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Brotcke Zumsteg A, Goosmann C, Brinkmann V, Morona R, Zychlinsky A. IcsA is a Shigella flexneri adhesin regulated by the type III secretion system and required for pathogenesis. Cell Host Microbe 2015; 15:435-45. [PMID: 24721572 DOI: 10.1016/j.chom.2014.03.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 01/20/2014] [Accepted: 02/24/2014] [Indexed: 01/05/2023]
Abstract
Following contact with the epithelium, the enteric intracellular bacterial pathogen Shigella flexneri invades epithelial cells and escapes intracellular phagosomal destruction using its type III secretion system (T3SS). The bacterium replicates within the host cell cytosol and spreads between cells using actin-based motility, which is mediated by the virulence factor IcsA (VirG). Whereas S. flexneri invasion is well characterized, adhesion mechanisms of the bacterium remain elusive. We found that IcsA also functions as an adhesin that is both necessary and sufficient to promote contact with host cells. As adhesion can be beneficial or deleterious depending on the host cell type, S. flexneri regulates IcsA-dependent adhesion. Activation of the T3SS in response to the bile salt deoxycholate triggers IcsA-dependent adhesion and enhances pathogen invasion. IcsA-dependent adhesion contributes to virulence in a mouse model of shigellosis, underscoring the importance of this adhesin to S. flexneri pathogenesis.
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Affiliation(s)
- Anna Brotcke Zumsteg
- Department of Cellular Microbiology, Max Planck Institute for Infection Biology, Berlin 13353, Germany
| | - Christian Goosmann
- Microscopy Core Facility, Max Planck Institute for Infection Biology, Berlin 13353, Germany
| | - Volker Brinkmann
- Microscopy Core Facility, Max Planck Institute for Infection Biology, Berlin 13353, Germany
| | - Renato Morona
- School of Molecular and Biomedical Science, University of Adelaide, Adelaide 5000, South Australia, Australia
| | - Arturo Zychlinsky
- Department of Cellular Microbiology, Max Planck Institute for Infection Biology, Berlin 13353, Germany.
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2
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A CRISPR/Cas system mediates bacterial innate immune evasion and virulence. Nature 2013; 497:254-7. [PMID: 23584588 PMCID: PMC3651764 DOI: 10.1038/nature12048] [Citation(s) in RCA: 303] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Accepted: 02/27/2013] [Indexed: 12/22/2022]
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3
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Llewellyn AC, Zhao J, Song F, Parvathareddy J, Xu Q, Napier BA, Laroui H, Merlin D, Bina JE, Cotter PA, Miller MA, Raetz CRH, Weiss DS. NaxD is a deacetylase required for lipid A modification and Francisella pathogenesis. Mol Microbiol 2012; 86:611-27. [PMID: 22966934 DOI: 10.1111/mmi.12004] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/17/2012] [Indexed: 11/30/2022]
Abstract
Modification of specific Gram-negative bacterial cell envelope components, such as capsule, O-antigen and lipid A, are often essential for the successful establishment of infection. Francisella species express lipid A molecules with unique characteristics involved in circumventing host defences, which significantly contribute to their virulence. In this study, we show that NaxD, a member of the highly conserved YdjC superfamily, is a deacetylase required for an important modification of the outer membrane component lipid A in Francisella. Mass spectrometry analysis revealed that NaxD is essential for the modification of a lipid A phosphate with galactosamine in Francisella novicida, a model organism for the study of highly virulent Francisella tularensis. Significantly, enzymatic assays confirmed that this protein is necessary for deacetylation of its substrate. In addition, NaxD was involved in resistance to the antimicrobial peptide polymyxin B and critical for replication in macrophages and in vivo virulence. Importantly, this protein is also required for lipid A modification in F. tularensis as well as Bordetella bronchiseptica. Since NaxD homologues are conserved among many Gram-negative pathogens, this work has broad implications for our understanding of host subversion mechanisms of other virulent bacteria.
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Affiliation(s)
- Anna C Llewellyn
- Department of Microbiology and Immunology, Microbiology and Molecular Genetics Program, Emory University, Atlanta, GA, USA; Emory Vaccine Center, Emory University, Atlanta, GA, USA
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4
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Fakih S, Podinovskaia M, Kong X, Schaible UE, Collins HL, Hider RC. Monitoring intracellular labile iron pools: A novel fluorescent iron(III) sensor as a potential non-invasive diagnosis tool. J Pharm Sci 2009; 98:2212-26. [PMID: 18823046 DOI: 10.1002/jps.21583] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The physiological and pathophysiological importance of intracellular redox active "labile" iron has created a significant need for improved noninvasive diagnostic tools to reliably monitor iron metabolism in living cells. In this context, fluorescent iron-sensitive chemosensors in combination with digital fluorescence spectroscopic methods have proven to be highly sensitive and indispensable tools to determine cellular iron homeostasis. Recently, application of fluorescent iron sensors has led to the identification of a complex sub-cellular iron compartmentation. Cell organelle-specific iron sensors will significantly contribute to enhance fundamental knowledge of cellular iron trafficking, representing a crucial prerequisite for the future development of therapeutic strategies in iron dysregulatory diseases. Here we present physicochemical characterization and functional investigation of a new 3-hydroxypyridin-4-one based fluorescent iron(III) sensor, exclusively monitoring labile iron pools in the endosomal/lysosomal compartments. In vitro studies of the fluorescein labeled probe were carried out in murine bone marrow derived macrophages. Endosomal/lysosomal accumulation of the probe was revealed by confocal microscopy. Flow cytometry analyses demonstrated high sensitivity of the probe towards exogenous alterations of intracellular iron concentrations as well as in response to the chelation potency of iron chelators, clinically approved for treatment of iron-overload related diseases.
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Affiliation(s)
- Sarah Fakih
- Department of Inorganic Chemistry, Georg-August-University of Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany.
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5
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Meissner F, Molawi K, Zychlinsky A. Superoxide dismutase 1 regulates caspase-1 and endotoxic shock. Nat Immunol 2008; 9:866-72. [PMID: 18604212 DOI: 10.1038/ni.1633] [Citation(s) in RCA: 249] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2008] [Accepted: 06/13/2008] [Indexed: 01/09/2023]
Abstract
Caspase-1 serves an essential function in the initiation of inflammation by proteolytically maturing the cytokines interleukin 1 beta and interleukin 18. Several Nod-like receptors activate caspase-1 in response to microbial and 'danger' signals by assembling cytosolic protein complexes called 'inflammasomes'. We show here that superoxide dismutase 1 (SOD1) regulates caspase-1 activation. In SOD1-deficient macrophages, higher superoxide production decreased the cellular redox potential and specifically inhibited caspase-1 by reversible oxidation and glutathionylation of the redox-sensitive cysteine residues Cys397 and Cys362. Conversely, hypoxic conditions abrogated caspase-1 inhibition. In vivo, SOD1-deficient mice produced less caspase-1-dependent cytokines and were less susceptible to lipopolysaccharide-induced septic shock. Our findings identify a physiological post-translational mechanism in the control of caspase-1-mediated inflammatory processes.
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Affiliation(s)
- Felix Meissner
- Department of Cellular Microbiology, Max Planck Institute for Infection Biology, 10117 Berlin, Germany
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6
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Identification of fevR, a novel regulator of virulence gene expression in Francisella novicida. Infect Immun 2008; 76:3473-80. [PMID: 18559431 DOI: 10.1128/iai.00430-08] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Francisella tularensis infects wild animals and humans to cause tularemia. This pathogen targets the cytosol of macrophages, where it replicates using the genes in the Francisella pathogenicity island (FPI). Virulence gene regulation in Francisella is complex, but transcriptional regulators MglA and SspA have been shown to regulate the expression of approximately 100 genes, including the entire FPI. We utilized a Francisella novicida transposon mutant library to identify additional regulatory factors and identified five additional genes that are essential for virulence gene expression. One regulatory gene, FTN_0480 (fevR, Francisella effector of virulence regulation), present in all Francisella species, is required for expression of the FPI genes and other genes in the MglA/SspA regulon. The expression of fevR is positively regulated by MglA. However, constitutive expression of fevR in an mglA mutant strain did not restore expression of the MglA/SspA regulon, demonstrating that mglA and fevR act in parallel to positively regulate virulence gene expression. Virulence studies revealed that fevR is essential for bacterial replication in macrophages and in mice, where we additionally show that fevR is required for the expression of genes in the MglA/SspA regulon in vivo. Thus, fevR is a crucial virulence gene in Francisella, required for the expression of virulence factors known to be essential for this pathogen's subversion of host defenses and pathogenesis in vivo.
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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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Affiliation(s)
- Susanne Paetzold
- Department of Cellular Microbiology, Max-Planck-Institut für Infektionsbiologie, Charité Platz 1, D-10117 Berlin, Germany
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Brotcke A, Weiss DS, Kim CC, Chain P, Malfatti S, Garcia E, Monack DM. Identification of MglA-regulated genes reveals novel virulence factors in Francisella tularensis. Infect Immun 2006; 74:6642-55. [PMID: 17000729 PMCID: PMC1698089 DOI: 10.1128/iai.01250-06] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The facultative intracellular bacterium Francisella tularensis causes the zoonotic disease tularemia. F. tularensis resides within host macrophages in vivo, and this ability is essential for pathogenesis. The transcription factor MglA is required for the expression of several Francisella genes that are necessary for replication in macrophages and for virulence in mice. We hypothesized that the identification of MglA-regulated genes in the Francisella genome by transcriptional profiling of wild-type and mglA mutant bacteria would lead to the discovery of new virulence factors utilized by F. tularensis. A total of 102 MglA-regulated genes were identified, the majority of which were positively regulated, including all of the Francisella pathogenicity island (FPI) genes. We mutated novel MglA-regulated genes and tested the mutants for their ability to replicate and induce cytotoxicity in macrophages and to grow in mice. Mutations in MglA-regulated genes within the FPI (pdpB and cds2) as well as outside the FPI (FTT0989, oppB, and FTT1209c) were either attenuated or hypervirulent in macrophages compared to the wild-type strain. All of these mutants exhibited decreased fitness in vivo in competition experiments with wild-type bacteria. We have identified five new Francisella virulence genes, and our results suggest that characterizations of additional MglA-regulated genes will yield further insights into the pathogenesis of this bacterium.
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Affiliation(s)
- Anna Brotcke
- Department of Microbiology and Immunology, Stanford University School of Medicine, 299 Campus Drive, Fairchild Bldg. D041, Stanford, CA 94305, USA
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9
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Pepys MB, Hawkins PN, Kahan MC, Tennent GA, Gallimore JR, Graham D, Sabin CA, Zychlinsky A, de Diego J. Proinflammatory effects of bacterial recombinant human C-reactive protein are caused by contamination with bacterial products, not by C-reactive protein itself. Circ Res 2005; 97:e97-103. [PMID: 16254214 PMCID: PMC1400607 DOI: 10.1161/01.res.0000193595.03608.08] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Intravenous administration to human volunteers of a commercial preparation of recombinant human C-reactive protein (CRP) produced in Escherichia coli was recently reported in this journal to induce an acute phase response of serum amyloid A protein (SAA) and of CRP itself, and to activate the coagulation system. The authors concluded that CRP is probably a mediator of atherothrombotic disease. Here we confirm that this recombinant CRP preparation was proinflammatory both for mouse macrophages in vitro and for mice in vivo, but show that pure natural human CRP had no such activity. Furthermore mice transgenic for human CRP, and expressing it throughout their lives, maintained normal concentrations of their most sensitive endogenous acute phase reactants, SAA and serum amyloid P component (SAP). The patterns of in vitro cytokine induction and of in vivo acute phase stimulation by the recombinant CRP preparation were consistent with contamination by bacterial products, and there was 46.6 EU of apparent endotoxin activity per mg of CRP in the bacterial product, compared with 0.9 EU per mg of our isolated natural human CRP preparation. The absence of any proinflammatory activity in natural CRP for macrophages or healthy mice strongly suggests that the in vivo effects of the recombinant preparation observed in humans were attributable to proinflammatory bacterial products and not human CRP.
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Affiliation(s)
- Mark B Pepys
- Centre for Amyloidosis and Acute Phase Proteins, Department of Medicine, Royal Free and University College Medical School, London, UK.
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Weiss DS, Takeda K, Akira S, Zychlinsky A, Moreno E. MyD88, but not toll-like receptors 4 and 2, is required for efficient clearance of Brucella abortus. Infect Immun 2005; 73:5137-43. [PMID: 16041030 PMCID: PMC1201196 DOI: 10.1128/iai.73.8.5137-5143.2005] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
It is not clear how the host initially recognizes and responds to infection by gram-negative pathogenic Brucella spp. It was previously shown (D. S. Weiss, B. Raupach, K. Takeda, S. Akira, and A. Zychlinsky, J. Immunol. 172:4463-4469, 2004) that the early macrophage response against gram-negative bacteria is mediated by Toll-like receptor 4 (TLR4), which signals in response to lipopolysaccharide (LPS). Brucella, however, has a noncanonical LPS which does not have potent immunostimulatory activity. We evaluated the kinetics of TLR4 activation and the cytokine response in murine macrophages after Brucella infection. We found that during infection of macrophages, Brucella avoids activation of TLR4 at 6 h but activates TLR4, TLR2, and myeloid differentiation factor 88 (MyD88) at 24 h postinfection. Interestingly, even though its activation is delayed, MyD88 is important for host defense against Brucella infection in vivo, since MyD88(-/-) mice do not clear the bacteria as efficiently as wild-type, TLR4(-/-), TLR2(-/-), or TLR4/TLR2(-/-) mice.
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Affiliation(s)
- David S Weiss
- Max-Planck Institut für Infektionsbiologie, Campus Charite Mitte, Schumannstrasse 21/22, Berlin D-10117, Germany
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Weiss DS, Raupach B, Takeda K, Akira S, Zychlinsky A. Toll-Like Receptors Are Temporally Involved in Host Defense. THE JOURNAL OF IMMUNOLOGY 2004; 172:4463-9. [PMID: 15034062 DOI: 10.4049/jimmunol.172.7.4463] [Citation(s) in RCA: 167] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Toll-like receptors (TLRs) are evolutionarily conserved proteins that recognize microbial molecules and initiate host defense. To investigate how TLRs work together to fight infections, we tested the role of TLRs in host defense against the Gram-negative bacterial pathogen, Salmonella. We show that TLR4 is critical for early cytokine production and killing of bacteria by murine macrophages. Interestingly, later on, TLR2, but not TLR4, is required for macrophage responses. Myeloid differentiation factor 88, an adaptor protein directly downstream of TLRs, is required for both early and late responses. TLR4, TLR2, and myeloid differentiation factor 88 are involved in murine host defense against Salmonella in vivo, which correlates with the defects in host defense observed in vitro. We propose a model where the sequential activation of TLRs tailors the immune response to different microbes.
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MESH Headings
- Acute Disease
- Adaptor Proteins, Signal Transducing
- Administration, Oral
- Animals
- Antigens, Bacterial/administration & dosage
- Antigens, Bacterial/immunology
- Antigens, Differentiation/genetics
- Blood Bactericidal Activity/immunology
- Cytotoxicity, Immunologic/genetics
- Down-Regulation/immunology
- Genetic Predisposition to Disease
- Immunity, Innate/genetics
- Macrophages/immunology
- Macrophages/microbiology
- Membrane Glycoproteins/agonists
- Membrane Glycoproteins/deficiency
- Membrane Glycoproteins/genetics
- Membrane Glycoproteins/physiology
- Mice
- Mice, Inbred C3H
- Mice, Inbred C57BL
- Mice, Knockout
- Myeloid Differentiation Factor 88
- Phenotype
- Receptors, Cell Surface/agonists
- Receptors, Cell Surface/deficiency
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/physiology
- Receptors, Immunologic/deficiency
- Receptors, Immunologic/genetics
- Salmonella Infections, Animal/genetics
- Salmonella Infections, Animal/immunology
- Salmonella Infections, Animal/microbiology
- Salmonella typhimurium/growth & development
- Salmonella typhimurium/immunology
- Signal Transduction/genetics
- Signal Transduction/immunology
- Time Factors
- Toll-Like Receptor 2
- Toll-Like Receptor 4
- Toll-Like Receptors
- Up-Regulation/immunology
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Affiliation(s)
- David S Weiss
- Department of Microbiology and Skirball Institute, New York University School of Medicine, New York, NY 10016, USA
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12
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Winau F, Schwierzeck V, Hurwitz R, Remmel N, Sieling PA, Modlin RL, Porcelli SA, Brinkmann V, Sugita M, Sandhoff K, Kaufmann SHE, Schaible UE. Saposin C is required for lipid presentation by human CD1b. Nat Immunol 2004; 5:169-74. [PMID: 14716313 DOI: 10.1038/ni1035] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2003] [Accepted: 12/22/2003] [Indexed: 11/09/2022]
Abstract
Lipids from Mycobacterium tuberculosis are presented through CD1 proteins to T lymphocytes in humans, but the accessory molecules required for antigen loading and presentation remain unidentified. Here we show that fibroblasts deficient in sphingolipid activator proteins (SAPs) transfected with CD1b failed to activate lipid-specific T cells. However, the T cell response was restored when fibroblasts were reconstituted with SAP-C but not other SAPs. Lipid antigen and SAP-C colocalized in lysosomal compartments, and liposome assays showed that SAP-C efficiently extracts antigen from membranes. Coprecipitation demonstrated direct molecular interaction between SAP-C and CD1b. We propose a model in which SAP-C exposes lipid antigens from intralysosomal membranes for loading onto CD1b. Thus, SAP-C represents a missing link in antigen presentation of lipids through CD1b to human T cells.
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Affiliation(s)
- Florian Winau
- Max-Planck-Institute for Infection Biology, Department of Immunology, Schumannstrasse 21-22, D-10117 Berlin, Germany
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