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Landeta C, Boyd D, Beckwith J. Disulfide bond formation in prokaryotes. Nat Microbiol 2018; 3:270-280. [PMID: 29463925 DOI: 10.1038/s41564-017-0106-2] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Accepted: 12/21/2017] [Indexed: 12/25/2022]
Abstract
Interest in protein disulfide bond formation has recently increased because of the prominent role of disulfide bonds in bacterial virulence and survival. The first discovered pathway that introduces disulfide bonds into cell envelope proteins consists of Escherichia coli enzymes DsbA and DsbB. Since its discovery, variations on the DsbAB pathway have been found in bacteria and archaea, probably reflecting specific requirements for survival in their ecological niches. One variation found amongst Actinobacteria and Cyanobacteria is the replacement of DsbB by a homologue of human vitamin K epoxide reductase. Many Gram-positive bacteria express enzymes involved in disulfide bond formation that are similar, but non-homologous, to DsbAB. While bacterial pathways promote disulfide bond formation in the bacterial cell envelope, some archaeal extremophiles express proteins with disulfide bonds both in the cytoplasm and in the extra-cytoplasmic space, possibly to stabilize proteins in the face of extreme conditions, such as growth at high temperatures. Here, we summarize the diversity of disulfide-bond-catalysing systems across prokaryotic lineages, discuss examples for understanding the biological basis of such systems, and present perspectives on how such systems are enabling advances in biomedical engineering and drug development.
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Affiliation(s)
- Cristina Landeta
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, USA
| | - Dana Boyd
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, USA
| | - Jon Beckwith
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, USA.
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2
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Deletion of the Major Facilitator Superfamily Transporter fptB Alters Host Cell Interactions and Attenuates Virulence of Type A Francisella tularensis. Infect Immun 2018; 86:IAI.00832-17. [PMID: 29311235 PMCID: PMC5820938 DOI: 10.1128/iai.00832-17] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 12/22/2017] [Indexed: 12/12/2022] Open
Abstract
Francisella tularensis is a Gram-negative, facultative, intracellular coccobacillus that can infect a wide variety of hosts. In humans, F. tularensis causes the zoonosis tularemia following insect bites, ingestion, inhalation, and the handling of infected animals. The fact that a very small inoculum delivered by the aerosol route can cause severe disease, coupled with the possibility of its use as an aerosolized bioweapon, has led to the classification of Francisella tularensis as a category A select agent and has renewed interest in the formulation of a vaccine. To this end, we engineered a type A strain SchuS4 derivative containing a targeted deletion of the major facilitator superfamily (MFS) transporter fptB. Based on the attenuating capacity of this deletion in the F. tularensis LVS background, we hypothesized that the deletion of this transporter would alter the intracellular replication and cytokine induction of the type A strain and attenuate virulence in the stringent C57BL/6J mouse model. Here we demonstrate that the deletion of fptB significantly alters the intracellular life cycle of F. tularensis, attenuating intracellular replication in both cell line-derived and primary macrophages and inducing a novel cytosolic escape delay. Additionally, we observed prominent differences in the in vitro cytokine profiles in human macrophage-like cells. The mutant was highly attenuated in the C57BL/6J mouse model and provided partial protection against virulent type A F. tularensis challenge. These results indicate a fundamental necessity for this nutrient transporter in the timely progression of F. tularensis through its replication cycle and in pathogenesis.
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Pavkova I, Kopeckova M, Klimentova J, Schmidt M, Sheshko V, Sobol M, Zakova J, Hozak P, Stulik J. The Multiple Localized Glyceraldehyde-3-Phosphate Dehydrogenase Contributes to the Attenuation of the Francisella tularensis dsbA Deletion Mutant. Front Cell Infect Microbiol 2017; 7:503. [PMID: 29322032 PMCID: PMC5732180 DOI: 10.3389/fcimb.2017.00503] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 11/22/2017] [Indexed: 12/14/2022] Open
Abstract
The DsbA homolog of Francisella tularensis was previously demonstrated to be required for intracellular replication and animal death. Disruption of the dsbA gene leads to a pleiotropic phenotype that could indirectly affect a number of different cellular pathways. To reveal the broad effects of DsbA, we compared fractions enriched in membrane proteins of the wild-type FSC200 strain with the dsbA deletion strain using a SILAC-based quantitative proteomic analysis. This analysis enabled identification of 63 proteins with significantly altered amounts in the dsbA mutant strain compared to the wild-type strain. These proteins comprise a quite heterogeneous group including hypothetical proteins, proteins associated with membrane structures, and potential secreted proteins. Many of them are known to be associated with F. tularensis virulence. Several proteins were selected for further studies focused on their potential role in tularemia's pathogenesis. Of them, only the gene encoding glyceraldehyde-3-phosphate dehydrogenase, an enzyme of glycolytic pathway, was found to be important for full virulence manifestations both in vivo and in vitro. We next created a viable mutant strain with deleted gapA gene and analyzed its phenotype. The gapA mutant is characterized by reduced virulence in mice, defective replication inside macrophages, and its ability to induce a protective immune response against systemic challenge with parental wild-type strain. We also demonstrate the multiple localization sites of this protein: In addition to within the cytosol, it was found on the cell surface, outside the cells, and in the culture medium. Recombinant GapA was successfully obtained, and it was shown that it binds host extracellular serum proteins like plasminogen, fibrinogen, and fibronectin.
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Affiliation(s)
- Ivona Pavkova
- Department of Molecular Pathology, Faculty of Military Health Science, University of Defence, Hradec Kralove, Czechia
| | - Monika Kopeckova
- Department of Molecular Pathology, Faculty of Military Health Science, University of Defence, Hradec Kralove, Czechia
| | - Jana Klimentova
- Department of Molecular Pathology, Faculty of Military Health Science, University of Defence, Hradec Kralove, Czechia
| | - Monika Schmidt
- Department of Molecular Pathology, Faculty of Military Health Science, University of Defence, Hradec Kralove, Czechia
| | - Valeria Sheshko
- Department of Molecular Pathology, Faculty of Military Health Science, University of Defence, Hradec Kralove, Czechia
| | - Margarita Sobol
- Department of Biology of the Cell Nucleus, Institute of Molecular Genetics ASCR v.v.i., Prague, Czechia
| | - Jitka Zakova
- Department of Molecular Pathology, Faculty of Military Health Science, University of Defence, Hradec Kralove, Czechia
| | - Pavel Hozak
- Department of Biology of the Cell Nucleus, Institute of Molecular Genetics ASCR v.v.i., Prague, Czechia.,Microscopy Centre-LM & EM, Institute of Molecular Genetics ASCR v.v.i., Prague, Czechia.,Division BIOCEV, Laboratory of Epigenetics of the Cell Nucleus, Institute of Molecular Genetics ASCR v.v.i., Vestec, Czechia
| | - Jiri Stulik
- Department of Molecular Pathology, Faculty of Military Health Science, University of Defence, Hradec Kralove, Czechia
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4
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Timofeev V, Bakhteeva I, Titareva G, Kopylov P, Christiany D, Mokrievich A, Dyatlov I, Vergnaud G. Russian isolates enlarge the known geographic diversity of Francisella tularensis subsp. mediasiatica. PLoS One 2017; 12:e0183714. [PMID: 28873421 PMCID: PMC5584958 DOI: 10.1371/journal.pone.0183714] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 08/09/2017] [Indexed: 11/18/2022] Open
Abstract
Francisella tularensis, a small Gram-negative bacterium, is capable of infecting a wide range of animals, including humans, and causes a plague-like disease called tularemia—a highly contagious disease with a high mortality rate. Because of these characteristics, F. tularensis is considered a potential agent of biological terrorism. Currently, F. tularensis is divided into four subspecies, which differ in their virulence and geographic distribution. Two of them, subsp. tularensis (primarily found in North America) and subsp. holarctica (widespread across the Northern Hemisphere), are responsible for tularemia in humans. Subsp. novicida is almost avirulent in humans. The fourth subspecies, subsp. mediasiatica, is the least studied because of its limited distribution and impact in human health. It is found only in sparsely populated regions of Central Asia. In this report, we describe the first focus of naturally circulating F. tularensis subsp. mediasiatica in Russia. We isolated and characterized 18 strains of this subspecies in the Altai region. All strains were highly virulent in mice. The virulence of subsp. mediasiatica in a vaccinated mouse model is intermediate between that of subsp. tularensis and subsp. holarctica. Based on a multiple-locus variable number tandem repeat analysis (MLVA), we show that the Altaic population of F. tularensis subsp. mediasiatica is genetically distinct from the classical Central Asian population, and probably is endemic to Southern Siberia. We propose to subdivide the mediasiatica subspecies into three phylogeographic groups, M.I, M.II and M.III.
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Affiliation(s)
- Vitalii Timofeev
- State Research Center for Applied Microbiology and Biotechnology (SRCAMB), Obolensk, Moscow Region, Russia
- * E-mail: (VT); (GV)
| | - Irina Bakhteeva
- State Research Center for Applied Microbiology and Biotechnology (SRCAMB), Obolensk, Moscow Region, Russia
| | - Galina Titareva
- State Research Center for Applied Microbiology and Biotechnology (SRCAMB), Obolensk, Moscow Region, Russia
| | - Pavel Kopylov
- State Research Center for Applied Microbiology and Biotechnology (SRCAMB), Obolensk, Moscow Region, Russia
| | - David Christiany
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette cedex, France
| | - Alexander Mokrievich
- State Research Center for Applied Microbiology and Biotechnology (SRCAMB), Obolensk, Moscow Region, Russia
| | - Ivan Dyatlov
- State Research Center for Applied Microbiology and Biotechnology (SRCAMB), Obolensk, Moscow Region, Russia
| | - Gilles Vergnaud
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette cedex, France
- * E-mail: (VT); (GV)
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Chen F, Cui G, Wang S, Nair MKM, He L, Qi X, Han X, Zhang H, Zhang JR, Su J. Outer membrane vesicle-associated lipase FtlA enhances cellular invasion and virulence in Francisella tularensis LVS. Emerg Microbes Infect 2017; 6:e66. [PMID: 28745311 PMCID: PMC5567169 DOI: 10.1038/emi.2017.53] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 05/16/2017] [Accepted: 05/22/2017] [Indexed: 01/10/2023]
Abstract
Francisella tularensis is a highly infectious intracellular pathogen that infects a wide range of host species and causes fatal pneumonic tularemia in humans. ftlA was identified as a potential virulence determinant of the F. tularensis live vaccine strain (LVS) in our previous transposon screen, but its function remained undefined. Here, we show that an unmarked deletion mutant of ftlA was avirulent in a pneumonia mouse model with a severely impaired capacity to infect host cells. Consistent with its sequence homology with GDSL lipase/esterase family proteins, the FtlA protein displayed lipolytic activity in both E. coli and F. tularensis with a preference for relatively short carbon-chain substrates. FtlA thus represents the first F. tularensis lipase to promote bacterial infection of host cells and in vivo fitness. As a cytoplasmic protein, we found that FtlA was secreted into the extracellular environment as a component of outer membrane vesicles (OMVs). Further confocal microscopy analysis revealed that the FtlA-containing OMVs isolated from F. tularensis LVS attached to the host cell membrane. Finally, the OMV-associated FtlA protein complemented the genetic deficiency of the ΔftlA mutant in terms of host cell infection when OMVs purified from the parent strain were co-incubated with the mutant bacteria. These lines of evidence strongly suggest that the FtlA lipase promotes F. tularensis adhesion and internalization by modifying bacterial and/or host molecule(s) when it is secreted as a component of OMVs.
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Affiliation(s)
- Fei Chen
- Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Guolin Cui
- Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Shuxia Wang
- Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | | | - Lihong He
- Center for Infectious Disease Research, School of Medicine, Tsinghua University, Beijing 100084, China
| | - Xinyi Qi
- Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Xiangmin Han
- Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Hanqi Zhang
- Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Jing-Ren Zhang
- Center for Infectious Disease Research, School of Medicine, Tsinghua University, Beijing 100084, China
| | - Jingliang Su
- Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
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Bröms JE, Meyer L, Sjöstedt A. A mutagenesis-based approach identifies amino acids in the N-terminal part of Francisella tularensis IglE that critically control Type VI system-mediated secretion. Virulence 2016; 8:821-847. [PMID: 27830989 PMCID: PMC5626337 DOI: 10.1080/21505594.2016.1258507] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The Gram-negative bacterium Francisella tularensis is the etiological agent of the zoonotic disease tularemia. Its life cycle is characterized by an ability to survive within phagocytic cells through phagosomal escape and replication in the cytosol, ultimately causing inflammasome activation and host cell death. Required for these processes is the Francisella Pathogenicity Island (FPI), which encodes a Type VI secretion system (T6SS) that is active during intracellular infection. In this study, we analyzed the role of the FPI-component IglE, a lipoprotein which we previously have shown to be secreted in a T6SS-dependent manner. We demonstrate that in F. tularensis LVS, IglE is an outer membrane protein. Upon infection of J774 cells, an ΔiglE mutant failed to escape from phagosomes, and subsequently, to multiply and cause cytopathogenicity. Moreover, ΔiglE was unable to activate the inflammasome, to inhibit LPS-stimulated secretion of TNF-α, and showed marked attenuation in the mouse model. In F. novicida, IglE was required for in vitro secretion of IglC and VgrG. A mutagenesis-based approach involving frameshift mutations and alanine substitution mutations within the first ∼ 38 residues of IglE revealed that drastic changes in the sequence of the extreme N-terminus (residues 2-6) were well tolerated and, intriguingly, caused hyper-secretion of IglE during intracellular infection, while even subtle mutations further downstream lead to impaired protein function. Taken together, this study highlights the importance of IglE in F. tularensis pathogenicity, and the contribution of the N-terminus for all of the above mentioned processes.
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Affiliation(s)
- Jeanette E Bröms
- a Department of Clinical Microbiology , Clinical Bacteriology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University , Umeå , Sweden
| | - Lena Meyer
- a Department of Clinical Microbiology , Clinical Bacteriology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University , Umeå , Sweden
| | - Anders Sjöstedt
- a Department of Clinical Microbiology , Clinical Bacteriology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University , Umeå , Sweden
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7
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Szewczyk J, Collet JF. The Journey of Lipoproteins Through the Cell: One Birthplace, Multiple Destinations. Adv Microb Physiol 2016; 69:1-50. [PMID: 27720009 DOI: 10.1016/bs.ampbs.2016.07.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Bacterial lipoproteins are a very diverse group of proteins characterized by the presence of an N-terminal lipid moiety that serves as a membrane anchor. Lipoproteins have a wide variety of crucial functions, ranging from envelope biogenesis to stress response. In Gram-negative bacteria, lipoproteins can be targeted to various destinations in the cell, including the periplasmic side of the cytoplasmic or outer membrane, the cell surface or the external milieu. The sorting mechanisms have been studied in detail in Escherichia coli, but exceptions to the rules established in this model bacterium exist in other bacteria. In this chapter, we will present the current knowledge on lipoprotein sorting in the cell. Our particular focus will be on the surface-exposed lipoproteins that appear to be much more common than previously assumed. We will discuss the different targeting strategies, provide numerous examples of surface-exposed lipoproteins and discuss the techniques used to assess their surface exposure.
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Affiliation(s)
- J Szewczyk
- WELBIO, Brussels, Belgium; de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - J-F Collet
- WELBIO, Brussels, Belgium; de Duve Institute, Université catholique de Louvain, Brussels, Belgium.
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8
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Bocian-Ostrzycka KM, Grzeszczuk MJ, Banaś AM, Jastrząb K, Pisarczyk K, Kolarzyk A, Łasica AM, Collet JF, Jagusztyn-Krynicka EK. Engineering of Helicobacter pylori Dimeric Oxidoreductase DsbK (HP0231). Front Microbiol 2016; 7:1158. [PMID: 27507968 PMCID: PMC4960241 DOI: 10.3389/fmicb.2016.01158] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 07/12/2016] [Indexed: 12/16/2022] Open
Abstract
The formation of disulfide bonds that are catalyzed by proteins of the Dsb (disulfide bond) family is crucial for the correct folding of many extracytoplasmic proteins. Thus, this formation plays an essential, pivotal role in the assembly of many virulence factors. The Helicobacter pylori disulfide bond-forming system is uncomplicated compared to the best-characterized Escherichia coli Dsb pathways. It possesses only two extracytoplasmic Dsb proteins named HP0377 and HP0231. As previously shown, HP0377 is a reductase involved in the process of cytochrome c maturation. Additionally, it also possesses disulfide isomerase activity. HP0231 was the first periplasmic dimeric oxidoreductase involved in disulfide generation to be described. Although HP0231 function is critical for oxidative protein folding, its structure resembles that of dimeric EcDsbG, which does not confer this activity. However, the HP0231 catalytic motifs (CXXC and the so-called cis-Pro loop) are identical to that of monomeric EcDsbA. To understand the functioning of HP0231, we decided to study the relations between its sequence, structure and activity through an extensive analysis of various HP0231 point mutants, using in vivo and in vitro strategies. Our work shows the crucial role of the cis-Pro loop, as changing valine to threonine in this motif completely abolishes the protein function in vivo. Functioning of HP0231 is conditioned by the combination of CXXC and the cis-Pro loop, as replacing the HP0231 CXXC motif by the motif from EcDsbG or EcDsbC results in bifunctional protein, at least in E. coli. We also showed that the dimerization domain of HP0231 ensures contact with its substrates. Moreover, the activity of this oxidase is independent on the structure of the catalytic domain. Finally, we showed that HP0231 chaperone activity is independent of its redox function.
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Affiliation(s)
- Katarzyna M Bocian-Ostrzycka
- Department of Bacterial Genetics, Faculty of Biology, Institute of Microbiology, University of Warsaw Warsaw, Poland
| | - Magdalena J Grzeszczuk
- Department of Bacterial Genetics, Faculty of Biology, Institute of Microbiology, University of Warsaw Warsaw, Poland
| | - Anna M Banaś
- Department of Bacterial Genetics, Faculty of Biology, Institute of Microbiology, University of Warsaw Warsaw, Poland
| | - Katarzyna Jastrząb
- Department of Bacterial Genetics, Faculty of Biology, Institute of Microbiology, University of Warsaw Warsaw, Poland
| | - Karolina Pisarczyk
- Department of Bacterial Genetics, Faculty of Biology, Institute of Microbiology, University of Warsaw Warsaw, Poland
| | - Anna Kolarzyk
- Department of Bacterial Genetics, Faculty of Biology, Institute of Microbiology, University of Warsaw Warsaw, Poland
| | - Anna M Łasica
- Department of Bacterial Genetics, Faculty of Biology, Institute of Microbiology, University of Warsaw Warsaw, Poland
| | - Jean-François Collet
- Walloon Excellence in Life Sciences and BiotechnologyBrussels, Belgium; de Duve Institute, Université Catholique de LouvainBrussels, Belgium
| | - Elżbieta K Jagusztyn-Krynicka
- Department of Bacterial Genetics, Faculty of Biology, Institute of Microbiology, University of Warsaw Warsaw, Poland
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Qin A, Zhang Y, Clark ME, Moore EA, Rabideau MM, Moreau GB, Mann BJ. Components of the type six secretion system are substrates of Francisella tularensis Schu S4 DsbA-like FipB protein. Virulence 2016; 7:882-894. [PMID: 27028889 PMCID: PMC5160417 DOI: 10.1080/21505594.2016.1168550] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
FipB, an essential virulence factor in the highly virulent Schu S4 strain of F. tularensis subsp. tularensis, shares sequence similarity with Disulfide Bond formation (Dsb) proteins, which can have oxidoreductase, isomerase, or chaperone activity. To further explore FipB's role in virulence potential substrates were identified by co-purification and 2D gel electrophoresis, followed by protein sequencing using mass spectrometry. A total of 119 potential substrates were identified. Proteins with predicted enzymatic activity were prevalent, and there were 19 proteins that had been previously identified as impacting virulence. Among the potential substrates were IglC, IglB, and PdpB, three components of the Francisella Type Six Secretion System (T6SS), which is also essential for virulence. T6SS are widespread in Gram-negative pathogens, but have not been reported to be dependent on Dsb-like proteins for assembly or function. The presented results suggest that FipB affects IglB and IglC substrates differently. In a fipB mutant there were differences in free sulfhydryl accessibility of IglC, but not IglB, when compared to wild-type bacteria. However, for both proteins FipB appears to act as a chaperone that facilitates proper folding and conformation. Understanding the role FipB plays the assembly and structure in this T6SS may reveal critical aspects of assembly that are common and novel among this widely distributed class of secretion systems.
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Affiliation(s)
- Aiping Qin
- a Department of Medicine , Division of Infectious Diseases, University of Virginia , Charlottesville , VA , USA
| | - Yan Zhang
- a Department of Medicine , Division of Infectious Diseases, University of Virginia , Charlottesville , VA , USA
| | - Melinda E Clark
- a Department of Medicine , Division of Infectious Diseases, University of Virginia , Charlottesville , VA , USA
| | - Emily A Moore
- a Department of Medicine , Division of Infectious Diseases, University of Virginia , Charlottesville , VA , USA
| | - Meaghan M Rabideau
- a Department of Medicine , Division of Infectious Diseases, University of Virginia , Charlottesville , VA , USA
| | - G Brett Moreau
- a Department of Medicine , Division of Infectious Diseases, University of Virginia , Charlottesville , VA , USA
| | - Barbara J Mann
- a Department of Medicine , Division of Infectious Diseases, University of Virginia , Charlottesville , VA , USA
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10
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Rowe HM, Huntley JF. From the Outside-In: The Francisella tularensis Envelope and Virulence. Front Cell Infect Microbiol 2015; 5:94. [PMID: 26779445 PMCID: PMC4688374 DOI: 10.3389/fcimb.2015.00094] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 12/07/2015] [Indexed: 12/20/2022] Open
Abstract
Francisella tularensis is a highly-infectious bacterium that causes the rapid, and often lethal disease, tularemia. Many studies have been performed to identify and characterize the virulence factors that F. tularensis uses to infect a wide variety of hosts and host cell types, evade immune defenses, and induce severe disease and death. This review focuses on the virulence factors that are present in the F. tularensis envelope, including capsule, LPS, outer membrane, periplasm, inner membrane, secretion systems, and various molecules in each of aforementioned sub-compartments. Whereas, no single bacterial molecule or molecular complex single-handedly controls F. tularensis virulence, we review here how diverse bacterial systems work in conjunction to subvert the immune system, attach to and invade host cells, alter phagosome/lysosome maturation pathways, replicate in host cells without being detected, inhibit apoptosis, and induce host cell death for bacterial release and infection of adjacent cells. Given that the F. tularensis envelope is the outermost layer of the bacterium, we highlight herein how many of these molecules directly interact with the host to promote infection and disease. These and future envelope studies are important to advance our collective understanding of F. tularensis virulence mechanisms and offer targets for future vaccine development efforts.
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Affiliation(s)
- Hannah M Rowe
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences Toledo, OH, USA
| | - Jason F Huntley
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences Toledo, OH, USA
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11
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Wilson MM, Bernstein HD. Surface-Exposed Lipoproteins: An Emerging Secretion Phenomenon in Gram-Negative Bacteria. Trends Microbiol 2015; 24:198-208. [PMID: 26711681 DOI: 10.1016/j.tim.2015.11.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 11/17/2015] [Accepted: 11/23/2015] [Indexed: 01/07/2023]
Abstract
Bacterial lipoproteins are hydrophilic proteins that are anchored to a cell membrane by N-terminally linked fatty acids. It is widely believed that nearly all lipoproteins produced by Gram-negative bacteria are either retained in the inner membrane (IM) or transferred to the inner leaflet of the outer membrane (OM). Lipoproteins that are exposed on the cell surface have also been reported but are generally considered to be rare. Results from a variety of recent studies, however, now suggest that the prevalence of surface-exposed lipoproteins has been underestimated. In this review we describe the evidence that the surface exposure of lipoproteins in Gram-negative bacteria is a widespread phenomenon and discuss possible mechanisms by which these proteins might be transported across the OM.
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Affiliation(s)
- Marlena M Wilson
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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12
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Plzakova L, Krocova Z, Kubelkova K, Macela A. Entry of Francisella tularensis into Murine B Cells: The Role of B Cell Receptors and Complement Receptors. PLoS One 2015; 10:e0132571. [PMID: 26161475 PMCID: PMC4498600 DOI: 10.1371/journal.pone.0132571] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 06/16/2015] [Indexed: 01/06/2023] Open
Abstract
Francisella tularensis, the etiological agent of tularemia, is an intracellular pathogen that dominantly infects and proliferates inside phagocytic cells but can be seen also in non-phagocytic cells, including B cells. Although protective immunity is known to be almost exclusively associated with the type 1 pathway of cellular immunity, a significant role of B cells in immune responses already has been demonstrated. Whether their role is associated with antibody-dependent or antibody-independent B cell functions is not yet fully understood. The character of early events during B cell–pathogen interaction may determine the type of B cell response regulating the induction of adaptive immunity. We used fluorescence microscopy and flow cytometry to identify the basic requirements for the entry of F. tularensis into B cells within in vivo and in vitro infection models. Here, we present data showing that Francisella tularensis subsp. holarctica strain LVS significantly infects individual subsets of murine peritoneal B cells early after infection. Depending on a given B cell subset, uptake of Francisella into B cells is mediated by B cell receptors (BCRs) with or without complement receptor CR1/2. However, F. tularensis strain FSC200 ΔiglC and ΔftdsbA deletion mutants are defective in the ability to enter B cells. Once internalized into B cells, F. tularensis LVS intracellular trafficking occurs along the endosomal pathway, albeit without significant multiplication. The results strongly suggest that BCRs alone within the B-1a subset can ensure the internalization process while the BCRs on B-1b and B-2 cells need co-signaling from the co receptor containing CR1/2 to initiate F. tularensis engulfment. In this case, fluidity of the surface cell membrane is a prerequisite for the bacteria’s internalization. The results substantially underline the functional heterogeneity of B cell subsets in relation to F. tularensis.
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Affiliation(s)
- Lenka Plzakova
- Department of Molecular Pathology and Biology, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czech Republic
| | - Zuzana Krocova
- Department of Molecular Pathology and Biology, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czech Republic
| | - Klara Kubelkova
- Department of Molecular Pathology and Biology, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czech Republic
- * E-mail:
| | - Ales Macela
- Department of Molecular Pathology and Biology, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czech Republic
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Senitkova I, Spidlova P, Stulik J. Cooperation of both, the FKBP_N-like and the DSBA-like, domains is necessary for the correct function of FTS_1067 protein involved in Francisella tularensis virulence and pathogenesis. Pathog Dis 2015; 73:ftv030. [PMID: 25896829 DOI: 10.1093/femspd/ftv030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/09/2015] [Indexed: 11/14/2022] Open
Abstract
Francisella tularensis the etiological agent of tularaemia is one of the most infectious human pathogen known. Our knowledge about its key virulence factors has increased recently but it still remains a lot to explore. One of the described essential virulence factors is membrane lipoprotein FTS_1067 (nomenclature of F. tularensis subsp. holarctica strain FSC200) with homology to the protein family of disulphide oxidoreductases DsbA. Lipoprotein consists of two different domains: the C-terminal DsbA_Com1-like domain (DSBA-like) and the N-terminal FKBP-type peptidyl-prolyl cis/trans isomerases (FKBP_N-like). To uncover the biological role of these domains, we created bacterial strain with deletion of the DSBA-like domain. This defect in gene coding for lipoprotein FTS_1067 led to high in vivo attenuation associated with the ability to induce host protective immunity. Analyses performed with the truncated recombinant protein showed that the absence of DSBA-like domain revealed the loss of thiol/disulphide oxidoreductase activity and, additionally, confirmed the role of the FKBP_N-like domain in the FTS_1067 oligomerization and chaperone-like function. Finally, we verified that only full-length form of FTS_1067 recombinant protein possesses the isomerase activity. Based on our results, we proposed that for the correct FTS_1067 protein function both domains are needed.
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Affiliation(s)
- Iva Senitkova
- Faculty of Military Health Sciences, University of Defence, Department of Molecular Pathology and Biology, Trebesska 1575, Hradec Kralove 50001, Czech Republic
| | - Petra Spidlova
- Faculty of Military Health Sciences, University of Defence, Department of Molecular Pathology and Biology, Trebesska 1575, Hradec Kralove 50001, Czech Republic
| | - Jiri Stulik
- Faculty of Military Health Sciences, University of Defence, Department of Molecular Pathology and Biology, Trebesska 1575, Hradec Kralove 50001, Czech Republic
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14
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Ren G, Champion MM, Huntley JF. Identification of disulfide bond isomerase substrates reveals bacterial virulence factors. Mol Microbiol 2014; 94:926-44. [PMID: 25257164 DOI: 10.1111/mmi.12808] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/23/2014] [Indexed: 01/22/2023]
Abstract
Bacterial pathogens are exposed to toxic molecules inside the host and require efficient systems to form and maintain correct disulfide bonds for protein stability and function. The intracellular pathogen Francisella tularensis encodes a disulfide bond formation protein ortholog, DsbA, which previously was reported to be required for infection of macrophages and mice. However, the molecular mechanisms by which F. tularensis DsbA contributes to virulence are unknown. Here, we demonstrate that F. tularensis DsbA is a bifunctional protein that oxidizes and, more importantly, isomerizes complex disulfide connectivity in substrates. A single amino acid in the conserved cis-proline loop of the DsbA thioredoxin domain was shown to modulate both isomerase activity and F. tularensis virulence. Trapping experiments in F. tularensis identified over 50 F. tularensis DsbA substrates, including outer membrane proteins, virulence factors, and many hypothetical proteins. Six of these hypothetical proteins were randomly selected and deleted, revealing two novel proteins, FTL_1548 and FTL_1709, which are required for F. tularensis virulence. We propose that the extreme virulence of F. tularensis is partially due to the bifunctional nature of DsbA, that many of the newly identified substrates are required for virulence, and that the development of future DsbA inhibitors could have broad anti-bacterial implications.
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Affiliation(s)
- Guoping Ren
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, 43614, USA
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