phosphorylated at tyrosine residues by host kinases. However, TepP phosphorylation occurs later than TARP, which together with the finding that Slc1 preferentially engages TARP in EBs leads us to postulate that these effectors are translocated into the host cell at different stages during C. trachomatis invasion. TepP co-immunoprecipitated with the scaffolding proteins CrkI-II during infection and Crk was recruited to EBs at entry sites where it remained associated with nascent inclusions. Importantly, C. trachomatis mutants lacking TepP failed to recruit CrkI-II to inclusions, providing genetic confirmation of a direct role for this effector in the recruitment of a host factor. Finally, endocervical epithelial cells infected with a tepP mutant showed altered expression of a subset of genes associated with innate immune responses. We propose a model wherein TepP acts downstream of TARP to recruit scaffolding proteins at entry sites to initiate and amplify signaling cascades important for the regulation of innate immune responses to Chlamydia.
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Affiliation(s)
- Yi-Shan Chen
- Department of Molecular Genetics and Microbiology and Center for Microbial Pathogenesis, Duke University Medical Center, Durham, North Carolina, United States of America
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Robert J. Bastidas
- Department of Molecular Genetics and Microbiology and Center for Microbial Pathogenesis, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Hector A. Saka
- Department of Molecular Genetics and Microbiology and Center for Microbial Pathogenesis, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Victoria K. Carpenter
- Department of Molecular Genetics and Microbiology and Center for Microbial Pathogenesis, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Kristian L. Richards
- Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, Florida, United States of America
| | - Gregory V. Plano
- Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, Florida, United States of America
| | - Raphael H. Valdivia
- Department of Molecular Genetics and Microbiology and Center for Microbial Pathogenesis, Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail:
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23
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Burkinshaw BJ, Strynadka NCJ. Assembly and structure of the T3SS. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1649-63. [PMID: 24512838 DOI: 10.1016/j.bbamcr.2014.01.035] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 01/27/2014] [Accepted: 01/29/2014] [Indexed: 02/06/2023]
Abstract
The Type III Secretion System (T3SS) is a multi-mega Dalton apparatus assembled from more than twenty components and is found in many species of animal and plant bacterial pathogens. The T3SS creates a contiguous channel through the bacterial and host membranes, allowing injection of specialized bacterial effector proteins directly to the host cell. In this review, we discuss our current understanding of T3SS assembly and structure, as well as highlight structurally characterized Salmonella effectors. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
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Affiliation(s)
- Brianne J Burkinshaw
- Department of Biochemistry and Molecular Biology, Center for Blood Research, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Natalie C J Strynadka
- Department of Biochemistry and Molecular Biology, Center for Blood Research, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
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24
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Dey S, Datta S. Interfacial residues of SpcS chaperone affects binding of effector toxin ExoT in Pseudomonas aeruginosa: novel insights from structural and computational studies. FEBS J 2014; 281:1267-80. [PMID: 24387107 DOI: 10.1111/febs.12704] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 12/06/2013] [Accepted: 12/23/2013] [Indexed: 12/12/2022]
Abstract
ExoT belongs to the family of type 3 secretion system (T3SS) effector toxins in Pseudomonas aeruginosa, known to be one of the major virulence determinant toxins that cause chronic and acute infections in immuno-compromised individuals, burn victims and cystic fibrosis patients. Here, we report the X-ray crystal structure of the amino terminal fragment of effector toxin ExoT, in complex with full-length homodimeric chaperone SpcS at 2.1 Å resolution. The full-length dimeric chaperone SpcS has the conserved α-β-β-β-α-β-β-α fold of class I chaperones, the characteristic hydrophobic patches for binding effector proteins and a conserved polar cavity at the dimeric interface. The stable crystallized amino terminal fragment of ExoT consists of a chaperone binding domain and a membrane localization domain that wraps around the dimeric chaperone. Site-directed mutagenesis experiments and a molecular dynamics study complement each other in revealing Asn65, Phe67 and Trp88 as critical dimeric interfacial residues that can strongly influence the effector-chaperone interactions.
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Affiliation(s)
- Supratim Dey
- Department of Structural Biology and Bioinformatics, Indian Institute of Chemical Biology, Kolkata, India
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25
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Abstract
Members of the order Chlamydiales comprise a group of exquisitely evolved parasites of eukaryotic hosts that extends from single-celled amoeba to mammals. The most notable are human pathogens and include the agent of oculogenital disease Chlamydia trachomatis, the respiratory pathogen C. pneumoniae, and the zoonotic agent C. psittaci. All of these species are obligate intracellular bacteria that develop within parasitophorous vesicles termed inclusions. This demanding lifestyle necessitates orchestrated entry into nonphagocytic cells, creation of a privileged intracellular niche, and subversion of potent host defenses. All chlamydial genomes contain the coding capacity for a nonflagellar type III secretion system, and this mechanism has arisen as an essential contributor to chlamydial virulence. The emergence of tractable approaches to the genetic manipulation of chlamydiae raises the possibility of explosive progress in understanding this important contributor to chlamydial pathogenesis. This minireview considers challenges and recent advances that have revealed how chlamydiae have maintained conserved aspects of T3S while exploiting diversification to yield a system that exerts a fundamental role in the unique biology of Chlamydia species.
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26
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Identification of novel type III secretion chaperone-substrate complexes of Chlamydia trachomatis. PLoS One 2013; 8:e56292. [PMID: 23431368 PMCID: PMC3576375 DOI: 10.1371/journal.pone.0056292] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 01/07/2013] [Indexed: 12/17/2022] Open
Abstract
Chlamydia trachomatis is an obligate intracellular bacterial pathogen of humans that uses a type III secretion (T3S) system to manipulate host cells through the delivery of effector proteins into their cytosol and membranes. The function of T3S systems depends on small bacterial cytosolic chaperone-like proteins, which bind T3S substrates and ensure their appropriate secretion. To find novel T3S chaperone-substrate complexes of C. trachomatis we first searched its genome for genes encoding proteins with features of T3S chaperones. We then systematically tested for interactions between candidate chaperones and chlamydial T3S substrates by bacterial two-hybrid. This revealed interactions between Slc1 (a known T3S chaperone) or CT584 and several T3S substrates. Co-immunoprecipation after protein expression in Yersinia enterocolitica and protein overlay binding assays indicated that Slc1 interacted with the N-terminal region of the known T3S substrates Tarp (a previously described substrate of Slc1), CT694, and CT695, and that CT584 interacted with a central region of CT082, which we identified as a C. trachomatis T3S substrate using Y. enterocolitica as a heterologous system. Further T3S assays in Yersinia indicated that Slc1 or CT584 increased the amount of secreted Tarp, CT694, and CT695, or CT082, respectively. Expression of CT584 increased the intra-bacterial stability of CT082, while Slc1 did not affect the stability of its substrates. Overall, this indicated that in C. trachomatis Slc1 is a chaperone of multiple T3S substrates and that CT584 is a chaperone of the newly identified T3S substrate CT082.
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A novel C-terminal region within the multicargo type III secretion chaperone CesT contributes to effector secretion. J Bacteriol 2012; 195:740-56. [PMID: 23222727 DOI: 10.1128/jb.01967-12] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The enteropathogenic Escherichia coli (EPEC) multicargo chaperone CesT interacts with at least 10 effector proteins and is central to pathogenesis. CesT has been implicated in coordinating effector hierarchy, although the mechanisms behind this regulation are poorly understood. To address this question, we set out to functionally characterize CesT with respect to roles in (i) effector binding, (ii) effector recruitment to the type III secretion system (T3SS), and (iii) effector translocation into host cells. A CesT variant expression library was screened in EPEC using a newly developed semi-high-throughput secretion assay. Among many deficient CesT variants, a predominant number were localized to a novel CesT C-terminal region. These CesT C-terminal variants exhibited normal effector binding yet reduced effector secretion levels. Structural correlation and thermal spectroscopy analyses of purified CesT variants implicated multiple surface-exposed residues, a terminal helix region, and a flexible C-terminal triple-serine stretch in effector secretion. Site-directed mutagenesis of the flexible CesT C-terminal triple-serine sequence produced differential effector secretion, implicating this region in secretion events. Infection assays further indicated that the C-terminal region of CesT was important for NleA translocation into host cells but was dispensable for Tir translocation. The findings implicate the CesT C terminus in effector secretion and contribute to a model for multiple-cargo chaperone function and effector translocation into host cells during infection.
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Role of EscP (Orf16) in injectisome biogenesis and regulation of type III protein secretion in enteropathogenic Escherichia coli. J Bacteriol 2012; 194:6029-45. [PMID: 22923600 DOI: 10.1128/jb.01215-12] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Enteropathogenic Escherichia coli employs a type III secretion system (T3SS) to translocate virulence effector proteins directly into enterocyte host cells, leading to diarrheal disease. The T3SS is encoded within the chromosomal locus of enterocyte effacement (LEE). The function of some of the LEE-encoded proteins remains unknown. Here we investigated the role of the Orf16 protein in T3SS biogenesis and function. An orf16 deletion mutant showed translocator and effector protein secretion profiles different from those of wild-type cells. The orf16 null strain produced T3S structures with abnormally long needles and filaments that caused weak hemolysis of red blood cells. Furthermore, the number of fully assembled T3SSs was also reduced in the orf16 mutant, indicating that Orf16, though not essential, is required for efficient T3SS assembly. Analysis of protein secretion revealed that Orf16 is a T3SS-secreted substrate and regulates the secretion of the inner rod component EscI. Both pulldown and yeast two-hybrid assays showed that Orf16 interacts with the C-terminal domain of an inner membrane component of the secretion apparatus, EscU; the inner rod protein EscI; the needle protein EscF; and the multieffector chaperone CesT. These results suggest that Orf16 regulates needle length and, along with EscU, participates in a substrate specificity switch from early substrates to translocators. Taken together, our results suggest that Orf16 acts as a molecular measuring device in a way similar to that of members of the Yersinia YscP and flagellar FliK protein family. Therefore, we propose that this protein be renamed EscP.
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