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Kulshrestha A, Maurya S, Gupta T, Roy R, Punnathanam SN, Ayappa KG. Conformational Flexibility Is a Key Determinant for the Lytic Activity of the Pore-Forming Protein, Cytolysin A. J Phys Chem B 2023; 127:69-84. [PMID: 36542809 DOI: 10.1021/acs.jpcb.2c05785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Several bacterial infections are mediated by pore-forming toxins (PFTs), a subclass of proteins that oligomerize on mammalian cell membranes forming lytic nanopores. Cytolysin A (ClyA), an α-PFT, undergoes a dramatic conformational change restructuring its two membrane-binding motifs (the β-tongue and the N-terminus helix), during pore formation. A complete molecular picture for this key transition and the driving force behind the secondary structure change upon membrane binding remain elusive. Using all-atom molecular dynamics (MD) simulations of the ClyA monomer and string method based free energy computations with path collective variables, we illustrate that an unfolded β-tongue motif is an on-pathway intermediate during the transition to the helix-turn-helix motif of the protomer. An aggregate of 28 μs of all-atom thermal unfolding MD simulations of wild-type ClyA and its single point mutants reveal that the membrane-binding motifs of the ClyA protein display high structural flexibility in water. However, point mutations in these motifs lead to a distinct reduction in the flexibility, especially in the β-tongue, thereby stabilizing the pretransition secondary structure. Resistance to unfolding was further corroborated by MD simulations of the β-tongue mutant motif in the membrane. Combined with the thermal unfolding simulations, we posit that the β-tongue as well as N-terminal mutants that lower the tendency to unfold and disorder the β-tongue are detrimental to pore formation by ClyA and its lytic activity. Erythrocyte turbidity and vesicle leakage assays indeed reveal a loss of activity for the β-tongue mutant, and delayed kinetics for the N-terminus mutants. On the other hand, a point mutation in the extracellular domain that did not abrogate lytic activity displayed similar unfolding characteristics as the wild type. Thus, attenuation of conformational flexibility in membrane-binding motifs correlates with reduced lytic and leakage activity. Combined with secondary structure changes observed in the membrane bound states, our study shows that the tendency to unfold in the β-tongue region is a critical step in the conformational transition and bistability of the ClyA protein and mutants that disrupt this tendency reduced pore formation. Overall, our finding suggests that inherent flexibility in the protein could play a wider and hitherto unrecognized role in membrane-mediated conformational transitions of PFTs and other membrane protein transformations.
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Affiliation(s)
- Avijeet Kulshrestha
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Satyaghosh Maurya
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Twinkle Gupta
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Rahul Roy
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, Karnataka 560012, India.,Center for BioSystems Science and Engineering, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Sudeep N Punnathanam
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - K Ganapathy Ayappa
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, Karnataka 560012, India
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2
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Worthy HL, Williamson LJ, Auhim HS, Leppla SH, Sastalla I, Jones DD, Rizkallah PJ, Berry C. The Crystal Structure of Bacillus cereus HblL 1. Toxins (Basel) 2021; 13:253. [PMID: 33807365 PMCID: PMC8065917 DOI: 10.3390/toxins13040253] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 03/26/2021] [Accepted: 03/29/2021] [Indexed: 02/07/2023] Open
Abstract
The Hbl toxin is a three-component haemolytic complex produced by Bacillus cereus sensu lato strains and implicated as a cause of diarrhoea in B. cereus food poisoning. While the structure of the HblB component of this toxin is known, the structures of the other components are unresolved. Here, we describe the expression of the recombinant HblL1 component and the elucidation of its structure to 1.36 Å. Like HblB, it is a member of the alpha-helical pore-forming toxin family. In comparison to other members of this group, it has an extended hydrophobic beta tongue region that may be involved in pore formation. Molecular docking was used to predict possible interactions between HblL1 and HblB, and suggests a head to tail dimer might form, burying the HblL1 beta tongue region.
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Affiliation(s)
- Harley L. Worthy
- School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AX, UK; (H.L.W.); (L.J.W.); (H.S.A.); (D.D.J.)
- The Henry Wellcome Building for Biocatalysis, Exeter University, Stocker Road, Exeter EX4 4QD, UK
| | - Lainey J. Williamson
- School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AX, UK; (H.L.W.); (L.J.W.); (H.S.A.); (D.D.J.)
| | - Husam Sabah Auhim
- School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AX, UK; (H.L.W.); (L.J.W.); (H.S.A.); (D.D.J.)
- Department of Biology, College of Science, University of Baghdad, Baghdad, Iraq
| | - Stephen H. Leppla
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA; (S.H.L.); (I.S.)
| | - Inka Sastalla
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA; (S.H.L.); (I.S.)
- Scientific Review Program, Division of Extramural Activities, NIAID, NIH, Rockville, MD 20892, USA
| | - D. Dafydd Jones
- School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AX, UK; (H.L.W.); (L.J.W.); (H.S.A.); (D.D.J.)
| | | | - Colin Berry
- School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AX, UK; (H.L.W.); (L.J.W.); (H.S.A.); (D.D.J.)
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3
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Sathyanarayana P, Visweswariah SS, Ayappa KG. Mechanistic Insights into Pore Formation by an α-Pore Forming Toxin: Protein and Lipid Bilayer Interactions of Cytolysin A. Acc Chem Res 2021; 54:120-131. [PMID: 33291882 DOI: 10.1021/acs.accounts.0c00551] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Pore forming toxins (PFTs) are the largest class of bacterial toxins playing a central role in bacterial pathogenesis. They are proteins specifically designed to form nanochannels in the membranes of target cells, ultimately resulting in cell death and establishing infection. PFTs are broadly classified as α- and β-PFTs, depending on secondary structures that form the transmembrane channel. A unique feature about this class of proteins is the drastic conformational changes and complex oligomerization pathways that occur upon exposure to the plasma membrane. A molecular understanding of pore formation has implications in designing novel intervention strategies to combat rising antimicrobial resistance, targeted-cancer therapy, as well as designing nanopores for specialized technologies. Central to unraveling the pore formation pathway is the availability of high resolution crystal structures. In this regard, β-toxins are better understood, when compared with α-toxins whose pore forming mechanisms are complicated by an incomplete knowledge of the driving forces for amphiphatic membrane-inserted helices to organize into functional pores. With the publication of the first crystal structure for an α-toxin, cytolysin A (ClyA), in 2009 we embarked on an extensive multiscale study to unravel its pore forming mechanism. This Account represents the collective mechanistic knowledge gained in our laboratories using a variety of experimental and theoretical techniques which include large scale molecular dynamics (MD) simulations, kinetic modeling studies, single-molecule fluorescence imaging, and super-resolution spectroscopy. We reported MD simulations of the ClyA protomer, oligomeric intermediates, and full pore complex in a lipid bilayer and mapped the conformational transitions that accompany membrane binding. Using single-molecule fluorescence imaging, the conformational transition was experimentally verified by analysis of various diffusion states of membrane bound ClyA. Importantly, we have uncovered a hitherto unknown putative cholesterol binding motif in the membrane-inserted helix of ClyA. Distinct binding pockets for cholesterol formed by adjacent membrane-inserted helices are revealed in MD simulations. Cholesterol appears to play a dual role by stabilizing both the membrane-inserted protomer as well as oligomeric intermediates. Molecular dynamics simulations and kinetic modeling studies suggest that the membrane-inserted arcs oligomerize reversibly to form the predominant transmembrane oligomeric intermediates during pore formation. We posit that this mechanistic understanding of the complex action of α-PFTs has implications in unraveling pore assembly across the wider family of bacterial toxins. With emerging antimicrobial resistance, alternate therapies may rely on disrupting pore functionality or oligomerization of these pathogenic determinants utilized by bacteria, and our study includes assessing the potential for dendrimers as pore blockers.
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Affiliation(s)
- Pradeep Sathyanarayana
- Centre for BioSystems Science and Engineering, Indian Institute of Science, Bangalore, India 560012
| | - Sandhya S. Visweswariah
- Centre for BioSystems Science and Engineering, Indian Institute of Science, Bangalore, India 560012
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, India 560012
| | - K. Ganapathy Ayappa
- Centre for BioSystems Science and Engineering, Indian Institute of Science, Bangalore, India 560012
- Department of Chemical Engineering, Indian Institute of Science, Bangalore, India 560012
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4
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Fuentes-Castillo D, Navas-Suárez PE, Gondim MF, Esposito F, Sacristán C, Fontana H, Fuga B, Piovani C, Kooij R, Lincopan N, Catão-Dias JL. Genomic characterization of multidrug-resistant ESBL-producing Escherichia coli ST58 causing fatal colibacillosis in critically endangered Brazilian merganser (Mergus octosetaceus). Transbound Emerg Dis 2020; 68:258-266. [PMID: 32544292 PMCID: PMC8246901 DOI: 10.1111/tbed.13686] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 06/03/2020] [Accepted: 06/08/2020] [Indexed: 12/12/2022]
Abstract
Even though antimicrobial‐resistant bacteria have begun to be detected in wildlife, raising important issues related to their transmission and persistence of clinically important pathogens in the environment, little is known about the role of these bacteria on wildlife health, especially on endangered species. The Brazilian merganser (Mergus octosetaceus) is one of the most threatened waterfowl in the world, classified as Critically Endangered by the International Union for Conservation of Nature. In 2019, a fatal case of sepsis was diagnosed in an 8‐day‐old Brazilian merganser inhabiting a zoological park. At necropsy, major gross lesions were pulmonary and hepatic congestion. Using microbiologic and genomic methods, we identified a multidrug‐resistant (MDR) extended‐spectrum β‐lactamase (ESBL) CTX‐M‐8‐producing Escherichia coli (designed as PMPU strain) belonging to the international clone ST58, in coelomic cavity, oesophagus, lungs, small intestine and cloaca samples. PMPU strain harboured a broad resistome against antibiotics (cephalosporins, tetracyclines, aminoglycosides, sulphonamides, trimethoprim and quinolones), domestic/hospital disinfectants and heavy metals (arsenic, mercury, lead, copper and silver). Additionally, the virulence of E. coli PMPU strain was confirmed using a wax moth (Galleria mellonella) infection model, and it was supported by the presence of virulence genes encoding toxins, adherence factors, invasins and iron acquisition systems. Broad resistome and virulome of PMPU contributed to therapeutic failure and death of the animal. In brief, we report for the first time a fatal colibacillosis by MDR ESBL‐producing E. coli in critically endangered Brazilian merganser, highlighting that besides colonization, critical priority pathogens are threatening wildlife. E. coli ST58 clone has been previously reported in humans, food‐producing animals, wildlife and environment, supporting broad adaptation and persistence at human–animal–environment interface.
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Affiliation(s)
- Danny Fuentes-Castillo
- Department of Pathology, School of Veterinary Medicine and Animal Sciences, University of São Paulo, São Paulo, Brazil.,One Health Brazilian Resistance Project (OneBR), São Paulo, Brazil
| | - Pedro Enrique Navas-Suárez
- Department of Pathology, School of Veterinary Medicine and Animal Sciences, University of São Paulo, São Paulo, Brazil
| | | | - Fernanda Esposito
- One Health Brazilian Resistance Project (OneBR), São Paulo, Brazil.,Department of Clinical Analysis, Faculty of Pharmacy, University of São Paulo, São Paulo, Brazil
| | - Carlos Sacristán
- Department of Pathology, School of Veterinary Medicine and Animal Sciences, University of São Paulo, São Paulo, Brazil
| | - Herrison Fontana
- One Health Brazilian Resistance Project (OneBR), São Paulo, Brazil.,Department of Clinical Analysis, Faculty of Pharmacy, University of São Paulo, São Paulo, Brazil
| | - Bruna Fuga
- One Health Brazilian Resistance Project (OneBR), São Paulo, Brazil.,Department of Clinical Analysis, Faculty of Pharmacy, University of São Paulo, São Paulo, Brazil.,Department of Microbiology, Instituto de Ciências Biomédicas, University of São Paulo, São Paulo, Brazil
| | | | | | - Nilton Lincopan
- One Health Brazilian Resistance Project (OneBR), São Paulo, Brazil.,Department of Clinical Analysis, Faculty of Pharmacy, University of São Paulo, São Paulo, Brazil.,Department of Microbiology, Instituto de Ciências Biomédicas, University of São Paulo, São Paulo, Brazil
| | - José Luiz Catão-Dias
- Department of Pathology, School of Veterinary Medicine and Animal Sciences, University of São Paulo, São Paulo, Brazil
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5
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Nevermann J, Silva A, Otero C, Oyarzún DP, Barrera B, Gil F, Calderón IL, Fuentes JA. Identification of Genes Involved in Biogenesis of Outer Membrane Vesicles (OMVs) in Salmonella enterica Serovar Typhi. Front Microbiol 2019; 10:104. [PMID: 30778340 PMCID: PMC6369716 DOI: 10.3389/fmicb.2019.00104] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 01/17/2019] [Indexed: 12/26/2022] Open
Abstract
Outer membrane vesicles (OMVs) are nano-sized proteoliposomes discharged from the cell envelope of Gram-negative bacteria. OMVs normally contain toxins, enzymes and other factors, and are used as vehicles in a process that has been considered a generalized, evolutionarily conserved delivery system among bacteria. Furthermore, OMVs can be used in biotechnological applications that require delivery of biomolecules, such as vaccines, remarking the importance of their study. Although it is known that Salmonella enterica serovar Typhi (S. Typhi), the etiological agent of typhoid fever in humans, delivers toxins (e.g., HlyE) via OMVs, there are no reports identifying genetic determinants of the OMV biogenesis in this serovar. In the present work, and with the aim to identify genes participating in OMV biogenesis in S. Typhi, we screened 15,000 random insertion mutants for increased HlyE secretion. We found 9 S. Typhi genes (generically called zzz genes) determining an increased HlyE secretion that were also involved in OMV biogenesis. The genes corresponded to ompA, nlpI, and tolR (envelope stability), rfaE and waaC (LPS synthesis), yipP (envC), mrcB (synthesis and remodeling of peptidoglycan), degS (stress sensor serine endopeptidase) and hns (global transcriptional regulator). We found that S. Typhi Δzzz mutants were prone to secrete periplasmic, functional proteins with a relatively good envelope integrity. In addition, we showed that zzz genes participate in OMV biogenesis, modulating different properties such as OMV size distribution, OMV yield and OMV protein cargo.
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Affiliation(s)
- Jan Nevermann
- Laboratorio de Genética y Patogénesis Bacteriana, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
| | - Andrés Silva
- Laboratorio de Genética y Patogénesis Bacteriana, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
| | - Carolina Otero
- Escuela de Química y Farmacia, Facultad de Medicina, Universidad Andres Bello, Santiago, Chile
| | - Diego P Oyarzún
- Center of Applied Nanosciences, Universidad Andres Bello, Santiago, Chile
| | - Boris Barrera
- Unidad de Microbiología, Hospital Clínico Universidad de Chile, Santiago, Chile
| | - Fernando Gil
- Microbiota-Host Interactions and Clostridia Research Group, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
| | - Iván L Calderón
- Laboratorio de Genética y Patogénesis Bacteriana, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
| | - Juan A Fuentes
- Laboratorio de Genética y Patogénesis Bacteriana, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
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6
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Giri Rao VVH, Desikan R, Ayappa KG, Gosavi S. Capturing the Membrane-Triggered Conformational Transition of an α-Helical Pore-Forming Toxin. J Phys Chem B 2016; 120:12064-12078. [DOI: 10.1021/acs.jpcb.6b09400] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- V. V. Hemanth Giri Rao
- Simons
Centre for the Study of Living Machines, National Centre for Biological
Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India
| | - Rajat Desikan
- Department
of Chemical Engineering, Indian Institute of Science, Bengaluru 560012, India
| | - K. Ganapathy Ayappa
- Department
of Chemical Engineering, Indian Institute of Science, Bengaluru 560012, India
- Centre
for Biosystems Science and Engineering, Indian Institute of Science, Bengaluru 560012, India
| | - Shachi Gosavi
- Simons
Centre for the Study of Living Machines, National Centre for Biological
Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India
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7
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Green J, Rolfe MD, Smith LJ. Transcriptional regulation of bacterial virulence gene expression by molecular oxygen and nitric oxide. Virulence 2014; 5:794-809. [PMID: 25603427 PMCID: PMC4601167 DOI: 10.4161/viru.27794] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Molecular oxygen (O2) and nitric oxide (NO) are diatomic gases that play major roles in infection. The host innate immune system generates reactive oxygen species and NO as bacteriocidal agents and both require O2 for their production. Furthermore, the ability to adapt to changes in O2 availability is crucial for many bacterial pathogens, as many niches within a host are hypoxic. Pathogenic bacteria have evolved transcriptional regulatory systems that perceive these gases and respond by reprogramming gene expression. Direct sensors possess iron-containing co-factors (iron–sulfur clusters, mononuclear iron, heme) or reactive cysteine thiols that react with O2 and/or NO. Indirect sensors perceive the physiological effects of O2 starvation. Thus, O2 and NO act as environmental cues that trigger the coordinated expression of virulence genes and metabolic adaptations necessary for survival within a host. Here, the mechanisms of signal perception by key O2- and NO-responsive bacterial transcription factors and the effects on virulence gene expression are reviewed, followed by consideration of these aspects of gene regulation in two major pathogens, Staphylococcus aureus and Mycobacterium tuberculosis.
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Key Words
- AIP, autoinducer peptide
- Arc, Aerobic respiratory control
- FNR
- FNR, fumarate nitrate reduction regulator
- GAF, cGMP-specific phosphodiesterase-adenylyl cyclase-FhlA domain
- Isc, iron–sulfur cluster biosynthesis machinery
- Mycobacterium tuberculosis
- NOX, NADPH oxidase
- PAS, Per-Amt-Sim domain
- RNS, reactive nitrogen species
- ROS, reactive oxygen species
- Staphylococcus aureus
- TB, tuberculosis
- WhiB-like proteins
- iNOS, inducible nitric oxide synthase
- iron–sulfur cluster
- nitric oxide sensors
- oxygen sensors
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Affiliation(s)
- Jeffrey Green
- a Krebs Institute; Molecular Biology & Biotechnology; University of Sheffield ; Western Bank , Sheffield , UK
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8
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Vaidyanathan MS, Sathyanarayana P, Maiti PK, Visweswariah SS, Ayappa KG. Lysis dynamics and membrane oligomerization pathways for Cytolysin A (ClyA) pore-forming toxin. RSC Adv 2014. [DOI: 10.1039/c3ra45159c] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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9
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Magalhães CA, Rossato SS, Barbosa AS, Santos TOD, Elias WP, Sircili MP, Piazza RMF. The ability of haemolysins expressed by atypical enteropathogenic Escherichia coli to bind to extracellular matrix components. Mem Inst Oswaldo Cruz 2011; 106:146-52. [PMID: 21537672 DOI: 10.1590/s0074-02762011000200005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Accepted: 12/01/2010] [Indexed: 01/29/2023] Open
Abstract
Typical and atypical enteropathogenic Escherichia coli (EPEC) are considered important bacterial causes of diarrhoea. Considering the repertoire of virulence genes, atypical EPEC (aEPEC) is a heterogeneous group, harbouring genes that are found in other diarrheagenic E. coli pathotypes, such as those encoding haemolysins. Haemolysins are cytolytic toxins that lyse host cells disrupting the function of the plasma membrane. In addition, these cytolysins mediate a connection to vascular tissue and/or blood components, such as plasma and cellular fibronectin. Therefore, we investigated the haemolytic activity of 72 aEPEC isolates and determined the correlation of this phenotype with the presence of genes encoding enterohaemolysins (Ehly) and cytolysin A (ClyA). In addition, the correlation between the expression of haemolysins and the ability of these secreted proteins to adhere to extracellular matrix (ECM) components was also assessed in this study. Our findings demonstrate that a subset of aEPEC presents haemolytic activity due to the expression of Ehlys and/or ClyA and that this activity is closely related to the ability of these isolates to bind to ECM components.
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10
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Mutations affecting export and activity of cytolysin A from Escherichia coli. J Bacteriol 2010; 192:4001-11. [PMID: 20511497 DOI: 10.1128/jb.01283-09] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Cytolysin A (known as ClyA, HlyE, and SheA) is a cytolytic pore-forming protein toxin found in several Escherichia coli and Salmonella enterica strains. The structure of its water-soluble monomeric form and that of dodecameric ClyA pores is known, but the mechanisms of ClyA export from bacterial cells and of pore assembly are only partially understood. Here we used site-directed mutagenesis to study the importance of different regions of the E. coli ClyA protein for export and activity. The data indicate that ClyA translocation to the periplasm requires several protein segments located closely adjacent to each other in the "tail" domain of the ClyA monomer, namely, the N- and C-terminal regions and the hydrophobic sequence ranging from residues 89 to 101. Deletion of most of the "head" domain of the monomer (residues 181 to 203), on the other hand, did not strongly affect ClyA secretion, suggesting that the tail domain plays a particular role in export. Furthermore, we found that the N-terminal amphipathic helix alphaA1 of ClyA is crucial for the formation and the properties of the transmembrane channel, and hence for hemolytic activity. Several mutations affecting the C-terminal helix alphaG, the "beta-tongue" region in the head domain, or the hydrophobic region in the tail domain of the ClyA monomer strongly impaired the hemolytic activity and reduced the activity toward planar lipid bilayer membranes but did not totally prevent formation of wild-type-like channels in these artificial membranes. The latter regions thus apparently promote membrane interaction without being directly required for pore formation in a lipid bilayer.
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11
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Hunt S, Green J, Artymiuk PJ. Hemolysin E (HlyE, ClyA, SheA) and Related Toxins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 677:116-26. [DOI: 10.1007/978-1-4419-6327-7_10] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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12
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Fuentes JA, Jofré MR, Villagra NA, Mora GC. RpoS- and Crp-dependent transcriptional control of Salmonella Typhi taiA and hlyE genes: role of environmental conditions. Res Microbiol 2009; 160:800-8. [PMID: 19835951 DOI: 10.1016/j.resmic.2009.09.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Revised: 09/23/2009] [Accepted: 09/24/2009] [Indexed: 10/20/2022]
Abstract
A novel pathogenicity island, SPI-18, carries the taiA-hlyE operon, encoding virulence factors in Salmonella Typhi. To determine the effects of certain environmental conditions on the expression of these genes, beta-galactosidase assays, RT-PCR reactions, western blot analyses and measurement of hemolytic activity were performed. The conditions studied are those likely found by S. Typhi during infection in the human host. We found RpoS-dependent transcriptional upregulation in low pH and high osmolarity for both genes. Our results show that oxygen depletion apparently did not affect transcription of the taiA-hlyE operon. On the other hand, the transcriptional regulator Crp, previously described as an activator of hlyE transcription in Escherichia coli, is involved in transcriptional repression of hlyE in S. Typhi. Moreover, addition of glucose to the growth medium results in decreasing the hlyE mRNA, suggesting that there is another factor related to catabolite repression different from Crp and involved in downregulation of hlyE in S. Typhi.
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Affiliation(s)
- Juan A Fuentes
- Laboratorio de Microbiología, Facultad de Ciencias Biológicas y Facultad de Medicina, Universidad Andres Bello, República 217, Santiago de Chile, Chile.
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13
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Mueller M, Grauschopf U, Maier T, Glockshuber R, Ban N. The structure of a cytolytic α-helical toxin pore reveals its assembly mechanism. Nature 2009; 459:726-30. [DOI: 10.1038/nature08026] [Citation(s) in RCA: 263] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Accepted: 03/24/2009] [Indexed: 11/09/2022]
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14
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Virulence genotyping of Escherichia coli isolates from avian cellulitis in relation to phylogeny. ACTA ACUST UNITED AC 2009. [DOI: 10.1007/s00580-009-0837-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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15
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Ryan RM, Green J, Williams PJ, Tazzyman S, Hunt S, Harmey JH, Kehoe SC, Lewis CE. Bacterial delivery of a novel cytolysin to hypoxic areas of solid tumors. Gene Ther 2009; 16:329-39. [PMID: 19177133 DOI: 10.1038/gt.2008.188] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The efficacy of current anti-cancer gene therapies is limited by the inability of gene vectors to penetrate the poorly vascularized, hypoxic regions of tumors, leaving these sites untreated. We describe a new approach for targeting gene therapy to these sites, which employs an attenuated strain of the non-pathogenic bacterium, Salmonella typhimurium, carrying an exogenous (that is, reporter or therapeutic) gene under the regulation of a new, highly hypoxia-inducible promoter (FF+20(*)). This bacterial vector was seen to rapidly migrate into, and thrive in, hypoxic areas of both mammary tumor spheroids grown in vitro and orthotopic mammary tumors after systemic injection. Using the reporter gene construct, FF+20(*)-lacZ, we show that bacterial expression of high levels of beta-galactosidase occurred only in hypoxic/necrotic sites of spheroids and tumors. We then replaced the reporter gene with one encoding a novel cytotoxic protein (HlyE) and showed that this was also expressed by bacteria only in hypoxic regions of murine mammary tumors. This resulted in a marked increase in tumor necrosis and reduced tumor growth. Our system represents a promising new strategy for delivering gene therapy to poorly vascularized regions of tumors and shows, for the first time, the efficacy of HlyE as an anti-tumor agent.
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Affiliation(s)
- R M Ryan
- Tumor Targeting Group, Academic Unit of Pathology, University of Sheffield Medical School, Sheffield, UK
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Andreeva-Kovalevskaya ZI, Solonin AS, Sineva EV, Ternovsky VI. Pore-forming proteins and adaptation of living organisms to environmental conditions. BIOCHEMISTRY (MOSCOW) 2009; 73:1473-92. [DOI: 10.1134/s0006297908130087] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Kouokam JC, Wai SN. OUTER MEMBRANE VESICLE-MEDIATED EXPORT OF A PORE-FORMING CYTOTOXIN FROM ESCHERICHIA COLI. TOXIN REV 2008. [DOI: 10.1080/15569540500320888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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von Rhein C, Bauer S, Simon V, Ludwig A. Occurrence and characteristics of the cytolysin A gene in Shigella strains and other members of the family Enterobacteriaceae. FEMS Microbiol Lett 2008; 287:143-8. [PMID: 18754791 DOI: 10.1111/j.1574-6968.2008.01290.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Cytolysin A (ClyA, HlyE, SheA) is a hemolytic pore-forming toxin found in Escherichia coli and Salmonella enterica serovars Typhi and Paratyphi A. In the present study, analysis of several Shigella strains revealed that they harbor only nonfunctional clyA gene copies that have been inactivated either by the integration of insertion sequence (IS) elements (Shigella dysenteriae, Shigella boydii, and Shigella sonnei strains) or by a frameshift mutation (Shigella flexneri). Shigella dysenteriae and S. boydii strains also exhibited IS-associated deletions at the clyA locus. PCR and Southern blot analyses as well as database searches indicated that clyA-related DNA sequences are completely absent in strains belonging to various other genera of the family Enterobacteriaceae. According to these data, ClyA may play a role only for a rather small subset of the enteric bacteria.
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Affiliation(s)
- Christine von Rhein
- Institut für Medizinische Mikrobiologie und Krankenhaushygiene, Klinikum der Johann Wolfgang Goethe-Universität, Paul-Ehrlich-Strasse 40, Frankfurt am Main, Germany
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Hunt S, Moir AJG, Tzokov S, Bullough PA, Artymiuk PJ, Green J. The formation and structure of Escherichia coli K-12 haemolysin E pores. Microbiology (Reading) 2008; 154:633-642. [DOI: 10.1099/mic.0.2007/011700-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Stuart Hunt
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Arthur J. G. Moir
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Svetomir Tzokov
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Per A. Bullough
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Peter J. Artymiuk
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Jeffrey Green
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
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Lithgow JK, Haider F, Roberts IS, Green J. Alternate SlyA and H-NS nucleoprotein complexes control hlyE expression in Escherichia coli K-12. Mol Microbiol 2007; 66:685-98. [PMID: 17892462 PMCID: PMC2156107 DOI: 10.1111/j.1365-2958.2007.05950.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Haemolysin E is a cytolytic pore-forming toxin found in several Escherichia coli and Salmonella enterica strains. Expression of hlyE is repressed by the global regulator H-NS (histone-like nucleoid structuring protein), but can be activated by the regulator SlyA. Expression of a chromosomal hlyE–lacZ fusion in an E. coli slyA mutant was reduced to 60% of the wild-type level confirming a positive role for SlyA. DNase I footprint analysis revealed the presence of two separate SlyA binding sites, one located upstream, the other downstream of the hlyE transcriptional start site. These sites overlap AT-rich H-NS binding sites. Footprint and gel shift data showed that whereas H-NS prevented binding of RNA polymerase (RNAP) at the hlyE promoter (PhlyE), SlyA allowed binding of RNAP, but inhibited binding of H-NS. Accordingly, in vitro transcription analyses showed that addition of SlyA protein relieved H-NS-mediated repression of hlyE. Based on these observations a model for SlyA/H-NS regulation of hlyE expression is proposed in which the relative concentrations of SlyA and H-NS govern the nature of the nucleoprotein complexes formed at PhlyE. When H-NS is dominant RNAP binding is inhibited and hlyE expression is silenced; when SlyA is dominant H-NS binding is inhibited allowing RNAP access to the promoter facilitating hlyE transcription.
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Affiliation(s)
- James K Lithgow
- Department of Molecular Biology and Biotechnology, The University of SheffieldWestern Bank, Sheffield S10 2TN, UK.
| | - Fouzia Haider
- Department of Molecular Biology and Biotechnology, The University of SheffieldWestern Bank, Sheffield S10 2TN, UK.
| | - Ian S Roberts
- 1.800 Stopford Building, Faculty of Life Sciences, University of ManchesterOxford Road, Manchester M13 9PT, UK.
| | - Jeffrey Green
- Department of Molecular Biology and Biotechnology, The University of SheffieldWestern Bank, Sheffield S10 2TN, UK.
- For correspondence. E-mail ; Tel. (+44) 114 222 4403; Fax (+44) 0114 222 2800
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Constantinidou C, Hobman JL, Griffiths L, Patel MD, Penn CW, Cole JA, Overton TW. A reassessment of the FNR regulon and transcriptomic analysis of the effects of nitrate, nitrite, NarXL, and NarQP as Escherichia coli K12 adapts from aerobic to anaerobic growth. J Biol Chem 2005; 281:4802-15. [PMID: 16377617 DOI: 10.1074/jbc.m512312200] [Citation(s) in RCA: 207] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The transcription factor FNR, the regulator of fumarate and nitrate reduction, regulates major changes as Escherichia coli adapts from aerobic to anaerobic growth. In an anaerobic glycerol/trimethylamine N-oxide/fumarate medium, the fnr mutant grew as well as the parental strain, E. coli K12 MG1655, enabling us to reveal the response to oxygen, nitrate, and nitrite in the absence of glucose repression or artifacts because of variations in growth rate. Hence, many of the discrepancies between previous microarray studies of the E. coli FNR regulon were resolved. The current microarray data confirmed 31 of the previously characterized FNR-regulated operons. Forty four operons not previously known to be included in the FNR regulon were activated by FNR, and a further 28 operons appeared to be repressed. For each of these operons, a match to the consensus FNR-binding site sequence was identified. The FNR regulon therefore minimally includes at least 103, and possibly as many as 115, operons. Comparison of transcripts in the parental strain and a narXL deletion mutant revealed that transcription of 51 operons is activated, directly or indirectly, by NarL, and a further 41 operons are repressed. The narP gene was also deleted from the narXL mutant to reveal the extent of regulation by phosphorylated NarP. Fourteen promoters were more active in the narP+ strain than in the mutant, and a further 37 were strongly repressed. This is the first report that NarP might function as a global repressor as well as a transcription activator. The data also revealed possible new defense mechanisms against reactive nitrogen species.
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Galen JE, Zhao L, Chinchilla M, Wang JY, Pasetti MF, Green J, Levine MM. Adaptation of the endogenous Salmonella enterica serovar Typhi clyA-encoded hemolysin for antigen export enhances the immunogenicity of anthrax protective antigen domain 4 expressed by the attenuated live-vector vaccine strain CVD 908-htrA. Infect Immun 2004; 72:7096-106. [PMID: 15557633 PMCID: PMC529119 DOI: 10.1128/iai.72.12.7096-7106.2004] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial live-vector vaccines aim to deliver foreign antigens to the immune system and induce protective immune responses, and surface-expressed or secreted antigens are generally more immunogenic than cytoplasmic constructs. We hypothesize that an optimum expression system will use an endogenous export system to avoid the need for large amounts of heterologous DNA encoding additional proteins. Here we describe the cryptic chromosomally encoded 34-kDa cytolysin A hemolysin of Salmonella enterica serovar Typhi (ClyA) as a novel export system for the expression of heterologous antigens in the supernatant of attenuated Salmonella serovar Typhi live-vector vaccine strains. We constructed a genetic fusion of ClyA to the reporter green fluorescent protein and showed that in Salmonella serovar Typhi CVD 908-htrA, the fusion protein retains biological activity in both domains and is exported into the supernatant of an exponentially growing live vector in the absence of detectable bacterial lysis. The utility of ClyA for enhancing the immunogenicity of an otherwise problematic antigen was demonstrated by engineering ClyA fused to the domain 4 (D4) moiety of Bacillus anthracis protective antigen (PA). A total of 11 of 15 mice immunized intranasally with Salmonella serovar Typhi exporting the protein fusion manifested fourfold or greater rises in serum anti-PA immunoglobulin G, compared with only 1 of 16 mice immunized with the live vector expressing cytoplasmic D4 (P = 0.0002). In addition, the induction of PA-specific gamma interferon and interleukin 5 responses was observed in splenocytes. This technology offers exceptional versatility for enhancing the immunogenicity of bacterial live-vector vaccines.
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Affiliation(s)
- James E Galen
- Center for Vaccine Development, Separtmrnt of Medicine, School of Medicine, University of Maryland, 685 W. Baltimore St., Baltimore, MD 21201, USA.
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