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Barrett BS, Markham AP, Esfandiary R, Picking WL, Picking WD, Joshi SB, Middaugh CR. Formulation and immunogenicity studies of type III secretion system needle antigens as vaccine candidates. J Pharm Sci 2010; 99:4488-96. [PMID: 20845448 PMCID: PMC3761878 DOI: 10.1002/jps.22180] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Bacterial infections caused by Shigella flexneri, Salmonella typhimurium, and Burkholderia pseudomallei are currently difficult to prevent due to the lack of a licensed vaccine. Here we present formulation and immunogenicity studies for the three type III secretion system (TTSS) needle proteins MxiH(Δ5), PrgI(Δ5), and BsaL(Δ5) (each truncated by five residues at its C terminus) as potential candidates for vaccine development. These antigens are found to be thermally stabilized by the presence of carbohydrates and polyols. Additionally, all adsorb readily to aluminum hydroxide apparently through a combination of hydrogen bonds and/or Van der Waals forces. The interaction of these proteins with the aluminum-based adjuvant changes with time resulting in varying degrees of irreversible binding. Peptide maps of desorbed protein, however, suggest that chemical changes are not responsible for this irreversible association. The ability of MxiH(Δ5) and PrgI(Δ5) to elicit strong humoral immune responses was tested in a murine model. When administered intramuscularly as monomers, the needle components exhibited dose dependent immunogenic behavior. The polymerized version of MxiH was exceptionally immunogenic even at low doses. The responses of both monomeric and polymerized forms were boosted by adsorption to an aluminum salt adjuvant.
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Affiliation(s)
- Brooke S. Barrett
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS, 66047
| | - Aaron P. Markham
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS, 66047
| | - Reza Esfandiary
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS, 66047
| | - Wendy L. Picking
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, 74078
| | - William D. Picking
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, 74078
| | - Sangeeta B. Joshi
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS, 66047
| | - C. Russell Middaugh
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS, 66047
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Berger C, Robin GP, Bonas U, Koebnik R. Membrane topology of conserved components of the type III secretion system from the plant pathogen Xanthomonas campestris pv. vesicatoria. Microbiology (Reading) 2010; 156:1963-1974. [DOI: 10.1099/mic.0.039248-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Type III secretion (T3S) systems play key roles in the assembly of flagella and the translocation of bacterial effector proteins into eukaryotic host cells. Eleven proteins which are conserved among Gram-negative plant and animal pathogenic bacteria have been proposed to build up the basal structure of the T3S system, which spans both inner and outer bacterial membranes. We studied six conserved proteins, termed Hrc, predicted to reside in the inner membrane of the plant pathogen Xanthomonas campestris pv. vesicatoria. The membrane topology of HrcD, HrcR, HrcS, HrcT, HrcU and HrcV was studied by translational fusions to a dual alkaline phosphatase–β-galactosidase reporter protein. Two proteins, HrcU and HrcV, were found to have the same membrane topology as the Yersinia homologues YscU and YscV. For HrcR, the membrane topology differed from the model for the homologue from Yersinia, YscR. For our data on three other protein families, exemplified by HrcD, HrcS and HrcT, we derived the first topology models. Our results provide what is believed to be the first complete model of the inner membrane topology of any bacterial T3S system and will aid in elucidating the architecture of T3S systems by ultrastructural analysis.
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Affiliation(s)
- Carolin Berger
- Institute of Biology, Department of Genetics, Martin-Luther-University, 06099 Halle, Germany
| | - Guillaume P. Robin
- Laboratoire Génome et Développement des Plantes, Université de Perpignan via Domitia–CNRS–IRD, UMR 5096, IRD Montpellier, France
| | - Ulla Bonas
- Institute of Biology, Department of Genetics, Martin-Luther-University, 06099 Halle, Germany
| | - Ralf Koebnik
- Laboratoire Génome et Développement des Plantes, Université de Perpignan via Domitia–CNRS–IRD, UMR 5096, IRD Montpellier, France
- Institute of Biology, Department of Genetics, Martin-Luther-University, 06099 Halle, Germany
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53
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Protein refolding is required for assembly of the type three secretion needle. Nat Struct Mol Biol 2010; 17:788-92. [PMID: 20543831 DOI: 10.1038/nsmb.1822] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2009] [Accepted: 04/01/2010] [Indexed: 12/30/2022]
Abstract
Pathogenic Gram-negative bacteria use a type three secretion system (TTSS) to deliver virulence factors into host cells. Although the order in which proteins incorporate into the growing TTSS is well described, the underlying assembly mechanisms are still unclear. Here we show that the TTSS needle protomer refolds spontaneously to extend the needle from the distal end. We developed a functional mutant of the needle protomer from Shigella flexneri and Salmonella typhimurium to study its assembly in vitro. We show that the protomer partially refolds from alpha-helix into beta-strand conformation to form the TTSS needle. Reconstitution experiments show that needle growth does not require ATP. Thus, like the structurally related flagellar systems, the needle elongates by subunit polymerization at the distal end but requires protomer refolding. Our studies provide a starting point to understand the molecular assembly mechanisms and the structure of the TTSS at atomic level.
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54
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Identification and characterization of small-molecule inhibitors of Yop translocation in Yersinia pseudotuberculosis. Antimicrob Agents Chemother 2010; 54:3241-54. [PMID: 20498321 DOI: 10.1128/aac.00364-10] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Type three secretion systems (TTSSs) are virulence factors found in many pathogenic Gram-negative species, including the family of pathogenic Yersinia spp. Yersinia pseudotuberculosis requires the translocation of a group of effector molecules, called Yops, to subvert the innate immune response and establish infection. Polarized transfer of Yops from bacteria to immune cells depends on several factors, including the presence of a functional TTSS, the successful attachment of Yersinia to the target cell, and translocon insertion into the target cell membrane. Here we employed a high-throughput screen to identify small molecules that block translocation of Yops into mammalian cells. We identified 6 compounds that inhibited translocation of effectors without affecting synthesis of TTSS components and secreted effectors, assembly of the TTSS, or secretion of effectors. One compound, C20, reduced adherence of Y. pseudotuberculosis to target cells. Additionally, the compounds caused leakage of Yops into the supernatant during infection and thus reduced polarized translocation. Furthermore, several molecules, namely, C20, C22, C24, C34, and C38, also inhibited ExoS-mediated cell rounding, suggesting that the compounds target factors that are conserved between Pseudomonas aeruginosa and Y. pseudotuberculosis. In summary, we have identified 6 compounds that specifically inhibit translocation of Yops into mammalian cells but not Yop synthesis or secretion.
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55
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Marteyn B, West N, Browning D, Cole J, Shaw J, Palm F, Mounier J, Prévost MC, Sansonetti P, Tang C. Modulation of Shigella virulence in response to available oxygen in vivo. Nature 2010; 465:355-8. [PMID: 20436458 PMCID: PMC3750455 DOI: 10.1038/nature08970] [Citation(s) in RCA: 240] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Accepted: 03/02/2010] [Indexed: 11/09/2022]
Abstract
Bacteria coordinate expression of virulence determinants in response to localized microenvironments in their hosts. Here we show that Shigella flexneri, which causes dysentery, encounters varying oxygen concentrations in the gastrointestinal tract, which govern activity of its type three secretion system (T3SS). The T3SS is essential for cell invasion and virulence. In anaerobic environments (for example, the gastrointestinal tract lumen), Shigella is primed for invasion and expresses extended T3SS needles while reducing Ipa (invasion plasmid antigen) effector secretion. This is mediated by FNR (fumarate and nitrate reduction), a regulator of anaerobic metabolism that represses transcription of spa32 and spa33, virulence genes that regulate secretion through the T3SS. We demonstrate there is a zone of relative oxygenation adjacent to the gastrointestinal tract mucosa, caused by diffusion from the capillary network at the tips of villi. This would reverse the anaerobic block of Ipa secretion, allowing T3SS activation at its precise site of action, enhancing invasion and virulence.
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Affiliation(s)
- Benoit Marteyn
- Centre for Molecular Microbiology and Infection, Department of Microbiology, Flowers Building, Imperial College London, London, SW7 2AZ, UK
| | - Nicholas West
- Centre for Molecular Microbiology and Infection, Department of Microbiology, Flowers Building, Imperial College London, London, SW7 2AZ, UK
| | - Douglas Browning
- School of Biosciences, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Jeffery Cole
- School of Biosciences, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Jonathan Shaw
- Division of Genomic Medicine, University of Sheffield Medical School, Beech Hill Road, Sheffield, S10 2RX, UK
| | - Fredrik Palm
- Department of Medical Cell Biology, Biomedical Center, Uppsala University, 751 23 Uppsala, Sweden
| | - Joelle Mounier
- Unité de Pathogénie Microbienne Moléculaire, and Unité INSERM786, Institut Pasteur, 28 rue du Dr Roux, F - 75724 Paris Cédex 15, France
| | - Marie-Christine Prévost
- Plate forme de Microscopie électronique, Institut Pasteur, 25 Rue du Docteur Roux, F-75724 Paris cedex 15, France
| | - Philippe Sansonetti
- Unité de Pathogénie Microbienne Moléculaire, and Unité INSERM786, Institut Pasteur, 28 rue du Dr Roux, F - 75724 Paris Cédex 15, France
- Collège de France, 11 Place Marcelin Berthelot, F-75231, Paris Cédex 05, France
| | - Christoph Tang
- Centre for Molecular Microbiology and Infection, Department of Microbiology, Flowers Building, Imperial College London, London, SW7 2AZ, UK
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56
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Diepold A, Amstutz M, Abel S, Sorg I, Jenal U, Cornelis GR. Deciphering the assembly of the Yersinia type III secretion injectisome. EMBO J 2010; 29:1928-40. [PMID: 20453832 DOI: 10.1038/emboj.2010.84] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Accepted: 04/13/2010] [Indexed: 01/05/2023] Open
Abstract
The assembly of the Yersinia enterocolitica type III secretion injectisome was investigated by grafting fluorescent proteins onto several components, YscC (outer-membrane (OM) ring), YscD (forms the inner-membrane (IM) ring together with YscJ), YscN (ATPase), and YscQ (putative C ring). The recombinant injectisomes were functional and appeared as fluorescent spots at the cell periphery. Epistasis experiments with the hybrid alleles in an array of injectisome mutants revealed a novel outside-in assembly order: whereas YscC formed spots in the absence of any other structural protein, formation of YscD foci required YscC, but not YscJ. We therefore propose that the assembly starts with YscC and proceeds through the connector YscD to YscJ, which was further corroborated by co-immunoprecipitation experiments. Completion of the membrane rings allowed the subsequent assembly of cytosolic components. YscN and YscQ attached synchronously, requiring each other, the interacting proteins YscK and YscL, but no further injectisome component for their assembly. These results show that assembly is initiated by the formation of the OM ring and progresses inwards to the IM ring and, finally, to a large cytosolic complex.
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Affiliation(s)
- Andreas Diepold
- Infection Biology, Biozentrum der Universität Basel, Basel, Switzerland
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57
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Kaminski RW, Oaks EV. Inactivated and subunit vaccines to prevent shigellosis. Expert Rev Vaccines 2010; 8:1693-704. [PMID: 19943764 DOI: 10.1586/erv.09.127] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Shigellosis remains a formidable disease globally, with children of the developing world bearing the greatest number of infections. The need for an affordable, safe and efficacious vaccine has persisted for decades. Vaccines to prevent shigellosis can be divided into living and nonliving approaches. Several nonliving Shigella vaccines are currently at different stages of development and show substantial promise. Outlined here is an overview of multiple nonliving vaccine technologies, highlighting their current status and recent advances in testing. In addition, gaps in the knowledge base regarding immune mechanisms of protection are explored.
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Affiliation(s)
- Robert W Kaminski
- Division of Bacterial and Rickettsial Diseases, Walter Reed Army Institute of Research, 503 Robert Grant Avenue, Silver Spring, MD 20910, USA
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58
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Timing is everything: the regulation of type III secretion. Cell Mol Life Sci 2009; 67:1065-75. [PMID: 20043184 PMCID: PMC2835726 DOI: 10.1007/s00018-009-0230-0] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Revised: 11/23/2009] [Accepted: 12/08/2009] [Indexed: 12/19/2022]
Abstract
Type Three Secretion Systems (T3SSs) are essential virulence determinants of many Gram-negative bacteria. The T3SS is an injection device that can transfer bacterial virulence proteins directly into host cells. The apparatus is made up of a basal body that spans both bacterial membranes and an extracellular needle that possesses a channel that is thought to act as a conduit for protein secretion. Contact with a host-cell membrane triggers the insertion of a pore into the target membrane, and effectors are translocated through this pore into the host cell. To assemble a functional T3SS, specific substrates must be targeted to the apparatus in the correct order. Recently, there have been many developments in our structural and functional understanding of the proteins involved in the regulation of secretion. Here we review the current understanding of protein components of the system thought to be involved in switching between different stages of secretion.
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59
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Pilar Alberdi M, Watson E, McAllister GE, Harris JD, Paxton EA, Thomson JR, Smith DG. Expression by Lawsonia intracellularis of type III secretion system components during infection. Vet Microbiol 2009; 139:298-303. [DOI: 10.1016/j.vetmic.2009.06.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Revised: 06/05/2009] [Accepted: 06/12/2009] [Indexed: 10/20/2022]
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60
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Spa15 of Shigella flexneri is secreted through the type III secretion system and prevents staurosporine-induced apoptosis. Infect Immun 2009; 77:5281-90. [PMID: 19805534 DOI: 10.1128/iai.00800-09] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Shigella flexneri is a gram-negative, facultative intracellular pathogen that invades the colonic epithelium and causes bacillary dysentery. We previously demonstrated that S. flexneri inhibits staurosporine-induced apoptosis in infected epithelial cells and that a DeltamxiE mutant is unable to inhibit apoptosis. Therefore, we hypothesized that an MxiE-regulated gene was responsible for protection of epithelial cells from apoptosis. Analysis of all MxiE-regulated genes yielded no mutants that lacked the ability to prevent apoptosis. Spa15, which is defined as a type III secretion system chaperone, was analyzed since it associates with MxiE. A Deltaspa15 mutant was unable to prevent staurosporine-induced apoptosis. C-terminal hemagglutinin-tagged spa15 was secreted by S. flexneri within 2 h in the Congo red secretion assay, and secretion was dependent on the type III secretion system. Spa15 was also secreted by Shigella in infected epithelial cells, as verified by immunofluorescence analysis. Spa15 secretion was decreased in the DeltamxiE mutant, which demonstrates why this mutant is unable to prevent staurosporine-induced apoptosis. Our data are the first to show that Spa15 is secreted in a type III secretion system-dependent fashion, and the absence of Spa15 in the Deltaspa15 mutant results in the loss of protection from staurosporine-induced apoptosis in epithelial cells. Thus, Spa15 contributes to the intracellular survival of Shigella by blocking apoptosis in the infected host cell.
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61
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Journet L, Hughes KT, Cornelis GR. Type III secretion: a secretory pathway serving both motility and virulence (Review). Mol Membr Biol 2009; 22:41-50. [PMID: 16092523 DOI: 10.1080/09687860500041858] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
'Type III secretion' (T3S) refers to a secretion pathway that is common to the flagellae of eubacteria and the injectisomes of some gram-negative bacteria. Flagellae are rotary nanomachines allowing motility but they contain a built-in secretion apparatus that exports their own distal components to the distal end of the growing structure where they polymerize. In some cases they have been shown to export non-flagellar proteins. Injectisomes are transkingdom communication apparatuses allowing bacteria docked at the surface of a eukaryotic cell membrane to inject effector proteins across the two bacterial membranes and the eukaryotic cell membrane. Both nanomachines share a similar basal body embedded in the two bacterial membranes, topped either by a hook and a filament or by a stiff short needle. Both appear to be assembled in the same fashion. They recognize their substrate by a loose N-terminal peptide signal and the help of individual chaperones of a new type.
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62
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Liposomes recruit IpaC to the Shigella flexneri type III secretion apparatus needle as a final step in secretion induction. Infect Immun 2009; 77:2754-61. [PMID: 19433542 DOI: 10.1128/iai.00190-09] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Shigella flexneri contact with enterocytes induces a burst of protein secretion via its type III secretion apparatus (TTSA) as an initial step in cellular invasion. We have previously reported that IpaD is positioned at the TTSA needle tip (M. Espina et al., Infect. Immuno. 74:4391-4400, 2006). From this position, IpaD senses small molecules in the environment to control the presentation of IpaB to the needle tip. This step occurs without type III secretion induction or IpaC recruitment to the S. flexneri surface. IpaC is then transported to the S. flexneri surface when target cell lipids are added, and this event presumably mimics host cell contact. Unlike IpaB mobilization, IpaC surface presentation is closely linked to secretion induction. This study demonstrates that sphingomyelin and cholesterol are key players in type III secretion induction and that they appear to interact with IpaB to elicit IpaC presentation at the TTSA needle tip. Furthermore, IpaB localization at the needle tip prior to membrane contact provides the optimal set of conditions for host cell invasion. Thus, the S. flexneri type III secretion system can be induced in a stepwise manner, with the first step being the stable association of IpaD with the needle tip, the second step being the sensing of small molecules by IpaD to mobilize IpaB to the tip, and the third step being the interaction of lipids with IpaB to induce IpaC localization at the needle tip concomitant with translocon insertion into the host membrane and type III secretion induction.
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63
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Fadouloglou VE, Bastaki MN, Ashcroft AE, Phillips SE, Panopoulos NJ, Glykos NM, Kokkinidis M. On the quaternary association of the type III secretion system HrcQB-C protein: Experimental evidence differentiates among the various oligomerization models. J Struct Biol 2009; 166:214-25. [DOI: 10.1016/j.jsb.2009.01.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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64
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Three-dimensional reconstruction of the Shigella T3SS transmembrane regions reveals 12-fold symmetry and novel features throughout. Nat Struct Mol Biol 2009; 16:477-85. [PMID: 19396171 PMCID: PMC2681179 DOI: 10.1038/nsmb.1599] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Accepted: 04/03/2009] [Indexed: 01/03/2023]
Abstract
Type III secretion systems (T3SSs) mediate bacterial protein translocation into eukaryotic cells, a process essential for virulence of many Gram-negative pathogens. They are composed of a cytoplasmic secretion machinery and a base that bridges both bacterial membranes, into which a hollow, external needle is embedded. When isolated, the latter two parts are termed the 'needle complex'. An incomplete understanding of the structure of the needle complex has hampered studies of T3SS function. To estimate the stoichiometry of its components, we measured the mass of its subdomains by scanning transmission electron microscopy (STEM). We determined subunit symmetries by analysis of top and side views within negatively stained samples in low-dose transmission electron microscopy (TEM). Application of 12-fold symmetry allowed generation of a 21-25-A resolution, three-dimensional reconstruction of the needle complex base, revealing many new features and permitting tentative docking of the crystal structure of EscJ, an inner membrane component.
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65
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Saier MH, Ma CH, Rodgers L, Tamang DG, Yen MR. Protein secretion and membrane insertion systems in bacteria and eukaryotic organelles. ADVANCES IN APPLIED MICROBIOLOGY 2009; 65:141-97. [PMID: 19026865 DOI: 10.1016/s0065-2164(08)00606-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Milton H Saier
- Division of Biological Sciences, University of California at San Diego, La Jolla, California 92093-0116, USA
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66
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Architectures and biogenesis of non-flagellar protein appendages in Gram-negative bacteria. EMBO J 2009; 27:2271-80. [PMID: 18668121 PMCID: PMC2500206 DOI: 10.1038/emboj.2008.155] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2008] [Accepted: 07/07/2008] [Indexed: 11/22/2022] Open
Abstract
Bacteria commonly expose non-flagellar proteinaceous appendages on their outer surfaces. These extracellular structures, called pili or fimbriae, are employed in attachment and invasion, biofilm formation, cell motility or protein and DNA transport across membranes. Over the past 15 years, the power of molecular and structural techniques has revolutionalized our understanding of the biogenesis, structure, function and mode of action of these bacterial organelles. Here, we review the five known classes of Gram-negative non-flagellar appendages from a biosynthetic and structural point of view.
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67
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Barrett BS, Picking WL, Picking WD, Middaugh CR. The response of type three secretion system needle proteins MxiHDelta5, BsaLDelta5, and PrgIDelta5 to temperature and pH. Proteins 2008; 73:632-43. [PMID: 18491382 DOI: 10.1002/prot.22085] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The type III secretion system (TTSS) is a specialized supramolecular injectisome composed of 25 or more proteins which form basal and extracellular domains and share gross architectural similarities with bacterial flagella. The extracellular component of the "needle complex" is primarily composed of a single monomeric subunit organized in a helical array surrounding a hollow pore and protrudes from the bacterial membrane. It is through this surface appendage that virulence factors are translocated to the host cell cytoplasm and thereby subvert normal host cell functions. We present here a comprehensive biophysical analysis of the dynamic conformational behavior of the truncated monomeric needle subunit proteins MxiH(Delta5) (Shigella flexneri), BsaL(Delta5) (Burkholderia pseudomallei), and PrgI(Delta5) (Salmonella typhimurium) as well as their thermal stability over a pH range of 3-8. Circular dichroism spectroscopy indicates the secondary structure is largely alpha helical in all three proteins, and surprisingly thermally labile with transition midpoints in the range of 35-50 degrees C over the pH range of 3-8. Additionally, at the concentrations examined, the very broad thermal transitions were >90% reversible. Second derivative UV absorbance spectroscopy data indicates some disruption of the protein's tertiary structure occurs at temperatures in the range of 29-46 degrees C. The difference in the pH of maximal stability for each of the proteins and the variation for each protein with respect to both secondary and tertiary structural elements is striking. It appears, that at physiological temperatures all three proteins experience intermediate non-native molten globule like states in which they display significant secondary structure in the absence of extensive tertiary interactions. Because of the size difference between the inner pore of the needle and the fully folded needle proteins, it seems clear that the needle subunits must be secreted in a partially or completely unfolded state to reach the distal tip of the needle for assembly. It is proposed that the formation of these intermediate states in the physiological temperature range may play a role in passage through the pore and needle assembly.
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Affiliation(s)
- Brooke S Barrett
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas 66047, USA
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68
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Minamino T, Imada K, Namba K. Mechanisms of type III protein export for bacterial flagellar assembly. MOLECULAR BIOSYSTEMS 2008; 4:1105-15. [PMID: 18931786 DOI: 10.1039/b808065h] [Citation(s) in RCA: 149] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Flagellar type III protein export is highly organized and well controlled in a timely manner by dynamic, specific and cooperative interactions among components of the export apparatus, allowing the huge and complex macromolecular assembly to be built efficiently. The bacterial flagellum, which is required for motility, consists of a rotary motor, a universal joint and a helical propeller. Most of the flagellar components are translocated to the distal, growing end of the flagellum for assembly through the central channel of the flagellum itself by the flagellar type III protein export apparatus, which is postulated to be located on the cytoplasmic side of the flagellar basal body. The export specificity switching machinery, which consists of at least two proteins that function as a molecular ruler and an export switch, respectively, monitors the state of hook-basal body assembly in the cell exterior and switches export specificity, thereby coupling sequential flagellar gene expression with the flagellar assembly process. The export ATPase complex composed of an ATPase and its regulator acts as a pilot to deliver its export substrate to the export gate and helps initial entry of the substrate N-terminal chain into a narrow pore of the export gate. The energy of ATP hydrolysis appears to be used to disassemble and release the ATPase complex from the protein about to be exported, and the rest of the successive unfolding/translocation process of the long polypeptide chain is driven solely by proton motive force (PMF), perhaps through biased one-dimensional Brownian diffusion. Interestingly, the subunits of the ATPase complex have significant sequence similarities to subunits of F(0)F(1)-ATP synthase, a rotary motor that drives the chemical reaction of ATP synthesis using PMF, and the entire crystal structure of the export ATPase is extremely similar to the alpha/beta subunits of F(0)F(1)-ATP synthase, suggesting that the flagellar export apparatus and F(0)F(1)-ATP synthase share the mechanism for their two distinct functions.
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Affiliation(s)
- Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
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69
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Dawson JE, Nicholson LK. Folding kinetics and thermodynamics of Pseudomonas syringae effector protein AvrPto provide insight into translocation via the type III secretion system. Protein Sci 2008; 17:1109-19. [PMID: 18577754 DOI: 10.1110/ps.034223.107] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
In order to infect their hosts, many Gram-negative bacteria translocate agents of infection, called effector proteins, through the type III secretion system (TTSS) into the host cytoplasm. This process is thought to require at least partial unfolding of these agents, raising the question of how an effector protein might unfold to enable its translocation and then refold once it reaches the host cytoplasm. AvrPto is a well-studied effector protein of Pseudomonas syringae pv tomato. The presence of a readily observed unfolded population of AvrPto in aqueous solution and the lack of a known secretion chaperone make it ideal for studying the kinetic and thermodynamic characteristics that facilitate translocation. Application of Nzz exchange spectroscopy revealed a global, two-state folding equilibrium with 16% unfolded population, a folding rate of 1.8 s(-1), and an unfolding rate of 0.33 s(-1) at pH 6.1. TrAvrPto stability increases with increasing pH, with only 2% unfolded population observed at pH 7.0. The R(1) relaxation of TrAvrPto, which is sensitive to both the global anisotropy of folded TrAvrPto and slow exchange between folded and unfolded conformations, provided independent verification of the global kinetic rate constants. Given the acidic apoplast in which the pathogen resides and the more basic host cytoplasm, these results offer an intriguing mechanism by which the pH dependence of stability and slow folding kinetics of AvrPto would allow efficient translocation of the unfolded form through the TTSS and refolding into its functional folded form once inside the host.
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Affiliation(s)
- Jennifer E Dawson
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
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70
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Abstract
Recent work by several groups has significantly expanded our knowledge of the structure, regulation of assembly, and function of components of the extracellular portion of the type III secretion system (T3SS) of Gram-negative bacteria. This perspective presents a structure-informed analysis of functional data and discusses three nonmutually exclusive models of how a key aspect of T3SS biology, the sensing of host cells, may be performed.
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71
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YscP and YscU switch the substrate specificity of the Yersinia type III secretion system by regulating export of the inner rod protein YscI. J Bacteriol 2008; 190:4252-62. [PMID: 18424518 DOI: 10.1128/jb.00328-08] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Pathogenic yersiniae utilize a type III secretion system to inject antihost factors, called Yops, directly into the cytosol of eukaryotic cells. The Yops are injected via a needle-like structure, comprising the YscF protein, on the bacterial surface. While the needle is being assembled, Yops cannot be secreted. YscP and YscU switch the substrate specificity of the secretion system to enable Yop export once the needle attains its proper length. Here, we demonstrate that the inner rod protein YscI plays a critical role in substrate specificity switching. We show that YscI is secreted by the type III secretion system and that YscI secretion by a yscP mutant is abnormally elevated. Furthermore, we show that mutations in the cytoplasmic domain of YscU reduce YscI secretion by the yscP null strain. We also demonstrate that mutants expressing one of three forms of YscI (those with mutations Q84A, L87A, and L96A) secrete substantial amounts of Yops yet exhibit severe defects in needle formation. In the absence of YscP, mutants with the same changes in YscI assemble needles but are unable to secrete Yops. Together, these results suggest that the formation of the inner rod, not the needle, is critical for substrate specificity switching and that YscP and YscU exert their effects on substrate export by controlling the secretion of YscI.
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72
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Betts HJ, Twiggs LE, Sal MS, Wyrick PB, Fields KA. Bioinformatic and biochemical evidence for the identification of the type III secretion system needle protein of Chlamydia trachomatis. J Bacteriol 2008; 190:1680-90. [PMID: 18165300 PMCID: PMC2258694 DOI: 10.1128/jb.01671-07] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Accepted: 12/17/2007] [Indexed: 12/28/2022] Open
Abstract
Chlamydia spp. express a functional type III secretion system (T3SS) necessary for pathogenesis and intracellular growth. However, certain essential components of the secretion apparatus have diverged to such a degree as to preclude their identification by standard homology searches of primary protein sequences. One example is the needle subunit protein. Electron micrographs indicate that chlamydiae possess needle filaments, and yet database searches fail to identify a SctF homologue. We used a bioinformatics approach to identify a likely needle subunit protein for Chlamydia. Experimental evidence indicates that this protein, designated CdsF, has properties consistent with it being the major needle subunit protein. CdsF is concentrated in the outer membrane of elementary bodies and is surface exposed as a component of an extracellular needle-like projection. During infection CdsF is detectable by indirect immunofluorescence in the inclusion membrane with a punctuate distribution adjacent to membrane-associated reticulate bodies. Biochemical cross-linking studies revealed that, like other SctF proteins, CdsF is able to polymerize into multisubunit complexes. Furthermore, we identified two chaperones for CdsF, termed CdsE and CdsG, which have many characteristics of the Pseudomonas spp. needle chaperones PscE and PscG, respectively. In aggregate, our data are consistent with CdsF representing at least one component of the extended Chlamydia T3SS injectisome. The identification of this secretion system component is essential for studies involving ectopic reconstitution of the Chlamydia T3SS. Moreover, we anticipate that CdsF could serve as an efficacious target for anti-Chlamydia neutralizing antibodies.
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Affiliation(s)
- H J Betts
- Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, FL 33101, USA
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73
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Molecular pathogenesis of Shigella spp.: controlling host cell signaling, invasion, and death by type III secretion. Clin Microbiol Rev 2008; 21:134-56. [PMID: 18202440 DOI: 10.1128/cmr.00032-07] [Citation(s) in RCA: 398] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Shigella spp. are gram-negative pathogenic bacteria that evolved from harmless enterobacterial relatives and may cause devastating diarrhea upon ingestion. Research performed over the last 25 years revealed that a type III secretion system (T3SS) encoded on a large plasmid is a key virulence factor of Shigella flexneri. The T3SS determines the interactions of S. flexneri with intestinal cells by consecutively translocating two sets of effector proteins into the target cells. Thus, S. flexneri controls invasion into EC, intra- and intercellular spread, macrophage cell death, as well as host inflammatory responses. Some of the translocated effector proteins show novel biochemical activities by which they intercept host cell signal transduction pathways. An understanding of the molecular mechanisms underlying Shigella pathogenesis will foster the development of a safe and efficient vaccine, which, in parallel with improved hygiene, should curb infections by this widespread pathogen.
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74
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Moraes TF, Spreter T, Strynadka NC. Piecing together the type III injectisome of bacterial pathogens. Curr Opin Struct Biol 2008; 18:258-66. [PMID: 18258424 DOI: 10.1016/j.sbi.2007.12.011] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2007] [Revised: 12/17/2007] [Accepted: 12/18/2007] [Indexed: 01/01/2023]
Abstract
The Type III secretion system is a bacterial 'injectisome' which allows Gram-negative bacteria to shuttle virulence proteins directly into the host cells they infect. This macromolecular assembly consists of more than 20 different proteins put together to collectively span three biological membranes. The recent T3SS crystal structures of the major oligomeric inner membrane ring, the helical needle filament, needle tip protein, the associated ATPase, and outer membrane pilotin together with electron microscopy reconstructions have dramatically furthered our understanding of how this protein translocator functions. The crucial details that describe how these proteins assemble into this oligomeric complex will need a hybrid of structural methodologies including EM, crystallography, and NMR to clarify the intra- and inter-molecular interactions between different structural components of the apparatus.
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Affiliation(s)
- Trevor F Moraes
- University of British Columbia, Biochemistry and Molecular Biology and the Center for Blood Research, Rm 4350 Life Sciences Center, 2350 Health Sciences Mall, Vancouver, Canada V6T 1Z3
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75
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Cytoplasmic targeting of IpaC to the bacterial pole directs polar type III secretion in Shigella. EMBO J 2008; 27:447-57. [PMID: 18188151 DOI: 10.1038/sj.emboj.7601976] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2007] [Accepted: 12/04/2007] [Indexed: 11/09/2022] Open
Abstract
Type III secretion (T3S) systems are largely used by pathogenic gram-negative bacteria to inject multiple effectors into eukaryotic cells. Upon cell contact, these bacterial microinjection devices insert two T3S substrates into host cell membranes, forming a so-called 'translocon' that is required for targeting of type III effectors in the cell cytosol. Here, we show that secretion of the translocon component IpaC of invasive Shigella occurs at the level of one bacterial pole during cell invasion. Using IpaC fusions with green fluorescent protein variants (IpaCi), we show that the IpaC cytoplasmic pool localizes at an old or new bacterial pole, where secretion occurs upon T3S activation. Deletions in ipaC identified domains implicated in polar localization. Only polar IpaCi derivatives inhibited T3S, while IpaCi fusions with diffuse cytoplasmic localization had no detectable effect on T3S. Moreover, the deletions that abolished polar localization led to secretion defects when introduced in ipaC. These results indicate that cytoplasmic polar localization directs secretion of IpaC at the pole of Shigella, and may represent a mandatory step for T3S.
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76
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Noguchi N, Yanagimoto K, Nakaminami H, Wakabayashi M, Iwai N, Wachi M, Sasatsu M. Anti-infectious Effect of S-Benzylisothiourea Compound A22, Which Inhibits the Actin-Like Protein, MreB, in Shigella flexneri. Biol Pharm Bull 2008; 31:1327-32. [DOI: 10.1248/bpb.31.1327] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Norihisa Noguchi
- Department of Microbiology, School of Pharmacy, Tokyo University of Pharmacy and Life Science
| | - Keita Yanagimoto
- Department of Microbiology, School of Pharmacy, Tokyo University of Pharmacy and Life Science
| | - Hidemasa Nakaminami
- Department of Microbiology, School of Pharmacy, Tokyo University of Pharmacy and Life Science
| | - Moeru Wakabayashi
- Department of Microbiology, School of Pharmacy, Tokyo University of Pharmacy and Life Science
| | - Noritaka Iwai
- Department of Bioengineering, Tokyo Institute of Technology
| | - Masaaki Wachi
- Department of Bioengineering, Tokyo Institute of Technology
| | - Masanori Sasatsu
- Department of Microbiology, School of Pharmacy, Tokyo University of Pharmacy and Life Science
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77
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Schroeder GN, Jann NJ, Hilbi H. Intracellular type III secretion by cytoplasmic Shigella flexneri promotes caspase-1-dependent macrophage cell death. MICROBIOLOGY-SGM 2007; 153:2862-2876. [PMID: 17768231 DOI: 10.1099/mic.0.2007/007427-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The Gram-negative bacterium Shigella flexneri triggers pro-inflammatory apoptotic cell death in macrophages, which is crucial for the onset of an acute inflammatory diarrhoea termed bacillary dysentery. The Mxi-Spa type III secretion system promotes bacterial uptake and escape into the cytoplasm, where, dependent on the translocator/effector protein IpaB, caspase-1 [interleukin (IL)-1beta-converting enzyme] and its substrate IL-1beta are activated. Here, we show that in the course of a macrophage infection, IpaB is secreted intracellularly for more than 1 h post-infection and progressively accumulates in aggregates on the bacterial surface. Concomitantly, the bacterial pool of IpaB is gradually depleted. The protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) dose-dependently inhibited the Mxi-Spa-dependent secretion of IpaB triggered by the dye Congo red in vitro and abolished translocation of IpaB into the host-cell cytoplasm of S. flexneri-infected macrophages. CCCP specifically inhibited S. flexneri-triggered macrophage death in a dose-dependent manner, even if added up to 60 min post-infection. Addition of CCCP 15 min after infection blocked macrophage cell death, the activation of caspase-1 and the maturation of IL-1beta, without affecting uptake or escape of S. flexneri from the phagosome. By contrast, CCCP used at the same concentration had no effect on ATP-induced caspase-1 activation or staurosporine-induced apoptosis. Our results indicate that under the conditions used, CCCP rapidly and specifically blocks bacterial type III secretion, and thus, intracellular type III secretion promotes cytotoxicity of S. flexneri.
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Affiliation(s)
- Gunnar N Schroeder
- Institute of Microbiology, Swiss Federal Institute of Technology (ETH) Zürich, Wolfgang-Pauli-Strasse 10, 8093 Zürich, Switzerland
| | - Naja J Jann
- Institute of Microbiology, Swiss Federal Institute of Technology (ETH) Zürich, Wolfgang-Pauli-Strasse 10, 8093 Zürich, Switzerland
| | - Hubert Hilbi
- Institute of Microbiology, Swiss Federal Institute of Technology (ETH) Zürich, Wolfgang-Pauli-Strasse 10, 8093 Zürich, Switzerland
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78
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Shibata S, Takahashi N, Chevance FFV, Karlinsey JE, Hughes KT, Aizawa SI. FliK regulates flagellar hook length as an internal ruler. Mol Microbiol 2007; 64:1404-15. [PMID: 17542929 DOI: 10.1111/j.1365-2958.2007.05750.x] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mechanism of length control of the flagellar hook is under debate between two theories. One claims that the FliK directly measures the hook length as a molecular ruler, while the other claims that the cytoplasmic substructure measures the amount of hook subunits to determine the hook length. Both agree that the FliK C-terminal domain catalyses the substrate-specificity switch to terminate hook elongation. In this study, we systematically created fliK mutants with deletions and insertions at various sites within the FliK N-terminal domain and analysed their effects on the final hook length. Insertions of peptide fragments from the Yersinia YscP into FliK gave rise to hooks with defined lengths, which was proportional to the molecular size of the FliK-YscP chimeras. Among fliK deletion mutants, only those with small truncations in three specific sites of FliK produced hooks of a defined, shortened length. For the majority of deletion mutants, FliK was secreted, but hook length was not controlled. On the other hand, for some deletion mutants FliK was not secreted, but the hook length was controlled, indicating that FliK secretion is not necessary for hook-length control. We conclude that FliK regulates hook length as an internal molecular ruler.
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Affiliation(s)
- Satoshi Shibata
- Department of Life Sciences, Prefectural University of Hiroshima, 562 Nanatsuka, Shobara, Hiroshima 727-0023, Japan
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79
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Kuwae A. [Functional analysis of proteins secreted via type III secretion system in Bordetella]. Nihon Saikingaku Zasshi 2007; 62:241-6. [PMID: 17575790 DOI: 10.3412/jsb.62.241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Affiliation(s)
- Asaomi Kuwae
- Laboratory of Bacterial Infection, Kitasato Institute for Life Sciences, Kitasato University, Tokyo 108-8641
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80
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Phalipon A, Sansonetti PJ. Shigella’
s ways of manipulating the host intestinal innate and adaptive immune system: a tool box for survival? Immunol Cell Biol 2007; 85:119-29. [PMID: 17213832 DOI: 10.1038/sj.icb7100025] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Shigella, a Gram-negative invasive enteropathogenic bacterium, causes the rupture, invasion and inflammatory destruction of the human colonic epithelium. This complex and aggressive process accounts for the symptoms of bacillary dysentery. The so-called invasive phenotype of Shigella is linked to expression of a type III secretory system (TTSS) injecting effector proteins into the epithelial cell membrane and cytoplasm, thereby inducing local but massive changes in the cell cytoskeleton that lead to bacterial internalization into non-phagocytic intestinal epithelial cells. The invasive phenotype also accounts for the potent pro-inflammatory capacity of the microorganism. Recent evidence indicates that a large part of the mucosal inflammation is initiated by intracellular sensing of bacterial peptidoglycan by cytosolic leucine-rich receptors of the NOD family, particularly NOD1, in epithelial cells. This causes activation of the nuclear factor kappa B and c-JunNH(2)-terminal-kinase pathways, with interleukin-8 appearing as a major chemokine mediating the inflammatory burst that is dominated by massive infiltration of the mucosa by polymorphonuclear leukocytes. Not unexpectedly, this inflammatory response, which is likely to be very harmful for the invading microbe, is regulated by the bacterium itself. A group of proteins encoded by Shigella, which are injected into target cells by the TTSS, has been recently recognized as a family of potent regulators of the innate immune response. These enzymes target key cellular functions that are essential in triggering the inflammatory response, and more generally defense responses of the intestinal mucosa. This review focuses on the mechanisms employed by Shigella to manipulate the host innate response in order to escape early bacterial killing, thus ensuring establishment of its infectious process. The escape strategies, the possible direct effect of Shigella on B and T lymphocytes, their impact on the development of adaptive immunity, and how they may help explain the limited protection induced by natural infection are discussed.
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Affiliation(s)
- Armelle Phalipon
- Unité de Pathogénie Microbienne Moléculaire, INSERM U786, Institut Pasteur 25, Rue du Dr Roux, Paris, France.
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81
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Morita-Ishihara T. Supramolecular Structure of the Shigella Type III Secretion Machinery. Biosci Microflora 2007. [DOI: 10.12938/bifidus.26.29] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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82
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Abstract
The type III secretion injectisome is a complex nanomachine that allows bacteria to deliver protein effectors across eukaryotic cellular membranes. In recent years, significant progress has been made in our understanding of its structure, assembly and mode of operation. The principal structural components of the injectisome, from the base located in the bacterial cytosol to the tip of the needle protruding from the cell surface, have been investigated in detail. The structures of several constituent proteins were solved at the atomic level and important insights into the assembly process have been gained. However, despite the ongoing concerted efforts of molecular and structural biologists, the role of many of the constituent components of this nanomachine remain unknown.
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Affiliation(s)
- Guy R Cornelis
- Biozentrum der Universität Basel, Klingelbergstrasse 50, CH-4056, Basel, Switzerland.
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83
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Davis AJ, Mecsas J. Mutations in the Yersinia pseudotuberculosis type III secretion system needle protein, YscF, that specifically abrogate effector translocation into host cells. J Bacteriol 2006; 189:83-97. [PMID: 17071752 PMCID: PMC1797200 DOI: 10.1128/jb.01396-06] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The trafficking of effectors, termed Yops, from Yersinia spp. into host cells is a multistep process that requires the type III secretion system (TTSS). The TTSS has three main structural parts: a base, a needle, and a translocon, which work together to ensure the polarized movement of Yops directly from the bacterial cytosol into the host cell cytosol. To understand the interactions that take place at the interface between the tip of the TTSS needle and the translocon, we developed a screen to identify mutations in the needle protein YscF that separated its function in secretion from its role in translocation. We identified 25 translocation-defective (TD) yscF mutants, which fall into five phenotypic classes. Some classes exhibit aberrant needle structure and/or reduced levels of Yop secretion, consistent with known functions for YscF. Strikingly, two yscF TD classes formed needles and secreted Yops normally but displayed distinct translocation defects. Class I yscF TD mutants showed diminished pore formation, suggesting incomplete pore insertion and/or assembly. Class II yscF TD mutants formed pores but showed nonpolar translocation, suggesting unstable needle-translocon interactions. These results indicate that YscF functions in Yop secretion and translocation can be genetically separated. Furthermore, the identification of YscF residues that are required for the assembly of the translocon and/or productive interactions with the translocon has allowed us to initiate the mapping of the needle-translocon interface.
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Affiliation(s)
- Alison J Davis
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Ave., Boston, MA 02111, USA
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84
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Espina M, Olive AJ, Kenjale R, Moore DS, Ausar SF, Kaminski RW, Oaks EV, Middaugh CR, Picking WD, Picking WL. IpaD localizes to the tip of the type III secretion system needle of Shigella flexneri. Infect Immun 2006; 74:4391-400. [PMID: 16861624 PMCID: PMC1539624 DOI: 10.1128/iai.00440-06] [Citation(s) in RCA: 138] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Shigella flexneri, the causative agent of shigellosis, is a gram-negative bacterial pathogen that initiates infection by invading cells within the colonic epithelium. Contact with host cell surfaces induces a rapid burst of protein secretion via the Shigella type III secretion system (TTSS). The first proteins secreted are IpaD, IpaB, and IpaC, with IpaB and IpaC being inserted into the host cell membrane to form a pore for translocating late effectors into the target cell cytoplasm. The resulting pathogen-host cross talk results in localized actin polymerization, membrane ruffling, and, ultimately, pathogen entry. IpaD is essential for host cell invasion, but its role in this process is just now coming to light. IpaD is a multifunctional protein that controls the secretion and presentation of IpaB and IpaC at the pathogen-host interface. We show here that antibodies recognizing the surface-exposed N terminus of IpaD neutralize Shigella's ability to promote pore formation in erythrocyte membranes. We further show that MxiH and IpaD colocalize on the bacterial surface. When TTSS needles were sheared from the Shigella surface, IpaD was found at only the needle tips. Consistent with this, IpaD localized to the exposed tips of needles that were still attached to the bacterium. Molecular analyses then showed that the IpaD C terminus is required for this surface localization and function. Furthermore, mutations that prevent IpaD surface localization also eliminate all IpaD-related functions. Thus, this study demonstrates that IpaD localizes to the TTSA needle tip, where it functions to control the secretion and proper insertion of translocators into host cell membranes.
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Affiliation(s)
- Marianela Espina
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas 66045, USA
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85
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Deane JE, Roversi P, Cordes FS, Johnson S, Kenjale R, Daniell S, Booy F, Picking WD, Picking WL, Blocker AJ, Lea SM. Molecular model of a type III secretion system needle: Implications for host-cell sensing. Proc Natl Acad Sci U S A 2006; 103:12529-33. [PMID: 16888041 PMCID: PMC1567912 DOI: 10.1073/pnas.0602689103] [Citation(s) in RCA: 136] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Type III secretion systems are essential virulence determinants for many Gram-negative bacterial pathogens. The type III secretion system consists of cytoplasmic, transmembrane, and extracellular domains. The extracellular domain is a hollow needle protruding above the bacterial surface and is held within a basal body that traverses both bacterial membranes. Effector proteins are translocated, via this external needle, directly into host cells, where they subvert normal cell functions to aid infection. Physical contact with host cells initiates secretion and leads to formation of a pore, thought to be contiguous with the needle channel, in the host-cell membrane. Here, we report the crystal structure of the Shigella flexneri needle subunit MxiH and a complete model for the needle assembly built into our three-dimensional EM reconstruction. The model, combined with mutagenesis data, reveals that signaling of host-cell contact is relayed through the needle via intersubunit contacts and suggests a mode of binding for a tip complex.
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Affiliation(s)
- Janet E. Deane
- *Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Pietro Roversi
- *Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Frank S. Cordes
- *Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Steven Johnson
- *Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
| | - Roma Kenjale
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045; and
| | - Sarah Daniell
- Department of Biological Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Frank Booy
- Department of Biological Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - William D. Picking
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045; and
| | - Wendy L. Picking
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045; and
| | - Ariel J. Blocker
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
| | - Susan M. Lea
- *Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
- To whom correspondence should be addressed. E-mail:
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86
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Albers SV, Szabó Z, Driessen AJM. Protein secretion in the Archaea: multiple paths towards a unique cell surface. Nat Rev Microbiol 2006; 4:537-47. [PMID: 16755286 DOI: 10.1038/nrmicro1440] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Archaea are similar to other prokaryotes in most aspects of cell structure but are unique with respect to the lipid composition of the cytoplasmic membrane and the structure of the cell surface. Membranes of archaea are composed of glycerol-ether lipids instead of glycerol-ester lipids and are based on isoprenoid side chains, whereas the cell walls are formed by surface-layer proteins. The unique cell surface of archaea requires distinct solutions to the problem of how proteins cross this barrier to be either secreted into the medium or assembled as appendages at the cell surface.
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Affiliation(s)
- Sonja-Verena Albers
- Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and the Materials Science Centre Plus, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands
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87
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Miura M, Terajima J, Izumiya H, Mitobe J, Komano T, Watanabe H. OspE2 of Shigella sonnei is required for the maintenance of cell architecture of bacterium-infected cells. Infect Immun 2006; 74:2587-95. [PMID: 16622194 PMCID: PMC1459745 DOI: 10.1128/iai.74.5.2587-2595.2006] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The OspE2 product of Shigella spp., the expression of which is regulated by the mxiE gene, is secreted through a type III secretion system into host cells. We investigated the function of OspE2 of Shigella sonnei by using cultured epithelial cells. Cells invaded by an ospE2 deletion mutant altered their morphology into the rounding shape, which was not due to cell death, whereas cells invaded by the wild-type strain kept their cell shape intact. The ospE2 mutation did not affect initial cell entry and multiplication in cells, but the mutant formed smaller-than-normal plaques on cell monolayers, indicating a deficiency in cell-to-cell spread by the bacteria. An mxiE deletion mutant also showed changes in cell morphology and deficiency in bacterial spread to adjacent cells. In cells invaded by the ospE2 mutant, disturbance of actin stress fibers was prominent at 3 h after invasion. Analysis of OspE2 localization indicated that the OspE2 protein accumulated on focal contact-like structures in the infected host cells. These results suggest that colocalization of the OspE2 protein in the focal contacts of infected cells may function to maintain an intact cell morphology. The morphological change induced by invasion of the ospE2 mutant may affect secondary bacterial transmission.
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Affiliation(s)
- Masashi Miura
- Department of Bacteriology, National Institute of Infectious Diseases, Shinjuku, Tokyo 162-8640, Japan
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88
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Sani M, Allaoui A, Fusetti F, Oostergetel GT, Keegstra W, Boekema EJ. Structural organization of the needle complex of the type III secretion apparatus of Shigella flexneri. Micron 2006; 38:291-301. [PMID: 16920362 DOI: 10.1016/j.micron.2006.04.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Revised: 04/11/2006] [Accepted: 04/11/2006] [Indexed: 01/27/2023]
Abstract
The secretion apparatus known as the needle complex (NC) from the bacterium Shigella flexneri was studied by single particle electron microscopy. The isolated intact NC appears in projection to be composed of a basal body consisting of seven rings and a protruding needle appendage. A comparison of averaged projections of the intact NC and its fragments revealed the organization of the NC into several major subcomplexes. One of these lacks an inner membrane ring of the basal body but still presents the needle appendage attached to four upper rings. The position of the needle appendage within these rings is variable, suggesting that the dissociated component is necessary for stabilizing the needle appendage. Averaged images of the subcomplex lacking the inner membrane basal rings show a thicker extension at the base of the needle appendage, called the socket. This socket was also found to be present in images of the basal body fragment isolated from mutants lacking the mxiH and mxiI genes. This suggests that the socket is not composed of MxiH and MxiI subunits, which form the needle appendage. A symmetry analysis of the basal body top view projections indicated that a peripheral protein component of the inner membrane ring is present in a ring with 24 copies, in contrast to the Salmonella typhimurium NC. A model is presented in which the NC is only associated to the outer- and inner-membranes with its first and seventh ring, respectively.
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Affiliation(s)
- Musa Sani
- Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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89
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Ogino T, Ohno R, Sekiya K, Kuwae A, Matsuzawa T, Nonaka T, Fukuda H, Imajoh-Ohmi S, Abe A. Assembly of the type III secretion apparatus of enteropathogenic Escherichia coli. J Bacteriol 2006; 188:2801-11. [PMID: 16585741 PMCID: PMC1447006 DOI: 10.1128/jb.188.8.2801-2811.2006] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enteropathogenic Escherichia coli (EPEC) secretes many Esps (E. coli-secreted proteins) and effectors via the type III secretion (TTS) system. We previously identified a novel needle complex (NC) composed of a basal body and a needle structure containing an expandable EspA sheath-like structure as a central part of the EPEC TTS apparatus. To further investigate the structure and protein components of the EPEC NC, we purified it in successive centrifugal steps. Finally, NCs with long EspA sheath-like structures could be separated from those with short needle structures on the basis of their densities. Although the highly purified NC appeared to lack an inner ring in the basal body, its core structure, composed of an outer ring and a central rod, was observed by transmission electron microscopy. Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry, Western blot, and immunoelectron microscopic analyses revealed that EscC was a major protein component of the outer ring in the core basal body. To investigate the mechanisms of assembly of the basal body, interactions between the presumed components of the EPEC TTS apparatus were analyzed by a glutathione S-transferase pulldown assay. The EscC outer ring protein was associated with both the EscF needle protein and EscD, a presumed inner membrane protein. EscF was also associated with EscJ, a presumed inner ring protein. Furthermore, escC, escD, and escJ mutant strains were unable to produce the TTS apparatus, and thereby the secretion of the Esp proteins and Tir effector was abolished. These results indicate that EscC, EscD, and EscJ are required for the formation of the TTS apparatus.
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Affiliation(s)
- Tomoaki Ogino
- Laboratory of Bacterial Infection, Kitasato Institute for Life Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
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90
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Darboe N, Kenjale R, Picking WL, Picking WD, Middaugh CR. Physical characterization of MxiH and PrgI, the needle component of the type III secretion apparatus from Shigella and Salmonella. Protein Sci 2006; 15:543-52. [PMID: 16501225 PMCID: PMC2249775 DOI: 10.1110/ps.051733506] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Shigella and Salmonella use similar type III secretion systems for delivering effector proteins into host cells. This secretion system consists of a base anchored in both bacterial membranes and an extracellular "needle" that forms a rod-like structure exposed on the pathogen surface. The needle is composed of multiple subunits of a single protein and makes direct contact with host cells to facilitate protein delivery. The proteins that make up the needle of Shigella and Salmonella are MxiH and PrgI, respectively. These proteins are attractive vaccine candidates because of their essential role in virulence and surface exposure. We therefore isolated, purified, and characterized the monomeric forms of MxiH and PrgI. Their far-UV circular dichroism spectra show structural similarities with hints of subtle differences in their secondary structure. Both proteins are highly helical and thermally unstable, with PrgI having a midpoint of thermal unfolding (Tm) near 37 degrees C and MxiH having a value near 42 degrees C. The two proteins also have comparable intrinsic stabilities as measured by chemically induced (urea) unfolding. MxiH, however, with a free energy of unfolding (DeltaG degrees 0,un) of 1.6 kcal/mol, is slightly more stable than PrgI (1.2 kcal/mol). The relatively low m-values obtained for the urea-induced unfolding of the proteins suggest that they undergo only a small change in solvent-accessible surface area. This argues that when MxiH and PrgI are incorporated into the needle complex, they obtain a more stable structural state through the introduction of protein-protein interactions.
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Affiliation(s)
- Numukunda Darboe
- Division of Biology, Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA
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91
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Yip CK, Strynadka NCJ. New structural insights into the bacterial type III secretion system. Trends Biochem Sci 2006; 31:223-30. [PMID: 16537106 DOI: 10.1016/j.tibs.2006.02.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Revised: 02/03/2006] [Accepted: 02/23/2006] [Indexed: 12/23/2022]
Abstract
The virulence-associated type III secretion system (T3SS) enables many Gram-negative bacterial pathogens to translocate proteins into the eukaryotic host cells that they infect. This unique protein transport process is mediated by the type III secretion apparatus (T3SA), a multisubunit membrane-spanning macromolecular assembly comprising >20 different proteins. Recent studies have identified biochemical and structural properties of the core T3SA, in addition to several components constituting this complex, with important implications for both the assembly process and the overall function of the T3SA.
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Affiliation(s)
- Calvin K Yip
- Department of Biochemistry and Molecular Biology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, Canada, V6T1Z3
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92
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Ono T, Park KS, Ueta M, Iida T, Honda T. Identification of proteins secreted via Vibrio parahaemolyticus type III secretion system 1. Infect Immun 2006; 74:1032-42. [PMID: 16428750 PMCID: PMC1360304 DOI: 10.1128/iai.74.2.1032-1042.2006] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vibrio parahaemolyticus, a gram-negative marine bacterium, is an important pathogen causing food-borne gastroenteritis or septicemia. Recent genome sequencing of the RIMD2210633 strain (a Kanagawa phenomenon-positive clinical isolate of serotype O3:K6) revealed that the strain has two sets of gene clusters that encode the type III secretion system (TTSS) apparatus. The first cluster, TTSS1, is located on the large chromosome, and the second, TTSS2, is on the small chromosome. Previously, we reported that TTSS1 is involved in the cytotoxicity of the RIMD2210633 strain against HeLa cells. Here, we analyzed proteins secreted via the TTSS apparatus encoded by TTSS1 by using two-dimensional gel electrophoresis and identified the proteins encoded by genes VP1680, VP1686, and VPA450. To investigate the roles of those secreted proteins, we constructed and analyzed a series of deletion mutants. Flow cytometry analysis using fluorescence-activated cell sorting with fluorescein isothiocyanate-labeled annexin V demonstrated that the TTSS1-dependent cell death was by apoptosis. The cytotoxicity to HeLa cells was related to one of the newly identified secreted proteins encoded by VP1680. Adenylate cyclase fusion protein studies proved that the newly identified secreted proteins were translocated into HeLa cells. Thus, these appear to be the TTSS effector proteins in V. parahaemolyticus.
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Affiliation(s)
- Takahiro Ono
- Department of Bacterial Infections, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan
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93
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Tatsuno I, Mundy R, Frankel G, Chong Y, Phillips AD, Torres AG, Kaper JB. The lpf gene cluster for long polar fimbriae is not involved in adherence of enteropathogenic Escherichia coli or virulence of Citrobacter rodentium. Infect Immun 2006; 74:265-72. [PMID: 16368980 PMCID: PMC1346640 DOI: 10.1128/iai.74.1.265-272.2006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Using the enteropathogenic Escherichia coli (EPEC) genome sequence, we found that EPEC E2348/69 has an lpfABCDE gene cluster homologous (about 60% identical at the protein level) to the Salmonella long polar fimbria (LPF) operon. To determine whether this operon is essential for adherence, the lpfABCD(E2)(3) genes were deleted from EPEC strain E2348/69 by allelic exchange. Analysis of the resulting EPECDeltalpfABCD(E23) strain showed no change in adherence to HeLa cells or to human intestinal biopsy cells in the in vitro organ culture (IVOC) system compared to the wild type. Sera from volunteers experimentally infected with E2348/69 showed no antibody response to the major subunit protein, LpfA. These results suggested that the lpf(E23) gene cluster is not necessary for EPEC adherence and attaching/effacing (A/E) lesion formation on human biopsy samples and is not expressed during human infection. We also identified an lpf gene cluster in Citrobacter rodentium strain ICC168 (lpf(cr)). A DeltalpfA(cr) mutant of ICC168 retained wild-type adherence and A/E lesion-forming activity on HeLa cells. C3H/HeJ mice were infected with a wild-type C. rodentium strain and its lpfA(cr) isogenic mutant. Both strains were recovered at high levels in stools, and there were no significant differences between the groups both in terms of the number of CFU/organ (colon and cecum) and in terms of the amount of hyperplasia, as measured by weight. Similar results were observed in a second mouse strain, C57BL/6. These data suggest that in addition to playing no apparent role in EPEC pathogenesis, lpf(cr) is not required for C. rodentium virulence in either the C3H/HeJ or C57BL/6 mouse model.
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Affiliation(s)
- Ichiro Tatsuno
- Center for Vaccine Development, University of Maryland School of Medicine, 685 West Baltimore Street, Baltimore, MD 21201, USA
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94
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Morita-Ishihara T, Ogawa M, Sagara H, Yoshida M, Katayama E, Sasakawa C. Shigella Spa33 Is an Essential C-ring Component of Type III Secretion Machinery. J Biol Chem 2006; 281:599-607. [PMID: 16246841 DOI: 10.1074/jbc.m509644200] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Type III secretion machinery (TTSM), composed of a needle, a basal body, and a C-ring compartment, delivers a subset of effectors into host cells. Here, we show that Shigella Spa33 is an essential component of the C-ring compartment involved in mediating the transit of various TTSM-associated translocated proteins. Electron microscopic analysis and pull-down assay revealed Spa33 to be localized beneath the TTSM via interaction with MxiG and MxiJ (basal body components). Spa33 is also capable of interacting with Spa47 (TTSM ATPase), MxiK, MxiN (required for the transit of MxiH, the needle component), Spa32 (required for determining needle length), and several effectors. Genetic and functional analyses of the Spa33 C-terminal region, which is highly conserved in the SpaO-YscQ-HrcQ(B)-FliN family, indicate that some of the conserved residues are crucial for needle formation via interactions with MxiN. Thus, Spa33 plays a central role as the C-ring component in recruiting/exporting TTSM-associated proteins.
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Affiliation(s)
- Tomoko Morita-Ishihara
- Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, International Research Center for Infectious Diseases, 4-6-1, Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
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95
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Tamura N, Murata Y, Mukaihara T. Isolation of Ralstonia solanacearum hrpB constitutive mutants and secretion analysis of hrpB-regulated gene products that share homology with known type III effectors and enzymes. MICROBIOLOGY-SGM 2005; 151:2873-2884. [PMID: 16151200 DOI: 10.1099/mic.0.28161-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The Hrp type III secretion system (TTSS) is essential for the pathogenicity of the Gram-negative plant pathogen Ralstonia solanacearum. To examine the secretion of type III effector proteins via the Hrp TTSS, a screen was done of mutants constitutively expressing the hrpB gene, which encodes an AraC-type transcriptional activator for the hrp regulon. A mutant was isolated that in an hrp-inducing medium expresses several hrpB-regulated genes 4.9-83-fold higher than the wild-type. R. solanacearum Hrp-secreted outer proteins PopA and PopC were secreted at high levels into the culture supernatants of the hrpB constitutive (hrpB(c)) mutant. Using hrpB(c) mutants, the extracellular secretion of several hrpB-regulated (hpx) gene products that share homology with known type III effectors and enzymes was examined. Hpx23, Hpx24 and Hpx25, which are similar in sequence to Pseudomonas syringae pv. tomato effector proteins HopPtoA1, HolPtoR and HopPtoD1, are also secreted via the Hrp TTSS in R. solanacearum. The secretion of two hpx gene products that share homology with known enzymes, glyoxalase I (Hpx19) and Nudix hydrolase (Hpx26), was also examined. Hpx19 is accumulated inside the cell, but interestingly, Hpx26 is secreted outside the cell as an Hrp-secreted outer protein, suggesting that Hpx19 functions intracellularly but Hpx26 is a novel effector protein of R. solanacearum.
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Affiliation(s)
- Naoyuki Tamura
- Research Institute for Biological Sciences, Okayama (RIBS), 7549-1 Yoshikawa, Kibichuo-cho, Okayama 716-1241, Japan
| | - Yukio Murata
- Research Institute for Biological Sciences, Okayama (RIBS), 7549-1 Yoshikawa, Kibichuo-cho, Okayama 716-1241, Japan
| | - Takafumi Mukaihara
- Research Institute for Biological Sciences, Okayama (RIBS), 7549-1 Yoshikawa, Kibichuo-cho, Okayama 716-1241, Japan
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96
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Parsot C. Shigellaspp. and enteroinvasiveEscherichia colipathogenicity factors. FEMS Microbiol Lett 2005; 252:11-8. [PMID: 16182469 DOI: 10.1016/j.femsle.2005.08.046] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2005] [Accepted: 08/17/2005] [Indexed: 10/25/2022] Open
Abstract
Bacteria of Shigella spp. (S. boydii, S. dysenteriae, S. flexneri and S. sonnei) and enteroinvasive Escherichia coli (EIEC) are responsible for shigellosis in humans, a disease characterized by the destruction of the colonic mucosa that is induced upon bacterial invasion. Shigella spp. and EIEC strains contain a virulence plasmid of approximately 220 kb that encodes determinants for entry into epithelial cells and dissemination from cell to cell. This review presents the current model on mechanisms of invasion of the colonic epithelium by these bacteria and focuses on their pathogenicity factors, particularly the virulence plasmid-encoded type III secretion system.
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Affiliation(s)
- Claude Parsot
- Unité de Pathogénie Microbienne Moléculaire, INSERM U389, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, France.
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97
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Mota LJ, Sorg I, Cornelis GR. Type III secretion: The bacteria-eukaryotic cell express. FEMS Microbiol Lett 2005; 252:1-10. [PMID: 16216444 DOI: 10.1016/j.femsle.2005.08.036] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2005] [Accepted: 08/17/2005] [Indexed: 10/25/2022] Open
Abstract
Type III secretion (T3S) is an export pathway used by Gram-negative pathogenic bacteria to inject bacterial proteins into the cytosol of eukaryotic host cells. This pathway is characterized by (i) a secretion nanomachine related to the bacterial flagellum, but usually topped by a stiff needle-like structure; (ii) the assembly in the eukaryotic cell membrane of a translocation pore formed by T3S substrates; (iii) a non-cleavable N-terminal secretion signal; (iv) T3S chaperones, assisting the secretion of some substrates; (v) a control mechanism ensuring protein delivery at the right place and time. Here, we review these different aspects focusing in open questions that promise exciting findings in the near future.
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Affiliation(s)
- Luís Jaime Mota
- Biozentrum der Universität Basel, Biozentrum, Klingelbergstrasse, 50-70 CH4051 Basel, Switzerland
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98
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Kenjale R, Wilson J, Zenk SF, Saurya S, Picking WL, Picking WD, Blocker A. The needle component of the type III secreton of Shigella regulates the activity of the secretion apparatus. J Biol Chem 2005; 280:42929-37. [PMID: 16227202 DOI: 10.1074/jbc.m508377200] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Gram-negative bacteria commonly interact with eukaryotic host cells by using type III secretion systems (TTSSs or secretons). TTSSs serve to transfer bacterial proteins into host cells. Two translocators, IpaB and IpaC, are first inserted with the aid of IpaD by Shigella into the host cell membrane. Then at least two supplementary effectors of cell invasion, IpaA and IpgD, are transferred into the host cytoplasm. How TTSSs are induced to secrete is unknown, but their activation appears to require direct contact of the external distal tip of the apparatus with the host cell. The extracellular domain of the TTSS is a hollow needle protruding 60 nm beyond the bacterial surface. The monomeric unit of the Shigella flexneri needle, MxiH, forms a superhelical assembly. To probe the role of the needle in the activation of the TTSS for secretion, we examined the structure-function relationship of MxiH by mutagenesis. Most point mutations led to normal needle assembly, but some led to polymerization or possible length control defects. In other mutants, secretion was constitutively turned "on." In a further set, it was "constitutively on" but experimentally "uninducible." Finally, upon induction of secretion, some mutants released only the translocators and not the effectors. Most types of mutants were defective in interactions with host cells. Together, these data indicate that the needle directly controls the activity of the TTSS and suggest that it may be used to "sense" host cells.
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Affiliation(s)
- Roma Kenjale
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
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99
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Okuda J, Toyotome T, Kataoka N, Ohno M, Abe H, Shimura Y, Seyedarabi A, Pickersgill R, Sasakawa C. Shigella effector IpaH9.8 binds to a splicing factor U2AF(35) to modulate host immune responses. Biochem Biophys Res Commun 2005; 333:531-9. [PMID: 15950937 DOI: 10.1016/j.bbrc.2005.05.145] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2005] [Accepted: 05/20/2005] [Indexed: 01/01/2023]
Abstract
Shigella effectors injected into the host cell via the type III secretion system are involved in various aspects of infection. Here, we show that one of the effectors, IpaH9.8, plays a role in modulating inflammatory responses to Shigella infection. In murine lung infection model, DeltaipaH9.8 mutant caused more severe inflammatory responses with increased pro-inflammatory cytokine production levels than did wild-type Shigella, which resulted in a 30-fold decrease in bacterial colonization. Binding assays revealed that IpaH9.8 has a specific affinity to U2AF(35), a mammalian splicing factor, which interferes with U2AF(35)-dependent splicing as assayed for IgM pre-mRNA. Reducing the U2AF(35) level in HeLa cells and infecting HeLa cells with wild-type caused a decrease in the expression of the il-8, RANTES, GM-CSF, and il-1beta genes as examined by RT-PCR. The results indicate that IpaH9.8 plays a role in Shigella infection to optimize the host inflammatory responses, thus facilitating bacterial colonization within the host epithelial cells.
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Affiliation(s)
- Jun Okuda
- Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo 108-8039, Japan
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100
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Quinaud M, Chabert J, Faudry E, Neumann E, Lemaire D, Pastor A, Elsen S, Dessen A, Attree I. The PscE-PscF-PscG complex controls type III secretion needle biogenesis in Pseudomonas aeruginosa. J Biol Chem 2005; 280:36293-300. [PMID: 16115870 DOI: 10.1074/jbc.m508089200] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Type III secretion (T3S) systems play key roles in pathogenicity of many Gram-negative bacteria and are employed to inject toxins directly into the cytoplasm of target cells. They are composed of over 20 different proteins that associate into a basal structure that traverses both inner and outer bacterial membranes and a hollow, needle-like structure through which toxins travel. The PscF protein is the main component of the Pseudomonas aeruginosa T3S needle. Here we demonstrate that PscF, when purified on its own, is able to form needle-like fibers of 8 nm in width and >1 microm in length. In addition, we demonstrate for the first time that the T3S needle subunit requires two cytoplasmic partners, PscE and PscG, in P. aeruginosa, which trap PscF in a ternary, 1:1:1 complex, thus blocking it in a monomeric state. Knock-out mutants deficient in PscE and PscG are non-cytotoxic, lack PscF, and are unable to export PscF encoded extrachromosomally. Temperature-scanning circular dichroism measurements show that the PscE-PscF-PscG complex is thermally stable and displays a cooperative unfolding/refolding pattern. Thus, PscE and PscG prevent PscF from polymerizing prematurely in the P. aeruginosa cytoplasm and keep it in a secretion prone conformation, strategies which may be shared by other pathogens that employ the T3S system for infection.
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Affiliation(s)
- Manuelle Quinaud
- Biochimie et Biophysique des Systèmes Intégrés, UMR 5092 CNRS/Commissariat à l'Energie Atomique (CEA)/Université Joseph Fourier (UJF), Département de Réponse et Dynamique Cellulaires, CEA Grenoble, 17 rue des Martyrs, 38054 Grenoble cedex 09, France
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