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Diepold A, Armitage JP. Type III secretion systems: the bacterial flagellum and the injectisome. Philos Trans R Soc Lond B Biol Sci 2016; 370:rstb.2015.0020. [PMID: 26370933 DOI: 10.1098/rstb.2015.0020] [Citation(s) in RCA: 139] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The flagellum and the injectisome are two of the most complex and fascinating bacterial nanomachines. At their core, they share a type III secretion system (T3SS), a transmembrane export complex that forms the extracellular appendages, the flagellar filament and the injectisome needle. Recent advances, combining structural biology, cryo-electron tomography, molecular genetics, in vivo imaging, bioinformatics and biophysics, have greatly increased our understanding of the T3SS, especially the structure of its transmembrane and cytosolic components, the transcriptional, post-transcriptional and functional regulation and the remarkable adaptivity of the system. This review aims to integrate these new findings into our current knowledge of the evolution, function, regulation and dynamics of the T3SS, and to highlight commonalities and differences between the two systems, as well as their potential applications.
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Affiliation(s)
- Andreas Diepold
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Judith P Armitage
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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102
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Amer AAA, Gurung JM, Costa TRD, Ruuth K, Zavialov AV, Forsberg Å, Francis MS. YopN and TyeA Hydrophobic Contacts Required for Regulating Ysc-Yop Type III Secretion Activity by Yersinia pseudotuberculosis. Front Cell Infect Microbiol 2016; 6:66. [PMID: 27446813 PMCID: PMC4914553 DOI: 10.3389/fcimb.2016.00066] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 06/03/2016] [Indexed: 11/29/2022] Open
Abstract
Yersinia bacteria target Yop effector toxins to the interior of host immune cells by the Ysc-Yop type III secretion system. A YopN-TyeA heterodimer is central to controlling Ysc-Yop targeting activity. A + 1 frameshift event in the 3-prime end of yopN can also produce a singular secreted YopN-TyeA polypeptide that retains some regulatory function even though the C-terminal coding sequence of this YopN differs greatly from wild type. Thus, this YopN C-terminal segment was analyzed for its role in type III secretion control. Bacteria producing YopN truncated after residue 278, or with altered sequence between residues 279 and 287, had lost type III secretion control and function. In contrast, YopN variants with manipulated sequence beyond residue 287 maintained full control and function. Scrutiny of the YopN-TyeA complex structure revealed that residue W279 functioned as a likely hydrophobic contact site with TyeA. Indeed, a YopNW279G mutant lost all ability to bind TyeA. The TyeA residue F8 was also critical for reciprocal YopN binding. Thus, we conclude that specific hydrophobic contacts between opposing YopN and TyeA termini establishes a complex needed for regulating Ysc-Yop activity.
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Affiliation(s)
- Ayad A A Amer
- Department of Molecular Biology, Umeå UniversityUmeå, Sweden; Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden
| | - Jyoti M Gurung
- Department of Molecular Biology, Umeå UniversityUmeå, Sweden; Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden
| | - Tiago R D Costa
- Department of Molecular Biology, Umeå UniversityUmeå, Sweden; Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden
| | - Kristina Ruuth
- Department of Molecular Biology, Umeå UniversityUmeå, Sweden; Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden
| | - Anton V Zavialov
- Department of Molecular Biology, Uppsala BioCenter, Swedish University of Agricultural SciencesUppsala, Sweden; Joint Biotechnology Laboratory, Department of Chemistry, University of TurkuTurku, Finland
| | - Åke Forsberg
- Department of Molecular Biology, Umeå UniversityUmeå, Sweden; Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden; Laboratory for Molecular Infection Medicine Sweden, Umeå UniversityUmeå, Sweden
| | - Matthew S Francis
- Department of Molecular Biology, Umeå UniversityUmeå, Sweden; Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden
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103
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Scheibner F, Schulz S, Hausner J, Marillonnet S, Büttner D. Type III-Dependent Translocation of HrpB2 by a Nonpathogenic hpaABC Mutant of the Plant-Pathogenic Bacterium Xanthomonas campestris pv. vesicatoria. Appl Environ Microbiol 2016; 82:3331-3347. [PMID: 27016569 PMCID: PMC4959247 DOI: 10.1128/aem.00537-16] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 03/21/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria employs a type III secretion (T3S) system to translocate effector proteins into plant cells. The T3S apparatus spans both bacterial membranes and is associated with an extracellular pilus and a channel-like translocon in the host plasma membrane. T3S is controlled by the switch protein HpaC, which suppresses secretion and translocation of the predicted inner rod protein HrpB2 and promotes secretion of translocon and effector proteins. We previously reported that HrpB2 interacts with HpaC and the cytoplasmic domain of the inner membrane protein HrcU (C. Lorenz, S. Schulz, T. Wolsch, O. Rossier, U. Bonas, and D. Büttner, PLoS Pathog 4:e1000094, 2008, http://dx.doi.org/10.1371/journal.ppat.1000094). However, the molecular mechanisms underlying the control of HrpB2 secretion are not yet understood. Here, we located a T3S and translocation signal in the N-terminal 40 amino acids of HrpB2. The results of complementation experiments with HrpB2 deletion derivatives revealed that the T3S signal of HrpB2 is essential for protein function. Furthermore, interaction studies showed that the N-terminal region of HrpB2 interacts with the cytoplasmic domain of HrcU, suggesting that the T3S signal of HrpB2 contributes to substrate docking. Translocation of HrpB2 is suppressed not only by HpaC but also by the T3S chaperone HpaB and its secreted regulator, HpaA. Deletion of hpaA, hpaB, and hpaC leads to a loss of pathogenicity but allows the translocation of fusion proteins between the HrpB2 T3S signal and effector proteins into leaves of host and non-host plants. IMPORTANCE The T3S system of the plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria is essential for pathogenicity and delivers effector proteins into plant cells. T3S depends on HrpB2, which is a component of the predicted periplasmic inner rod structure of the secretion apparatus. HrpB2 is secreted during the early stages of the secretion process and interacts with the cytoplasmic domain of the inner membrane protein HrcU. Here, we localized the secretion and translocation signal of HrpB2 in the N-terminal 40 amino acids and show that this region is sufficient for the interaction with the cytoplasmic domain of HrcU. Our results suggest that the T3S signal of HrpB2 is required for the docking of HrpB2 to the secretion apparatus. Furthermore, we provide experimental evidence that the N-terminal region of HrpB2 is sufficient to target effector proteins for translocation in a nonpathogenic X. campestris pv. vesicatoria strain.
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Affiliation(s)
- Felix Scheibner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Steve Schulz
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Jens Hausner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | | | - Daniela Büttner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
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104
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Sun WSW, Chen JW, Wu YC, Tsai HY, Kuo YL, Syu WJ. Expression Regulation of Polycistronic lee3 Genes of Enterohaemorrhagic Escherichia coli. PLoS One 2016; 11:e0155578. [PMID: 27182989 PMCID: PMC4868261 DOI: 10.1371/journal.pone.0155578] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 05/01/2016] [Indexed: 01/21/2023] Open
Abstract
Enterohaemorrhagic Escherichia coli O157:H7 (EHEC) carries a pathogenic island LEE that is consisted mainly of five polycistronic operons. In the lee3 operon, mpc is the first gene and has been reported to down regulate the type-3 secretion system of EHEC when its gene product is over-expressed. Furthermore, mpc has been suggested to have a regulation function via translation but the mechanism remains unclear. To clarify this hypothesis, we dissected the polycistron and examined the translated products. We conclude that translation of mpc detrimentally governs the translation of the second gene, escV, which in turn affects the translation of the third gene, escN. Then sequentially, escN affects the expression of the downstream genes. Furthermore, we located a critical cis element within the mpc open-reading frame that plays a negative role in the translation-dependent regulation of lee3. Using qRT-PCR, we found that the amount of mpc RNA transcript present in EHEC was relatively limited when compared to any other genes within lee3. Taken together, when the transcription of LEE is activated, expression of mpc is tightly controlled by a restriction of the RNA transcript of mpc, translation of which is then critical for the efficient production of the operon’s downstream gene products.
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Affiliation(s)
- Wei-Sheng W. Sun
- Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei, Taiwan, R.O.C
- Taiwan International Graduate Program in Molecular Medicine, Academia Sinica, Taipei, Taiwan, R.O.C
| | - Jenn-Wei Chen
- Department of Microbiology and Immunology, National Cheng-Kung University, Tainan, Taiwan, R.O.C
| | - Yi-Chih Wu
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan, R.O.C
| | - Hsing-Yuan Tsai
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan, R.O.C
| | - Yu-Liang Kuo
- Department of Medical Imaging and Radiological Sciences, Chung Shan Medical University, Taichung, Taiwan, R.O.C
- Department of Medical Imaging, Chung Shan Medical University Hospital, Taichung, Taiwan, R.O.C
| | - Wan-Jr Syu
- Taiwan International Graduate Program in Molecular Medicine, Academia Sinica, Taipei, Taiwan, R.O.C
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan, R.O.C
- * E-mail:
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105
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Shen DK, Blocker AJ. MxiA, MxiC and IpaD Regulate Substrate Selection and Secretion Mode in the T3SS of Shigella flexneri. PLoS One 2016; 11:e0155141. [PMID: 27171191 PMCID: PMC4865121 DOI: 10.1371/journal.pone.0155141] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 04/25/2016] [Indexed: 11/19/2022] Open
Abstract
Type III secretion systems (T3SSs) are central virulence devices for many Gram-negative bacterial pathogens of humans, animals & plants. Upon physical contact with eukaryotic host cells, they translocate virulence-mediating proteins, known as effectors, into them during infection. T3SSs are gated from the outside by host-cell contact and from the inside via two cytoplasmic negative regulators, MxiC and IpaD in Shigella flexneri, which together control the effector secretion hierarchy. Their absence leads to premature and increased secretion of effectors. Here, we investigated where and how these regulators act. We demonstrate that the T3SS inner membrane export apparatus protein MxiA plays a role in substrate selection. Indeed, using a genetic screen, we identified two amino acids located on the surface of MxiA's cytoplasmic region (MxiAC) which, when mutated, upregulate late effector expression and, in the case of MxiAI674V, also secretion. The cytoplasmic region of MxiA, but not MxiAN373D and MxiAI674V, interacts directly with the C-terminus of MxiC in a two-hybrid assay. Efficient T3S requires a cytoplasmic ATPase and the proton motive force (PMF), which is composed of the ΔΨ and the ΔpH. MxiA family proteins and their regulators are implicated in utilization of the PMF for protein export. However, our MxiA point mutants show similar PMF utilisation to wild-type, requiring primarily the ΔΨ. On the other hand, lack of MxiC or IpaD, renders the faster T3S seen increasingly dependent on the ΔpH. Therefore, MxiA, MxiC and IpaD act together to regulate substrate selection and secretion mode in the T3SS of Shigella flexneri.
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Affiliation(s)
- Da-Kang Shen
- School of Cellular & Molecular Medicine, Faculty of Biomedical Sciences, University of Bristol, Bristol, United Kingdom
| | - Ariel J. Blocker
- Schools of Cellular & Molecular Medicine and Biochemistry, Faculty of Biomedical Sciences, University of Bristol, Bristol, United Kingdom
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106
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Mutagenesis and Functional Analysis of the Bacterial Arginine Glycosyltransferase Effector NleB1 from Enteropathogenic Escherichia coli. Infect Immun 2016; 84:1346-1360. [PMID: 26883593 DOI: 10.1128/iai.01523-15] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 02/10/2016] [Indexed: 01/07/2023] Open
Abstract
Enteropathogenic Escherichia coli (EPEC) interferes with host cell signaling by injecting virulence effector proteins into enterocytes via a type III secretion system (T3SS). NleB1 is a novel T3SS glycosyltransferase effector from EPEC that transfers a single N-acetylglucosamine (GlcNAc) moiety in an N-glycosidic linkage to Arg(117) of the Fas-associated death domain protein (FADD). GlcNAcylation of FADD prevents the assembly of the canonical death-inducing signaling complex and inhibits Fas ligand (FasL)-induced cell death. Apart from the DXD catalytic motif of NleB1, little is known about other functional sites in the enzyme. In the present study, members of a library of 22 random transposon-based, in-frame, linker insertion mutants of NleB1 were tested for their ability to block caspase-8 activation in response to FasL during EPEC infection. Immunoblot analysis of caspase-8 cleavage showed that 17 mutant derivatives of NleB1, including the catalytic DXD mutant, did not inhibit caspase-8 activation. Regions of interest around the insertion sites with multiple or single amino acid substitutions were examined further. Coimmunoprecipitation studies of 34 site-directed mutants showed that the NleB1 derivatives with the E253A, Y219A, and PILN(63-66)AAAA (in which the PILN motif from residues 63 to 66 was changed to AAAA) mutations bound to but did not GlcNAcylate FADD. A further mutant derivative, the PDG(236-238)AAA mutant, did not bind to or GlcNAcylate FADD. Infection of mice with the EPEC-like mouse pathogen Citrobacter rodentium expressing NleBE253A and NleBY219A showed that these strains were attenuated, indicating the importance of residues E253 and Y219 in NleB1 virulence in vivo In summary, we identified new amino acid residues critical for NleB1 activity and confirmed that these are required for the virulence function of NleB1.
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107
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Abstract
Cryo-electron tomography (cryo-ET) has emerged as a leading technique for three-dimensional visualization of large macromolecular complexes and their conformational changes in their native cellular environment. However, the resolution and potential applications of cryo-ET are fundamentally limited by specimen thickness, preventing high-resolution in situ visualization of macromolecular structures in many bacteria (such as Escherichia coli and Salmonella enterica). Minicells, which were discovered nearly 50 years ago, have recently been exploited as model systems to visualize molecular machines in situ, due to their smaller size and other unique properties. In this review, we discuss strategies for producing minicells and highlight their use in the study of chemotactic signaling, protein secretion, and DNA translocation. In combination with powerful genetic tools and advanced imaging techniques, minicells provide a springboard for in-depth structural studies of bacterial macromolecular complexes in situ and therefore offer a unique approach for gaining novel structural insights into many important processes in microbiology.
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108
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Gold V, Kudryashev M. Recent progress in structure and dynamics of dual-membrane-spanning bacterial nanomachines. Curr Opin Struct Biol 2016; 39:1-7. [PMID: 26995496 DOI: 10.1016/j.sbi.2016.03.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 03/03/2016] [Accepted: 03/04/2016] [Indexed: 02/05/2023]
Abstract
Advances in hard-ware and soft-ware for electron cryo-microscopy and tomography have provided unprecedented structural insights into large protein complexes in bacterial membranes. Tomographic volumes of native complexes in situ, combined with other structural and functional data, reveal functionally important conformational changes. Here, we review recent progress in elucidating the structure and mechanism of dual-membrane-spanning nanomachines involved in bacterial motility, adhesion, pathogenesis and biofilm formation, including the type IV pilus assembly machinery and the type III and VI secretions systems. We highlight how these new structural data shed light on the assembly and action of such machines and discuss future directions for more detailed mechanistic understanding of these massive, fascinating complexes.
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Affiliation(s)
- Vicki Gold
- Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany.
| | - Mikhail Kudryashev
- Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany; Buchmann Institute for Molecular Life Sciences, Goethe University of Frankfurt, Max-von-Laue Str. 17, 60438 Frankfurt am Main, Germany.
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109
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Campbell-Valois FX, Pontier SM. Implications of Spatiotemporal Regulation of Shigella flexneri Type Three Secretion Activity on Effector Functions: Think Globally, Act Locally. Front Cell Infect Microbiol 2016; 6:28. [PMID: 27014638 PMCID: PMC4783576 DOI: 10.3389/fcimb.2016.00028] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 02/23/2016] [Indexed: 11/13/2022] Open
Abstract
Shigella spp. are Gram-negative bacterial pathogens that infect human colonic epithelia and cause bacterial dysentery. These bacteria express multiple copies of a syringe-like protein complex, the Type Three Secretion apparatus (T3SA), which is instrumental in the etiology of the disease. The T3SA triggers the plasma membrane (PM) engulfment of the bacteria by host cells during the initial entry process. It then enables bacteria to escape the resulting phagocytic-like vacuole. Freed bacteria form actin comets to move in the cytoplasm, which provokes bacterial collision with the inner leaflet of the PM. This phenomenon culminates in T3SA-dependent secondary uptake and vacuolar rupture in neighboring cells in a process akin to what is observed during entry and named cell-to-cell spread. The activity of the T3SA of Shigella flexneri was recently demonstrated to display an on/off regulation during the infection. While the T3SA is active when bacteria are in contact with PM-derived compartments, it switches to an inactive state when bacteria are released within the cytosol. These observations indicate that effector proteins transiting through the T3SA are therefore translocated in a highly time and space constrained fashion, likely impacting on their cellular distribution. Herein, we present what is currently known about the composition, the assembly and the regulation of the T3SA activity and discuss the consequences of the on/off regulation of T3SA on Shigella effector properties and functions during the infection. Specific examples that will be developed include the role of effectors IcsB and VirA in the escape from LC3/ATG8-positive vacuoles formed during cell-to-cell spread and of IpaJ protease activity against N-miristoylated proteins. The conservation of a similar regulation of T3SA activity in other pathogens such as Salmonella or Enteropathogenic Escherichia coli will also be briefly discussed.
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Affiliation(s)
- F-X Campbell-Valois
- Department of Chemistry and Biomolecular Sciences, University of Ottawa Ottawa, ON, Canada
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110
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Russo BC, Stamm LM, Raaben M, Kim CM, Kahoud E, Robinson LR, Bose S, Queiroz AL, Herrera BB, Baxt LA, Mor-Vaknin N, Fu Y, Molina G, Markovitz DM, Whelan SP, Goldberg MB. Intermediate filaments enable pathogen docking to trigger type 3 effector translocation. Nat Microbiol 2016; 1:16025. [PMID: 27572444 PMCID: PMC5006386 DOI: 10.1038/nmicrobiol.2016.25] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 02/03/2016] [Indexed: 12/31/2022]
Abstract
Type 3 secretion systems (T3SSs) of bacterial pathogens translocate bacterial effector proteins that mediate disease into the eukaryotic cytosol. Effectors traverse the plasma membrane through a translocon pore formed by T3SS proteins. In a genome-wide selection, we identified the intermediate filament vimentin as required for infection by the T3SS-dependent pathogen S. flexneri. We found that vimentin is required for efficient T3SS translocation of effectors by S. flexneri and other pathogens that use T3SS, Salmonella enterica serovar Typhimurium and Yersinia pseudotuberculosis. Vimentin and the intestinal epithelial intermediate filament keratin 18 interact with the C-terminus of the Shigella translocon pore protein IpaC. Vimentin and its interaction with IpaC are dispensable for pore formation, but are required for stable docking of S. flexneri to cells; moreover, stable docking triggers effector secretion. These findings establish that stable docking of the bacterium specifically requires intermediate filaments, is a process distinct from pore formation, and is a prerequisite for effector secretion.
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Affiliation(s)
- Brian C. Russo
- Division of Infectious Diseases, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Luisa M. Stamm
- Division of Infectious Diseases, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Matthijs Raaben
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Caleb M. Kim
- Division of Infectious Diseases, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Emily Kahoud
- Division of Infectious Diseases, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Lindsey R. Robinson
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Sayantan Bose
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Ana L. Queiroz
- Division of Infectious Diseases, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Bobby Brooke Herrera
- Division of Infectious Diseases, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Leigh A. Baxt
- Division of Infectious Diseases, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Nirit Mor-Vaknin
- Division of Infectious Diseases, Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, MI 48109, USA
| | - Yang Fu
- Division of Infectious Diseases, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Gabriel Molina
- Division of Infectious Diseases, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - David M. Markovitz
- Division of Infectious Diseases, Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, MI 48109, USA
| | - Sean P. Whelan
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Marcia B. Goldberg
- Division of Infectious Diseases, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA
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111
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Zilkenat S, Franz-Wachtel M, Stierhof YD, Galán JE, Macek B, Wagner S. Determination of the Stoichiometry of the Complete Bacterial Type III Secretion Needle Complex Using a Combined Quantitative Proteomic Approach. Mol Cell Proteomics 2016; 15:1598-609. [PMID: 26900162 DOI: 10.1074/mcp.m115.056598] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Indexed: 11/06/2022] Open
Abstract
Precisely knowing the stoichiometry of their components is critical for investigating structure, assembly, and function of macromolecular machines. This has remained a technical challenge in particular for large, hydrophobic membrane-spanning protein complexes. Here, we determined the stoichiometry of a type III secretion system of Salmonella enterica serovar Typhimurium using two complementary protocols of gentle complex purification combined with peptide concatenated standard and synthetic stable isotope-labeled peptide-based mass spectrometry. Bacterial type III secretion systems are cell envelope-spanning effector protein-delivery machines essential for colonization and survival of many Gram-negative pathogens and symbionts. The membrane-embedded core unit of these secretion systems, termed the needle complex, is composed of a base that anchors the machinery to the inner and outer membranes, a hollow filament formed by inner rod and needle subunits that serves as conduit for substrate proteins, and a membrane-embedded export apparatus facilitating substrate translocation. Structural analyses have revealed the stoichiometry of the components of the base, but the stoichiometry of the essential hydrophobic export apparatus components and of the inner rod protein remain unknown. Here, we provide evidence that the export apparatus of type III secretion systems contains five SpaP, one SpaQ, one SpaR, and one SpaS. We confirmed that the previously suggested stoichiometry of nine InvA is valid for assembled needle complexes and describe a loose association of InvA with other needle complex components that may reflect its function. Furthermore, we present evidence that not more than six PrgJ form the inner rod of the needle complex. Providing this structural information will facilitate efforts to obtain an atomic view of type III secretion systems and foster our understanding of the function of these and related flagellar machines. Given that other virulence-associated bacterial secretion systems are similar in their overall buildup and complexity, the presented approach may also enable their stoichiometry elucidation.
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Affiliation(s)
- Susann Zilkenat
- From the ‡University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Section of Cellular and Molecular Microbiology, Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
| | - Mirita Franz-Wachtel
- §University of Tübingen, Proteome Center Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - York-Dieter Stierhof
- ¶University of Tübingen, Center for Plant Molecular Biology (ZMBP), Auf der Morgenstelle 32, 72076 Tübingen, Germany
| | - Jorge E Galán
- ‖Yale University School of Medicine, Department of Microbial Pathogenesis, 295 Congress Ave, New Haven, CT
| | - Boris Macek
- §University of Tübingen, Proteome Center Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Samuel Wagner
- From the ‡University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Section of Cellular and Molecular Microbiology, Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany; **German Center for Infection Research (DZIF), Partner-site Tübingen, Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
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112
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Picking WL, Picking WD. The Many Faces of IpaB. Front Cell Infect Microbiol 2016; 6:12. [PMID: 26904511 PMCID: PMC4746235 DOI: 10.3389/fcimb.2016.00012] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 01/22/2016] [Indexed: 12/15/2022] Open
Abstract
The type III secretion system (T3SS) is Shigella's most important virulence factor. The T3SS apparatus (T3SA) is comprised of an envelope-spanning basal body and an external needle topped by a tip complex protein called IpaD. This nanomachine is used to deliver effector proteins into host cells to promote pathogen entry. A key component of the matured T3SS needle tip complex is the translocator protein IpaB. IpaB can exist in multiple states when prepared as a recombinant protein, however, it has also been described as having additional roles in Shigella pathogenesis. This mini-review will briefly describe some of the features of IpaB as a T3SS needle tip protein, as a pore-forming translocator protein and as an effector protein. Reflection on the potential importance of the different in vitro states of IpaB on its function and importance in serotype-independent vaccines is also provided.
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Affiliation(s)
- Wendy L Picking
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of Kansas Lawrence, KS, USA
| | - William D Picking
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of Kansas Lawrence, KS, USA
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Portaliou AG, Tsolis KC, Loos MS, Zorzini V, Economou A. Type III Secretion: Building and Operating a Remarkable Nanomachine. Trends Biochem Sci 2016; 41:175-189. [DOI: 10.1016/j.tibs.2015.09.005] [Citation(s) in RCA: 121] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Revised: 09/16/2015] [Accepted: 09/18/2015] [Indexed: 12/21/2022]
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114
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McDowell MA, Marcoux J, McVicker G, Johnson S, Fong YH, Stevens R, Bowman LAH, Degiacomi MT, Yan J, Wise A, Friede ME, Benesch JLP, Deane JE, Tang CM, Robinson CV, Lea SM. Characterisation of Shigella Spa33 and Thermotoga FliM/N reveals a new model for C-ring assembly in T3SS. Mol Microbiol 2015; 99:749-66. [PMID: 26538516 PMCID: PMC4832279 DOI: 10.1111/mmi.13267] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2015] [Indexed: 11/06/2022]
Abstract
Flagellar type III secretion systems (T3SS) contain an essential cytoplasmic‐ring (C‐ring) largely composed of two proteins FliM and FliN, whereas an analogous substructure for the closely related non‐flagellar (NF) T3SS has not been observed in situ. We show that the spa33 gene encoding the putative NF‐T3SS C‐ring component in Shigella flexneri is alternatively translated to produce both full‐length (Spa33‐FL) and a short variant (Spa33‐C), with both required for secretion. They associate in a 1:2 complex (Spa33‐FL/C2) that further oligomerises into elongated arrays in vitro. The structure of Spa33‐C2 and identification of an unexpected intramolecular pseudodimer in Spa33‐FL reveal a molecular model for their higher order assembly within NF‐T3SS. Spa33‐FL and Spa33‐C are identified as functional counterparts of a FliM–FliN fusion and free FliN respectively. Furthermore, we show that Thermotoga maritima
FliM and FliN form a 1:3 complex structurally equivalent to Spa33‐FL/C2, allowing us to propose a unified model for C‐ring assembly by NF‐T3SS and flagellar‐T3SS.
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Affiliation(s)
| | - Julien Marcoux
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Gareth McVicker
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Steven Johnson
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Yu Hang Fong
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Rebecca Stevens
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Lesley A H Bowman
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | | | - Jun Yan
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Adam Wise
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Miriam E Friede
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | | | - Janet E Deane
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Christoph M Tang
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | | | - Susan M Lea
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
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115
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Structure of a bacterial type III secretion system in contact with a host membrane in situ. Nat Commun 2015; 6:10114. [PMID: 26656452 PMCID: PMC4682100 DOI: 10.1038/ncomms10114] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 11/03/2015] [Indexed: 12/16/2022] Open
Abstract
Many bacterial pathogens of animals and plants use a conserved type III secretion system (T3SS) to inject virulence effector proteins directly into eukaryotic cells to subvert host functions. Contact with host membranes is critical for T3SS activation, yet little is known about T3SS architecture in this state or the conformational changes that drive effector translocation. Here we use cryo-electron tomography and sub-tomogram averaging to derive the intact structure of the primordial Chlamydia trachomatis T3SS in the presence and absence of host membrane contact. Comparison of the averaged structures demonstrates a marked compaction of the basal body (4 nm) occurs when the needle tip contacts the host cell membrane. This compaction is coupled to a stabilization of the cytosolic sorting platform–ATPase. Our findings reveal the first structure of a bacterial T3SS from a major human pathogen engaged with a eukaryotic host, and reveal striking ‘pump-action' conformational changes that underpin effector injection. Bacterial type III secretion systems (T3SSs) inject virulence effector proteins into eukaryotic cells and are activated by host membrane contact. Here the authors report the in situ structure of the Chlamydia trachomatis T3SS in the presence or absence of host membrane, and observe compaction of the basal body embedded in the bacterial envelope.
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116
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Role of autocleavage in the function of a type III secretion specificity switch protein in Salmonella enterica serovar Typhimurium. mBio 2015; 6:e01459-15. [PMID: 26463164 PMCID: PMC4620466 DOI: 10.1128/mbio.01459-15] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Type III secretion systems (T3SSs) are multiprotein machines employed by many Gram-negative bacteria to inject bacterial effector proteins into eukaryotic host cells to promote bacterial survival and colonization. The core unit of T3SSs is the needle complex, a supramolecular structure that mediates the passage of the secreted proteins through the bacterial envelope. A distinct feature of the T3SS is that protein export occurs in a strictly hierarchical manner in which proteins destined to form the needle complex filament and associated structures are secreted first, followed by the secretion of effectors and the proteins that will facilitate their translocation through the target host cell membrane. The secretion hierarchy is established by complex mechanisms that involve several T3SS-associated components, including the “switch protein,” a highly conserved, inner membrane protease that undergoes autocatalytic cleavage. It has been proposed that the autocleavage of the switch protein is the trigger for substrate switching. We show here that autocleavage of the Salmonella enterica serovar Typhimurium switch protein SpaS is an unregulated process that occurs after its folding and before its incorporation into the needle complex. Needle complexes assembled with a precleaved form of SpaS function in a manner indistinguishable from that of the wild-type form. Furthermore, an engineered mutant of SpaS that is processed by an external protease also displays wild-type function. These results demonstrate that the cleavage event per se does not provide a signal for substrate switching but support the hypothesis that cleavage allows the proper conformation of SpaS to render it competent for its switching function. Bacterial interaction with eukaryotic hosts often involves complex molecular machines for targeted delivery of bacterial effector proteins. One such machine, the type III secretion system of some Gram-negative bacteria, serves to inject a multitude of structurally diverse bacterial proteins into the host cell. Critical to the function of these systems is their ability to secrete proteins in a strict hierarchical order, but it is unclear how the mechanism of switching works. Central to the switching mechanism is a highly conserved inner membrane protease that undergoes autocatalytic cleavage. Although it has been suggested previously that the autocleavage event is the trigger for substrate switching, we show here that this is not the case. Rather, our results show that cleavage allows the proper conformation of the protein to render it competent for its switching function. These findings may help develop inhibitors of type III secretion machines that offer novel therapeutic avenues to treat various infectious diseases.
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Edwardsiella tarda EscE (Orf13 Protein) Is a Type III Secretion System-Secreted Protein That Is Required for the Injection of Effectors, Secretion of Translocators, and Pathogenesis in Fish. Infect Immun 2015; 84:2-10. [PMID: 26459509 DOI: 10.1128/iai.00986-15] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 10/03/2015] [Indexed: 11/20/2022] Open
Abstract
The type III secretion system (T3SS) of Edwardsiella tarda is crucial for its intracellular survival and pathogenesis in fish. The orf13 gene (escE) of E. tarda is located 84 nucleotides (nt) upstream of esrC in the T3SS gene cluster. We found that EscE is secreted and translocated in a T3SS-dependent manner and that amino acids 2 to 15 in the N terminus were required for a completely functional T3SS in E. tarda. Deletion of escE abolished the secretion of T3SS translocators, as well as the secretion and translocation of T3SS effectors, but did not influence their intracellular protein levels in E. tarda. Complementation of the escE mutant with a secretion-incompetent EscE derivative restored the secretion of translocators and effectors. Interestingly, the effectors that were secreted and translocated were positively correlated with the EscE protein level in E. tarda. The escE mutant was attenuated in the blue gourami fish infection model, as its 50% lethal dose (LD50) increased to 4 times that of the wild type. The survival rate of the escE mutant-strain-infected fish was 69%, which was much higher than that of the fish infected with the wild-type bacteria (6%). Overall, EscE represents a secreted T3SS regulator that controls effector injection and translocator secretion, thus contributing to E. tarda pathogenesis in fish. The homology of EscE within the T3SSs of other bacterial species suggests that the mechanism of secretion and translocation control used by E. tarda may be commonly used by other bacterial pathogens.
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118
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Ruano-Gallego D, Álvarez B, Fernández LÁ. Engineering the Controlled Assembly of Filamentous Injectisomes in E. coli K-12 for Protein Translocation into Mammalian Cells. ACS Synth Biol 2015; 4:1030-41. [PMID: 26017572 PMCID: PMC4603727 DOI: 10.1021/acssynbio.5b00080] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
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Bacterial pathogens containing type
III protein secretion systems
(T3SS) assemble large needle-like protein complexes in the bacterial
envelope, called injectisomes, for translocation of protein effectors
into host cells. The application of these “molecular syringes”
for the injection of proteins into mammalian cells is hindered by
their structural and genomic complexity, requiring multiple polypeptides
encoded along with effectors in various transcriptional units (TUs)
with intricate regulation. In this work, we have rationally designed
the controlled expression of the filamentous injectisomes found in
enteropathogenic Escherichia coli (EPEC) in the nonpathogenic strain E. coli K-12. All structural components of EPEC injectisomes, encoded in
a genomic island called the locus of enterocyte effacement
(LEE), were engineered in five TUs (eLEEs) excluding effectors, promoters
and transcriptional regulators. These eLEEs were placed under the
control of the IPTG-inducible promoter Ptac and integrated into specific
chromosomal sites of E. coli K-12 using a marker-less
strategy. The resulting strain, named synthetic injector E.
coli (SIEC), assembles filamentous injectisomes similar to
those in EPEC. SIEC injectisomes form pores in the host plasma membrane
and are able to translocate T3-substrate proteins (e.g., translocated intimin receptor, Tir) into the cytoplasm of HeLa
cells reproducing the phenotypes of intimate attachment and polymerization
of actin-pedestals elicited by EPEC bacteria. Hence, SIEC strain allows
the controlled expression of functional filamentous injectisomes for
efficient translocation of proteins with T3S-signals into mammalian
cells.
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Affiliation(s)
- David Ruano-Gallego
- Department of Microbial Biotechnology,
Centro Nacional de Biotecnología, Consejo Superior de Investigaciones
Científicas (CSIC), Campus UAM Cantoblanco, 28049 Madrid, Spain
| | - Beatriz Álvarez
- Department of Microbial Biotechnology,
Centro Nacional de Biotecnología, Consejo Superior de Investigaciones
Científicas (CSIC), Campus UAM Cantoblanco, 28049 Madrid, Spain
| | - Luis Ángel Fernández
- Department of Microbial Biotechnology,
Centro Nacional de Biotecnología, Consejo Superior de Investigaciones
Científicas (CSIC), Campus UAM Cantoblanco, 28049 Madrid, Spain
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119
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Login FH, Wolf-Watz H. YscU/FlhB of Yersinia pseudotuberculosis Harbors a C-terminal Type III Secretion Signal. J Biol Chem 2015; 290:26282-91. [PMID: 26338709 DOI: 10.1074/jbc.m114.633677] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Indexed: 12/20/2022] Open
Abstract
All type III secretion systems (T3SS) harbor a member of the YscU/FlhB family of proteins that is characterized by an auto-proteolytic process that occurs at a conserved cytoplasmic NPTH motif. We have previously demonstrated that YscUCC, the C-terminal peptide generated by auto-proteolysis of Yersinia pseudotuberculosis YscU, is secreted by the T3SS when bacteria are grown in Ca(2+)-depleted medium at 37 °C. Here, we investigated the secretion of this early T3S-substrate and showed that YscUCC encompasses a specific C-terminal T3S signal within the 15 last residues (U15). U15 promoted C-terminal secretion of reporter proteins like GST and YopE lacking its native secretion signal. Similar to the "classical" N-terminal secretion signal, U15 interacted with the ATPase YscN. Although U15 is critical for YscUCC secretion, deletion of the C-terminal secretion signal of YscUCC did neither affect Yop secretion nor Yop translocation. However, these deletions resulted in increased secretion of YscF, the needle subunit. Thus, these results suggest that YscU via its C-terminal secretion signal is involved in regulation of the YscF secretion.
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Affiliation(s)
- Frédéric H Login
- From the Department of Molecular Biology and The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, SE-901 87 Umeå, Sweden
| | - Hans Wolf-Watz
- From the Department of Molecular Biology and The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, SE-901 87 Umeå, Sweden
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120
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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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121
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Notti RQ, Bhattacharya S, Lilic M, Stebbins CE. A common assembly module in injectisome and flagellar type III secretion sorting platforms. Nat Commun 2015; 6:7125. [PMID: 25994170 PMCID: PMC4443714 DOI: 10.1038/ncomms8125] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 04/07/2015] [Indexed: 12/26/2022] Open
Abstract
Translocating proteins across the double membrane of Gram-negative bacteria, type III secretion systems (T3SS) occur in two evolutionarily related forms: injectisomes, delivering virulence factors into host cells, and the flagellar system, secreting the polymeric filament used for motility. While both systems share related elements of a cytoplasmic sorting platform that facilitates the hierarchical secretion of protein substrates, its assembly and regulation remain unclear. Here we describe a module mediating the assembly of the sorting platform in both secretion systems, and elucidate the structural basis for segregation of homologous components among these divergent T3SS subtypes sharing a common cytoplasmic milieu. These results provide a foundation for the subtype-specific assembly of T3SS sorting platforms and will support further mechanistic analysis and anti-virulence drug design.
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Affiliation(s)
- Ryan Q Notti
- 1] Laboratory of Structural Microbiology, Rockefeller University, 1230 York Avenue, New York, New York 10065, USA [2] Tri-Institutional Medical Scientist Training Program, Weill Cornell Medical College, 1300 York Avenue, New York, New York 10021, USA
| | - Shibani Bhattacharya
- New York Structural Biology Center, 89 Convent Avenue, New York, New York 10027, USA
| | - Mirjana Lilic
- Laboratory of Structural Microbiology, Rockefeller University, 1230 York Avenue, New York, New York 10065, USA
| | - C Erec Stebbins
- Laboratory of Structural Microbiology, Rockefeller University, 1230 York Avenue, New York, New York 10065, USA
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122
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Costa TRD, Felisberto-Rodrigues C, Meir A, Prevost MS, Redzej A, Trokter M, Waksman G. Secretion systems in Gram-negative bacteria: structural and mechanistic insights. Nat Rev Microbiol 2015; 13:343-59. [DOI: 10.1038/nrmicro3456] [Citation(s) in RCA: 655] [Impact Index Per Article: 72.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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123
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Monlezun L, Liebl D, Fenel D, Grandjean T, Berry A, Schoehn G, Dessein R, Faudry E, Attree I. PscI is a type III secretion needle anchoring protein within vitropolymerization capacities. Mol Microbiol 2015; 96:419-36. [DOI: 10.1111/mmi.12947] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/22/2015] [Indexed: 12/20/2022]
Affiliation(s)
- Laura Monlezun
- INSERM; UMR-S 1036; Biology of Cancer and Infection; Grenoble France
- CNRS; Bacterial Pathogenesis and Cellular Responses; ERL 5261 Grenoble France
- Université Grenoble Alpes; F-38041 Grenoble France
- CEA; DSV/iRTSV; F-38054 Grenoble France
| | - David Liebl
- INSERM; UMR-S 1036; Biology of Cancer and Infection; Grenoble France
- CNRS; Bacterial Pathogenesis and Cellular Responses; ERL 5261 Grenoble France
- Université Grenoble Alpes; F-38041 Grenoble France
- CEA; DSV/iRTSV; F-38054 Grenoble France
| | - Daphna Fenel
- Université Grenoble Alpes; Institut de Biologie Structurale (IBS); 71 avenue des Martyrs 38044 Grenoble France
- CNRS; IBS; F-38044 Grenoble France
- CEA; IBS; F-38044 Grenoble France
| | - Teddy Grandjean
- Groupe de Recherche Translationnelle de la Relation Hôte-Pathogène; Faculté de Médecine de l'Université de Lille; 59000 Lille France
| | - Alice Berry
- INSERM; UMR-S 1036; Biology of Cancer and Infection; Grenoble France
- CNRS; Bacterial Pathogenesis and Cellular Responses; ERL 5261 Grenoble France
- Université Grenoble Alpes; F-38041 Grenoble France
- CEA; DSV/iRTSV; F-38054 Grenoble France
| | - Guy Schoehn
- Université Grenoble Alpes; Institut de Biologie Structurale (IBS); 71 avenue des Martyrs 38044 Grenoble France
- CNRS; IBS; F-38044 Grenoble France
- CEA; IBS; F-38044 Grenoble France
- Unit for Virus Host Cell Interactions UMI 3265 (UJF-EMBL-CNRS); 38027 Grenoble France
| | - Rodrigue Dessein
- Groupe de Recherche Translationnelle de la Relation Hôte-Pathogène; Faculté de Médecine de l'Université de Lille; 59000 Lille France
| | - Eric Faudry
- INSERM; UMR-S 1036; Biology of Cancer and Infection; Grenoble France
- CNRS; Bacterial Pathogenesis and Cellular Responses; ERL 5261 Grenoble France
- Université Grenoble Alpes; F-38041 Grenoble France
- CEA; DSV/iRTSV; F-38054 Grenoble France
| | - Ina Attree
- INSERM; UMR-S 1036; Biology of Cancer and Infection; Grenoble France
- CNRS; Bacterial Pathogenesis and Cellular Responses; ERL 5261 Grenoble France
- Université Grenoble Alpes; F-38041 Grenoble France
- CEA; DSV/iRTSV; F-38054 Grenoble France
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124
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Lee PC, Rietsch A. Fueling type III secretion. Trends Microbiol 2015; 23:296-300. [PMID: 25701111 DOI: 10.1016/j.tim.2015.01.012] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 01/19/2015] [Accepted: 01/27/2015] [Indexed: 10/24/2022]
Abstract
Type III secretion systems (T3SSs) are complex nanomachines that export proteins from the bacterial cytoplasm across the cell envelope in a single step. They are at the core of the machinery used to assemble the bacterial flagellum, and the needle complex many Gram-negative pathogens use to inject effector proteins into host cells and cause disease. Several models have been put forward to explain how this export is energized, and the mechanism has been the subject of considerable debate. Here we present an overview of these models and discuss their relative merits. Recent evidence suggests that the proton motive force (pmf) is the primary energy source for type III secretion, although contribution from refolding of secreted proteins has not been ruled out. The mechanism by which the pmf is converted to protein export remains enigmatic.
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Affiliation(s)
- Pei-Chung Lee
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Arne Rietsch
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, OH 44106-4960, USA.
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125
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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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126
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SepD/SepL-dependent secretion signals of the type III secretion system translocator proteins in enteropathogenic Escherichia coli. J Bacteriol 2015; 197:1263-75. [PMID: 25645555 DOI: 10.1128/jb.02401-14] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The type III protein secretion system (T3SS) encoded by the locus of enterocyte effacement (LEE) is essential for the pathogenesis of attaching/effacing bacterial pathogens, including enteropathogenic Escherichia coli (EPEC), enterohemorrhagic E. coli (EHEC), and Citrobacter rodentium. These pathogens use the T3SS to sequentially secrete three categories of proteins: the T3SS needle and inner rod protein components; the EspA, EspB, and EspD translocators; and many LEE- and non-LEE-encoded effectors. SepD and SepL are essential for translocator secretion, and mutations in either lead to hypersecretion of effectors. However, how SepD and SepL control translocator secretion and secretion hierarchy between translocators and effectors is poorly understood. In this report, we show that the secreted T3SS components, the translocators, and both LEE- and non-LEE-encoded effectors all carry N-terminal type III secretion and translocation signals. These signals all behave like those of the effectors and are sufficient for mediating type III secretion and translocation by wild-type EPEC and hypersecretion by the sepD and sepL mutants. Our results extended previous observations and suggest that the secretion hierarchy of the different substrates is determined by a signal other than the N-terminal secretion signal. We identified a domain located immediately downstream of the N-terminal secretion signal in the translocator EspB that is required for SepD/SepL-dependent secretion. We further demonstrated that this EspB domain confers SepD/SepL- and CesAB-dependent secretion on the secretion signal of effector EspZ. Our results thus suggest that SepD and SepL control and regulate secretion hierarchy between translocators and effectors by recognizing translocator-specific export signals. IMPORTANCE Many bacterial pathogens use a syringe-like protein secretion apparatus, termed the type III protein secretion system (T3SS), to secrete and inject numerous proteins directly into the host cells to cause disease. The secreted proteins perform different functions at various stages during infection and are classified into three substrate categories (T3SS components, translocators, and effectors). They all contain secretion signals at their N termini, but how their secretion hierarchy is determined is poorly understood. Here, we show that the N-terminal secretion signals from different substrate categories all behave the same and do not confer substrate specificity. We further characterize the secretion signals of the translocators and identify a translocator-specific signal, demonstrating that substrate-specific secretion signals are required in regulating T3SS substrate hierarchy.
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127
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Targeting of plant pattern recognition receptor-triggered immunity by bacterial type-III secretion system effectors. Curr Opin Microbiol 2015; 23:14-22. [DOI: 10.1016/j.mib.2014.10.009] [Citation(s) in RCA: 190] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 10/16/2014] [Accepted: 10/24/2014] [Indexed: 01/08/2023]
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128
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Composition, formation, and regulation of the cytosolic c-ring, a dynamic component of the type III secretion injectisome. PLoS Biol 2015; 13:e1002039. [PMID: 25591178 PMCID: PMC4295842 DOI: 10.1371/journal.pbio.1002039] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 12/02/2014] [Indexed: 11/28/2022] Open
Abstract
The injectisome is a membrane complex through which some bacteria can inject effector proteins into host cells. This study reveals that the cytosolic C-ring structure has a dynamic relationship to the rest of the injectisome, with implications for the regulation of secretion. Many gram-negative pathogens employ a type III secretion injectisome to translocate effector proteins into eukaryotic host cells. While the structure of the distal “needle complex” is well documented, the composition and role of the functionally important cytosolic complex remain less well understood. Using functional fluorescent fusions, we found that the C-ring, an essential and conserved cytosolic component of the system, is composed of ~22 copies of SctQ (YscQ in Yersinia enterocolitica), which require the presence of YscQC, the product of an internal translation initiation site in yscQ, for their cooperative assembly. Photoactivated localization microscopy (PALM) reveals that in vivo, YscQ is present in both a free-moving cytosolic and a stable injectisome-bound state. Notably, fluorescence recovery after photobleaching (FRAP) shows that YscQ exchanges between the injectisome and the cytosol, with a t½ of 68 ± 8 seconds when injectisomes are secreting. In contrast, the secretin SctC (YscC) and the major export apparatus component SctV (YscV) display minimal exchange. Under non-secreting conditions, the exchange rate of YscQ is reduced to t½ = 134 ± 16 seconds, revealing a correlation between C-ring exchange and injectisome activity, which indicates a possible role for C-ring stability in regulation of type III secretion. The stabilization of the C-ring depends on the presence of the functional ATPase SctN (YscN). These data provide new insights into the formation and composition of the injectisome and present a novel aspect of type III secretion, the exchange of C-ring subunits, which is regulated with respect to secretion. The type III secretion system, also known as the injectisome, is a key virulence factor in many gram-negative bacteria, and is responsible for the transmission of bacterial proteins directly into host cells. While some elements of the system are well characterized, the cytosolic components involved in substrate recognition and handling are not well understood. One of the major questions is the role of the C-ring, an essential yet enigmatic cytosolic injectisome member. We used fluorescence microscopy to analyze the architecture and behavior of the C-ring in live Y. enterocolitica bacteria, a human pathogen. We found that in vivo, the C-ring assembles cooperatively with the help of additional copies of its own C-terminal fragment and has a highly dynamic structure, with C-ring subunits exchanging between the working injectisomes and a cytosolic pool. The rate of exchange is different between secreting and non-secreting injectisomes and depends on the function of the type III secretion ATPase, indicating that the stability of the complex is altered when functioning. This dynamic behaviour raises the possibility that the C-ring is a regulator of targeted protein delivery by the type III secretion system and makes the C-ring a viable target for the development of novel anti-virulence drugs.
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129
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Visualization of the type III secretion sorting platform of Shigella flexneri. Proc Natl Acad Sci U S A 2015; 112:1047-52. [PMID: 25583506 DOI: 10.1073/pnas.1411610112] [Citation(s) in RCA: 170] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Bacterial type III secretion machines are widely used to inject virulence proteins into eukaryotic host cells. These secretion machines are evolutionarily related to bacterial flagella and consist of a large cytoplasmic complex, a transmembrane basal body, and an extracellular needle. The cytoplasmic complex forms a sorting platform essential for effector selection and needle assembly, but it remains largely uncharacterized. Here we use high-throughput cryoelectron tomography (cryo-ET) to visualize intact machines in a virulent Shigella flexneri strain genetically modified to produce minicells capable of interaction with host cells. A high-resolution in situ structure of the intact machine determined by subtomogram averaging reveals the cytoplasmic sorting platform, which consists of a central hub and six spokes, with a pod-like structure at the terminus of each spoke. Molecular modeling of wild-type and mutant machines allowed us to propose a model of the sorting platform in which the hub consists mainly of a hexamer of the Spa47 ATPase, whereas the MxiN protein comprises the spokes and the Spa33 protein forms the pods. Multiple contacts among those components are essential to align the Spa47 ATPase with the central channel of the MxiA protein export gate to form a unique nanomachine. The molecular architecture of the Shigella type III secretion machine and its sorting platform provide the structural foundation for further dissecting the mechanisms underlying type III secretion and pathogenesis and also highlight the major structural distinctions from bacterial flagella.
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130
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Banfield MJ. Perturbation of host ubiquitin systems by plant pathogen/pest effector proteins. Cell Microbiol 2014; 17:18-25. [PMID: 25339602 PMCID: PMC4312480 DOI: 10.1111/cmi.12385] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Revised: 09/26/2014] [Accepted: 10/09/2014] [Indexed: 12/26/2022]
Abstract
Microbial pathogens and pests of animals and plants secrete effector proteins into host cells, altering cellular physiology to the benefit of the invading parasite. Research in the past decade has delivered significant new insights into the molecular mechanisms of how these effector proteins function, with a particular focus on modulation of host immunity-related pathways. One host system that has emerged as a common target of effectors is the ubiquitination system in which substrate proteins are post-translationally modified by covalent conjugation with the small protein ubiquitin. This modification, typically via isopeptide bond formation through a lysine side chain of ubiquitin, can result in target degradation, relocalization, altered activity or affect protein–protein interactions. In this review, I focus primarily on how effector proteins from bacterial and filamentous pathogens of plants and pests perturb host ubiquitination pathways that ultimately include the 26S proteasome. The activities of these effectors, in how they affect ubiquitin pathways in plants, reveal how pathogens have evolved to identify and exploit weaknesses in this system that deliver increased pathogen fitness.
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Affiliation(s)
- Mark J Banfield
- Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK
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131
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Archuleta TL, Spiller BW. A gatekeeper chaperone complex directs translocator secretion during type three secretion. PLoS Pathog 2014; 10:e1004498. [PMID: 25375170 PMCID: PMC4222845 DOI: 10.1371/journal.ppat.1004498] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Accepted: 10/02/2014] [Indexed: 11/18/2022] Open
Abstract
Many Gram-negative bacteria use Type Three Secretion Systems (T3SS) to deliver effector proteins into host cells. These protein delivery machines are composed of cytosolic components that recognize substrates and generate the force needed for translocation, the secretion conduit, formed by a needle complex and associated membrane spanning basal body, and translocators that form the pore in the target cell. A defined order of secretion in which needle component proteins are secreted first, followed by translocators, and finally effectors, is necessary for this system to be effective. While the secreted effectors vary significantly between organisms, the ∼20 individual protein components that form the T3SS are conserved in many pathogenic bacteria. One such conserved protein, referred to as either a plug or gatekeeper, is necessary to prevent unregulated effector release and to allow efficient translocator secretion. The mechanism by which translocator secretion is promoted while effector release is inhibited by gatekeepers is unknown. We present the structure of the Chlamydial gatekeeper, CopN, bound to a translocator-specific chaperone. The structure identifies a previously unknown interface between gatekeepers and translocator chaperones and reveals that in the gatekeeper-chaperone complex the canonical translocator-binding groove is free to bind translocators. Structure-based mutagenesis of the homologous complex in Shigella reveals that the gatekeeper-chaperone-translocator complex is essential for translocator secretion and for the ordered secretion of translocators prior to effectors. Type Three Secretion Systems (T3SS) are essential virulence factors found in many pathogenic Gram-negative bacteria. These machines aid infection by delivering bacterial proteins into host cells where these proteins modulate host processes and help establish a niche for the bacteria. Protein delivery occurs in a highly regulated manner in which proteins involved in early steps in infection, or necessary to build the secretion conduit, are typically secreted before other substrates, a phenomenon termed secretion hierarchy. This study presents the structure of a molecular complex that physically links one class of early substrates, components of the secretion pore termed translocators, to a gatekeeper protein, a protein that has been implicated in the secretion hierarchy. Disruption of this interaction in Shigella disrupts the secretion of translocators, while supporting increased secretion of effectors, resulting in phenotypes indistinguishable from a gatekeeper deletion, and leading to the conclusion that a gatekeeper-chaperone-translocator complex is a critical component of the T3SS.
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Affiliation(s)
- Tara L. Archuleta
- Chemical and Physical Biology Program, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Benjamin W. Spiller
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- * E-mail:
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132
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Plano GV, Schesser K. The Yersinia pestis type III secretion system: expression, assembly and role in the evasion of host defenses. Immunol Res 2014; 57:237-45. [PMID: 24198067 DOI: 10.1007/s12026-013-8454-3] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Yersinia pestis, the etiologic agent of plague, utilizes a type III secretion system (T3SS) to subvert the defenses of its mammalian hosts. T3SSs are complex nanomachines that allow bacterial pathogens to directly inject effector proteins into eukaryotic cells. The Y. pestis T3SS is not expressed during transit through the flea vector, but T3SS gene expression is rapidly thermoinduced upon entry into a mammalian host. Assembly of the T3S apparatus is a highly coordinated process that requires the homo- and hetero-oligomerization over 20 Yersinia secretion (Ysc) proteins, several assembly intermediates and the T3S process to complete the assembly of the rod and external needle structures. The activation of effector secretion is controlled by the YopN/TyeA/SycN/YscB complex, YscF and LcrG in response to extracellular calcium and/or contact with a eukaryotic cell. Cell contact triggers the T3S process including the secretion and assembly of a pore-forming translocon complex that facilitates the translocation of effector proteins, termed Yersinia outer proteins (Yops), across the eukaryotic membrane. Within the host cell, the Yop effector proteins function to inhibit bacterial phagocytosis and to suppress the production of pro-inflammatory cytokines.
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Affiliation(s)
- Gregory V Plano
- Department of Microbiology and Immunology, University of Miami Miller School of Medicine, 1600 NW 10th Avenue, Miami, FL, 33136, USA,
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133
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Gao B, Lara-Tejero M, Lefebre M, Goodman AL, Galán JE. Novel components of the flagellar system in epsilonproteobacteria. mBio 2014; 5:e01349-14. [PMID: 24961693 PMCID: PMC4073491 DOI: 10.1128/mbio.01349-14] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2014] [Accepted: 06/02/2014] [Indexed: 12/13/2022] Open
Abstract
UNLABELLED Motility is essential for the pathogenesis of many bacterial species. Most bacteria move using flagella, which are multiprotein filaments that rotate propelled by a cell wall-anchored motor using chemical energy. Although some components of the flagellar apparatus are common to many bacterial species, recent studies have shown significant differences in the flagellar structures of different bacterial species. The molecular bases for these differences, however, are not understood. The flagella from epsilonproteobacteria, which include the bacterial pathogens Campylobacter jejuni and Helicobacter pylori, are among the most divergent. Using next-generation sequencing combined with transposon mutagenesis, we have conducted a comprehensive high-throughput genetic screen in Campylobacter jejuni, which identified several novel components of its flagellar system. Biochemical analyses detected interactions between the identified proteins and known components of the flagellar machinery, and in vivo imaging located them to the bacterial poles, where flagella assemble. Most of the identified new components are conserved within but restricted to epsilonproteobacteria. These studies provide insight into the divergent flagella of this group of bacteria and highlight the complexity of this remarkable structure, which has adapted to carry out its conserved functions in the context of widely diverse bacterial species. IMPORTANCE Motility is essential for the normal physiology and pathogenesis of many bacterial species. Most bacteria move using flagella, which are multiprotein filaments that rotate propelled by a motor that uses chemical energy as fuel. Although some components of the flagellar apparatus are common to many bacterial species, recent studies have shown significant divergence in the flagellar structures across bacterial species. However, the molecular bases for these differences are not understood. The flagella from epsilonproteobacteria, which include the bacterial pathogens Campylobacter jejuni and Helicobacter pylori, are among the most divergent. We conducted a comprehensive genetic screen in Campylobacter jejuni and identified several novel components of the flagellar system. These studies provide important information to understand how flagella have adapted to function in the context of widely diverse sets of bacterial species and bring unique insight into the evolution and function of this remarkable bacterial organelle.
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Affiliation(s)
- Beile Gao
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Maria Lara-Tejero
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Matthew Lefebre
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, USA
| | | | - Jorge E Galán
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, USA
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134
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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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135
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Li J, Sun W, Guo Z, Lu C, Shen Y. Fusaric acid modulates Type Three Secretion System of Salmonella enterica serovar Typhimurium. Biochem Biophys Res Commun 2014; 449:455-9. [PMID: 24853802 DOI: 10.1016/j.bbrc.2014.05.044] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Accepted: 05/06/2014] [Indexed: 10/25/2022]
Abstract
Natural small-molecule products are promising lead compounds for developing a generation of novel antimicrobials agents to meet the challenge of antibiotic-resistant pathogens. To facilitate the search for novel anti-virulence agents, we chose a virulence factor of Type Three Secretion System (T3SS) as a drug target to screen candidates from a small-molecule library in our laboratory. This study demonstrated fusaric acid had dramatically inhibitory effects on secretion of Salmonella island 1 (SPI-1) effector proteins and invasion of Salmonella into HeLa cells. Moreover, fusaric acid had no inhibitory effects on bacterial growth and viability of host cells. Protein HilA is a key regulator of SPI-1 in Salmonella, which affects transcription of SPI-1 effectors and SPI-1 apparatus genes. In this study, fusaric acid (FA) did not affect secretion of SPI-1 effectors in HilA over-expressed strain, suggesting it did not affect the transcription of SPI-1. In addition, fusaric acid did not affect the protein level of apparatus protein PrgH in SPI-1 needle complex. As a result, we proposed fusaric acid had an inhibitory effect on SPI-1 probably depending on its influence on SicA/InvF. In summary, fusaric acid is a novel inhibitor of T3SS with potential for further developing novel anti-virulence agents.
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Affiliation(s)
- Jianfang Li
- School of Pharmaceutical Sciences, Shandong University of Traditional Chinese Medicine, Jinan 250355, China; Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China
| | - Weiyang Sun
- School of Pharmaceutical Sciences, Shandong University of Traditional Chinese Medicine, Jinan 250355, China
| | - Zhixing Guo
- Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China
| | - Chunhua Lu
- Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China
| | - Yuemao Shen
- Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China.
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136
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Control of type III secretion activity and substrate specificity by the cytoplasmic regulator PcrG. Proc Natl Acad Sci U S A 2014; 111:E2027-36. [PMID: 24778208 DOI: 10.1073/pnas.1402658111] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Pathogenic Gram-negative bacteria use syringe-like type III secretion systems (T3SS) to inject effector proteins directly into targeted host cells. Effector secretion is triggered by host cell contact, and before contact is prevented by a set of conserved regulators. How these regulators interface with the T3SS apparatus to control secretion is unclear. We present evidence that the proton motive force (pmf) drives T3SS secretion in Pseudomonas aeruginosa, and that the cytoplasmic regulator PcrG interacts with distinct components of the T3SS apparatus to control two important aspects of effector secretion: (i) It coassembles with a second regulator (Pcr1) on the inner membrane T3SS component PcrD to prevent effectors from accessing the T3SS, and (ii) In conjunction with PscO, it controls protein secretion activity by modulating the ability of T3SS to convert pmf.
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137
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Abstract
Salmonella enterica serovar Typhimurium is a food-borne pathogen that causes severe gastroenteritis. The ability of Salmonella to cause disease depends on two type III secretion systems (T3SSs) encoded in two distinct Salmonella pathogenicity islands, 1 and 2 (SPI1 and SPI2, respectively). S. Typhimurium encodes a solo LuxR homolog, SdiA, which can detect the acyl-homoserine lactones (AHLs) produced by other bacteria and upregulate the rck operon and the srgE gene. SrgE is predicted to encode a protein of 488 residues with a coiled-coil domain between residues 345 and 382. In silico studies have provided conflicting predictions as to whether SrgE is a T3SS substrate. Therefore, in this work, we tested the hypothesis that SrgE is a T3SS effector by two methods, a β-lactamase activity assay and a split green fluorescent protein (GFP) complementation assay. SrgE with β-lactamase fused to residue 40, 100, 150, or 300 was indeed expressed and translocated into host cells, but SrgE with β-lactamase fused to residue 400 or 488 was not expressed, suggesting interference by the coiled-coil domain. Similarly, SrgE with GFP S11 fused to residue 300, but not to residue 488, was expressed and translocated into host cells. With both systems, translocation into host cells was dependent upon SPI2. A phylogenetic analysis indicated that srgE is found only within Salmonella enterica subspecies. It is found sporadically within both typhoidal and nontyphoidal serovars, although the SrgE protein sequences found within typhoidal serovars tend to cluster separately from those found in nontyphoidal serovars, suggesting functional diversification.
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138
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EscO, a functional and structural analog of the flagellar FliJ protein, is a positive regulator of EscN ATPase activity of the enteropathogenic Escherichia coli injectisome. J Bacteriol 2014; 196:2227-41. [PMID: 24706741 DOI: 10.1128/jb.01551-14] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Type III secretion systems (T3SSs) are multiprotein molecular devices used by many Gram-negative bacterial pathogens to translocate effector proteins into eukaryotic cells. A T3SS is also used for protein export in flagellar assembly, which promotes bacterial motility. The two systems are evolutionarily related, possessing highly conserved components in their export apparatuses. Enteropathogenic Escherichia coli (EPEC) employs a T3SS, encoded by genes in the locus of enterocyte effacement (LEE) pathogenicity island, to colonize the human intestine and cause diarrheal disease. In the present work, we investigated the role of the LEE-encoded EscO protein (previously Orf15 or EscA) in T3SS biogenesis. We show that EscO shares similar properties with the flagellar FliJ and the Yersinia YscO protein families. Our findings demonstrate that EscO is essential for secretion of all categories of T3SS substrates. Consistent with its central role in protein secretion, it was found to interact with the ATPase EscN and its negative regulator, EscL, of the export apparatus. Moreover, we show that EscO stimulates EscN enzymatic activity; however, it is unable to upregulate ATP hydrolysis in the presence of EscL. Remarkably, EscO partially restored the swimming defect of a Salmonella flagellar fliJ mutant and was able to stimulate the ATPase activity of FliI. Overall, our data indicate that EscO is the virulence counterpart of the flagellar FliJ protein.
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139
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Abrusci P, McDowell MA, Lea SM, Johnson S. Building a secreting nanomachine: a structural overview of the T3SS. Curr Opin Struct Biol 2014; 25:111-7. [PMID: 24704748 PMCID: PMC4045390 DOI: 10.1016/j.sbi.2013.11.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 11/05/2013] [Accepted: 11/06/2013] [Indexed: 12/21/2022]
Abstract
To fulfill complex biological tasks, such as locomotion and protein translocation, bacteria assemble macromolecular nanomachines. One such nanodevice, the type III secretion system (T3SS), has evolved to provide a means of transporting proteins from the bacterial cytoplasm across the periplasmic and extracellular spaces. T3SS can be broadly classified into two highly homologous families: the flagellar T3SS which drive cell motility, and the non-flagellar T3SS (NF-T3SS) that inject effector proteins into eukaryotic host cells, a trait frequently associated with virulence. Although the structures and symmetries of ancillary components of the T3SS have diversified to match requirements of different species adapted to different niches, recent genetic, molecular and structural studies demonstrate that these systems are built by arranging homologous modular protein assemblies.
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Affiliation(s)
- Patrizia Abrusci
- Sir William Dunn School of Pathology, Oxford University, South Parks Road, Oxford OX1 3RE, United Kingdom
| | - Melanie A McDowell
- Sir William Dunn School of Pathology, Oxford University, South Parks Road, Oxford OX1 3RE, United Kingdom
| | - Susan M Lea
- Sir William Dunn School of Pathology, Oxford University, South Parks Road, Oxford OX1 3RE, United Kingdom.
| | - Steven Johnson
- Sir William Dunn School of Pathology, Oxford University, South Parks Road, Oxford OX1 3RE, United Kingdom
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140
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Diepold A, Wagner S. Assembly of the bacterial type III secretion machinery. FEMS Microbiol Rev 2014; 38:802-22. [PMID: 24484471 DOI: 10.1111/1574-6976.12061] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Revised: 01/02/2014] [Accepted: 01/13/2014] [Indexed: 11/29/2022] Open
Abstract
Many bacteria that live in contact with eukaryotic hosts, whether as symbionts or as pathogens, have evolved mechanisms that manipulate host cell behaviour to their benefit. One such mechanism, the type III secretion system, is employed by Gram-negative bacterial species to inject effector proteins into host cells. This function is reflected by the overall shape of the machinery, which resembles a molecular syringe. Despite the simplicity of the concept, the type III secretion system is one of the most complex known bacterial nanomachines, incorporating one to more than hundred copies of up to twenty different proteins into a multi-MDa transmembrane complex. The structural core of the system is the so-called needle complex that spans the bacterial cell envelope as a tripartite ring system and culminates in a needle protruding from the bacterial cell surface. Substrate targeting and translocation are accomplished by an export machinery consisting of various inner membrane embedded and cytoplasmic components. The formation of such a multimembrane-spanning machinery is an intricate task that requires precise orchestration. This review gives an overview of recent findings on the assembly of type III secretion machines, discusses quality control and recycling of the system and proposes an integrated assembly model.
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Affiliation(s)
- Andreas Diepold
- Department of Biochemistry, University of Oxford, Oxford, UK
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141
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Burkinshaw BJ, Strynadka NCJ. Assembly and structure of the T3SS. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1649-63. [PMID: 24512838 DOI: 10.1016/j.bbamcr.2014.01.035] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 01/27/2014] [Accepted: 01/29/2014] [Indexed: 02/06/2023]
Abstract
The Type III Secretion System (T3SS) is a multi-mega Dalton apparatus assembled from more than twenty components and is found in many species of animal and plant bacterial pathogens. The T3SS creates a contiguous channel through the bacterial and host membranes, allowing injection of specialized bacterial effector proteins directly to the host cell. In this review, we discuss our current understanding of T3SS assembly and structure, as well as highlight structurally characterized Salmonella effectors. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
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Affiliation(s)
- Brianne J Burkinshaw
- Department of Biochemistry and Molecular Biology, Center for Blood Research, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Natalie C J Strynadka
- Department of Biochemistry and Molecular Biology, Center for Blood Research, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
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142
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Chang JH, Desveaux D, Creason AL. The ABCs and 123s of bacterial secretion systems in plant pathogenesis. ANNUAL REVIEW OF PHYTOPATHOLOGY 2014; 52:317-45. [PMID: 24906130 DOI: 10.1146/annurev-phyto-011014-015624] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Bacteria have many export and secretion systems that translocate cargo into and across biological membranes. Seven secretion systems contribute to pathogenicity by translocating proteinaceous cargos that can be released into the extracellular milieu or directly into recipient cells. In this review, we describe these secretion systems and how their complexities and functions reflect differences in the destinations, states, functions, and sizes of the translocated cargos as well as the architecture of the bacterial cell envelope. We examine the secretion systems from the perspective of pathogenic bacteria that proliferate within plant tissues and highlight examples of translocated proteins that contribute to the infection and disease of plant hosts.
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Affiliation(s)
- Jeff H Chang
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon 97331; ,
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143
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The inner rod protein controls substrate switching and needle length in a Salmonella type III secretion system. Proc Natl Acad Sci U S A 2013; 111:817-22. [PMID: 24379359 DOI: 10.1073/pnas.1319698111] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Type III secretion machines are essential for the biology of many bacteria that are pathogenic or symbiotic for animals, plants, or insects. They exert their function by delivering bacterial effector proteins into target eukaryotic cells. The core component of these machines is the needle complex, a multiprotein structure that spans the bacterial envelope and serves as a conduit for proteins that transit this secretion pathway. The needle complex is composed of a multiring base embedded in the bacterial envelope and a filament-like structure, the needle, that projects from the bacterial surface and is linked to the base by the inner rod. Assembly of the needle complex proceeds in a step-wise fashion that is initiated by the assembly of the base and is followed by the export of the building subunits for the needle and inner rod substructures. Once assembled, the needle complex reprograms its specificity and becomes competent for the secretion of effector proteins. Here through genetic, biochemical, and electron microscopy analyses of the Salmonella inner rod protein subunit PrgJ we present evidence that the assembly of the inner rod dictates the timing of substrate switching and needle length. Furthermore, the identification of mutations in PrgJ that specifically alter the hierarchy of protein secretion provides additional support for a complex role of the inner rod substructure in type III secretion.
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Structure of a pathogenic type 3 secretion system in action. Nat Struct Mol Biol 2013; 21:82-7. [PMID: 24317488 DOI: 10.1038/nsmb.2722] [Citation(s) in RCA: 129] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Accepted: 10/22/2013] [Indexed: 12/20/2022]
Abstract
Type 3 secretion systems use 3.5-megadalton syringe-like, membrane-embedded 'injectisomes', each containing an ~800-Å-long needle complex to connect intracellular compartments of infectious bacteria and hosts. Here we identify requirements for substrate association with, transport through and exit from the injectisome of Salmonella enterica serovar Typhimurium. This guided the design of substrates that become trapped within the secretion path and enabled visualization of injectisomes in action in situ. We used cryo-EM to define the secretion path, providing a structural explanation as to why effector proteins must be unfolded during transport. Furthermore, trapping of a heterologous substrate in the needle prevents secretion of natural bacterial effectors. Together, the data reveal the path of protein secretion across multiple membranes and show that mechanisms rejecting unacceptable substrates can be undermined, and transport of bacterial effectors across an already assembled type 3 secretion system can be inhibited.
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145
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Hu M, Yang Y, Meng C, Pan Z, Jiao X. Responses of macrophages against Salmonella infection compared with phagocytosis. In Vitro Cell Dev Biol Anim 2013; 49:778-84. [PMID: 23949781 DOI: 10.1007/s11626-013-9672-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Accepted: 07/18/2013] [Indexed: 02/07/2023]
Abstract
To explore the responses of host cell after infection with live Salmonella compared with phagocytosis to dead bacteria, the responses of mouse macrophage after infection with Salmonella enteritidis C50041 and the fixed C50041 (C50041-d) were analyzed. Results indicated that the cytotoxicity induced by C50041 was stronger than C50041-d. Similar changing trends of mitochondrial membrane potential, intracellular concentration of calcium ions, reactive oxygen species and nitric oxide were found between C50041 and C50041-d infection. But the cell responses against C50041 were earlier and stronger than C50041-d. LC3 expression of macrophage induced by C50041 was lower than C50041-d. C50041 significantly inhibited the production of tumor necrosis factor and interleukin (IL)-6. Whereas intracellular caspase-1 activation and IL-1β release induced by C50041 were stronger than C50041-d, caspase-1 activation and IL-1β release are the innate defense responses of macrophage. Therefore, it will be beneficial to explore the use of this pathway in the control of Salmonella infection.
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Affiliation(s)
- Maozhi Hu
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, 225009, People's Republic of China
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Common and distinct structural features of Salmonella injectisome and flagellar basal body. Sci Rep 2013; 3:3369. [PMID: 24284544 PMCID: PMC3842551 DOI: 10.1038/srep03369] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 11/13/2013] [Indexed: 12/22/2022] Open
Abstract
Bacterial pathogens use an injectisome to deliver virulence proteins into eukaryotic host cells. The bacterial flagellum and injectisome export their component proteins for self-assembly. These two systems show high structural similarities and are classified as the type III secretion system, but it remains elusive how similar they are in situ because the structures of these complexes isolated from cells and visualized by electron cryomicroscopy have shown only the export channel and housing for the export apparatus. Here we report in situ structures of Salmonella injectisome and flagellum by electron cryotomography. The injectisome lacks the flagellar basal body C-ring, but a wing-like disc and a globular density corresponding to the export gate platform and ATPase hexamer ring, respectively, are stably attached through thin connectors, revealing yet unidentified common architectures of the two systems. The ATPase ring is far from the disc, suggesting that both apparatuses are observed in an export-off state.
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147
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Barison N, Gupta R, Kolbe M. A sophisticated multi-step secretion mechanism: how the type 3 secretion system is regulated. Cell Microbiol 2013; 15:1809-17. [PMID: 23927570 DOI: 10.1111/cmi.12178] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 07/31/2013] [Accepted: 08/01/2013] [Indexed: 11/28/2022]
Abstract
Many Gram-negative pathogens utilize type 3 secretion systems (T3SSs) for a successful infection. The T3SS is a large macromolecular complex which spans both bacterial membranes and delivers effector proteins into the host cell. The infection requires spatiotemporal control of diverse sets of secreted effectors and various mechanisms have evolved to regulate T3SS in response to external stimuli. This review will describe mechanisms that may control type 3 secretion, revealing a multi-step regulatory strategy. We then propose an updated model of T3SS that illustrates different stages of secretion and integrates the most recent structural and functional data.
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Affiliation(s)
- Nicola Barison
- Max-Planck-Institute for Infection Biology, Cellular Microbiology, Charitéplatz 1, 10117, Berlin, Germany
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Kidwai AS, Mushamiri I, Niemann GS, Brown RN, Adkins JN, Heffron F. Diverse secreted effectors are required for Salmonella persistence in a mouse infection model. PLoS One 2013; 8:e70753. [PMID: 23950998 PMCID: PMC3741292 DOI: 10.1371/journal.pone.0070753] [Citation(s) in RCA: 27] [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: 03/09/2013] [Accepted: 06/26/2013] [Indexed: 01/08/2023] Open
Abstract
Salmonella enterica serovar Typhimurium causes typhoid-like disease in mice and is a model of typhoid fever in humans. One of the hallmarks of typhoid is persistence, the ability of the bacteria to survive in the host weeks after infection. Virulence factors called effectors facilitate this process by direct transfer to the cytoplasm of infected cells thereby subverting cellular processes. Secretion of effectors to the cell cytoplasm takes place through multiple routes, including two separate type III secretion (T3SS) apparati as well as outer membrane vesicles. The two T3SS are encoded on separate pathogenicity islands, SPI-1 and -2, with SPI-1 more strongly associated with the intestinal phase of infection, and SPI-2 with the systemic phase. Both T3SS are required for persistence, but the effectors required have not been systematically evaluated. In this study, mutations in 48 described effectors were tested for persistence. We replaced each effector with a specific DNA barcode sequence by allelic exchange and co-infected with a wild-type reference to calculate the ratio of wild-type parent to mutant at different times after infection. The competitive index (CI) was determined by quantitative PCR in which primers that correspond to the barcode were used for amplification. Mutations in all but seven effectors reduced persistence demonstrating that most effectors were required. One exception was CigR, a recently discovered effector that is widely conserved throughout enteric bacteria. Deletion of cigR increased lethality, suggesting that it may be an anti-virulence factor. The fact that almost all Salmonella effectors are required for persistence argues against redundant functions. This is different from effector repertoires in other intracellular pathogens such as Legionella.
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Affiliation(s)
- Afshan S. Kidwai
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Ivy Mushamiri
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, Oregon, United States of America
| | - George S. Niemann
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Roslyn N. Brown
- Center for Bioproducts and Bioenergy, Washington State University, Richland, Washington, United States of America
| | - Joshua N. Adkins
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Fred Heffron
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, Oregon, United States of America
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Engineering the type III secretion system in non-replicating bacterial minicells for antigen delivery. Nat Commun 2013; 4:1590. [PMID: 23481398 PMCID: PMC3693737 DOI: 10.1038/ncomms2594] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Accepted: 02/08/2013] [Indexed: 01/28/2023] Open
Abstract
Type III protein secretion systems are being considered for vaccine development as virtually any protein antigen can be engineered for delivery by these nanomachines into the class I antigen presentation pathway to stimulate antigen-specific CD8(+) T cells. A limitation in the use of this system is that it requires live virulence-attenuated bacteria, which may preclude its use in certain populations such as children and the immunocompromised. Here we report the engineering of the Salmonella Typhimurium type III secretion system in achromosomal, non-replicating nanoparticles derived from bacterial minicells. The engineered system is shown to be functional and capable of delivering heterologous antigens to the class I antigen presentation pathway stimulating immune responses both in vitro and in vivo. This antigen delivery platform offers a novel approach for vaccine development and cellular immunotherapy.
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150
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More Evidence for Secretion Signals within the mRNA of Type 3 Secreted Effectors. J Bacteriol 2013; 195:2117-8. [DOI: 10.1128/jb.00303-13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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