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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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Huang LY, Shi ZX, Yuan J, Hu FQ. [Expression profile analysis of host HeLa cells invasived by Shigella flexneri 2a]. WEI SHENG WU XUE BAO = ACTA MICROBIOLOGICA SINICA 2007; 47:810-816. [PMID: 18062254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The changes of genes expression in HeLa cell during the invasion with Shigella species for 1h and 3h were analyzed by cDNA microarrays. The data showed that the expression levels of 752 genes were altered twice or greater as compared with the control 509 of them were up-regulated, and 306 were down-regulated. It was supposed that some signal pathways in HeLa cell were activated, then many genes were induced, and at last comprehensive cell responses were produced, so that HeLa cell could prevent against Shigella species infection. Two striking difference cDNA fragments TNFR 1B and ERBB2, which were up-regulated in the host epithelial cell during Shigella infection, analyzed expression by real time RT-PCR as determined by cDNA arrays. We suggested they play important roles in response to the invasive S. flexneri 2457T. Based on the results of gene expression alterations, the molecular pathogenic mechanism of Shigella species could be greatly and deeply understood, and the strategy for prevention against and treatment for shigellosis would be formed.
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Núñez-Samudio V, Landires I. El síndrome de Ekiri como una complicación de la shigellosis. Enferm Infecc Microbiol Clin 2007; 25:492-3. [PMID: 17692219 DOI: 10.1157/13108716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Paetzold S, Lourido S, Raupach B, Zychlinsky A. Shigella flexneri phagosomal escape is independent of invasion. Infect Immun 2007; 75:4826-30. [PMID: 17664266 PMCID: PMC2044536 DOI: 10.1128/iai.00454-07] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Infections with Salmonella enterica serovar Typhimurium and Shigella flexneri result in mucosal inflammation in response to epithelial cell invasion and macrophage cytotoxicity. These processes are mediated by type III secretion systems encoded in homologous virulence loci in the two species, namely, Salmonella pathogenicity island 1 (SPI-1), carried in the genome, and the Shigella entry region (SER), carried in a large virulence plasmid. Here we show that SPI-1 can functionally complement a deletion of SER in S. flexneri, restoring invasion of epithelial cells, macrophage cytotoxicity, and phagosomal escape. Furthermore, S. flexneri phagosomal escape requires the SER and another gene(s) carried on the large virulence plasmid. We demonstrate that the processes of invasion and phagosomal escape can be uncoupled in S. flexneri.
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Boulette ML, Payne SM. Anaerobic regulation of Shigella flexneri virulence: ArcA regulates Fur and iron acquisition genes. J Bacteriol 2007; 189:6957-67. [PMID: 17660284 PMCID: PMC2045222 DOI: 10.1128/jb.00621-07] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Invasion and plaque formation in epithelial monolayers are routinely used to assess the virulence of Shigella flexneri, a causative agent of dysentery. A modified plaque assay was developed to identify factors contributing to the virulence of S. flexneri under the anaerobic conditions present in the colon. This assay demonstrated the importance of the ferrous iron transport system Feo, as well as the global transcription factors Fur, ArcA, and Fnr, for Shigella plaque formation in anoxic environments. Transcriptional analyses of S. flexneri iron transport genes indicated that anaerobic conditions activated feoABC while repressing genes encoding two other iron transport systems, the ABC transporter Sit and the Iuc/Iut aerobactin siderophore synthesis and transport system. The anaerobic transcription factors ArcA and Fnr activated expression of feoABC, while ArcA repressed iucABCD iutA. Transcription of fur, encoding the iron-responsive transcriptional repressor of bacterial iron acquisition, was also repressed anaerobically in an ArcA-dependent manner.
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Hurt JK, Olgen S, Garcia GA. Site-specific modification of Shigella flexneri virF mRNA by tRNA-guanine transglycosylase in vitro. Nucleic Acids Res 2007; 35:4905-13. [PMID: 17626052 PMCID: PMC1950534 DOI: 10.1093/nar/gkm473] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Revised: 05/15/2007] [Accepted: 05/29/2007] [Indexed: 11/18/2022] Open
Abstract
Shigella flexneri is an enteropathogen responsible for severe dysentery in humans. VirF is a key transcriptional regulator that activates the expression of the downstream virulence factors required for cellular invasion and cell-to-cell spread of this pathogen. There are several environmental factors that induce the translation of VirF including temperature, pH, osmolarity and post-transcriptional RNA modification. Durand and colleagues (vacC, a virulence-associated chromosomal locus of Shigella flexneri, is homologous to tgt, a gene encoding tRNA-guanine transglycosylase of Escherichia coli K-12. J. Bacteriol., 176, 4627-4634) have demonstrated a correlation between VirF and tRNA-guanine transglycosylase (TGT), which catalyzes the exchange of the hypermodified base queuine for the guanine in the wobble position of certain tRNAs. They characterized tgt- mutant S. flexneri strains in which the translation of VirF is markedly reduced and the bacteria are unable to invade host cells. Although the function of TGT is to modify tRNA, we report that the virF mRNA is recognized by the Escherichia coli TGT (99% identity to the S. flexneri TGT) in vitro. Further, we show that this recognition results in the site-specific modification of a single base in the virF mRNA. In the context of previous reports that small molecule binding motifs ('riboswitches') in mRNAs modulate mRNA conformation and translation, our observations suggest that TGT may modulate the translation of VirF by base modification of the VirF encoding mRNA.
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Veenendaal AKJ, Hodgkinson JL, Schwarzer L, Stabat D, Zenk SF, Blocker AJ. The type III secretion system needle tip complex mediates host cell sensing and translocon insertion. Mol Microbiol 2007; 63:1719-30. [PMID: 17367391 DOI: 10.1111/j.1365-2958.2007.05620.x] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Type III secretion systems (T3SSs) are essential virulence determinants of many Gram-negative bacterial pathogens. The Shigella T3SS consists of a cytoplasmic bulb, a transmembrane region and a hollow 'needle' protruding from the bacterial surface. Physical contact with host cells initiates secretion and leads to assembly of a pore, formed by IpaB and IpaC, in the host cell membrane, through which proteins that facilitate host cell invasion are translocated. As the needle is implicated in host cell sensing and secretion regulation, its tip should contain components that initiate host cell contact. Through biochemical and immunological studies of wild-type and mutant Shigella T3SS needles, we reveal tip complexes of differing compositions and functional states, which appear to represent the molecular events surrounding host cell sensing and pore formation. Our studies indicate that the interaction between IpaB and IpaD at needle tips is key to host cell sensing, orchestration of IpaC secretion and its subsequent assembly at needle tips. This allows insertion into the host cell membrane of a translocation pore that is continuous with the needle.
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Prunier AL, Schuch R, Fernández RE, Maurelli AT. Genetic structure of the nadA and nadB antivirulence loci in Shigella spp. J Bacteriol 2007; 189:6482-6. [PMID: 17586625 PMCID: PMC1951923 DOI: 10.1128/jb.00525-07] [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: 11/20/2022] Open
Abstract
Comparison of nadA and nadB in 14 Shigella strains and enteroinvasive Escherichia coli versus E. coli showed that at least one locus is altered in all strains. These observations explain the characteristic nicotinic acid auxotrophy of Shigella organisms and are consistent with the previously identified antivirulence nature of these genes for these pathogens.
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Man YS, Trolove C, Tattersall D, Thomas AC, Papakonstantinopoulou A, Patel D, Scott C, Chong J, Jagger DJ, O’Toole EA, Navsaria H, Curtis MA, Kelsell DP. A deafness-associated mutant human connexin 26 improves the epithelial barrier in vitro. J Membr Biol 2007; 218:29-37. [PMID: 17581693 PMCID: PMC2845879 DOI: 10.1007/s00232-007-9025-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2007] [Accepted: 04/04/2007] [Indexed: 01/21/2023]
Abstract
A large proportion of recessive nonsyndromic hearing loss is due to mutations in the GJB2 gene encoding connexin 26 (Cx26), a component of a gap junction. Within different ethnic groups there are specific common recessive mutations, each with a relatively high carrier frequency, suggesting the possibility of heterozygous advantage. Carriers of the R143W GJB2 allele, the most prevalent in the African population, present with a thicker epidermis than noncarriers. In this study, we show that (R143W)Cx26-expressing keratinocytes form a significantly thicker epidermis in an organotypic coculture skin model. In addition, we show increased migration of cells expressing (R143W)Cx26 compared to (WT)Cx26-overexpressing cells. We also demonstrate that cells expressing (R143W)Cx26 are significantly less susceptible to cellular invasion by the enteric pathogen Shigella flexneri than (WT)Cx26-expressing cells. These in vitro studies suggest an advantageous effect of (R143W)Cx26 in epithelial cells.
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Kramer RW, Slagowski NL, Eze NA, Giddings KS, Morrison MF, Siggers KA, Starnbach MN, Lesser CF. Yeast functional genomic screens lead to identification of a role for a bacterial effector in innate immunity regulation. PLoS Pathog 2007; 3:e21. [PMID: 17305427 PMCID: PMC1797620 DOI: 10.1371/journal.ppat.0030021] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2006] [Accepted: 01/02/2007] [Indexed: 11/18/2022] Open
Abstract
Numerous bacterial pathogens manipulate host cell processes to promote infection and ultimately cause disease through the action of proteins that they directly inject into host cells. Identification of the targets and molecular mechanisms of action used by these bacterial effector proteins is critical to understanding pathogenesis. We have developed a systems biological approach using the yeast Saccharomyces cerevisiae that can expedite the identification of cellular processes targeted by bacterial effector proteins. We systematically screened the viable yeast haploid deletion strain collection for mutants hypersensitive to expression of the Shigella type III effector OspF. Statistical data mining of the results identified several cellular processes, including cell wall biogenesis, which when impaired by a deletion caused yeast to be hypersensitive to OspF expression. Microarray experiments revealed that OspF expression resulted in reversed regulation of genes regulated by the yeast cell wall integrity pathway. The yeast cell wall integrity pathway is a highly conserved mitogen-activated protein kinase (MAPK) signaling pathway, normally activated in response to cell wall perturbations. Together these results led us to hypothesize and subsequently demonstrate that OspF inhibited both yeast and mammalian MAPK signaling cascades. Furthermore, inhibition of MAPK signaling by OspF is associated with attenuation of the host innate immune response to Shigella infection in a mouse model. These studies demonstrate how yeast systems biology can facilitate functional characterization of pathogenic bacterial effector proteins. Many bacterial pathogens use specialized secretion systems to deliver effector proteins directly into host cells. The effector proteins mediate the subversion or inhibition of host cell processes to promote survival of the pathogens. Although these proteins are critical elements of pathogenesis, relatively few are well characterized. They often lack significant homology to proteins of known function, and they present special challenges, biological and practical, to study in vivo. For example, their functions often appear to be redundant or synergistic, and the organisms that produce them can be dangerous or difficult to culture, requiring special facilities. The yeast Saccharomyces cerevisiae has recently emerged as a model system to both identify and functionally characterize effector proteins. This work describes how genome-wide phenotypic screens and mRNA profiling of yeast expressing the Shigella effector OspF led to the discovery that OspF inhibits mitogen-activated protein kinase signaling in both yeast and mammalian cells. This inhibition of mitogen-activated protein kinase signaling is associated with attenuation of the host innate immune response. This study demonstrates how yeast functional genomic studies can contribute to the understanding of pathogenic effector proteins.
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Purdy GE, Fisher CR, Payne SM. IcsA surface presentation in Shigella flexneri requires the periplasmic chaperones DegP, Skp, and SurA. J Bacteriol 2007; 189:5566-73. [PMID: 17526712 PMCID: PMC1951818 DOI: 10.1128/jb.00483-07] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A Shigella flexneri degP mutant, which was defective for plaque formation in Henle cell monolayers, had a reduced amount of IcsA detectable on the bacterial surface with antibody. However, the mutant secreted IcsA to the outer membrane at wild-type levels. This suggests that IcsA adopts an altered conformation in the outer membrane of the degP mutant with reduced exposure on the cell surface. IcsA is, therefore, unlikely to be accessible to actin-nucleating proteins within the eukaryotic cell cytoplasm, which is required for bacterial movement within the host cell and cell-to-cell spread. The degP mutant was somewhat more sensitive to detergents, antibiotics, and the antimicrobial peptide magainin, indicating that the degP phenotype was not limited to IcsA surface presentation. The plaque defect of the degP mutant, which is independent of DegP protease activity, was suppressed by overexpression of the periplasmic chaperone Skp but not by SurA. S. flexneri skp and surA mutants failed to form plaques in Henle cell monolayers and were defective in cell surface presentation and polar localization of IcsA. Therefore, the three periplasmic folding factors DegP, Skp, and SurA were all required for IcsA localization and plaque formation by S. flexneri.
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Clark CS, Maurelli AT. Shigella flexneri inhibits staurosporine-induced apoptosis in epithelial cells. Infect Immun 2007; 75:2531-9. [PMID: 17339354 PMCID: PMC1865761 DOI: 10.1128/iai.01866-06] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2006] [Revised: 12/26/2006] [Accepted: 02/21/2007] [Indexed: 01/19/2023] Open
Abstract
Shigella flexneri is a facultative intracellular organism that causes bacillary dysentery. The Shigella IpaB protein activates caspase 1 in macrophages, which eventually leads to apoptosis. In contrast, epithelial cells infected with Shigella undergo a stress response but do not die. Therefore, the objective of this study was to determine if Shigella has the ability to inhibit apoptosis in epithelial cells. A modified gentamicin protection assay was used to investigate if HeLa cells infected with S. flexneri are able to resist the induction of apoptosis following treatment with 4 microM of staurosporine. Nuclear staining and immunofluorescence revealed that infected cells remained healthy while uninfected cells appeared apoptotic. Only uninfected cells had detectable levels of activated caspase 3 upon immunofluorescence, and this was verified by Western blot analysis. Despite interfering with caspase 3 activation, Shigella-infected cells treated with staurosporine did have cytochrome c release and caspase 9 activation, indicating that Shigella protects epithelial cells from apoptosis by inhibiting caspase 3 activation. Analysis of S. flexneri mutants showed that invasion and a functional type III secretion system were required to block apoptosis. In addition, a mutant with a deletion in mxiE, which encodes a transcriptional activator for genes induced intracellularly, failed to inhibit apoptosis. Therefore, protection of epithelial cells from apoptosis by S. flexneri is regulated by one or more of the bacterial genes under the control of mxiE. We believe that S. flexneri, like other pathogens, inhibits apoptosis in epithelial cells but causes apoptosis in macrophages to ensure survival inside the host.
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63
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Arbibe L, Sansonetti P. [Shigella flexneri modulates host cell epigenetic information as a strategy to shape the transcriptional response]. Med Sci (Paris) 2007; 23:238-40. [PMID: 17349276 DOI: 10.1051/medsci/2007233238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Turner EC, Dorman CJ. H-NS antagonism in Shigella flexneri by VirB, a virulence gene transcription regulator that is closely related to plasmid partition factors. J Bacteriol 2007; 189:3403-13. [PMID: 17307842 PMCID: PMC1855880 DOI: 10.1128/jb.01813-06] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The VirB protein of Shigella flexneri is a positive regulator of the major virulence operons of this enteroinvasive intracellular pathogen. VirB resembles no other transcription factor but is strongly homologous to plasmid partition proteins. We found that the binding of the VirB protein to the promoter region of the icsB virulence gene induced hypersensitivity to cleavage by DNase I over a region to which the H-NS repressor protein binds and completely abolished the protection of this sequence from DNase I by H-NS. In the absence of H-NS, the VirB protein had no additive effect on the ability of the icsB promoter to form an open transcription complex, indicating that VirB is not involved in the recruitment of RNA polymerase to the promoter or in open complex formation. Similarly, VirB did not stimulate promoter function in an in vitro transcription assay but acted as an antagonist of H-NS-mediated repression. A sequence located upstream of the icsB promoter and related to cis-acting elements involved in plasmid partitioning was required for promoter derepression by VirB. Alterations to one heptameric motif within this DNA sequence attenuated VirB binding and derepression of icsB transcription.
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Olive AJ, Kenjale R, Espina M, Moore DS, Picking WL, Picking WD. Bile salts stimulate recruitment of IpaB to the Shigella flexneri surface, where it colocalizes with IpaD at the tip of the type III secretion needle. Infect Immun 2007; 75:2626-9. [PMID: 17296762 PMCID: PMC1865747 DOI: 10.1128/iai.01599-06] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Shigella flexneri uses its type III secretion apparatus (TTSA) to deliver invasins into human cells. This TTSA possesses an external needle with IpaD at its tip. We now show that deoxycholate promotes the stable recruitment of IpaB to the needle tip without inducing a rapid burst of type III secretion. The maintenance of IpaB at the needle tip requires a stable association of IpaD with the Shigella surface. This is the first demonstration of a translocator protein being stably associated with the TTSA needle.
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Johnson S, Roversi P, Espina M, Olive A, Deane JE, Birket S, Field T, Picking WD, Blocker AJ, Galyov EE, Picking WL, Lea SM. Self-chaperoning of the type III secretion system needle tip proteins IpaD and BipD. J Biol Chem 2007; 282:4035-44. [PMID: 17077085 PMCID: PMC1894746 DOI: 10.1074/jbc.m607945200] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Bacteria expressing type III secretion systems (T3SS) have been responsible for the deaths of millions worldwide, acting as key virulence elements in diseases ranging from plague to typhoid fever. The T3SS is composed of a basal body, which traverses both bacterial membranes, and an external needle through which effector proteins are secreted. We report multiple crystal structures of two proteins that sit at the tip of the needle and are essential for virulence: IpaD from Shigella flexneri and BipD from Burkholderia pseudomallei. The structures reveal that the N-terminal domains of the molecules are intramolecular chaperones that prevent premature oligomerization, as well as sharing structural homology with proteins involved in eukaryotic actin rearrangement. Crystal packing has allowed us to construct a model for the tip complex that is supported by mutations designed using the structure.
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Sani M, Botteaux A, Parsot C, Sansonetti P, Boekema EJ, Allaoui A. IpaD is localized at the tip of the Shigella flexneri type III secretion apparatus. Biochim Biophys Acta Gen Subj 2007; 1770:307-11. [PMID: 17110044 DOI: 10.1016/j.bbagen.2006.10.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Revised: 10/03/2006] [Accepted: 10/11/2006] [Indexed: 12/23/2022]
Abstract
Type III secretion (T3S) systems are used by numerous Gram-negative pathogenic bacteria to inject virulence proteins into animal and plant host cells. The core of the T3S apparatus, known as the needle complex, is composed of a basal body transversing both bacterial membranes and a needle protruding above the bacterial surface. In Shigella flexneri, IpaD is required to inhibit the activity of the T3S apparatus prior to contact of bacteria with host and has been proposed to assist translocation of bacterial proteins into host cells. We investigated the localization of IpaD by electron microscopy analysis of cross-linked bacteria and mildly purified needle complexes. This analysis revealed the presence of a distinct density at the needle tip. A combination of single particle analysis, immuno-labeling and biochemical analysis, demonstrated that IpaD forms part of the structure at the needle tip. Anti-IpaD antibodies were shown to block entry of bacteria into epithelial cells.
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Abstract
Hfq plays an important role in cellular physiology by regulating the expression of several genes. Hfq synthesis in Escherichia coli is subject to auto-repression at translational level. Studies with Shigella flexneri show that hfq transcription is regulated by a pleiotropic regulator, DksA. Comparison of gene expression profiles of wild type and dksA mutant S. flexneri determined that hfq expression was reduced in the dksA mutant. As DksA is required for stress resistance and plaque formation in cultured cell monolayers, a measure of virulence, we assessed the role of Hfq in the dksA virulence phenotype. Expression of hfq in the dksA mutant restored plaque formation, and an hfq mutant failed to form plaques. Thus, DksA plays a role in regulating hfq gene expression and this regulation is important for S. flexneri virulence. In an in vitro transcription assay, addition of DksA increased transcription of hfq and this effect was greatest with one of the known hfq promoters. Addition of ppGpp, a stringent response molecule, along with DksA in the in vitro transcription assay resulted in a further increase in transcription of hfq, indicating that DksA is required for maximal transcription of hfq during both exponential and stringent response growth conditions.
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Hakemi Vala M, Nowroozi J, Ghazi F, Nabavi Tabatabai P, Haghighi S. Comparing invasive and non-invasive of isolated Shigella flexneri by electron microscopy of cell culture, SDS-PAGE and Congo red method. IRANIAN BIOMEDICAL JOURNAL 2007; 11:47-52. [PMID: 18051704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
BACKGROUND The aim of this study was to compare invasive and non-invasive strains of Shigella flexneri isolated from Tehran by a 120 kDa protein band by SDS-PAGE, electron microscopy of cell culture and Congo red dye methods. METHODS S. flexneri strains were isolated by standard bacterial methods from fecal specimens of children attending to the 3 children's hospitals. Phenotype analysis for screening virulent of strains of S. flexneri was done on a plate of tryptic soy agar contained 0.003% Congo red dye. Whole membrane protein preparations were used to examine the protein profiles of the inner and outer membrane of these Gram-negative bacteria. The protein mixture was electrophoresed through a polyacrylamide gel. The gel was stained with Coomassie brilliant blue R250 and destained with ethanol and acetic acid. HeLa cell culture was done by two-step preparations: one for light microscopy and the other for electron microscopy. RESULTS Some of S. flexneri (46%) were Congo red positive colonies. S. flexneri with negative Congo red phenotype could not enter the HeLa cell culture. A 120 kDa protein band was found in 46% of these bacteria which could enter into HeLa cell culture. Pseudopod structures which facilitate bacterial cell-to-cell spread were readily identified by electron microscopy. DISCUSSION Since the existence of 120-kDa protein band was corresponded to enter of S. flexneri into the HeLa cell culture and correlated with Congo red dye positive, for identification of invasive and non-invasive S. flexneri strains, the use of a 120-kDa protein band by SDS-PAGE or a simple, rapid and very cheap Congo red dye method is recommended. Because, there are some deaths due to Shigella sp. in our country, notification on the isolation of these bacteria in both children hospitals laboratories and private clinical laboratories is important.
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Izard T, Tran Van Nhieu G, Bois PRJ. Shigella applies molecular mimicry to subvert vinculin and invade host cells. ACTA ACUST UNITED AC 2006; 175:465-75. [PMID: 17088427 PMCID: PMC2064523 DOI: 10.1083/jcb.200605091] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Shigella flexneri, the causative agent of bacillary dysentery, injects invasin proteins through a type III secretion apparatus upon contacting the host cell, which triggers pathogen internalization. The invasin IpaA is essential for S. flexneri pathogenesis and binds to the cytoskeletal protein vinculin to facilitate host cell entry. We report that IpaA harbors two vinculin-binding sites (VBSs) within its C-terminal domain that bind to and activate vinculin in a mutually exclusive fashion. Only the highest affinity C-terminal IpaA VBS is necessary for efficient entry and cell–cell spread of S. flexneri, whereas the lower affinity VBS appears to contribute to vinculin recruitment at entry foci of the pathogen. Finally, the crystal structures of vinculin in complex with the VBSs of IpaA reveal the mechanism by which IpaA subverts vinculin's functions, where S. flexneri utilizes a remarkable level of molecular mimicry of the talin–vinculin interaction to activate vinculin. Mimicry of vinculin's interactions may therefore be a general mechanism applied by pathogens to infect the host cell.
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Zurawski DV, Mitsuhata C, Mumy KL, McCormick BA, Maurelli AT. OspF and OspC1 are Shigella flexneri type III secretion system effectors that are required for postinvasion aspects of virulence. Infect Immun 2006; 74:5964-76. [PMID: 16988276 PMCID: PMC1594884 DOI: 10.1128/iai.00594-06] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Shigella flexneri is the causative agent of dysentery, and its pathogenesis is mediated by a type III secretion system (T3SS). S. flexneri secretes effector proteins into the eukaryotic cell via the T3SS, and these proteins usurp host cellular functions to the benefit of the bacteria. OspF and OspC1 are known to be secreted by S. flexneri, but their functions are unknown. We transformed S. flexneri with a plasmid that expresses a two-hemagglutinin tag (2HA) in frame with OspF or OspC1 and verified that these proteins are secreted in a T3SS-dependent manner. Immunofluorescence of HeLa cells infected with S. flexneri expressing OspF-2HA or OspC1-2HA revealed that both proteins localize in the nucleus and cytoplasm of host cells. To elucidate the function of these T3SS effectors, we constructed DeltaospF and DeltaospC1 deletion mutants by allelic exchange. We found that DeltaospF and DeltaospC1 mutants invade host cells and form plaques in confluent monolayers similar to wild-type S. flexneri. However, in the polymorphonuclear (PMN) cell migration assay, a decrease in neutrophil migration was observed for both mutants in comparison to the migration of wild-type bacteria. Moreover, infection of polarized T84 intestinal cells infected with DeltaospF and DeltaospC1 mutants resulted in decreased phosphorylation of extracellular signal-regulated kinase 1/2 in comparison to that of T84 cells infected with wild-type S. flexneri. To date, these are the first examples of T3SS effectors implicated in mitogen-activated protein kinase kinase/extracellular signal-regulated kinase pathway activation. Ultimately, OspF and OspC1 are essential for PMN transepithelial migration, a phenotype associated with increased inflammation and bacterial access to the submucosa, which are fundamental aspects of S. flexneri pathogenesis.
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72
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Yoshida S, Handa Y, Suzuki T, Ogawa M, Suzuki M, Tamai A, Abe A, Katayama E, Sasakawa C. Microtubule-severing activity of Shigella is pivotal for intercellular spreading. Science 2006; 314:985-9. [PMID: 17095701 DOI: 10.1126/science.1133174] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Some pathogenic bacteria actually invade the cytoplasm of their target host cells. Invasive bacteria acquire the propulsive force to move by recruiting actin and inducing its polymerization. Here we show that Shigella movement within the cytoplasm was severely hindered by microtubules and that the bacteria destroyed surrounding microtubules by secreting VirA by means of the type III secretion system. Degradation of microtubules by VirA was dependent on its alpha-tubulin-specific cysteine protease-like activity. virA mutants did not move within the host cytoplasm and failed to move into adjacent cells.
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73
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Burton EA, Pendergast AM, Aballay A. The Caenorhabditis elegans ABL-1 tyrosine kinase is required for Shigella flexneri pathogenesis. Appl Environ Microbiol 2006; 72:5043-51. [PMID: 16820504 PMCID: PMC1489310 DOI: 10.1128/aem.00558-06] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Shigellosis is a diarrheal disease caused by the gram-negative bacterium Shigella flexneri. Following ingestion of the bacterium, S. flexneri interferes with innate immunity, establishes an infection within the human colon, and initiates an inflammatory response that results in destruction of the tissue lining the gut. Examination of host cell factors required for S. flexneri pathogenesis in vivo has proven difficult due to limited host susceptibility. Here we report the development of a pathogenesis system that involves the use of Caenorhabditis elegans as a model organism to study S. flexneri virulence determinants and host molecules required for pathogenesis. We show that S. flexneri-mediated killing of C. elegans correlates with bacterial accumulation in the intestinal tract of the animal. The S. flexneri virulence plasmid, which encodes a type III secretory system as well as various virulence determinants crucial for pathogenesis in mammalian systems, was found to be required for maximal C. elegans killing. Additionally, we demonstrate that ABL-1, the C. elegans homolog of the mammalian c-Abl nonreceptor tyrosine kinase ABL1, is required for S. flexneri pathogenesis in nematodes. These data demonstrate the feasibility of using C. elegans to study S. flexneri pathogenesis in vivo and provide insight into host factors that contribute to S. flexneri pathogenesis.
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74
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Espina M, Ausar SF, Middaugh CR, Picking WD, Picking WL. Spectroscopic and calorimetric analyses of invasion plasmid antigen D (IpaD) from Shigella flexneri reveal the presence of two structural domains. Biochemistry 2006; 45:9219-27. [PMID: 16866368 DOI: 10.1021/bi060625v] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Shigella flexneri is a facultative intracellular pathogen that causes severe gastroenteritis in humans. Invasion plasmid antigen D (IpaD) is an essential participant in Shigella invasion of intestinal cells, but no detailed structural information is available to help understand the proposed role of IpaD in invasion or its interaction with other invasion proteins. Therefore, the secondary and tertiary structure and thermal stability of IpaD as well as selected IpaD deletion mutants were investigated using Fourier transform infrared (FTIR), circular dichroism (CD), and both intrinsic and extrinsic fluorescence spectroscopies. The energetics of thermal unfolding were also evaluated by differential scanning calorimetry (DSC). Secondary-structure analysis by CD and FTIR suggests that that IpaD is primarily alpha-helical with characteristics of a intramolecular coiled coil. Thermal studies revealed that the unfolding of IpaD is a complex process consisting of two transitions centered near 59 and 80 degrees C. A comparison of the data obtained with the intact protein and selected deletion mutants indicated that the lower temperature transition is a reversible event attributable to the unfolding of a small domain located at the N terminus of IpaD. In contrast, the thermal unfolding of the proposed major and highly stable C-terminal domain was irreversible and led to protein aggregation. When the results are taken together, they strongly support the idea that IpaD has two independent folding domains.
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MESH Headings
- Antigens, Bacterial/chemistry
- Antigens, Bacterial/genetics
- Antigens, Bacterial/metabolism
- Antigens, Bacterial/physiology
- Bacterial Proteins/chemistry
- Bacterial Proteins/genetics
- Bacterial Proteins/metabolism
- Bacterial Proteins/physiology
- Calorimetry, Differential Scanning/methods
- Circular Dichroism
- Plasmids
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Sequence Deletion
- Shigella flexneri/chemistry
- Shigella flexneri/pathogenicity
- Spectrometry, Fluorescence
- Spectrophotometry, Ultraviolet
- Spectroscopy, Fourier Transform Infrared/methods
- Virulence
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75
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Walker R. Quinine sulfate inhibits invasion of Salmonella typhimurium and Shigella flexneri: a preliminary study. J Travel Med 2006; 13:324; author reply 324. [PMID: 16987134 DOI: 10.1111/j.1708-8305.2006.0063_1.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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