151
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Panopoulos NJ. A Career on Both Sides of the Atlantic: Memoirs of a Molecular Plant Pathologist. ANNUAL REVIEW OF PHYTOPATHOLOGY 2017; 55:1-21. [PMID: 28777925 DOI: 10.1146/annurev-phyto-080516-035506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
This article recounts the experiences that shaped my career as a molecular plant pathologist. It focuses primarily on technical and conceptual developments in molecular phytobacteriology, shares some personal highlights and untold stories that impacted my professional development, and describes the early years of agricultural biotechnology. Writing this article required reflection on events occurring over several decades that were punctuated by a mid-career relocation across the Atlantic. I hope it will still be useful, informative, and enjoyable to read. An extended version of the abstract is provided in the Supplemental Materials , available online.
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Affiliation(s)
- Nickolas J Panopoulos
- Professor Emeritus, Department of Environmental Science, Policy and Management, University of California, Berkeley, California 94619
- Department of Biology, University of Crete, Heraklion, GR-71003, Greece;
- Hellenic Agricultural Academy, Agricultural University of Athens, 118 55 Athens, Greece
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152
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Davicino RC, Méndez-Huergo SP, Eliçabe RJ, Stupirski JC, Autenrieth I, Di Genaro MS, Rabinovich GA. Galectin-1–Driven Tolerogenic Programs AggravateYersinia enterocoliticaInfection by Repressing Antibacterial Immunity. THE JOURNAL OF IMMUNOLOGY 2017; 199:1382-1392. [DOI: 10.4049/jimmunol.1700579] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 06/15/2017] [Indexed: 12/19/2022]
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153
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A dynamic and adaptive network of cytosolic interactions governs protein export by the T3SS injectisome. Nat Commun 2017; 8:15940. [PMID: 28653671 PMCID: PMC5490264 DOI: 10.1038/ncomms15940] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 05/15/2017] [Indexed: 12/03/2022] Open
Abstract
Many bacteria use a type III secretion system (T3SS) to inject effector proteins into host cells. Selection and export of the effectors is controlled by a set of soluble proteins at the cytosolic interface of the membrane spanning type III secretion ‘injectisome’. Combining fluorescence microscopy, biochemical interaction studies and fluorescence correlation spectroscopy, we show that in live Yersinia enterocolitica bacteria these soluble proteins form complexes both at the injectisome and in the cytosol. Binding to the injectisome stabilizes these cytosolic complexes, whereas the free cytosolic complexes, which include the type III secretion ATPase, constitute a highly dynamic and adaptive network. The extracellular calcium concentration, which triggers activation of the T3SS, directly influences the cytosolic complexes, possibly through the essential component SctK/YscK, revealing a potential mechanism involved in the regulation of type III secretion. Bacterial type III secretion systems (T3SS) play important roles in pathogenesis. Here, Diepold et al. show the dynamic nature of complexes formed of essential T3SS components in live bacteria, and that extracellular calcium concentrations influence these cytosolic complexes likely via SctK/YscK.
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154
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de Souza Santos M, Salomon D, Orth K. T3SS effector VopL inhibits the host ROS response, promoting the intracellular survival of Vibrio parahaemolyticus. PLoS Pathog 2017. [PMID: 28640881 PMCID: PMC5481031 DOI: 10.1371/journal.ppat.1006438] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The production of antimicrobial reactive oxygen species by the nicotinamide dinucleotide phosphate (NADPH) oxidase complex is an important mechanism for control of invading pathogens. Herein, we show that the gastrointestinal pathogen Vibrio parahaemolyticus counteracts reactive oxygen species (ROS) production using the Type III Secretion System 2 (T3SS2) effector VopL. In the absence of VopL, intracellular V. parahaemolyticus undergoes ROS-dependent filamentation, with concurrent limited growth. During infection, VopL assembles actin into non-functional filaments resulting in a dysfunctional actin cytoskeleton that can no longer mediate the assembly of the NADPH oxidase at the cell membrane, thereby limiting ROS production. This is the first example of how a T3SS2 effector contributes to the intracellular survival of V. parahaemolyticus, supporting the establishment of a protective intracellular replicative niche.
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Affiliation(s)
- Marcela de Souza Santos
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Dor Salomon
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Kim Orth
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- * E-mail:
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155
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Abstract
Periodontitis is an extremely prevalent disease worldwide and is driven by complex dysbiotic microbiota. Here we analyzed the transcriptional activity of the periodontal pocket microbiota from all domains of life as well as the human host in health and chronic periodontitis. Bacteria showed strong enrichment of 18 KEGG functional modules in chronic periodontitis, including bacterial chemotaxis, flagellar assembly, type III secretion system, type III CRISPR-Cas system, and two component system proteins. Upregulation of these functions was driven by the red-complex pathogens and candidate pathogens, e.g. Filifactor alocis, Prevotella intermedia, Fretibacterium fastidiosum and Selenomonas sputigena. Nine virulence factors were strongly up-regulated, among them the arginine deiminase arcA from Porphyromonas gingivalis and Mycoplasma arginini. Viruses and archaea accounted for about 0.1% and 0.22% of total putative mRNA reads, respectively, and a protozoan, Entamoeba gingivalis, was highly enriched in periodontitis. Fourteen human transcripts were enriched in periodontitis, including a gene for a ferric iron binding protein, indicating competition with the microbiota for iron, and genes associated with cancer, namely nucleolar phosphoprotein B23, ankyrin-repeat domain 30B-like protein and beta-enolase. The data provide evidence on the level of gene expression in vivo for the potentially severe impact of the dysbiotic microbiota on human health.
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156
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De Nisco NJ, Kanchwala M, Li P, Fernandez J, Xing C, Orth K. The cytotoxic type 3 secretion system 1 of Vibrio rewires host gene expression to subvert cell death and activate cell survival pathways. Sci Signal 2017; 10:10/479/eaal4501. [PMID: 28512145 DOI: 10.1126/scisignal.aal4501] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Bacterial effectors potently manipulate host signaling pathways. The marine bacterium Vibrio parahaemolyticus (V. para) delivers effectors into host cells through two type 3 secretion systems (T3SSs). T3SS1 is vital for V. para survival in the environment, whereas T3SS2 causes acute gastroenteritis in human hosts. Although the natural host is undefined, T3SS1 effectors attack highly conserved cellular processes and pathways to orchestrate nonapoptotic cell death. To understand how the concerted action of T3SS1 effectors globally affects host cell signaling, we compared gene expression changes over time in primary fibroblasts infected with V. para that have a functional T3SS1 (T3SS1+) to those in cells infected with V. para lacking T3SS1 (T3SS1-). Overall, the host transcriptional response to both T3SS1+ and T3SS1-V. para was rapid, robust, and temporally dynamic. T3SS1 rewired host gene expression by specifically altering the expression of 398 genes. Although T3SS1 effectors targeted host cells at the posttranslational level to cause cytotoxicity, V. para T3SS1 also precipitated a host transcriptional response that initially activated cell survival and repressed cell death networks. The increased expression of several key prosurvival transcripts mediated by T3SS1 depended on a host signaling pathway that is silenced posttranslationally later in infection. Together, our analysis reveals a complex interplay between the roles of T3SS1 as both a transcriptional and posttranslational manipulator of host cell signaling.
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Affiliation(s)
- Nicole J De Nisco
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Mohammed Kanchwala
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Peng Li
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jessie Fernandez
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Chao Xing
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.,Department of Clinical Sciences, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Kim Orth
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. .,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.,Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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157
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Kühn S, Lopez-Montero N, Chang YY, Sartori-Rupp A, Enninga J. Imaging macropinosomes during Shigella infections. Methods 2017; 127:12-22. [PMID: 28522322 DOI: 10.1016/j.ymeth.2017.05.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 04/11/2017] [Accepted: 05/10/2017] [Indexed: 12/21/2022] Open
Abstract
Macropinocytosis is the uptake of extracellular fluid within vesicles of varying size that takes place during numerous cellular processes in a large variety of cells. A growing number of pathogens, including viruses, parasites, and bacteria are known to induce macropinocytosis during their entry into targeted host cells. We have recently discovered that the human enteroinvasive, bacterial pathogen Shigella causes in situ macropinosome formation during its entry into epithelial cells. These infection-associated macropinosomes are not generated to ingest the bacteria, but are instead involved in Shigella's intracellular niche formation. They make contacts with the phagocytosed shigellae to promote vacuolar membrane rupture and their cytosolic release. Here, we provide an overview of the different imaging approaches that are currently used to analyze macropinocytosis during infectious processes with a focus on Shigella entry. We detail the advantages and disadvantages of genetically encoded reporters as well as chemical probes to trace fluid phase uptake. In addition, we report how such reporters can be combined with ultrastructural approaches for correlative light electron microscopy either in thin sections or within large volumes. The combined imaging techniques introduced here provide a detailed characterization of macropinosomes during bacterial entry, which, apart from Shigella, are relevant for numerous other ones, including Salmonella, Brucella or Mycobacteria.
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Affiliation(s)
- Sonja Kühn
- Department of Cell Biology and Infection, Institut Pasteur, Paris, France
| | | | - Yuen-Yan Chang
- Department of Cell Biology and Infection, Institut Pasteur, Paris, France
| | - Anna Sartori-Rupp
- Department of Cell Biology and Infection, Institut Pasteur, Paris, France
| | - Jost Enninga
- Department of Cell Biology and Infection, Institut Pasteur, Paris, France.
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158
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Bacterial thiol oxidoreductases - from basic research to new antibacterial strategies. Appl Microbiol Biotechnol 2017; 101:3977-3989. [PMID: 28409380 PMCID: PMC5403849 DOI: 10.1007/s00253-017-8291-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 04/03/2017] [Accepted: 04/04/2017] [Indexed: 12/15/2022]
Abstract
The recent, rapid increase in bacterial antimicrobial resistance has become a major public health concern. One approach to generate new classes of antibacterials is targeting virulence rather than the viability of bacteria. Proteins of the Dsb system, which play a key role in the virulence of many pathogenic microorganisms, represent potential new drug targets. The first part of the article presents current knowledge of how the Dsb system impacts function of various protein secretion systems that influence the virulence of many pathogenic bacteria. Next, the review describes methods used to study the structure, biochemistry, and microbiology of the Dsb proteins and shows how these experiments broaden our knowledge about their function. The lessons gained from basic research have led to a specific search for inhibitors blocking the Dsb networks.
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159
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A Novel Mechanism for Protein Delivery by the Type 3 Secretion System for Extracellularly Secreted Proteins. mBio 2017; 8:mBio.00184-17. [PMID: 28351918 PMCID: PMC5371411 DOI: 10.1128/mbio.00184-17] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
The type 3 secretion system (T3SS) is essential for bacterial virulence through delivering effector proteins directly into the host cytosol. Here, we identified an alternative delivery mechanism of virulence factors mediated by the T3SS, which consists of the association of extracellularly secreted proteins from bacteria with the T3SS to gain access to the host cytosol. Both EspC, a protein secreted as an enteropathogenic Escherichia coli (EPEC) autotransporter, and YopH, a protein detected on the surface of Yersinia, require a functional T3SS for host cell internalization; here we provide biophysical and molecular evidence to support the concept of the EspC translocation mechanism, which requires (i) an interaction between EspA and an EspC middle segment, (ii) an EspC translocation motif (21 residues that are shared with the YopH translocation motif), (iii) increases in the association and dissociation rates of EspC mediated by EspA interacting with EspD, and (iv) an interaction of EspC with the EspD/EspB translocon pore. Interestingly, this novel mechanism does not exclude the injection model (i.e., EspF) operating through the T3SS conduit; therefore, T3SS can be functioning as an internal conduit or as an external railway, which can be used to reach the translocator pore, and this mechanism appears to be conserved among different T3SS-dependent pathogens. The type 3 secretion system is essential for injection of virulence factors, which are delivered directly into the cytosol of the host cells for usurping and subverting host processes. Recent studies have shown that these effectors proteins indeed travel inside an “injectisome” conduit through a single step of translocation by connecting the bacterium and host cell cytoplasms. However, all findings are not compatible with this model. For example, both YopH, a protein detected on the surface of Yersinia, and EspC, an autotransporter protein secreted by enteropathogenic E. coli, require a functional T3SS for host cell translocation. Both proteins have an intermediate extracellular step before their T3SS-dependent translocation. Here, we show an alternative delivery mechanism for these extracellularly secreted virulence factors that are then incorporated into the T3SS to enter the cells; this novel mechanism coexists with but diverges from the canonical injection model that involves the passage of the protein inside the injectisome.
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160
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Li L, Li RF, Ming ZH, Lu GT, Tang JL. Identification of a novel type III secretion-associated outer membrane-bound protein from Xanthomonas campestris pv. campestris. Sci Rep 2017; 7:42724. [PMID: 28198457 PMCID: PMC5309889 DOI: 10.1038/srep42724] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 01/13/2017] [Indexed: 12/31/2022] Open
Abstract
Many bacterial pathogens employ the type III secretion system (T3SS) to translocate effector proteins into eukaryotic cells to overcome host defenses. To date, most of our knowledge about the T3SS molecular architecture comes from the studies on animal pathogens. In plant pathogens, nine Hrc proteins are believed to be structural components of the T3SS, of which HrcC and HrcJ form the outer and inner rings of the T3SS, respectively. Here, we demonstrated that a novel outer membrane-bound protein (HpaM) of Xanthomonas campestris pv. campestris is critical for the type III secretion and is structurally and functionally conserved in phytopathogenic Xanthomonas spp. We showed that the C-terminus of HpaM extends into the periplasm to interact physically with HrcJ and the middle part of HpaM interacts physically with HrcC. It is clear that the outer and inner rings compose the main basal body of the T3SS apparatus in animal pathogens. Therefore, we presume that HpaM may act as a T3SS structural component, or play a role in assisting assembling or affecting the stability of the T3SS apparatus. HpaM is a highly prevalent and specific protein in Xanthomonas spp., suggesting that the T3SS of Xanthomonas is distinctive in some aspects from other pathogens.
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Affiliation(s)
- Lei Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
| | - Rui-Fang Li
- Guangxi Key Laboratory of Biology for Crop Diseases and Insect Pests, Plant Protection Research Institute, Guangxi Academy of Agricultural Sciences, 174 Daxue Road, Nanning, Guangxi 530007, China
| | - Zhen-Hua Ming
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
| | - Guang-Tao Lu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
| | - Ji-Liang Tang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
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161
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Cao SY, Liu WB, Tan YF, Yang HY, Zhang TT, Wang T, Wang XY, Song YJ, Yang RF, Du ZM. An Interaction between the Inner Rod Protein YscI and the Needle Protein YscF Is Required to Assemble the Needle Structure of the Yersinia Type Three Secretion System. J Biol Chem 2017; 292:5488-5498. [PMID: 28196868 DOI: 10.1074/jbc.m116.743591] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 02/09/2017] [Indexed: 11/06/2022] Open
Abstract
The type III secretion system is a highly conserved virulence mechanism that is widely distributed in Gram-negative bacteria. It has a syringe-like structure composed of a multi-ring basal body that spans the bacterial envelope and a projecting needle that delivers virulence effectors into host cells. Here, we showed that the Yersinia inner rod protein YscI directly interacts with the needle protein YscF inside the bacterial cells and that this interaction depends on amino acid residues 83-102 in the carboxyl terminus of YscI. Alanine substitution of Trp-85 or Ser-86 abrogated the binding of YscI to YscF as well as needle assembly and the secretion of effectors (Yops) and the needle tip protein LcrV. However, yscI null mutants that were trans-complemented with YscI mutants that bind YscF still assembled the needle and secreted Yops, demonstrating that a direct interaction between YscF and YscI is critical for these processes. Consistently, YscI mutants that did not bind YscF resulted in greatly decreased HeLa cell cytotoxicity. Together, these results show that YscI participates in needle assembly by directly interacting with YscF.
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Affiliation(s)
- Shi-Yang Cao
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Wan-Bin Liu
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Ya-Fang Tan
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Hui-Ying Yang
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Ting-Ting Zhang
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Tong Wang
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Xiao-Yi Wang
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Ya-Jun Song
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Rui-Fu Yang
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Zong-Min Du
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
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162
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Freitag CM, Strijbis K, van Putten JPM. Host cell binding of the flagellar tip protein of Campylobacter jejuni. Cell Microbiol 2017; 19. [PMID: 28008697 DOI: 10.1111/cmi.12714] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 12/16/2016] [Indexed: 12/29/2022]
Abstract
Flagella are nanofibers that drive bacterial movement. The filaments are generally composed of thousands of tightly packed flagellin subunits with a terminal cap protein, named FliD. Here, we report that the FliD protein of the bacterial pathogen Campylobacter jejuni binds to host cells. Live-cell imaging and confocal microscopy showed initial contact of the bacteria with epithelial cells via the flagella tip. Recombinant FliD protein bound to the surface of intestinal epithelial cells in a dose-dependent fashion. Search for the FliD binding site on the host cell using cells with defined glycosylation defects indicated glycosaminoglycans as a putative target. Heparinase treatment of wild type cells and an excess of soluble heparin abolished FliD binding. Binding assays showed direct and specific binding of FliD to heparin. Addition of an excess of purified FliD or heparin reduced the attachment of viable C. jejuni to the host cells. The host cell binding domain of FliD was mapped to the central region of the protein. Overall, our results indicate that the C. jejuni flagellar tip protein FliD acts as an attachment factor that interacts with cell surface heparan sulfate glycosaminoglycan receptors.
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Affiliation(s)
- Claudia M Freitag
- Department of Infectious Diseases and Immunology, Utrecht University, Utrecht, The Netherlands
| | - Karin Strijbis
- Department of Infectious Diseases and Immunology, Utrecht University, Utrecht, The Netherlands
| | - Jos P M van Putten
- Department of Infectious Diseases and Immunology, Utrecht University, Utrecht, The Netherlands
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163
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Structural basis for the recognition and degradation of host TRIM proteins by Salmonella effector SopA. Nat Commun 2017; 8:14004. [PMID: 28084320 PMCID: PMC5241803 DOI: 10.1038/ncomms14004] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 11/21/2016] [Indexed: 12/25/2022] Open
Abstract
The hallmark of Salmonella Typhimurium infection is an acute intestinal inflammatory response, which is mediated through the action of secreted bacterial effector proteins. The pro-inflammatory Salmonella effector SopA is a HECT-like E3 ligase, which was previously proposed to activate host RING ligases TRIM56 and TRIM65. Here we elucidate an inhibitory mechanism of TRIM56 and TRIM65 targeting by SopA. We present the crystal structure of SopA in complex with the RING domain of human TRIM56, revealing the atomic details of their interaction and the basis for SopA selectivity towards TRIM56 and TRIM65. Structure-guided biochemical analysis shows that SopA inhibits TRIM56 E3 ligase activity by occluding the E2-interacting surface of TRIM56. We further demonstrate that SopA ubiquitinates TRIM56 and TRIM65, resulting in their proteasomal degradation during infection. Our results provide the basis for how a bacterial HECT ligase blocks host RING ligases and exemplifies the multivalent power of bacterial effectors during infection.
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164
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The Ruler Protein EscP of the Enteropathogenic Escherichia coli Type III Secretion System Is Involved in Calcium Sensing and Secretion Hierarchy Regulation by Interacting with the Gatekeeper Protein SepL. mBio 2017; 8:mBio.01733-16. [PMID: 28049143 PMCID: PMC5210495 DOI: 10.1128/mbio.01733-16] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The type III secretion system (T3SS) is a multiprotein complex that plays a central role in the virulence of many Gram-negative bacterial pathogens. To ensure that effector proteins are efficiently translocated into the host cell, bacteria must be able to sense their contact with the host cell. In this study, we found that EscP, which was previously shown to function as the ruler protein of the enteropathogenic Escherichia coli T3SS, is also involved in the switch from the secretion of translocator proteins to the secretion of effector proteins. In addition, we demonstrated that EscP can interact with the gatekeeper protein SepL and that the EscP-SepL complex dissociates upon a calcium concentration drop. We suggest a model in which bacterial contact with the host cell is accompanied by a drop in the calcium concentration that causes SepL-EscP complex dissociation and triggers the secretion of effector proteins. IMPORTANCE The emergence of multidrug-resistant bacterial strains, especially those of pathogenic bacteria, has serious medical and clinical implications. At the same time, the development and approval of new antibiotics have been limited for years. Recently, antivirulence drugs have received considerable attention as a novel antibiotic strategy that specifically targets bacterial virulence rather than growth, an approach that applies milder evolutionary pressure on the bacteria to develop resistance. A highly attractive target for the development of antivirulence compounds is the type III secretion system, a specialized secretory system possessed by many Gram-negative bacterial pathogens for injecting virulence factors (effectors) into host cells. In this study, we shed light on the molecular mechanism that allows bacteria to sense their contact with the host cell and to respond with the timed secretion of effector proteins. Understanding this critical step for bacterial virulence may provide a new therapeutic strategy.
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165
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Condry DLJ, Nilles ML. Analysis of Type III Secretion System Secreted Proteins. Methods Mol Biol 2017; 1531:93-99. [PMID: 27837484 DOI: 10.1007/978-1-4939-6649-3_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Secreted proteins of the T3SS vary from genus to genus. How secretion is induced in vitro also depends on the genus of bacteria. However, once those proteins are isolated the method for analyzing those proteins is largely the same. The following chapter outlines the specific induction of Yersinia secreted proteins and uniform analysis of those secreted proteins.
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Affiliation(s)
- Danielle L Jessen Condry
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, USA.
| | - Matthew L Nilles
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, USA
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166
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Abstract
Type III secretion (T3S) systems are found in a large number of gram-negative bacteria where they function to manipulate the biology of infected hosts. Hosts targeted by T3S systems are widely distributed in nature and are represented by animals and plants. T3S systems are found in diverse genera of bacteria and they share a common core structure and function. Effector proteins are delivered by T3S systems into targeted host cells without prior secretion of the effectors into the environment. Instead, an assembled translocon structure functions to translocate effectors across eukaryotic cell membranes. In many cases, T3S systems are essential virulence factors and in some instances they promote symbiotic interactions.
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Affiliation(s)
- Danielle L Jessen Condry
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, USA.
| | - Matthew L Nilles
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, USA
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167
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Ho O, Rogne P, Edgren T, Wolf-Watz H, Login FH, Wolf-Watz M. Characterization of the Ruler Protein Interaction Interface on the Substrate Specificity Switch Protein in the Yersinia Type III Secretion System. J Biol Chem 2016; 292:3299-3311. [PMID: 28039361 DOI: 10.1074/jbc.m116.770255] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 12/29/2016] [Indexed: 12/29/2022] Open
Abstract
Many pathogenic Gram-negative bacteria use the type III secretion system (T3SS) to deliver effector proteins into eukaryotic host cells. In Yersinia, the switch to secretion of effector proteins is induced first after intimate contact between the bacterium and its eukaryotic target cell has been established, and the T3SS proteins YscP and YscU play a central role in this process. Here we identify the molecular details of the YscP binding site on YscU by means of nuclear magnetic resonance (NMR) spectroscopy. The binding interface is centered on the C-terminal domain of YscU. Disrupting the YscU-YscP interaction by introducing point mutations at the interaction interface significantly reduced the secretion of effector proteins and HeLa cell cytotoxicity. Interestingly, the binding of YscP to the slowly self-cleaving YscU variant P264A conferred significant protection against autoproteolysis. The YscP-mediated inhibition of YscU autoproteolysis suggests that the cleavage event may act as a timing switch in the regulation of early versus late T3SS substrates. We also show that YscUC binds to the inner rod protein YscI with a dissociation constant (Kd ) of 3.8 μm and with 1:1 stoichiometry. The significant similarity among different members of the YscU, YscP, and YscI families suggests that the protein-protein interactions discussed in this study are also relevant for other T3SS-containing Gram-negative bacteria.
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Affiliation(s)
- Oanh Ho
- Department of Chemistry, Chemical Biological Centre
| | - Per Rogne
- Department of Chemistry, Chemical Biological Centre
| | - Tomas Edgren
- Department of Molecular Biology and The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, S-901 87 Umeå, Sweden
| | - Hans Wolf-Watz
- Department of Molecular Biology and The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, S-901 87 Umeå, Sweden
| | - Frédéric H Login
- Department of Molecular Biology and The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, S-901 87 Umeå, Sweden.
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Jneid B, Moreau K, Plaisance M, Rouaix A, Dano J, Simon S. Role of T3SS-1 SipD Protein in Protecting Mice against Non-typhoidal Salmonella Typhimurium. PLoS Negl Trop Dis 2016; 10:e0005207. [PMID: 27992422 PMCID: PMC5167260 DOI: 10.1371/journal.pntd.0005207] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 10/25/2016] [Indexed: 11/24/2022] Open
Abstract
Background Salmonella enterica species are enteric pathogens that cause severe diseases ranging from self-limiting gastroenteritis to enteric fever and sepsis in humans. These infectious diseases are still the major cause of morbidity and mortality in low-income countries, especially in children younger than 5 years and immunocompromised adults. Vaccines targeting typhoidal diseases are already marketed, but none protect against non-typhoidal Salmonella. The existence of multiple non-typhoidal Salmonella serotypes as well as emerging antibiotic resistance highlight the need for development of a broad-spectrum protective vaccine. All Salmonella spp. utilize two type III Secretion Systems (T3SS 1 and 2) to initiate infection, allow replication in phagocytic cells and induce systemic disease. T3SS-1, which is essential to invade epithelial cells and cross the barrier, forms an extracellular needle and syringe necessary to inject effector proteins into the host cell. PrgI and SipD form, respectively, the T3SS-1 needle and the tip complex at the top of the needle. Because they are common and highly conserved in all virulent Salmonella spp., they might be ideal candidate antigens for a subunit-based, broad-spectrum vaccine. Principal Findings We investigated the immunogenicity and protective efficacy of PrgI and SipD administered by subcutaneous, intranasal and oral routes, alone or combined, in a mouse model of Salmonella intestinal challenge. Robust IgG (in all immunization routes) and IgA (in intranasal and oral immunization routes) antibody responses were induced against both proteins, particularly SipD. Mice orally immunized with SipD alone or SipD combined with PrgI were protected against lethal intestinal challenge with Salmonella Typhimurium (100 Lethal Dose 50%) depending on antigen, route and adjuvant. Conclusions and Significance Salmonella T3SS SipD is a promising antigen for the development of a protective Salmonella vaccine, and could be developed for vaccination in tropical endemic areas to control infant mortality. Salmonella are bacteria responsible for a high global burden of invasive diseases, especially in South and South-East Asia (mainly enteric fever due to Salmonella Typhi) and sub-Saharan Africa (mainly invasive Non-Typhoidal Salmonella, iNTS). This iNTS disease has emerged as a prominent cause of systemic infection in children and immunocompromised African adults, with an associated case fatality of 20–25%. Because licensed vaccines only protect against enteric fever, there is a crucial need to develop a new broad-spectrum vaccine effective against enteric fever and iNTS that can be administered safely to children under 2 years old. The virulence of Salmonella depends on two type III secretion systems (T3SS-1 and T3SS-2) necessary for invasion, replication, intracellular survival and dissemination of the bacteria. Two structural proteins of T3SS-1 (essential for crossing the epithelial barrier) are highly conserved among Salmonella spp. and might be good candidates for a broad-spectrum vaccine. The current study describes the protective effect elicited by these proteins in a murine model. A specific immune response was generated against our antigens and provided protection against Salmonella Typhimurium oral infection. Such a candidate vaccine offers promising perspectives to control Salmonella diseases.
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Affiliation(s)
- Bakhos Jneid
- Service de Pharmacologie et Immunoanalyse (SPI), CEA, INRA, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Karine Moreau
- Service de Pharmacologie et Immunoanalyse (SPI), CEA, INRA, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Marc Plaisance
- Service de Pharmacologie et Immunoanalyse (SPI), CEA, INRA, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Audrey Rouaix
- Service de Pharmacologie et Immunoanalyse (SPI), CEA, INRA, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Julie Dano
- Service de Pharmacologie et Immunoanalyse (SPI), CEA, INRA, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Stéphanie Simon
- Service de Pharmacologie et Immunoanalyse (SPI), CEA, INRA, Université Paris-Saclay, Gif-sur-Yvette, France
- * E-mail:
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169
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Abstract
Type III secretion systems (T3SSs) afford Gram-negative bacteria an intimate means of altering the biology of their eukaryotic hosts--the direct delivery of effector proteins from the bacterial cytoplasm to that of the eukaryote. This incredible biophysical feat is accomplished by nanosyringe "injectisomes," which form a conduit across the three plasma membranes, peptidoglycan layer, and extracellular space that form a barrier to the direct delivery of proteins from bacterium to host. The focus of this chapter is T3SS function at the structural level; we will summarize the core findings that have shaped our understanding of the structure and function of these systems and highlight recent developments in the field. In turn, we describe the T3SS secretory apparatus, consider its engagement with secretion substrates, and discuss the posttranslational regulation of secretory function. Lastly, we close with a discussion of the future prospects for the interrogation of structure-function relationships in the T3SS.
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170
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Ekestubbe S, Bröms JE, Edgren T, Fällman M, Francis MS, Forsberg Å. The Amino-Terminal Part of the Needle-Tip Translocator LcrV of Yersinia pseudotuberculosis Is Required for Early Targeting of YopH and In vivo Virulence. Front Cell Infect Microbiol 2016; 6:175. [PMID: 27995096 PMCID: PMC5136540 DOI: 10.3389/fcimb.2016.00175] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Accepted: 11/21/2016] [Indexed: 12/20/2022] Open
Abstract
Type III secretion systems (T3SS) are dedicated to targeting anti-host effector proteins into the cytosol of the host cell to promote bacterial infection. Delivery of the effectors requires three specific translocator proteins, of which the hydrophilic translocator, LcrV, is located at the tip of the T3SS needle and is believed to facilitate insertion of the two hydrophobic translocators into the host cell membrane. Here we used Yersinia as a model to study the role of LcrV in T3SS mediated intracellular effector targeting. Intriguingly, we identified N-terminal lcrV mutants that, similar to the wild-type protein, efficiently promoted expression, secretion and intracellular levels of Yop effectors, yet they were impaired in their ability to inhibit phagocytosis by J774 cells. In line with this, the YopH mediated dephosphorylation of Focal Adhesion Kinase early after infection was compromised when compared to the wild type strain. This suggests that the mutants are unable to promote efficient delivery of effectors to their molecular targets inside the host cell upon host cell contact. The significance of this was borne out by the fact that the mutants were highly attenuated for virulence in the systemic mouse infection model. Our study provides both novel and significant findings that establish a role for LcrV in early targeting of effectors in the host cell.
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Affiliation(s)
- Sofie Ekestubbe
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå UniversityUmeå, Sweden; Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden
| | - Jeanette E Bröms
- Department of Clinical Microbiology, Umeå University Umeå, Sweden
| | - Tomas Edgren
- Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå University Umeå, Sweden
| | - Maria Fällman
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå UniversityUmeå, Sweden; Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden
| | - Matthew S Francis
- Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå University Umeå, Sweden
| | - Åke Forsberg
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå UniversityUmeå, Sweden; Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden
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171
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Shi L, Yu B, Cai CH, Huang JD. Angiogenic inhibitors delivered by the type III secretion system of tumor-targeting Salmonella typhimurium safely shrink tumors in mice. AMB Express 2016; 6:56. [PMID: 27558018 PMCID: PMC4996802 DOI: 10.1186/s13568-016-0226-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 08/10/2016] [Indexed: 12/19/2022] Open
Abstract
Despite of a growing number of bacterial species that apparently exhibit intrinsic tumor-targeting properties, no bacterium is able to inhibit tumor growth completely in the immunocompetent hosts, due to its poor dissemination inside the tumors. Oxygen and inflammatory reaction form two barriers and restrain the spread of the bacteria inside the tumors. Here, we engineered a Salmonella typhimurium strain named ST8 which is safe and has limited ability to spread beyond the anaerobic regions of tumors. When injected systemically to tumor-bearing immunocompetent mice, ST8 accumulated in tumors at levels at least 100-fold greater than parental obligate anaerobic strain ST4. ST8/pSEndo harboring therapeutic plasmids encoding Endostatin fused with a secreted protein SopA could target vasculature at the tumor periphery, can stably maintain and safely deliver a therapeutic vector, release angiogenic inhibitors through a type III secretion system (T3SS) to interfere with the pro-angiogenic action of growth factors in tumors. Mice with murine CT26 colon cancer that had been injected with ST8/pSEndo showed efficient tumor suppression by inducing more severe necrosis and inhibiting blooding vessel density within tumors. Our findings provide a therapeutic platform for indirectly acting therapeutic strategies such as anti-angiogenesis and immune therapy.
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172
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A Method for Characterizing the Type III Secretion System's Contribution to Pathogenesis: Homologous Recombination to Generate Yersinia pestis Type III Secretion System Mutants. Methods Mol Biol 2016. [PMID: 27837489 DOI: 10.1007/978-1-4939-6649-3_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
The type III (T3S) secretion system of many gram-negative bacteria is a surface-exposed protein secretion apparatus used to directly inject bacterial effector molecules into eukaryotic cells. These effector molecules contribute to bacterial pathogenesis in many ways, and have been shown to be crucial for infectivity. Here, we describe a protocol for using homologous recombination to generate T3S system mutants to assess the role of different T3S system proteins in bacterial pathogenesis.
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173
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Alvine TD, Bradley DS, Nilles ML. Mouse Immunization with Purified Needle Proteins from Type III Secretion Systems and the Characterization of the Immune Response to These Proteins. Methods Mol Biol 2016; 1531:193-201. [PMID: 27837493 DOI: 10.1007/978-1-4939-6649-3_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
Abstract
Many Gram-negative pathogens utilize a type III secretion (T3S) system to directly deliver effector molecules into host eukaryotic cells to manipulate cellular processes. These surface-exposed syringe-like structures are highly conserved, necessary for pathogenesis, and hence are therapeutic targets against a number of Gram-negative pathogens. Here we describe a protocol for using purified needle proteins to immunize mice, and subsequently, ways to characterize the immune response to immunization.
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Affiliation(s)
- Travis D Alvine
- Department of Biomedical Sciences, University of North Dakota, 1301 Columbia Road North, Stop 9037, Grand Forks, ND, 58202, USA
| | - David S Bradley
- Department of Biomedical Sciences, University of North Dakota, 1301 Columbia Road North, Stop 9037, Grand Forks, ND, 58202, USA.
| | - Matthew L Nilles
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, USA
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174
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Isolation of Type III Secretion System Needle Complexes by Shearing. Methods Mol Biol 2016. [PMID: 27837481 DOI: 10.1007/978-1-4939-6649-3_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Type III secretion (T3S) needle proteins are essential for the pathogenesis of many gram-negative bacteria. The needle component of the T3S system serves as the conduit for the translocation of effector proteins from the cytoplasm of many gram-negative bacteria into their target eukaryotic cells. Despite substantial advances that have been made in their characterization, a lot is still unknown about their interactions with other T3S system proteins and their roles in modulating host immune responses during infections. Critical to achieving this knowledge is the ability to isolate these needle proteins in their stable, native form. In this chapter, we describe a modified, streamlined isolation strategy for native forms of these T3S system needle proteins. We also present assays to detect the presence and quantification of these needle proteins.
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175
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Schreiber KJ, Baudin M, Hassan JA, Lewis JD. Die another day: Molecular mechanisms of effector-triggered immunity elicited by type III secreted effector proteins. Semin Cell Dev Biol 2016; 56:124-133. [DOI: 10.1016/j.semcdb.2016.05.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 05/02/2016] [Indexed: 11/27/2022]
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176
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Radomski N, Einenkel R, Müller A, Knittler MR. Chlamydia-host cell interaction not only from a bird's eye view: some lessons fromChlamydia psittaci. FEBS Lett 2016; 590:3920-3940. [DOI: 10.1002/1873-3468.12295] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2016] [Revised: 07/06/2016] [Accepted: 07/07/2016] [Indexed: 12/13/2022]
Affiliation(s)
- Nadine Radomski
- Friedrich-Loeffler-Institut; Institute of Immunology; Isle of Riems Germany
| | - Rebekka Einenkel
- Friedrich-Loeffler-Institut; Institute of Immunology; Isle of Riems Germany
| | - Anne Müller
- Friedrich-Loeffler-Institut; Institute of Immunology; Isle of Riems Germany
| | - Michael R Knittler
- Friedrich-Loeffler-Institut; Institute of Immunology; Isle of Riems Germany
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177
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Hou M, Chen R, Yang D, Núñez G, Wang Z, Wang Q, Zhang Y, Liu Q. Identification and functional characterization of EseH, a new effector of the type III secretion system ofEdwardsiella piscicida. Cell Microbiol 2016; 19. [DOI: 10.1111/cmi.12638] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 05/30/2016] [Accepted: 06/17/2016] [Indexed: 12/26/2022]
Affiliation(s)
- Mingyu Hou
- State Key Laboratory of Bioreactor Engineering; East China University of Science and Technology; Shanghai 200237 China
| | - Ran Chen
- State Key Laboratory of Bioreactor Engineering; East China University of Science and Technology; Shanghai 200237 China
| | - Dahai Yang
- State Key Laboratory of Bioreactor Engineering; East China University of Science and Technology; Shanghai 200237 China
- Shanghai Engineering Research Center of Marine Cultured Animal Vaccines; Shanghai 200237 China
- Shanghai Collaborative Innovation Center for Biomanufacturing; Shanghai 200237 China
| | - Gabriel Núñez
- Department of Pathology and Comprehensive Cancer Center; University of Michigan; Ann Arbor MI 48109 USA
| | - Zhuang Wang
- State Key Laboratory of Bioreactor Engineering; East China University of Science and Technology; Shanghai 200237 China
| | - Qiyao Wang
- State Key Laboratory of Bioreactor Engineering; East China University of Science and Technology; Shanghai 200237 China
- Shanghai Engineering Research Center of Marine Cultured Animal Vaccines; Shanghai 200237 China
- Shanghai Collaborative Innovation Center for Biomanufacturing; Shanghai 200237 China
| | - Yuanxing Zhang
- State Key Laboratory of Bioreactor Engineering; East China University of Science and Technology; Shanghai 200237 China
- Shanghai Engineering Research Center of Marine Cultured Animal Vaccines; Shanghai 200237 China
- Shanghai Collaborative Innovation Center for Biomanufacturing; Shanghai 200237 China
| | - Qin Liu
- State Key Laboratory of Bioreactor Engineering; East China University of Science and Technology; Shanghai 200237 China
- Shanghai Engineering Research Center of Marine Cultured Animal Vaccines; Shanghai 200237 China
- Shanghai Collaborative Innovation Center for Biomanufacturing; Shanghai 200237 China
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178
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Monteiro R, Ageorges V, Rojas-Lopez M, Schmidt H, Weiss A, Bertin Y, Forano E, Jubelin G, Henderson IR, Livrelli V, Gobert AP, Rosini R, Soriani M, Desvaux M. A secretome view of colonisation factors in Shiga toxin-encodingEscherichia coli(STEC): from enterohaemorrhagicE. coli(EHEC) to related enteropathotypes. FEMS Microbiol Lett 2016; 363:fnw179. [DOI: 10.1093/femsle/fnw179] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/18/2016] [Indexed: 12/25/2022] Open
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179
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Miller KA, Chaand M, Gregoire S, Yoshida T, Beck LA, Ivanov AI, Dziejman M. Characterization of V. cholerae T3SS-dependent cytotoxicity in cultured intestinal epithelial cells. Cell Microbiol 2016; 18:1857-1870. [PMID: 27302486 DOI: 10.1111/cmi.12629] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Accepted: 06/01/2016] [Indexed: 12/22/2022]
Abstract
AM-19226 is a pathogenic, non-O1/non-O139 serogroup strain of Vibrio cholerae that uses a Type 3 Secretion System (T3SS) mediated mechanism to colonize host tissues and disrupt homeostasis, causing cholera. Co-culturing the Caco2-BBE human intestinal epithelial cell line with AM-19226 in the presence of bile results in rapid mammalian cell death that requires a functional T3SS. We examined the role of bile, sought to identify the mechanism, and evaluated the contributions of T3SS translocated effectors in in vitro cell death. Our results suggest that Caco2-BBE cytotoxicity does not proceed by apoptotic or necrotic mechanisms, but rather displays characteristics consistent with osmotic lysis. Cell death was preceded by disassembly of epithelial junctions and reorganization of the cortical membrane skeleton, although neither cell death nor cell-cell disruption required VopM or VopF, two effectors known to alter actin dynamics. Using deletion strains, we identified a subset of AM-19226 Vops that are required for host cell death, which were previously assigned roles in protein translocation and colonization, suggesting that they function other than to promote cytotoxicity. The collective results therefore suggest that cooperative Vop activities are required to achieve cytotoxicity in vitro, or alternatively, that translocon pores destabilize the membrane in a bile dependent manner.
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Affiliation(s)
- Kelly A Miller
- Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Mudit Chaand
- Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Stacy Gregoire
- Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Takeshi Yoshida
- Department of Dermatology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Lisa A Beck
- Department of Dermatology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Andrei I Ivanov
- Gastroenterology and Hepatology Division, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Michelle Dziejman
- Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
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180
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Avraham R, Haseley N, Fan A, Bloom-Ackermann Z, Livny J, Hung DT. A highly multiplexed and sensitive RNA-seq protocol for simultaneous analysis of host and pathogen transcriptomes. Nat Protoc 2016; 11:1477-91. [DOI: 10.1038/nprot.2016.090] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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181
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Smith RP, Paxman JJ, Scanlon MJ, Heras B. Targeting Bacterial Dsb Proteins for the Development of Anti-Virulence Agents. Molecules 2016; 21:molecules21070811. [PMID: 27438817 PMCID: PMC6273893 DOI: 10.3390/molecules21070811] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 05/21/2016] [Accepted: 05/25/2016] [Indexed: 11/22/2022] Open
Abstract
Recent years have witnessed a dramatic increase in bacterial antimicrobial resistance and a decline in the development of novel antibiotics. New therapeutic strategies are urgently needed to combat the growing threat posed by multidrug resistant bacterial infections. The Dsb disulfide bond forming pathways are potential targets for the development of antimicrobial agents because they play a central role in bacterial pathogenesis. In particular, the DsbA/DsbB system catalyses disulfide bond formation in a wide array of virulence factors, which are essential for many pathogens to establish infections and cause disease. These redox enzymes are well placed as antimicrobial targets because they are taxonomically widespread, share low sequence identity with human proteins, and many years of basic research have provided a deep molecular understanding of these systems in bacteria. In this review, we discuss disulfide bond catalytic pathways in bacteria and their significance in pathogenesis. We also review the use of different approaches to develop inhibitors against Dsb proteins as potential anti-virulence agents, including fragment-based drug discovery, high-throughput screening and other structure-based drug discovery methods.
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Affiliation(s)
- Roxanne P Smith
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Kingsbury Drive, Bundoora, Vic 3083, Australia.
| | - Jason J Paxman
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Kingsbury Drive, Bundoora, Vic 3083, Australia.
| | - Martin J Scanlon
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Royal Parade, Parkville, Vic 3052, Australia.
| | - Begoña Heras
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Kingsbury Drive, Bundoora, Vic 3083, Australia.
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182
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Elhenawy W, Bording-Jorgensen M, Valguarnera E, Haurat MF, Wine E, Feldman MF. LPS Remodeling Triggers Formation of Outer Membrane Vesicles in Salmonella. mBio 2016; 7:e00940-16. [PMID: 27406567 PMCID: PMC4958258 DOI: 10.1128/mbio.00940-16] [Citation(s) in RCA: 100] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 06/09/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Outer membrane vesicles (OMV) are proposed to mediate multiple functions during pathogenesis and symbiosis. However, the mechanisms responsible for OMV formation remain poorly understood. It has been shown in eukaryotic membranes that lipids with an inverted-cone shape favor the formation of positive membrane curvatures. Based on these studies, we formulated the hypothesis that lipid A deacylation might impose shape modifications that result in the curvature of the outer membrane (OM) and subsequent OMV formation. We tested the effect of lipid A remodeling on OMV biogenesis employing Salmonella enterica serovar Typhimurium as a model organism. Expression of the lipid A deacylase PagL resulted in increased vesiculation, without inducing an envelope stress response. Mass spectrometry analysis revealed profound differences in the patterns of lipid A in OM and OMV, with accumulation of deacylated lipid A forms exclusively in OMV. OMV biogenesis by intracellular bacteria upon macrophage infection was drastically reduced in a pagL mutant strain. We propose a novel mechanism for OMV biogenesis requiring lipid A deacylation in the context of a multifactorial process that involves the orchestrated remodeling of the outer membrane. IMPORTANCE The role of lipid remodeling in vesiculation is well documented in eukaryotes. Similarly, bacteria produce membrane-derived vesicles; however, the molecular mechanisms underlying their production are yet to be determined. In this work, we investigated the role of outer membrane remodeling in OMV biogenesis in S Typhimurium. We showed that the expression of the lipid A deacylase PagL results in overvesiculation with deacylated lipid A accumulation exclusively in OMV. An S Typhimurium ΔpagL strain showed a significant reduction in intracellular OMV secretion relative to the wild-type strain. Our results suggest a novel mechanism for OMV biogenesis that involves outer membrane remodeling through lipid A modification. Understanding how OMV are produced by bacteria is important to advance our understanding of the host-pathogen interactions.
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Affiliation(s)
- Wael Elhenawy
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | | | - Ezequiel Valguarnera
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, St. Louis, Missouri, USA
| | - M Florencia Haurat
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Eytan Wine
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - Mario F Feldman
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, St. Louis, Missouri, USA
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183
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Diepold A, Armitage JP. Type III secretion systems: the bacterial flagellum and the injectisome. Philos Trans R Soc Lond B Biol Sci 2016; 370:rstb.2015.0020. [PMID: 26370933 DOI: 10.1098/rstb.2015.0020] [Citation(s) in RCA: 139] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The flagellum and the injectisome are two of the most complex and fascinating bacterial nanomachines. At their core, they share a type III secretion system (T3SS), a transmembrane export complex that forms the extracellular appendages, the flagellar filament and the injectisome needle. Recent advances, combining structural biology, cryo-electron tomography, molecular genetics, in vivo imaging, bioinformatics and biophysics, have greatly increased our understanding of the T3SS, especially the structure of its transmembrane and cytosolic components, the transcriptional, post-transcriptional and functional regulation and the remarkable adaptivity of the system. This review aims to integrate these new findings into our current knowledge of the evolution, function, regulation and dynamics of the T3SS, and to highlight commonalities and differences between the two systems, as well as their potential applications.
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Affiliation(s)
- Andreas Diepold
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Judith P Armitage
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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184
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Li P, Rivera-Cancel G, Kinch LN, Salomon D, Tomchick DR, Grishin NV, Orth K. Bile salt receptor complex activates a pathogenic type III secretion system. eLife 2016; 5:e15718. [PMID: 27377244 PMCID: PMC4933562 DOI: 10.7554/elife.15718] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 06/07/2016] [Indexed: 11/26/2022] Open
Abstract
Bile is an important component of the human gastrointestinal tract with an essential role in food absorption and antimicrobial activities. Enteric bacterial pathogens have developed strategies to sense bile as an environmental cue to regulate virulence genes during infection. We discovered that Vibrio parahaemolyticus VtrC, along with VtrA and VtrB, are required for activating the virulence type III secretion system 2 in response to bile salts. The VtrA/VtrC complex activates VtrB in the presence of bile salts. The crystal structure of the periplasmic domains of the VtrA/VtrC heterodimer reveals a β-barrel with a hydrophobic inner chamber. A co-crystal structure of VtrA/VtrC with bile salt, along with biophysical and mutational analysis, demonstrates that the hydrophobic chamber binds bile salts and activates the virulence network. As part of a family of conserved signaling receptors, VtrA/VtrC provides structural and functional insights into the evolutionarily conserved mechanism used by bacteria to sense their environment.
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Affiliation(s)
- Peng Li
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Giomar Rivera-Cancel
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Lisa N Kinch
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States
| | - Dor Salomon
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Diana R Tomchick
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
| | - Nick V Grishin
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
| | - Kim Orth
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, United States
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States
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185
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Zhou Y, Liu LY, He TT, Laghari ZA, Nie P, Gao Q, Xie HX. Edwardsiella tarda EsaE (Orf19 protein) is required for the secretion of type III substrates, and pathogenesis in fish. Vet Microbiol 2016; 190:12-18. [DOI: 10.1016/j.vetmic.2016.05.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 04/14/2016] [Accepted: 05/09/2016] [Indexed: 10/21/2022]
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186
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Wang H, Avican K, Fahlgren A, Erttmann SF, Nuss AM, Dersch P, Fallman M, Edgren T, Wolf-Watz H. Increased plasmid copy number is essential for Yersinia T3SS function and virulence. Science 2016; 353:492-5. [PMID: 27365311 DOI: 10.1126/science.aaf7501] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 06/22/2016] [Indexed: 12/31/2022]
Abstract
Pathogenic bacteria have evolved numerous virulence mechanisms that are essential for establishing infections. The enterobacterium Yersinia uses a type III secretion system (T3SS) encoded by a 70-kilobase, low-copy, IncFII-class virulence plasmid. We report a novel virulence strategy in Y. pseudotuberculosis in which this pathogen up-regulates the plasmid copy number during infection. We found that an increased dose of plasmid-encoded genes is indispensable for virulence and substantially elevates the expression and function of the T3SS. Remarkably, we observed direct, tight coupling between plasmid replication and T3SS function. This regulatory pathway provides a framework for further exploration of the environmental sensing mechanisms of pathogenic bacteria.
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Affiliation(s)
- He Wang
- Umeå Centre for Microbial Research (UCMR), Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden. Laboratory for Molecular Infection Medicine Sweden (MIMS), Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden
| | - Kemal Avican
- Umeå Centre for Microbial Research (UCMR), Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden. Laboratory for Molecular Infection Medicine Sweden (MIMS), Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden
| | - Anna Fahlgren
- Umeå Centre for Microbial Research (UCMR), Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden
| | - Saskia F Erttmann
- Umeå Centre for Microbial Research (UCMR), Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden. Laboratory for Molecular Infection Medicine Sweden (MIMS), Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden
| | - Aaron M Nuss
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Petra Dersch
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Maria Fallman
- Umeå Centre for Microbial Research (UCMR), Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden. Laboratory for Molecular Infection Medicine Sweden (MIMS), Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden
| | - Tomas Edgren
- Umeå Centre for Microbial Research (UCMR), Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden.
| | - Hans Wolf-Watz
- Umeå Centre for Microbial Research (UCMR), Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden. Laboratory for Molecular Infection Medicine Sweden (MIMS), Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden.
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187
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Modulation of Stat-1 in Human Macrophages Infected with Different Species of Intracellular Pathogenic Bacteria. J Immunol Res 2016; 2016:5086928. [PMID: 27437406 PMCID: PMC4942631 DOI: 10.1155/2016/5086928] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 06/08/2016] [Indexed: 01/14/2023] Open
Abstract
The infection of human macrophages by pathogenic bacteria induces different signaling pathways depending on the type of cellular receptors involved in the microorganism entry and on their mechanism(s) of survival and replication in the host cell. It was reported that Stat proteins play an important role in this process. In the present study, we investigate the changes in Stat-1 activation (phosphorylation in p-tyr701) after uptake of two Gram-positive (Listeria monocytogenes and Staphylococcus aureus) and two Gram-negative bacteria (Salmonella typhimurium and Legionella pneumophila) characterized by their varying abilities to enter, survive, and replicate in human macrophages. Comparing the results obtained with Gram-negative and Gram-positive bacteria, Stat-1 activation in macrophages does not seem to be related to LPS content. The p-tyr701Stat-1 expression levels were found to be independent of the internalized bacterial number and IFN-γ release. On the contrary, Jak/Stat-1 pathway activation only occurs when an active infection has been established in the host macrophage, and it is plausible that the differences in the expression levels of p-tyr701Stat-1 could be due to different survival mechanisms or to differences in bacteria life cycles within macrophages.
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188
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Krezalek MA, Skowron KB, Guyton KL, Shakhsheer B, Hyoju S, Alverdy JC. The intestinal microbiome and surgical disease. Curr Probl Surg 2016; 53:257-93. [PMID: 27497246 DOI: 10.1067/j.cpsurg.2016.06.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 06/07/2016] [Indexed: 12/12/2022]
Affiliation(s)
- Monika A Krezalek
- Department of Surgery, Center for Surgical Infection Research and Therapeutics, Pritzker School of Medicine, University of Chicago, Chicago, IL
| | - Kinga B Skowron
- Department of Surgery, Center for Surgical Infection Research and Therapeutics, Pritzker School of Medicine, University of Chicago, Chicago, IL
| | - Kristina L Guyton
- Department of Surgery, Center for Surgical Infection Research and Therapeutics, Pritzker School of Medicine, University of Chicago, Chicago, IL
| | - Baddr Shakhsheer
- Department of Surgery, Center for Surgical Infection Research and Therapeutics, Pritzker School of Medicine, University of Chicago, Chicago, IL
| | - Sanjiv Hyoju
- Department of Surgery, Center for Surgical Infection Research and Therapeutics, Pritzker School of Medicine, University of Chicago, Chicago, IL
| | - John C Alverdy
- Department of Surgery, Center for Surgical Infection Research and Therapeutics, Pritzker School of Medicine, University of Chicago, Chicago, IL.
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189
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Berneking L, Schnapp M, Rumm A, Trasak C, Ruckdeschel K, Alawi M, Grundhoff A, Kikhney AG, Koch-Nolte F, Buck F, Perbandt M, Betzel C, Svergun DI, Hentschke M, Aepfelbacher M. Immunosuppressive Yersinia Effector YopM Binds DEAD Box Helicase DDX3 to Control Ribosomal S6 Kinase in the Nucleus of Host Cells. PLoS Pathog 2016; 12:e1005660. [PMID: 27300509 PMCID: PMC4907486 DOI: 10.1371/journal.ppat.1005660] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 05/05/2016] [Indexed: 02/07/2023] Open
Abstract
Yersinia outer protein M (YopM) is a crucial immunosuppressive effector of the plaque agent Yersinia pestis and other pathogenic Yersinia species. YopM enters the nucleus of host cells but neither the mechanisms governing its nucleocytoplasmic shuttling nor its intranuclear activities are known. Here we identify the DEAD-box helicase 3 (DDX3) as a novel interaction partner of Y. enterocolitica YopM and present the three-dimensional structure of a YopM:DDX3 complex. Knockdown of DDX3 or inhibition of the exportin chromosomal maintenance 1 (CRM1) increased the nuclear level of YopM suggesting that YopM exploits DDX3 to exit the nucleus via the CRM1 export pathway. Increased nuclear YopM levels caused enhanced phosphorylation of Ribosomal S6 Kinase 1 (RSK1) in the nucleus. In Y. enterocolitica infected primary human macrophages YopM increased the level of Interleukin-10 (IL-10) mRNA and this effect required interaction of YopM with RSK and was enhanced by blocking YopM's nuclear export. We propose that the DDX3/CRM1 mediated nucleocytoplasmic shuttling of YopM determines the extent of phosphorylation of RSK in the nucleus to control transcription of immunosuppressive cytokines.
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Affiliation(s)
- Laura Berneking
- Institute of Medical Microbiology, Virology and Hygiene, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany
| | - Marie Schnapp
- Institute of Medical Microbiology, Virology and Hygiene, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany
| | - Andreas Rumm
- Institute of Medical Microbiology, Virology and Hygiene, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany
| | - Claudia Trasak
- Institute of Medical Microbiology, Virology and Hygiene, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany
| | - Klaus Ruckdeschel
- Institute of Medical Microbiology, Virology and Hygiene, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany
| | - Malik Alawi
- Bioinformatics Core, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Heinrich-Pette-Institute (HPI), Leibniz Institute for Experimental Virology, Research Group Virus Genomics, Hamburg, Germany
| | - Adam Grundhoff
- Heinrich-Pette-Institute (HPI), Leibniz Institute for Experimental Virology, Research Group Virus Genomics, Hamburg, Germany
| | - Alexey G. Kikhney
- European Molecular Biology Laboratory (EMBL), Hamburg Outstation, Hamburg, Germany
| | | | - Friedrich Buck
- Institute of Clinical Chemistry, University Medical Center, Hamburg, Germany
| | - Markus Perbandt
- Institute of Medical Microbiology, Virology and Hygiene, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany
- Institute of Biochemistry and Molecular Biology, University of Hamburg, Laboratory of Structural Biology of Infection and Inflammation, Hamburg, Germany
- The Hamburg Centre for Ultrafast Imaging, Hamburg, Germany
| | - Christian Betzel
- Institute of Biochemistry and Molecular Biology, University of Hamburg, Laboratory of Structural Biology of Infection and Inflammation, Hamburg, Germany
| | - Dmitri I. Svergun
- European Molecular Biology Laboratory (EMBL), Hamburg Outstation, Hamburg, Germany
| | - Moritz Hentschke
- Institute of Medical Microbiology, Virology and Hygiene, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany
| | - Martin Aepfelbacher
- Institute of Medical Microbiology, Virology and Hygiene, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany
- * E-mail:
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190
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Tőke O, Vonderviszt F. Amphipathic helical ordering of the flagellar secretion signal of Salmonella flagellin. Biochem Biophys Res Commun 2016; 476:641-647. [PMID: 27264954 DOI: 10.1016/j.bbrc.2016.06.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 06/02/2016] [Indexed: 01/22/2023]
Abstract
Export of external flagellar proteins requires a signal located within their N-terminal disordered part, however, these regions do not share any significant sequence similarity suggesting that the secondary/tertiary structure might be important for recognition by the export gate. NMR experiments were performed to reveal the conformational properties of the flagellin signal sequence in vitro. It assumed a largely disordered fluctuating structure in aqueous environment, but acquired a folded structure containing an amphipathic helical portion in 50% MeOH or upon addition of SDS micelles which are known to promote hydrophobic interactions. Our observations raise the possibility that the signal sequence may partially undergo amphipathic helical ordering upon interaction with the recognition unit of the flagellar export machinery in a similar way as revealed for protein import into intracellular eukaryotic organelles mediated by targeting signals of high diversity.
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Affiliation(s)
- Orsolya Tőke
- Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok krt. 2, H-1117, Budapest, Hungary
| | - Ferenc Vonderviszt
- Bio-Nanosystems Laboratory, Research Institute of Chemical and Process Engineering, University of Pannonia, Egyetem u. 10, H-8200, Veszprém, Hungary; Institute of Technical Physics and Materials Science, Centre for Energy Research, Konkoly-Thege u. 29-33, H-1121, Budapest, Hungary.
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191
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Fiskin E, Bionda T, Dikic I, Behrends C. Global Analysis of Host and Bacterial Ubiquitinome in Response to Salmonella Typhimurium Infection. Mol Cell 2016; 62:967-981. [PMID: 27211868 DOI: 10.1016/j.molcel.2016.04.015] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 03/08/2016] [Accepted: 04/12/2016] [Indexed: 12/14/2022]
Abstract
Ubiquitination serves as a critical signal in the host immune response to infection. Many pathogens have evolved strategies to exploit the ubiquitin (Ub) system to promote their own survival through a complex interplay between host defense machinery and bacterial virulence factors. Here we report dynamic changes in the global ubiquitinome of host epithelial cells and invading pathogen in response to Salmonella Typhimurium infection. The most significant alterations in the host ubiquitinome concern components of the actin cytoskeleton, NF-κB and autophagy pathways, and the Ub and RHO GTPase systems. Specifically, infection-induced ubiquitination promotes CDC42 activity and linear ubiquitin chain formation, both being required for NF-κB activation. Conversely, the bacterial ubiquitinome exhibited extensive ubiquitination of various effectors and several outer membrane proteins. Moreover, we reveal that bacterial Ub-modifying enzymes modulate a unique subset of host targets, affecting different stages of Salmonella infection.
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Affiliation(s)
- Evgenij Fiskin
- Institute of Biochemistry II, Goethe University School of Medicine, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany
| | - Tihana Bionda
- Institute of Biochemistry II, Goethe University School of Medicine, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany
| | - Ivan Dikic
- Institute of Biochemistry II, Goethe University School of Medicine, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany; Buchmann Institute for Molecular Life Sciences, Goethe University, Max-von-Laue-Strasse 15, 60438 Frankfurt am Main, Germany; Department of Immunology and Medical Genetics, School of Medicine, University of Split, Soltanska 2, 21 000 Split, Croatia.
| | - Christian Behrends
- Institute of Biochemistry II, Goethe University School of Medicine, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany.
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192
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Rios AC, Moutinho CG, Pinto FC, Del Fiol FS, Jozala A, Chaud MV, Vila MMDC, Teixeira JA, Balcão VM. Alternatives to overcoming bacterial resistances: State-of-the-art. Microbiol Res 2016; 191:51-80. [PMID: 27524653 DOI: 10.1016/j.micres.2016.04.008] [Citation(s) in RCA: 125] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 03/28/2016] [Accepted: 04/21/2016] [Indexed: 12/23/2022]
Abstract
Worldwide, bacterial resistance to chemical antibiotics has reached such a high level that endangers public health. Presently, the adoption of alternative strategies that promote the elimination of resistant microbial strains from the environment is of utmost importance. This review discusses and analyses several (potential) alternative strategies to current chemical antibiotics. Bacteriophage (or phage) therapy, although not new, makes use of strictly lytic phage particles as an alternative, or a complement, in the antimicrobial treatment of bacterial infections. It is being rediscovered as a safe method, because these biological entities devoid of any metabolic machinery do not possess any affinity whatsoever to eukaryotic cells. Lysin therapy is also recognized as an innovative antimicrobial therapeutic option, since the topical administration of preparations containing purified recombinant lysins with amounts in the order of nanograms, in infections caused by Gram-positive bacteria, demonstrated a high therapeutic potential by causing immediate lysis of the target bacterial cells. Additionally, this therapy exhibits the potential to act synergistically when combined with certain chemical antibiotics already available on the market. Another potential alternative antimicrobial therapy is based on the use of antimicrobial peptides (AMPs), amphiphilic polypeptides that cause disruption of the bacterial membrane and can be used in the treatment of bacterial, fungal and viral infections, in the prevention of biofilm formation, and as antitumoral agents. Interestingly, bacteriocins are a common strategy of bacterial defense against other bacterial agents, eliminating the potential opponents of the former and increasing the number of available nutrients in the environment for their own growth. They can be applied in the food industry as biopreservatives and as probiotics, and also in fighting multi-resistant bacterial strains. The use of antibacterial antibodies promises to be extremely safe and effective. Additionally, vaccination emerges as one of the most promising preventive strategies. All these will be tackled in detail in this review paper.
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Affiliation(s)
- Alessandra C Rios
- LaBNUS-Biomaterials and Nanotechnology Laboratory, i(bs)2i(bs)(2)-intelligent biosensing and biomolecule stabilization research group, University of Sorocaba, Sorocaba/SP, Brazil
| | - Carla G Moutinho
- CEB-Centre of Biological Engineering, University of Minho, Braga, Portugal; University Fernando Pessoa, Porto, Portugal
| | | | - Fernando S Del Fiol
- LaBNUS-Biomaterials and Nanotechnology Laboratory, i(bs)2i(bs)(2)-intelligent biosensing and biomolecule stabilization research group, University of Sorocaba, Sorocaba/SP, Brazil
| | - Angela Jozala
- LaBNUS-Biomaterials and Nanotechnology Laboratory, i(bs)2i(bs)(2)-intelligent biosensing and biomolecule stabilization research group, University of Sorocaba, Sorocaba/SP, Brazil
| | - Marco V Chaud
- LaBNUS-Biomaterials and Nanotechnology Laboratory, i(bs)2i(bs)(2)-intelligent biosensing and biomolecule stabilization research group, University of Sorocaba, Sorocaba/SP, Brazil
| | - Marta M D C Vila
- LaBNUS-Biomaterials and Nanotechnology Laboratory, i(bs)2i(bs)(2)-intelligent biosensing and biomolecule stabilization research group, University of Sorocaba, Sorocaba/SP, Brazil
| | - José A Teixeira
- CEB-Centre of Biological Engineering, University of Minho, Braga, Portugal
| | - Victor M Balcão
- LaBNUS-Biomaterials and Nanotechnology Laboratory, i(bs)2i(bs)(2)-intelligent biosensing and biomolecule stabilization research group, University of Sorocaba, Sorocaba/SP, Brazil; CEB-Centre of Biological Engineering, University of Minho, Braga, Portugal.
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193
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Intramacrophage Infection Reinforces the Virulence of Edwardsiella tarda. J Bacteriol 2016; 198:1534-42. [PMID: 26953340 DOI: 10.1128/jb.00978-15] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Accepted: 03/01/2016] [Indexed: 01/30/2023] Open
Abstract
UNLABELLED Edwardsiella tarda is an important pathogenic bacterium that can replicate in macrophages. However, how the intramacrophage infection process affects the virulence of this bacterium is essentially unknown. Here, we show that E. tarda replicates and induces a caspase-1-dependent cell pyroptosis in a murine macrophage model. Via pyroptosis, intracellular E. tarda escapes to the extracellular milieu, forming a unique bacterial population. Being different from the bacteria cultured alone, this unique population possesses a reprogrammed transcriptional profile, particularly with upregulated type III secretion system (T3SS)/T6SS cluster genes. Subsequent studies revealed that the macrophage-released population gains enhanced infectivity for host epithelial cells and increases resistance to multiple host defenses and hence displays significantly promoted virulence in vivo Further studies indicated that T3SS is essentially required for the macrophage infection process, while T6SS contributes to infection-induced bacterial virulence. Altogether, this work demonstrates that E. tarda can utilize macrophages as a niche for virulence priming and for spreading infection, suggesting a positive role for intramacrophage infection in bacterial pathogenesis. IMPORTANCE Many pathogens can replicate in macrophages, which is crucial for their pathogenesis. To survive in the macrophage cell, pathogens are likely to require fitness genes to counteract multiple host-killing mechanisms. Here, Edwardsiella tarda is proved to exit from macrophages during infection. This macrophage-released population displays a reprogrammed transcriptional profile with significantly upregulated type III secretion system (T3SS)/T6SS-related genes. Furthermore, both enhanced infectivity in epithelial cells and activated resistance to complex host defenses were conferred on this macrophage-primed population, which consequently promoted the full virulence of E. tarda in vivo Our work provides evidence that E. tarda can utilize macrophages as a niche for virulence priming and for spreading infection, highlighting the importance of the intramacrophage infection cycle for the pathogenesis of E. tarda.
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194
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Visualizing the Translocation and Localization of Bacterial Type III Effector Proteins by Using a Genetically Encoded Reporter System. Appl Environ Microbiol 2016; 82:2700-2708. [PMID: 26921426 PMCID: PMC4836418 DOI: 10.1128/aem.03418-15] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 02/19/2016] [Indexed: 12/25/2022] Open
Abstract
Bacterial type III secretion system (T3SS) effector proteins are critical determinants of infection for many animal and plant pathogens. However, monitoring of the translocation and delivery of these important virulence determinants has proved to be technically challenging. Here, we used a genetically engineered LOV (light-oxygen-voltage) sensing domain derivative to monitor the expression, translocation, and localization of bacterial T3SS effectors. We found the Escherichia coli O157:H7 bacterial effector fusion Tir-LOV was functional following its translocation and localized to the host cell membrane in discrete foci, demonstrating that LOV-based reporters can be used to visualize the effector translocation with minimal manipulation and interference. Further evidence for the versatility of the reporter was demonstrated by fusing LOV to the C terminus of the Shigella flexneri effector IpaB. IpaB-LOV localized preferentially at bacterial poles before translocation. We observed the rapid translocation of IpaB-LOV in a T3SS-dependent manner into host cells, where it localized at the bacterial entry site within membrane ruffles.
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195
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Strains, Mechanism, and Perspective: Salmonella-Based Cancer Therapy. Int J Microbiol 2016; 2016:5678702. [PMID: 27190519 PMCID: PMC4848419 DOI: 10.1155/2016/5678702] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 03/11/2016] [Accepted: 03/20/2016] [Indexed: 01/21/2023] Open
Abstract
Recently, investigation of bacterial-based tumor therapy has regained focus due to progress in molecular, cellular, and microbial biology. Many bacteria such as Salmonella, Listeria, Escherichia, and Clostridium have proved to have tumor targeting and in some cases even tumor-destroying phenotypes. Furthermore, bacterial clinical treatments for cancer have been improved by combination with other therapeutic methods such as chemotherapeutic drugs and radioactive agents. Synthetic biology techniques have also driven the development of new bacterial-based cancer therapies. However, basic questions about the mechanisms of bacterial-mediated tumor targeting and destruction are still being elucidated. In this review, we focus on three tumor-therapeutic Salmonella models, the most intensively studied bacterial genus in this field. One of these Salmonella models is our Salmonella enterica serovar Typhimurium LT2 derived strain CRC2631, engineered to minimize toxicity but maximize tumor-targeting and destruction effects. The other two are VNP20009 and A1-R. We compare the means by which these therapeutic candidate strain models were selected for study, their tumor targeting and tumor destruction phenotypes in vitro and in vivo, and what is currently known about the mechanisms by which they target and destroy tumors.
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196
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Anuforom O, Wallace GR, Buckner MMC, Piddock LJV. Ciprofloxacin and ceftriaxone alter cytokine responses, but not Toll-like receptors, to Salmonella infection in vitro. J Antimicrob Chemother 2016; 71:1826-33. [PMID: 27076102 DOI: 10.1093/jac/dkw092] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 02/28/2016] [Indexed: 12/20/2022] Open
Abstract
OBJECTIVES Antibiotics that enhance host natural defences to infection offer an alternative approach to treating infections. However, mechanisms underlying such processes are poorly understood. The aim of this study was to investigate the effects of clinically relevant concentrations of two antibiotics on bacterial interactions with murine macrophages. METHODS Adhesion of Salmonella Typhimurium SL1344 to and invasion by Salmonella Typhimurium SL1344 of antibiotic-treated or untreated J774 murine macrophages were measured using a tissue culture infection model. Expression of genes central to the Toll-like receptor (TLR) signalling pathway of macrophages infected with Salmonella was analysed using the RT(2) Profiler PCR Array. Cytokine production was measured by ELISA. RESULTS Adhesion of Salmonella Typhimurium SL1344 to J774 macrophage monolayers was increased when macrophages were exposed to ciprofloxacin and ceftriaxone, while invasion was decreased by ciprofloxacin. Expression of IL-1β and TNF-α mRNA was greater in SL1344-infected macrophages that had been treated with ciprofloxacin or ceftriaxone than in macrophages exposed to antibiotics alone or SL1344 alone. TLR mRNA was down-regulated by SL1344 infection, a response that was not altered by antibiotic pretreatment. CONCLUSIONS Clinically relevant concentrations of two antibiotics differentially enhanced the response of immune cells and their interaction with bacteria, increasing bacterial adhesion to macrophages and increasing cytokine production. As increased expression of IL-1β fosters apoptosis of Salmonella-infected macrophages and clearance by neutrophils, the immunomodulatory potential of these antibiotics may explain, in part, why these two drugs continue to be used to treat salmonellosis successfully.
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Affiliation(s)
- Olachi Anuforom
- Antimicrobials Research Group, Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Graham R Wallace
- Centre for Translational Inflammation, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Michelle M C Buckner
- Antimicrobials Research Group, Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Laura J V Piddock
- Antimicrobials Research Group, Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
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Zhang D, Burroughs AM, Vidal ND, Iyer LM, Aravind L. Transposons to toxins: the provenance, architecture and diversification of a widespread class of eukaryotic effectors. Nucleic Acids Res 2016; 44:3513-33. [PMID: 27060143 PMCID: PMC4857004 DOI: 10.1093/nar/gkw221] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 03/22/2016] [Indexed: 01/13/2023] Open
Abstract
Enzymatic effectors targeting nucleic acids, proteins and other cellular components are the mainstay of conflicts across life forms. Using comparative genomics we identify a large class of eukaryotic proteins, which include effectors from oomycetes, fungi and other parasites. The majority of these proteins have a characteristic domain architecture with one of several N-terminal 'Header' domains, which are predicted to play a role in trafficking of these effectors, including a novel version of the Ubiquitin fold. The Headers are followed by one or more diverse C-terminal domains, such as restriction endonuclease (REase), protein kinase, HNH endonuclease, LK-nuclease (a RNase) and multiple distinct peptidase domains, which are predicted to carry their toxicity determinants. The most common types of these proteins appear to have originated from prokaryotic transposases (e.g. TN7 and Mu) and combine a CDC6/ORC1-STAND clade NTPase domain with a C-terminal REase domain. Other than the so-called Crinkler effectors of oomycetes and fungi, these effectors are encoded by other eukaryotic parasites such as trypanosomatids (the RHS proteins) and the rhizarian Plasmodiophora, and symbionts like Capsaspora Remarkably, we also find these proteins in free-living eukaryotes, including several viridiplantae, fungi, amoebozoans and animals. These versions might either still be transposons or function in other poorly understood eukaryote-specific inter-organismal and inter-genomic conflicts. These include the Medea1 selfish element of Tribolium that spreads via post-zygotic killing. We present a unified mechanism for the recombination-dependent diversification and action of this widespread class of molecular weaponry deployed across diverse conflicts ranging from parasitic to free-living forms.
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Affiliation(s)
- Dapeng Zhang
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - A Maxwell Burroughs
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Newton D Vidal
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Lakshminarayan M Iyer
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - L Aravind
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
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198
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Gold V, Kudryashev M. Recent progress in structure and dynamics of dual-membrane-spanning bacterial nanomachines. Curr Opin Struct Biol 2016; 39:1-7. [PMID: 26995496 DOI: 10.1016/j.sbi.2016.03.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 03/03/2016] [Accepted: 03/04/2016] [Indexed: 02/05/2023]
Abstract
Advances in hard-ware and soft-ware for electron cryo-microscopy and tomography have provided unprecedented structural insights into large protein complexes in bacterial membranes. Tomographic volumes of native complexes in situ, combined with other structural and functional data, reveal functionally important conformational changes. Here, we review recent progress in elucidating the structure and mechanism of dual-membrane-spanning nanomachines involved in bacterial motility, adhesion, pathogenesis and biofilm formation, including the type IV pilus assembly machinery and the type III and VI secretions systems. We highlight how these new structural data shed light on the assembly and action of such machines and discuss future directions for more detailed mechanistic understanding of these massive, fascinating complexes.
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Affiliation(s)
- Vicki Gold
- Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany.
| | - Mikhail Kudryashev
- Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main, Germany; Buchmann Institute for Molecular Life Sciences, Goethe University of Frankfurt, Max-von-Laue Str. 17, 60438 Frankfurt am Main, Germany.
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199
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Identification of protein secretion systems in bacterial genomes. Sci Rep 2016; 6:23080. [PMID: 26979785 PMCID: PMC4793230 DOI: 10.1038/srep23080] [Citation(s) in RCA: 242] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 02/24/2016] [Indexed: 01/08/2023] Open
Abstract
Bacteria with two cell membranes (diderms) have evolved complex systems for protein secretion. These systems were extensively studied in some model bacteria, but the characterisation of their diversity has lagged behind due to lack of standard annotation tools. We built online and standalone computational tools to accurately predict protein secretion systems and related appendages in bacteria with LPS-containing outer membranes. They consist of models describing the systems’ components and genetic organization to be used with MacSyFinder to search for T1SS-T6SS, T9SS, flagella, Type IV pili and Tad pili. We identified ~10,000 candidate systems in bacterial genomes, where T1SS and T5SS were by far the most abundant and widespread. All these data are made available in a public database. The recently described T6SSiii and T9SS were restricted to Bacteroidetes, and T6SSii to Francisella. The T2SS, T3SS, and T4SS were frequently encoded in single-copy in one locus, whereas most T1SS were encoded in two loci. The secretion systems of diderm Firmicutes were similar to those found in other diderms. Novel systems may remain to be discovered, since some clades of environmental bacteria lacked all known protein secretion systems. Our models can be fully customized, which should facilitate the identification of novel systems.
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200
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Abstract
Eukaryotic cells utilize the ubiquitin (Ub) system for maintaining a balanced functioning of cellular pathways. Although the Ub system is exclusive to eukaryotes, prokaryotic bacteria have developed an armory of Ub ligase enzymes that are capable of employing the Ub systems of various hosts, ranging from plant to animal cells. These enzymes have been acquired through the evolution and can be classified into three main classes, RING (really interesting new gene), HECT (homologous to the E6-AP carboxyl terminus) and NEL (novel E3 ligases). In this review we describe the roles played by different classes of bacterial Ub ligases in infection and pathogenicity. We also provide an overview of the different mechanisms by which bacteria mimic specific components of the host Ub system and outline the gaps in our current understanding of their functions. Additionally, we discuss approaches and experimental tools for validating this class of enzymes as potential novel antibacterial therapy targets.
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