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Connolly SM, Erwin AL, Sabb M, Hanks JL, Chang L, Torrez RM, Caso GC, Campbell AM, Mosalaganti S, Cover TL, Ohi MD. Structural Analysis of Membrane-associated Forms of Helicobacter pylori VacA Toxin. J Mol Biol 2024; 436:168432. [PMID: 38161000 PMCID: PMC11090358 DOI: 10.1016/j.jmb.2023.168432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 11/27/2023] [Accepted: 12/27/2023] [Indexed: 01/03/2024]
Abstract
Helicobacter pylori colonizes the stomach in about half of the human population, leading to an increased risk of peptic ulcer disease and gastric cancer. H. pylori secretes an 88 kDa VacA toxin that contributes to pathogenesis. VacA assembles into oligomeric complexes in solution and forms anion-selective channels in cell membranes. Cryo-electron microscopy (cryo-EM) analyses of VacA oligomers in solution provided insights into VacA oligomerization but failed to reveal the structure of the hydrophobic N-terminal region predicted to be a pore-forming domain. In this study, we incubated VacA with liposomes and used single particle cryo-EM to analyze detergent-extracted VacA oligomers. A 3D structure of detergent-solubilized VacA hexamers revealed the presence of six α-helices extending from the center of the oligomers, a feature not observed in previous studies of water-soluble VacA oligomers. Cryo-electron tomography analysis and 2D averages of VacA associated with liposomes confirmed that central regions of the membrane-associated VacA oligomers can insert into the lipid bilayer. However, insertion is heterogenous, with some membrane-associated oligomers appearing only partially inserted and others sitting on top of the bilayer. These studies indicate that VacA undergoes a conformational change when contacting the membrane and reveal an α-helical region positioned to extend into the membrane. Although the reported VacA 3D structure does not represent a selective anion channel, our combined single particle 3D analysis, cryo-electron tomography, and modeling allow us to propose a model for the structural organization of the VacA N-terminus in the context of a hexamer as it inserts into the membrane.
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Affiliation(s)
- Sarah M Connolly
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Amanda L Erwin
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA; Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Megan Sabb
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Jessica L Hanks
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Louise Chang
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Rachel M Torrez
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Georgia C Caso
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Anne M Campbell
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Shyamal Mosalaganti
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA; Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Timothy L Cover
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN, USA; Veterans Affairs Tennessee Valley Healthcare System, Nashville, TN, USA.
| | - Melanie D Ohi
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA; Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.
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Baral B, Kandpal M, Ray A, Jana A, Yadav DS, Sachin K, Mishra A, Baig MS, Jha HC. Helicobacter pylori and Epstein-Barr virus infection in cell polarity alterations. Folia Microbiol (Praha) 2024; 69:41-57. [PMID: 37672163 DOI: 10.1007/s12223-023-01091-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Accepted: 08/28/2023] [Indexed: 09/07/2023]
Abstract
The asymmetrical distribution of the cellular organelles inside the cell is maintained by a group of cell polarity proteins. The maintenance of polarity is one of the vital host defense mechanisms against pathogens, and the loss of it contributes to infection facilitation and cancer progression. Studies have suggested that infection of viruses and bacteria alters cell polarity. Helicobacter pylori and Epstein-Barr virus are group I carcinogens involved in the progression of multiple clinical conditions besides gastric cancer (GC) and Burkitt's lymphoma, respectively. Moreover, the coinfection of both these pathogens contributes to a highly aggressive form of GC. H. pylori and EBV target the host cell polarity complexes for their pathogenesis. H. pylori-associated proteins like CagA, VacA OipA, and urease were shown to imbalance the cellular homeostasis by altering the cell polarity. Similarly, EBV-associated genes LMP1, LMP2A, LMP2B, EBNA3C, and EBNA1 also contribute to altered cell asymmetry. This review summarized all the possible mechanisms involved in cell polarity deformation in H. pylori and EBV-infected epithelial cells. We have also discussed deregulated molecular pathways like NF-κB, TGF-β/SMAD, and β-catenin in H. pylori, EBV, and their coinfection that further modulate PAR, SCRIB, or CRB polarity complexes in epithelial cells.
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Affiliation(s)
- Budhadev Baral
- Infection Bioengineering Group, Department of Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, Simrol, Indore, Madhya Pradesh, 453552, India
| | - Meenakshi Kandpal
- Infection Bioengineering Group, Department of Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, Simrol, Indore, Madhya Pradesh, 453552, India
| | - Anushka Ray
- Infection Bioengineering Group, Department of Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, Simrol, Indore, Madhya Pradesh, 453552, India
| | - Ankit Jana
- Infection Bioengineering Group, Department of Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, Simrol, Indore, Madhya Pradesh, 453552, India
| | - Dhirendra Singh Yadav
- Central Forensic Science Laboratory, Pune, DFSS, Ministry of Home Affairs, Govt. of India, Talegaon MIDC Phase-1, Near JCB Factory, Pune, Maharashtra, 410506, India
| | - Kumar Sachin
- Himalayan School of Biosciences, Swami Rama Himalayan University, Swami Ram Nagar, Jolly Grant, Dehradun, Uttarakhand, 248 016, India
| | - Amit Mishra
- Department of Bioscience & Bioengineering, Indian Institute of Technology Jodhpur, NH 65 Nagaur Road, Karwar, Jodhpur District, Rajasthan, 342037, India
| | - Mirza S Baig
- Department of Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, Simrol, Indore, Madhya Pradesh, 453552, India
| | - Hem Chandra Jha
- Infection Bioengineering Group, Department of Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, Simrol, Indore, Madhya Pradesh, 453552, India.
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3
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Wei BR, Zhao YJ, Cheng YF, Huang C, Zhang F. Helicobacter pylori infection and Parkinson's Disease: etiology, pathogenesis and levodopa bioavailability. Immun Ageing 2024; 21:1. [PMID: 38166953 PMCID: PMC10759355 DOI: 10.1186/s12979-023-00404-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2023] [Accepted: 12/11/2023] [Indexed: 01/05/2024]
Abstract
Parkinson's disease (PD), a neurodegenerative disorder with an unknown etiology, is primarily characterized by the degeneration of dopamine (DA) neurons. The prevalence of PD has experienced a significant surge in recent years. The unidentified etiology poses limitations to the development of effective therapeutic interventions for this condition. Helicobacter pylori (H. pylori) infection has affected approximately half of the global population. Mounting evidences suggest that H. pylori infection plays an important role in PD through various mechanisms. The autotoxin produced by H. pylori induces pro-inflammatory cytokines release, thereby facilitating the occurrence of central inflammation that leads to neuronal damage. Simultaneously, H. pylori disrupts the equilibrium of gastrointestinal microbiota with an overgrowth of bacteria in the small intestinal known as small intestinal bacterial overgrowth (SIBO). This dysbiosis of the gut flora influences the central nervous system (CNS) through microbiome-gut-brain axis. Moreover, SIBO hampers levodopa absorption and affects its therapeutic efficacy in the treatment of PD. Also, H. pylori promotes the production of defensins to regulate the permeability of the blood-brain barrier, facilitating the entry of harmful factors into the CNS. In addition, H. pylori has been found to induce gastroparesis, resulting in a prolonged transit time for levodopa to reach the small intestine. H. pylori may exploit levodopa to facilitate its own growth and proliferation, or it can inflict damage to the gastrointestinal mucosa, leading to gastrointestinal ulcers and impeding levodopa absorption. Here, this review focused on the role of H. pylori infection in PD from etiology, pathogenesis to levodopa bioavailability.
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Affiliation(s)
- Bang-Rong Wei
- Key Laboratory of Basic Pharmacology of Ministry of Education and Joint International Research Laboratory of Ethnomedicine of Ministry of Education and Key Laboratory of Basic Pharmacology of Guizhou Province and Laboratory Animal Centre, Zunyi Medical University, Zunyi, Guizhou, China
| | - Yu-Jia Zhao
- Key Laboratory of Basic Pharmacology of Ministry of Education and Joint International Research Laboratory of Ethnomedicine of Ministry of Education and Key Laboratory of Basic Pharmacology of Guizhou Province and Laboratory Animal Centre, Zunyi Medical University, Zunyi, Guizhou, China
| | - Yu-Feng Cheng
- Key Laboratory of Basic Pharmacology of Ministry of Education and Joint International Research Laboratory of Ethnomedicine of Ministry of Education and Key Laboratory of Basic Pharmacology of Guizhou Province and Laboratory Animal Centre, Zunyi Medical University, Zunyi, Guizhou, China
| | - Chun Huang
- The Fifth People's Hospital of Chongqing, Chongqing, China
| | - Feng Zhang
- Key Laboratory of Basic Pharmacology of Ministry of Education and Joint International Research Laboratory of Ethnomedicine of Ministry of Education and Key Laboratory of Basic Pharmacology of Guizhou Province and Laboratory Animal Centre, Zunyi Medical University, Zunyi, Guizhou, China.
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Jarzab M, Skorko-Glonek J. There Are No Insurmountable Barriers: Passage of the Helicobacter pylori VacA Toxin from Bacterial Cytoplasm to Eukaryotic Cell Organelle. MEMBRANES 2023; 14:11. [PMID: 38248700 PMCID: PMC10821523 DOI: 10.3390/membranes14010011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 12/20/2023] [Accepted: 12/23/2023] [Indexed: 01/23/2024]
Abstract
The Gram-negative bacterium Helicobacter pylori is a very successful pathogen, one of the most commonly identified causes of bacterial infections in humans worldwide. H. pylori produces several virulence factors that contribute to its persistence in the hostile host habitat and to its pathogenicity. The most extensively studied are cytotoxin-associated gene A (CagA) and vacuolating cytotoxin A (VacA). VacA is present in almost all H. pylori strains. As a secreted multifunctional toxin, it assists bacterial colonization, survival, and proliferation during long-lasting infections. To exert its effect on gastric epithelium and other cell types, VacA undergoes several modifications and crosses multiple membrane barriers. Once inside the gastric epithelial cell, VacA disrupts many cellular-signaling pathways and processes, leading mainly to changes in the efflux of various ions, the depolarization of membrane potential, and perturbations in endocytic trafficking and mitochondrial function. The most notable effect of VacA is the formation of vacuole-like structures, which may lead to apoptosis. This review focuses on the processes involved in VacA secretion, processing, and entry into host cells, with a particular emphasis on the interaction of the mature toxin with host membranes and the formation of transmembrane pores.
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Affiliation(s)
| | - Joanna Skorko-Glonek
- Department of General and Medical Biochemistry, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland;
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Seeger AY, Zaidi F, Alhayek S, Jones RM, Zohair H, Holland RL, Kim IJ, Blanke SR. Host cell sensing and restoration of mitochondrial function and metabolism within Helicobacter pylori VacA intoxicated cells. mBio 2023; 14:e0211723. [PMID: 37815365 PMCID: PMC10653863 DOI: 10.1128/mbio.02117-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Accepted: 08/23/2023] [Indexed: 10/11/2023] Open
Abstract
IMPORTANCE Persistent human gastric infection with Helicobacter pylori is the single most important risk factor for development of gastric malignancy, which is one of the leading causes of cancer-related deaths worldwide. An important virulence factor for Hp colonization and severity of gastric disease is the protein exotoxin VacA, which is secreted by the bacterium and modulates functional properties of gastric cells. VacA acts by damaging mitochondria, which impairs host cell metabolism through impairment of energy production. Here, we demonstrate that intoxicated cells have the capacity to detect VacA-mediated damage, and orchestrate the repair of mitochondrial function, thereby restoring cellular health and vitality. This study provides new insights into cellular recognition and responses to intracellular-acting toxin modulation of host cell function, which could be relevant for the growing list of pathogenic microbes and viruses identified that target mitochondria as part of their virulence strategies.
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Affiliation(s)
- Ami Y. Seeger
- Department of Microbiology, University of Illinois, Urbana, Illinois, USA
| | - Faisal Zaidi
- Department of Microbiology, University of Illinois, Urbana, Illinois, USA
| | - Sammy Alhayek
- Department of Microbiology, University of Illinois, Urbana, Illinois, USA
| | - Rachel M. Jones
- Department of Microbiology, University of Illinois, Urbana, Illinois, USA
| | - Huzaifa Zohair
- Department of Microbiology, University of Illinois, Urbana, Illinois, USA
| | - Robin L. Holland
- Department of Pathobiology, University of Illinois, Urbana, Illinois, USA
| | - Ik-Jung Kim
- Department of Microbiology, University of Illinois, Urbana, Illinois, USA
- Buck Institute for Research on Aging, Novato, California, USA
| | - Steven R. Blanke
- Department of Microbiology, University of Illinois, Urbana, Illinois, USA
- Department of Pathobiology, University of Illinois, Urbana, Illinois, USA
- Department of Biomedical and Translational Medicine, University of Illinois, Urbana, Illinois, USA
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Functional Properties of Oligomeric and Monomeric Forms of Helicobacter pylori VacA Toxin. Infect Immun 2021; 89:e0034821. [PMID: 34543122 DOI: 10.1128/iai.00348-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Helicobacter pylori VacA is a secreted toxin that assembles into water-soluble oligomeric structures and forms anion-selective membrane channels. Acidification of purified VacA enhances its activity in cell culture assays. Sites of protomer-protomer contact within VacA oligomers have been identified by cryoelectron microscopy, and in the current study, we validated several of these interactions by chemical cross-linking and mass spectrometry. We then mutated amino acids at these contact sites and analyzed the effects of the alterations on VacA oligomerization and activity. VacA proteins with amino acid charge reversals at interprotomer contact sites retained the capacity to assemble into water-soluble oligomers and retained cell-vacuolating activity. Introduction of paired cysteine substitutions at these sites resulted in formation of disulfide bonds between adjacent protomers. Negative-stain electron microscopy and single-particle two-dimensional class analysis revealed that wild-type VacA oligomers disassemble when exposed to acidic pH, whereas the mutant proteins with paired cysteine substitutions retain an oligomeric state at acidic pH. Acid-activated wild-type VacA caused vacuolation of cultured cells, whereas acid-activated mutant proteins with paired cysteine substitutions lacked cell-vacuolating activity. Treatment of these mutant proteins with both low pH and a reducing agent resulted in VacA binding to cells, VacA internalization, and cell vacuolation. Internalization of a nonoligomerizing mutant form of VacA by host cells was detected without a requirement for acid activation. Collectively, these results enhance our understanding of the molecular interactions required for VacA oligomerization and support a model in which toxin activity depends on interactions of monomeric VacA with host cells.
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7
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Ansari S, Yamaoka Y. Role of vacuolating cytotoxin A in Helicobacter pylori infection and its impact on gastric pathogenesis. Expert Rev Anti Infect Ther 2020; 18:987-996. [PMID: 32536287 DOI: 10.1080/14787210.2020.1782739] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Introduction Helicobacter pylori causes, via the influence of several virulence factors, persistent infection of the stomach, which leads to severe complications. Vacuolating cytotoxin A (VacA) is observed in almost all clinical strains of H. pylori; however, only some strains produce the toxigenic and pathogenic VacA, which is influenced by the gene sequence variations. VacA exerts its action by causing cell vacuolation and apoptosis. We performed a PubMed search to review the latest literatures published in English language. Areas covered Articles regarding H. pylori VacA and its genotypes, architecture, internalization, and role in gastric infection and pathogenicity are reviewed. We included the search for recently published literature until January 2020. Expert opinion H. pylori VacA plays a crucial role in severe gastric pathogenicity. In addition, VacA mediated in vivo bacterial survival leads to persistent infection and an enhanced bacterial evasion from the action of antibiotics and the innate host defense system, which leads to drug evasion. VacA as a co-stimulator for the CagA phosphorylation may exert a synergistic effect playing an important role in the CagA-mediated pathogenicity.
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Affiliation(s)
- Shamshul Ansari
- Department of Microbiology, Chitwan Medical College , Bharatpur, Nepal
| | - Yoshio Yamaoka
- Department of Environmental and Preventive Medicine, Oita University Faculty of Medicine , Yufu, Oita, Japan.,Global Oita Medical Advanced Research Center for Health , Yufu, Oita, Japan.,Department of Medicine, Gastroenterology and Hepatology Section, Baylor College of Medicine , Houston, TX, USA.,Borneo Medical and Health Research Centre, Universiti Malaysia Sabah , Kota Kinabaru, Malaysia
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8
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Functional Properties of Helicobacter pylori VacA Toxin m1 and m2 Variants. Infect Immun 2020; 88:IAI.00032-20. [PMID: 32284370 DOI: 10.1128/iai.00032-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 04/05/2020] [Indexed: 12/14/2022] Open
Abstract
Helicobacter pylori colonizes the gastric mucosa and secretes a pore-forming toxin (VacA). Two main types of VacA, m1 and m2, can be distinguished by phylogenetic analysis. Type m1 forms of VacA have been extensively studied, but there has been relatively little study of m2 forms. In this study, we generated H. pylori strains producing chimeric proteins in which VacA m1 segments of a parental strain were replaced by corresponding m2 sequences. In comparison to the parental m1 VacA protein, a chimeric protein (designated m2/m1) containing m2 sequences in the N-terminal portion of the m region was less potent in causing vacuolation of HeLa cells, AGS gastric cells, and AZ-521 duodenal cells and had reduced capacity to cause membrane depolarization or death of AZ-521 cells. Consistent with the observed differences in activity, the chimeric m2/m1 VacA protein bound to cells at reduced levels compared to the binding levels of the parental m1 protein. The presence of two strain-specific insertions or deletions within or adjacent to the m region did not influence toxin activity. Experiments with human gastric organoids grown as monolayers indicated that m1 and m2/m1 forms of VacA had similar cell-vacuolating activities. Interestingly, both forms of VacA bound preferentially to the basolateral surface of organoid monolayers and caused increased cell vacuolation when interacting with the basolateral surface compared to the apical surface. These data provide insights into functional correlates of sequence variation in the VacA midregion (m region).
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9
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Activity and Functional Importance of Helicobacter pylori Virulence Factors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1149:35-56. [PMID: 31016624 DOI: 10.1007/5584_2019_358] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Helicobacter pylori is a very successful Gram-negative pathogen colonizing the stomach of humans worldwide. Infections with this bacterium can generate pathologies ranging from chronic gastritis and peptic ulceration to gastric cancer. The best characterized H. pylori virulence factors that cause direct cell damage include an effector protein encoded by the cytotoxin-associated gene A (CagA), a type IV secretion system (T4SS) encoded in the cag-pathogenicity island (cag PAI), vacuolating cytotoxin A (VacA), γ-glutamyl transpeptidase (GGT), high temperature requirement A (HtrA, a serine protease) and cholesterol glycosyl-transferase (CGT). Since these H. pylori factors are either surface-exposed, secreted or translocated, they can directly interact with host cell molecules and are able to hijack cellular functions. Studies on these bacterial factors have progressed substantially in recent years. Here, we review the current status in the characterization of signaling cascades by these factors in vivo and in vitro, which comprise the disruption of cell-to-cell junctions, induction of membrane rearrangements, cytoskeletal dynamics, proliferative, pro-inflammatory, as well as, pro-apoptotic and anti-apoptotic responses or immune evasion. The impact of these signal transduction modules in the pathogenesis of H. pylori infections is discussed.
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10
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Su M, Erwin AL, Campbell AM, Pyburn TM, Salay LE, Hanks JL, Lacy DB, Akey DL, Cover TL, Ohi MD. Cryo-EM Analysis Reveals Structural Basis of Helicobacter pylori VacA Toxin Oligomerization. J Mol Biol 2019; 431:1956-1965. [PMID: 30954575 PMCID: PMC6625667 DOI: 10.1016/j.jmb.2019.03.029] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 03/29/2019] [Accepted: 03/29/2019] [Indexed: 12/13/2022]
Abstract
Helicobacter pylori colonizes the human stomach and contributes to the development of gastric cancer and peptic ulcer disease. H. pylori secretes a pore-forming toxin called vacuolating cytotoxin A (VacA), which contains two domains (p33 and p55) and assembles into oligomeric structures. Using single-particle cryo-electron microscopy, we have determined low-resolution structures of a VacA dodecamer and heptamer, as well as a 3.8-Å structure of the VacA hexamer. These analyses show that VacA p88 consists predominantly of a right-handed beta-helix that extends from the p55 domain into the p33 domain. We map the regions of p33 and p55 involved in hexamer assembly, model how interactions between protomers support heptamer formation, and identify surfaces of VacA that likely contact membrane. This work provides structural insights into the process of VacA oligomerization and identifies regions of VacA protomers that are predicted to contact the host cell surface during channel formation.
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Affiliation(s)
- Min Su
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Amanda L Erwin
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA; Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Anne M Campbell
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37212, USA
| | - Tasia M Pyburn
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37212, USA
| | - Lauren E Salay
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37212, USA
| | - Jessica L Hanks
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - D Borden Lacy
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University School of Medicine, Nashville, TN 37212, USA; Veterans Affairs Tennessee Valley Healthcare System, Nashville, TN 37212, USA
| | - David L Akey
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Timothy L Cover
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37212, USA; Department of Pathology, Microbiology, and Immunology, Vanderbilt University School of Medicine, Nashville, TN 37212, USA; Veterans Affairs Tennessee Valley Healthcare System, Nashville, TN 37212, USA.
| | - Melanie D Ohi
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA; Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA.
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11
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Cryo-EM structures of Helicobacter pylori vacuolating cytotoxin A oligomeric assemblies at near-atomic resolution. Proc Natl Acad Sci U S A 2019; 116:6800-6805. [PMID: 30894496 PMCID: PMC6452728 DOI: 10.1073/pnas.1821959116] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Helicobacter pylori infects nearly half of the world’s population and is the primary cause of various gastric diseases. It has evolved various virulence factors to aid its host colonization and infection, including the vacuolating cytotoxin A (VacA) that is responsible for the pathogenesis of H. pylori-related diseases. Here, we resolve multiple structures of the water-soluble VacA oligomeric assemblies using cryoelectron microscopy (cryo-EM) at near-atomic resolution. These studies suggest a model of structural changes of functional VacA hexamer needed for the pore-formation process across the membrane and highlight the capability of cryo-EM to resolve multiple structure snapshots from a single specimen at near-atomic resolution. Human gastric pathogen Helicobacter pylori (H. pylori) is the primary risk factor for gastric cancer and is one of the most prevalent carcinogenic infectious agents. Vacuolating cytotoxin A (VacA) is a key virulence factor secreted by H. pylori and induces multiple cellular responses. Although structural and functional studies of VacA have been extensively performed, the high-resolution structure of a full-length VacA protomer and the molecular basis of its oligomerization are still unknown. Here, we use cryoelectron microscopy to resolve 10 structures of VacA assemblies, including monolayer (hexamer and heptamer) and bilayer (dodecamer, tridecamer, and tetradecamer) oligomers. The models of the 88-kDa full-length VacA protomer derived from the near-atomic resolution maps are highly conserved among different oligomers and show a continuous right-handed β-helix made up of two domains with extensive domain–domain interactions. The specific interactions between adjacent protomers in the same layer stabilizing the oligomers are well resolved. For double-layer oligomers, we found short- and/or long-range hydrophobic interactions between protomers across the two layers. Our structures and other previous observations lead to a mechanistic model wherein VacA hexamer would correspond to the prepore-forming state, and the N-terminal region of VacA responsible for the membrane insertion would undergo a large conformational change to bring the hydrophobic transmembrane region to the center of the oligomer for the membrane channel formation.
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12
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Scida S, Russo M, Miraglia C, Leandro G, Franzoni L, Meschi T, De' Angelis GL, Di Mario F. Relationship between Helicobacter pylori infection and GERD. ACTA BIO-MEDICA : ATENEI PARMENSIS 2018; 89:40-43. [PMID: 30561416 PMCID: PMC6502218 DOI: 10.23750/abm.v89i8-s.7918] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Indexed: 12/13/2022]
Abstract
Gastroesophageal reflux disease (GERD) is due to the chronic exposure of the esophageal mucosa to acid secretion from the stomach. Helicobacter pylori (H.p.) infection, is a risk factor for the development of peptic ulcer, atrophic gastritis and gastric cancer, and causes various effects on gastric function. The relationship between GERD and H.pylori infection is still subject of debate.Background and aim: In literature no clear causal relationship has been established between GERD and H. pylori infection, although some papers support the onset of esophagitis in patients in whom the infection has been cured. Aim of this work is to review the most recent literature data about the relationship between reflux disease and H. pylori infection. Methods: Articles reviewed were found through literature searches on PubMed, Google Scholar using keywords such as gastroesophageal reflux disease, Helicobacter pylori, acid-related disorders, GERD and esophagitis. (www.actabiomedica.it)
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Affiliation(s)
- Serena Scida
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Parma.
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13
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Abstract
Helicobacter pylori, a Gram-negative bacterium, is a well-known risk factor for gastric cancer. H. pylori vacuolating cytotoxin A (VacA) is a secreted pore-forming toxin that induces a wide range of cellular responses. Like many other bacterial toxins, VacA has been hypothesized to utilize lipid rafts to gain entry into host cells. Here, we used giant plasma membrane vesicles (GPMVs) as a model system to understand the preferential partitioning of VacA into lipid rafts. We show that a wild-type (WT) toxin predominantly associates with the raft phase. Acid activation of VacA enhances binding of the toxin to GPMVs but is not required for raft partitioning. VacA mutant proteins with alterations at the amino terminus (resulting in impaired membrane channel formation) and a nonoligomerizing VacA mutant protein retain the ability to preferentially associate with lipid rafts. Consistent with these results, the isolated VacA p55 domain was capable of binding to lipid rafts. We conclude that the affinity of VacA for rafts is independent of its capacity to oligomerize or form membrane channels.
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McClain MS, Beckett AC, Cover TL. Helicobacter pylori Vacuolating Toxin and Gastric Cancer. Toxins (Basel) 2017; 9:toxins9100316. [PMID: 29023421 PMCID: PMC5666363 DOI: 10.3390/toxins9100316] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Revised: 10/03/2017] [Accepted: 10/05/2017] [Indexed: 12/13/2022] Open
Abstract
Helicobacter pylori VacA is a channel-forming toxin unrelated to other known bacterial toxins. Most H. pylori strains contain a vacA gene, but there is marked variation among strains in VacA toxin activity. This variation is attributable to strain-specific variations in VacA amino acid sequences, as well as variations in the levels of VacA transcription and secretion. In this review, we discuss epidemiologic studies showing an association between specific vacA allelic types and gastric cancer, as well as studies that have used animal models to investigate VacA activities relevant to gastric cancer. We also discuss the mechanisms by which VacA-induced cellular alterations may contribute to the pathogenesis of gastric cancer.
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Affiliation(s)
- Mark S McClain
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
| | - Amber C Beckett
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
| | - Timothy L Cover
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
- Veterans Affairs Tennessee Valley Healthcare System, Nashville, TN 37212, USA.
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15
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Goleij Z, Mahmoodzadeh Hosseini H, Amin M, Halabian R, Imani Fooladi AA. Prokaryotic toxins provoke different types of cell deaths in the eukaryotic cells. TOXIN REV 2017. [DOI: 10.1080/15569543.2017.1294180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Zoleikha Goleij
- Applied Microbiology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran and
| | | | - Mohsen Amin
- Department of Drug and Food Control, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran
| | - Raheleh Halabian
- Applied Microbiology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran and
| | - Abbas Ali Imani Fooladi
- Applied Microbiology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran and
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16
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Abstract
Mitochondria are the "power house" of a cell continuously generating ATP to ensure its proper functioning. The constant production of ATP via oxidative phosphorylation demands a large electrochemical force that drives protons across the highly selective and low-permeable mitochondrial inner membrane. Besides the conventional role of generating ATP, mitochondria also play an active role in calcium signaling, generation of reactive oxygen species (ROS), stress responses, and regulation of cell-death pathways. Deficiencies in these functions result in several pathological disorders like aging, cancer, diabetes, neurodegenerative and cardiovascular diseases. A plethora of ion channels and transporters are present in the mitochondrial inner and outer membranes which work in concert to preserve the ionic equilibrium of a cell for the maintenance of cell integrity, in physiological as well as pathophysiological conditions. For, e.g., mitochondrial cation channels KATP and BKCa play a significant role in cardioprotection from ischemia-reperfusion injury. In addition to the cation channels, mitochondrial anion channels are equally essential, as they aid in maintaining electro-neutrality by regulating the cell volume and pH. This chapter focusses on the information on molecular identity, structure, function, and physiological relevance of mitochondrial chloride channels such as voltage dependent anion channels (VDACs), uncharacterized mitochondrial inner membrane anion channels (IMACs), chloride intracellular channels (CLIC) and the aspects of forthcoming chloride channels.
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Affiliation(s)
- Devasena Ponnalagu
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N. 15th Street, Room 8154, Mail Stop 488, Philadelphia, PA, 19102-1192, USA
| | - Harpreet Singh
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N. 15th Street, Room 8154, Mail Stop 488, Philadelphia, PA, 19102-1192, USA.
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17
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Pyburn TM, Foegeding NJ, González-Rivera C, McDonald NA, Gould KL, Cover TL, Ohi MD. Structural organization of membrane-inserted hexamers formed by Helicobacter pylori VacA toxin. Mol Microbiol 2016; 102:22-36. [PMID: 27309820 PMCID: PMC5035229 DOI: 10.1111/mmi.13443] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2016] [Indexed: 01/08/2023]
Abstract
Helicobacter pylori colonizes the human stomach and is a potential cause of peptic ulceration or gastric adenocarcinoma. H. pylori secretes a pore-forming toxin known as vacuolating cytotoxin A (VacA). The 88 kDa secreted VacA protein, composed of an N-terminal p33 domain and a C-terminal p55 domain, assembles into water-soluble oligomers. The structural organization of membrane-bound VacA has not been characterized in any detail and the role(s) of specific VacA domains in membrane binding and insertion are unclear. We show that membrane-bound VacA organizes into hexameric oligomers. Comparison of the two-dimensional averages of membrane-bound and soluble VacA hexamers generated using single particle electron microscopy reveals a structural difference in the central region of the oligomers (corresponding to the p33 domain), suggesting that membrane association triggers a structural change in the p33 domain. Analyses of the isolated p55 domain and VacA variants demonstrate that while the p55 domain can bind membranes, the p33 domain is required for membrane insertion. Surprisingly, neither VacA oligomerization nor the presence of putative transmembrane GXXXG repeats in the p33 domain is required for membrane insertion. These findings provide new insights into the process by which VacA binds and inserts into the lipid bilayer to form membrane channels.
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Affiliation(s)
- Tasia M Pyburn
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232
| | - Nora J Foegeding
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232
| | - Christian González-Rivera
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN, 37232
| | - Nathan A McDonald
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232
| | - Kathleen L Gould
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232
| | - Timothy L Cover
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN, 37232
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, 37232
- Veterans Affairs Tennessee Valley Healthcare System, Nashville, TN, 37212
| | - Melanie D Ohi
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232.
- Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232.
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18
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A Nonoligomerizing Mutant Form of Helicobacter pylori VacA Allows Structural Analysis of the p33 Domain. Infect Immun 2016; 84:2662-70. [PMID: 27382020 PMCID: PMC4995914 DOI: 10.1128/iai.00254-16] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 06/24/2016] [Indexed: 12/17/2022] Open
Abstract
Helicobacter pylori secretes a pore-forming VacA toxin that has structural features and activities substantially different from those of other known bacterial toxins. VacA can assemble into multiple types of water-soluble flower-shaped oligomeric structures, and most VacA activities are dependent on its capacity to oligomerize. The 88-kDa secreted VacA protein can undergo limited proteolysis to yield two domains, designated p33 and p55. The p33 domain is required for membrane channel formation and intracellular toxic activities, and the p55 domain has an important role in mediating VacA binding to cells. Previous studies showed that the p55 domain has a predominantly β-helical structure, but no structural data are available for the p33 domain. We report here the purification and analysis of a nonoligomerizing mutant form of VacA secreted by H. pylori The nonoligomerizing 88-kDa mutant protein retains the capacity to enter host cells but lacks detectable toxic activity. Analysis of crystals formed by the monomeric protein reveals that the β-helical structure of the p55 domain extends into the C-terminal portion of p33. Fitting the p88 structural model into an electron microscopy map of hexamers formed by wild-type VacA (predicted to be structurally similar to VacA membrane channels) reveals that p55 and the β-helical segment of p33 localize to peripheral arms but do not occupy the central region of the hexamers. We propose that the amino-terminal portion of p33 is unstructured when VacA is in a monomeric form and that it undergoes a conformational change during oligomer assembly.
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19
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Foegeding NJ, Caston RR, McClain MS, Ohi MD, Cover TL. An Overview of Helicobacter pylori VacA Toxin Biology. Toxins (Basel) 2016; 8:toxins8060173. [PMID: 27271669 PMCID: PMC4926140 DOI: 10.3390/toxins8060173] [Citation(s) in RCA: 129] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2016] [Revised: 05/18/2016] [Accepted: 05/27/2016] [Indexed: 12/11/2022] Open
Abstract
The VacA toxin secreted by Helicobacter pylori enhances the ability of the bacteria to colonize the stomach and contributes to the pathogenesis of gastric adenocarcinoma and peptic ulcer disease. The amino acid sequence and structure of VacA are unrelated to corresponding features of other known bacterial toxins. VacA is classified as a pore-forming toxin, and many of its effects on host cells are attributed to formation of channels in intracellular sites. The most extensively studied VacA activity is its capacity to stimulate vacuole formation, but the toxin has many additional effects on host cells. Multiple cell types are susceptible to VacA, including gastric epithelial cells, parietal cells, T cells, and other types of immune cells. This review focuses on the wide range of VacA actions that are detectable in vitro, as well as actions of VacA in vivo that are relevant for H. pylori colonization of the stomach and development of gastric disease.
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Affiliation(s)
- Nora J Foegeding
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
| | - Rhonda R Caston
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
| | - Mark S McClain
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
| | - Melanie D Ohi
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37232, USA.
| | - Timothy L Cover
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
- Veterans Affairs Tennessee Valley Healthcare System, Nashville, TN 37212, USA.
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20
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Junaid M, Linn AK, Javadi MB, Al-Gubare S, Ali N, Katzenmeier G. Vacuolating cytotoxin A (VacA) - A multi-talented pore-forming toxin from Helicobacter pylori. Toxicon 2016; 118:27-35. [PMID: 27105670 DOI: 10.1016/j.toxicon.2016.04.037] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 03/12/2016] [Accepted: 04/18/2016] [Indexed: 12/18/2022]
Abstract
Helicobacter pylori is associated with severe and chronic diseases of the stomach and duodenum such as peptic ulcer, non-cardial adenocarcinoma and gastric lymphoma, making Helicobacter pylori the only bacterial pathogen which is known to cause cancer. The worldwide rate of incidence for these diseases is extremely high and it is estimated that about half of the world's population is infected with H. pylori. Among the bacterial virulence factors is the vacuolating cytotoxin A (VacA), which represents an important determinant of pathogenicity. Intensive characterization of VacA over the past years has provided insight into an ample variety of mechanisms contributing to host-pathogen interactions. The toxin is considered as an important target for ongoing research for several reasons: i) VacA displays unique features and structural properties and its mechanism of action is unrelated to any other known bacterial toxin; ii) the toxin is involved in disease progress and colonization by H. pylori of the stomach; iii) VacA is a potential and promising candidate for the inclusion as antigen in a vaccine directed against H. pylori and iv) the vacA gene is characterized by a high allelic diversity, and allelic variants contribute differently to the pathogenicity of H. pylori. Despite the accumulation of substantial data related to VacA over the past years, several aspects of VacA-related activity have been characterized only to a limited extent. The biologically most significant effect of VacA activity on host cells is the formation of membrane pores and the induction of vacuole formation. This review discusses recent findings and advances on structure-function relations of the H. pylori VacA toxin, in particular with a view to membrane channel formation, oligomerization, receptor binding and apoptosis.
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Affiliation(s)
- Muhammad Junaid
- Department of Pharmacy, Division of Pharmacology, University of Malakand, Khyber Pakhtunkhwa 18550, Pakistan; Bacterial Toxin Research Cluster, Institute of Molecular Biosciences, Mahidol University, Nakornpathom 73170, Thailand.
| | - Aung Khine Linn
- Bacterial Toxin Research Cluster, Institute of Molecular Biosciences, Mahidol University, Nakornpathom 73170, Thailand.
| | - Mohammad Bagher Javadi
- Bacterial Toxin Research Cluster, Institute of Molecular Biosciences, Mahidol University, Nakornpathom 73170, Thailand.
| | - Sarbast Al-Gubare
- Bacterial Toxin Research Cluster, Institute of Molecular Biosciences, Mahidol University, Nakornpathom 73170, Thailand.
| | - Niaz Ali
- Department of Basic Medical Sciences, Khyber Medical University, Peshawar 25000, Pakistan.
| | - Gerd Katzenmeier
- Bacterial Toxin Research Cluster, Institute of Molecular Biosciences, Mahidol University, Nakornpathom 73170, Thailand.
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21
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Liu X, He B, Cho WC, Pan Y, Chen J, Ying H, Wang F, Lin K, Peng H, Wang S. A systematic review on the association between the Helicobacter pylori vacA i genotype and gastric disease. FEBS Open Bio 2016; 6:409-17. [PMID: 27419046 PMCID: PMC4856419 DOI: 10.1002/2211-5463.12046] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 01/20/2016] [Accepted: 02/16/2016] [Indexed: 12/16/2022] Open
Abstract
Helicobacter pylori (H. pylori) has been recognized as a cause of gastrointestinal diseases and progress of the pathology of gastrointestinal diseases is related to the genotype of H. pylori. Published studies have indicated that the H. pylori vacuolating cytotoxin gene A (vacA) i1/i2 genotype is associated with peptic ulcer disease (PUD) and gastric cancer (GC), but their conclusions are inconsistent. This study aimed to further assess the risk of vacA i gene for PUD and/or GC. A systematic search was conducted across three main electronic databases (PubMed, Web of Science, and CNKI). A meta-analysis was then performed on the pooled data of the published articles to estimate the overall influence of vacA i polymorphisms on PUD and/or GC by crude odds ratio (OR) with 95% confidence intervals (CI). The reliability of the results were confirmed by publication bias and sensitivity analysis of included studies. A total of 14 studies were selected according to the specific inclusion and exclusion criteria. The pooled results revealed that patients with GC were more vulnerable to infection by H. pylori i1 genotype (OR = 5.12; 95% CI: 2.66-9.85; P < 0.001) than those with chronic gastritis or nonulcer disease. Moreover, the results of subgroup analysis indicated that the i1 genotype of H. pylori was associated with an increased GC risk (OR = 10.89; 95% CI: 4.11-20.88; P < 0.001) in the Middle Asian population. The H. pylori vacA i1 genotype is associated with an increased GC risk, especially in the Middle Asian population.
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Affiliation(s)
- Xian Liu
- Central Laboratory Nanjing First Hospital Nanjing Medical University Jiangsu China
| | - Bangshun He
- Central Laboratory Nanjing First Hospital Nanjing Medical University Jiangsu China
| | - William C Cho
- Department of Clinical Oncology Queen Elizabeth Hospital Hong Kong China
| | - Yuqin Pan
- Central Laboratory Nanjing First Hospital Nanjing Medical University Jiangsu China
| | - Jie Chen
- Department of Life Sciences Nanjing Normal University Jiangsu China
| | - Houqun Ying
- Medical College Southeast University Nanjing Jiangsu China
| | - Feng Wang
- Central Laboratory Nanjing First Hospital Nanjing Medical University Jiangsu China
| | - Kang Lin
- Central Laboratory Nanjing First Hospital Nanjing Medical University Jiangsu China
| | - Hongxin Peng
- Medical College Southeast University Nanjing Jiangsu China
| | - Shukui Wang
- Central Laboratory Nanjing First Hospital Nanjing Medical University Jiangsu China
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22
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Nishiyama Y, Ohmichi T, Kazami S, Iwasaki H, Mano K, Nagumo Y, Kudo F, Ichikawa S, Iwabuchi Y, Kanoh N, Eguchi T, Osada H, Usui T. Vicenistatin induces early endosome-derived vacuole formation in mammalian cells. Biosci Biotechnol Biochem 2016; 80:902-10. [PMID: 27104762 DOI: 10.1080/09168451.2015.1132152] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Homotypic fusion of early endosomes is important for efficient protein trafficking and sorting. The key controller of this process is Rab5 which regulates several effectors and PtdInsPs levels, but whose mechanisms are largely unknown. Here, we report that vicenistatin, a natural product, enhanced homotypic fusion of early endosomes and induced the formation of large vacuole-like structures in mammalian cells. Unlike YM201636, another early endosome vacuolating compound, vicenistatin did not inhibit PIKfyve activity in vitro but activated Rab5-PAS pathway in cells. Furthermore, vicenistatin increased the membrane surface fluidity of cholesterol-containing liposomes in vitro, and cholesterol deprivation from the plasma membrane stimulated vicenistatin-induced vacuolation in cells. These results suggest that vicenistatin is a novel compound that induces the formation of vacuole-like structures by activating Rab5-PAS pathway and increasing membrane fluidity.
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Affiliation(s)
- Yuko Nishiyama
- a Graduate School of Life and Environmental Sciences , University of Tsukuba , Tsukuba , Japan
| | - Tomohiro Ohmichi
- a Graduate School of Life and Environmental Sciences , University of Tsukuba , Tsukuba , Japan
| | - Sayaka Kazami
- b Chemical Biology Research Group, RIKEN CSRS , Wako, Japan
| | - Hiroki Iwasaki
- a Graduate School of Life and Environmental Sciences , University of Tsukuba , Tsukuba , Japan
| | - Kousuke Mano
- c Graduate School of Pharmaceutical Sciences , Tohoku University , Sendai , Japan
| | - Yoko Nagumo
- a Graduate School of Life and Environmental Sciences , University of Tsukuba , Tsukuba , Japan
| | - Fumitaka Kudo
- d Graduate School of Science and Engineering , Tokyo Institute of Technology , Tokyo , Japan
| | - Sosaku Ichikawa
- e Faculty of Life and Environmental Sciences , University of Tsukuba , Tsukuba , Japan
| | - Yoshiharu Iwabuchi
- c Graduate School of Pharmaceutical Sciences , Tohoku University , Sendai , Japan
| | - Naoki Kanoh
- c Graduate School of Pharmaceutical Sciences , Tohoku University , Sendai , Japan
| | - Tadashi Eguchi
- d Graduate School of Science and Engineering , Tokyo Institute of Technology , Tokyo , Japan
| | - Hiroyuki Osada
- b Chemical Biology Research Group, RIKEN CSRS , Wako, Japan
| | - Takeo Usui
- e Faculty of Life and Environmental Sciences , University of Tsukuba , Tsukuba , Japan
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23
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Effects of crude extracted proteins from supernatant of BCF-P and EGF on acid secretion. Mol Cell Toxicol 2015. [DOI: 10.1007/s13273-015-0034-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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24
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Ayala G, Escobedo-Hinojosa WI, Cruz-Herrera CFDL, Romero I. Exploring alternative treatments for Helicobacter pylori infection. World J Gastroenterol 2014; 20:1450-1469. [PMID: 24587621 PMCID: PMC3925854 DOI: 10.3748/wjg.v20.i6.1450] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 12/21/2013] [Accepted: 01/05/2014] [Indexed: 02/06/2023] Open
Abstract
Helicobacter pylori (H. pylori) is a successful pathogen that can persist in the stomach of an infected person for their entire life. It provokes chronic gastric inflammation that leads to the development of serious gastric diseases such as peptic ulcers, gastric cancer and Mucosa associated lymphoid tissue lymphoma. It is known that these ailments can be avoided if the infection by the bacteria can be prevented or eradicated. Currently, numerous antibiotic-based therapies are available. However, these therapies have several inherent problems, including the appearance of resistance to the antibiotics used and associated adverse effects, the risk of re-infection and the high cost of antibiotic therapy. The delay in developing a vaccine to prevent or eradicate the infection has furthered research into new therapeutic approaches. This review summarises the most relevant recent studies on vaccine development and new treatments using natural resources such as plants, probiotics and nutraceuticals. In addition, novel alternatives based on microorganisms, peptides, polysaccharides, and intragastric violet light irradiation are presented. Alternative therapies have not been effective in eradicating the bacteria but have been shown to maintain low bacterial levels. Nevertheless, some of them are useful in preventing the adverse effects of antibiotics, modulating the immune response, gastroprotection, and the general promotion of health. Therefore, those agents can be used as adjuvants of allopathic anti-H. pylori eradication therapy.
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Abstract
Gastric adenocarcinoma is a leading cause of cancer-related death worldwide, and Helicobacter pylori infection is one of the strongest known risk factors for this malignancy. H. pylori strains exhibit a high level of genetic diversity, and the risk of gastric cancer is higher in persons carrying certain strain types (for example, those that contain a cag pathogenicity island or type s1 vacA alleles) than in persons carrying other strain types. Additional risk factors for gastric cancer include specific human genetic polymorphisms and specific dietary preferences (for example, a high-salt diet or a diet deficient in fruits and vegetables). Finally, iron-deficiency anemia is a risk factor for gastric cancer. Recent studies have provided evidence that several dietary risk factors for gastric cancer directly impact H. pylori virulence. In this review article, we discuss mechanisms by which diet can modulate H. pylori virulence and thereby influence gastric cancer risk.
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Affiliation(s)
- Timothy L Cover
- Division of Infectious Diseases; Vanderbilt University School of Medicine; Nashville, TN USA,Department of Pathology, Microbiology, and Immunology; Vanderbilt University School of Medicine; Nashville, TN USA,Veterans Affairs Tennessee Valley Healthcare System; Nashville, TN USA
| | - Richard M Peek, Jr
- Division of Gastroenterology, Department of Medicine; Vanderbilt University School of Medicine; Nashville, TN USA,Correspondence to: Richard M Peek, Jr,
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26
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Posselt G, Backert S, Wessler S. The functional interplay of Helicobacter pylori factors with gastric epithelial cells induces a multi-step process in pathogenesis. Cell Commun Signal 2013; 11:77. [PMID: 24099599 PMCID: PMC3851490 DOI: 10.1186/1478-811x-11-77] [Citation(s) in RCA: 142] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Accepted: 10/01/2013] [Indexed: 12/16/2022] Open
Abstract
Infections with the human pathogen Helicobacter pylori (H. pylori) can lead to severe gastric diseases ranging from chronic gastritis and ulceration to neoplastic changes in the stomach. Development and progress of H. pylori-associated disorders are determined by multifarious bacterial factors. Many of them interact directly with host cells or require specific receptors, while others enter the host cytoplasm to derail cellular functions. Several adhesins (e.g. BabA, SabA, AlpA/B, or OipA) establish close contact with the gastric epithelium as an important first step in persistent colonization. Soluble H. pylori factors (e.g. urease, VacA, or HtrA) have been suggested to alter cell survival and intercellular adhesions. Via a type IV secretion system (T4SS), H. pylori also translocates the effector cytotoxin-associated gene A (CagA) and peptidoglycan directly into the host cytoplasm, where cancer- and inflammation-associated signal transduction pathways can be deregulated. Through these manifold possibilities of interaction with host cells, H. pylori interferes with the complex signal transduction networks in its host and mediates a multi-step pathogenesis.
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Affiliation(s)
- Gernot Posselt
- Division of Molecular Biology, Department of Microbiology, Paris-Lodron University, Salzburg, Austria.
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27
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Chambers MG, Pyburn TM, González-Rivera C, Collier SE, Eli I, Yip CK, Takizawa Y, Lacy DB, Cover TL, Ohi MD. Structural analysis of the oligomeric states of Helicobacter pylori VacA toxin. J Mol Biol 2012. [PMID: 23178866 DOI: 10.1016/j.jmb.2012.11.020] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Helicobacter pylori is a Gram-negative bacterium that colonizes the human stomach and contributes to peptic ulceration and gastric adenocarcinoma. H. pylori secretes a pore-forming exotoxin known as vacuolating toxin (VacA). VacA contains two distinct domains, designated p33 and p55, and assembles into large "snowflake"-shaped oligomers. Thus far, no structural data are available for the p33 domain, which is essential for membrane channel formation. Using single-particle electron microscopy and the random conical tilt approach, we have determined the three-dimensional structures of six VacA oligomeric conformations at ~15-Å resolution. The p55 domain, composed primarily of β-helical structures, localizes to the peripheral arms, while the p33 domain consists of two globular densities that localize within the center of the complexes. By fitting the VacA p55 crystal structure into the electron microscopy densities, we have mapped inter-VacA interactions that support oligomerization. In addition, we have examined VacA variants/mutants that differ from wild-type (WT) VacA in toxin activity and/or oligomeric structural features. Oligomers formed by VacA∆6-27, a mutant that fails to form membrane channels, lack an organized p33 central core. Mixed oligomers containing both WT and VacA∆6-27 subunits also lack an organized core. Oligomers formed by a VacA s2m1 chimera (which lacks cell-vacuolating activity) and VacAΔ301-328 (which retains vacuolating activity) each contain p33 central cores similar to those of WT oligomers. By providing the most detailed view of the VacA structure to date, these data offer new insights into the toxin's channel-forming component and the intermolecular interactions that underlie oligomeric assembly.
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Affiliation(s)
- Melissa G Chambers
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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28
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Helicobacter pylori VacA: a new perspective on an invasive chloride channel. Microbes Infect 2012; 14:1026-33. [DOI: 10.1016/j.micinf.2012.07.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Revised: 06/29/2012] [Accepted: 07/02/2012] [Indexed: 12/17/2022]
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29
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Kim IJ, Blanke SR. Remodeling the host environment: modulation of the gastric epithelium by the Helicobacter pylori vacuolating toxin (VacA). Front Cell Infect Microbiol 2012; 2:37. [PMID: 22919629 PMCID: PMC3417592 DOI: 10.3389/fcimb.2012.00037] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 03/05/2012] [Indexed: 12/13/2022] Open
Abstract
Virulence mechanisms underlying Helicobacter pylori persistence and disease remain poorly understood, in part, because the factors underlying disease risk are multifactorial and complex. Among the bacterial factors that contribute to the cumulative pathophysiology associated with H. pylori infections, the vacuolating cytotoxin (VacA) is one of the most important. Analogous to a number of H. pylori genes, the vacA gene exhibits allelic mosaicism, and human epidemiological studies have revealed that several families of toxin alleles are predictive of more severe disease. Animal model studies suggest that VacA may contribute to pathogenesis in several ways. VacA functions as an intracellular-acting protein exotoxin. However, VacA does not fit the current prototype of AB intracellular-acting bacterial toxins, which elaborate modulatory effects through the action of an enzymatic domain translocated inside host cells. Rather, VacA may represent an alternative prototype for AB intracellular acting toxins that modulate cellular homeostasis by forming ion-conducting intracellular membrane channels. Although VacA seems to form channels in several different membranes, one of the most important target sites is the mitochondrial inner membrane. VacA apparently take advantage of an unusual intracellular trafficking pathway to mitochondria, where the toxin is imported and depolarizes the inner membrane to disrupt mitochondrial dynamics and cellular energy homeostasis as a mechanism for engaging the apoptotic machinery within host cells. VacA remodeling of the gastric environment appears to be fine-tuned through the action of the Type IV effector protein CagA which, in part, limits the cytotoxic effects of VacA in cells colonized by H. pylori.
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Affiliation(s)
- Ik-Jung Kim
- Department of Microbiology, Institute for Genomic Biology, University of Illinois, Urbana IL, USA
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Boquet P, Ricci V. Intoxication strategy of Helicobacter pylori VacA toxin. Trends Microbiol 2012; 20:165-74. [PMID: 22364673 DOI: 10.1016/j.tim.2012.01.008] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Revised: 01/13/2012] [Accepted: 01/24/2012] [Indexed: 02/09/2023]
Abstract
VacA toxin from the cancer-inducing bacterium Helicobacter pylori is currently classified as a pore-forming toxin but is also considered a multifunctional toxin, apparently causing many pleiotropic cell effects. However, an increasing body of evidence suggests that VacA could be the prototype of a new class of monofunctional A-B toxins in which the A subunit exhibits pore-forming instead of enzymatic activity. Thus, VacA may use a peculiar mechanism of action, allowing it to intoxicate the human stomach. By combining the action of a cell-binding domain, a specific intracellular trafficking pathway and a novel mitochondrion-targeting sequence, the VacA pore-forming domain is selectively delivered to the inner mitochondrial membrane to efficiently kill target epithelial cells by apoptosis.
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Affiliation(s)
- Patrice Boquet
- Department of Clinical Bacteriology, Nice University Hospital, 151 Route de Saint Antoine de Ginestière, 06202 Nice Cedex 03, France.
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Rassow J. Helicobacter pylori vacuolating toxin A and apoptosis. Cell Commun Signal 2011; 9:26. [PMID: 22044628 PMCID: PMC3266207 DOI: 10.1186/1478-811x-9-26] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 11/01/2011] [Indexed: 12/16/2022] Open
Abstract
VacA, the vacuolating cytotoxin A of Helicobacter pylori, induces apoptosis in epithelial cells of the gastic mucosa and in leukocytes. VacA is released by the bacteria as a protein of 88 kDa. At the outer surface of host cells, it binds to the sphingomyelin of lipid rafts. At least partially, binding to the cells is facilitated by different receptor proteins. VacA is internalized by a clathrin-independent mechanism and initially accumulates in GPI-anchored proteins-enriched early endosomal compartments. Together with early endosomes, VacA is distributed inside the cells. Most of the VacA is eventually contained in the membranes of vacuoles. VacA assembles in hexameric oligomers forming an anion channel of low conductivity with a preference for chloride ions. In parallel, a significant fraction of VacA can be transferred from endosomes to mitochondria in a process involving direct endosome-mitochondria juxtaposition. Inside the mitochondria, VacA accumulates in the mitochondrial inner membrane, probably forming similar chloride channels as observed in the vacuoles. Import into mitochondria is mediated by the hydrophobic N-terminus of VacA. Apoptosis is triggered by loss of the mitochondrial membrane potential, recruitment of Bax and Bak, and release of cytochrome c.
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Affiliation(s)
- Joachim Rassow
- Ruhr-Universität Bochum, Institut für Physiologische Chemie, Medizinische Fakultät, Gebäude MA3, D-44780 Bochum, Germany.
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Sewald X, Jiménez-Soto L, Haas R. PKC-dependent endocytosis of the Helicobacter pylori vacuolating cytotoxin in primary T lymphocytes. Cell Microbiol 2010; 13:482-96. [DOI: 10.1111/j.1462-5822.2010.01551.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Peek RM, Fiske C, Wilson KT. Role of innate immunity in Helicobacter pylori-induced gastric malignancy. Physiol Rev 2010; 90:831-58. [PMID: 20664074 DOI: 10.1152/physrev.00039.2009] [Citation(s) in RCA: 164] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Helicobacter pylori colonizes the majority of persons worldwide, and the ensuing gastric inflammatory response is the strongest singular risk factor for peptic ulceration and gastric cancer. However, only a fraction of colonized individuals ever develop clinically significant outcomes. Disease risk is combinatorial and can be modified by bacterial factors, host responses, and/or specific interactions between host and microbe. Several H. pylori constituents that are required for colonization or virulence have been identified, and their ability to manipulate the host innate immune response will be the focus of this review. Identification of bacterial and host mediators that augment disease risk has profound ramifications for both biomedical researchers and clinicians as such findings will not only provide mechanistic insights into inflammatory carcinogenesis but may also serve to identify high-risk populations of H. pylori-infected individuals who can then be targeted for therapeutic intervention.
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Affiliation(s)
- Richard M Peek
- Division of Gastroenterology, Department of Medicine, Vanderbilt University School of Medicine, and Veterans Affairs Tennessee Valley Healthcare System, Nashville, Tennessee 37232-2279, USA.
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Sun J, Wu Y, Su Z, Liu Z, Su B, Liu Z, Liu W, Zhao H, Tana, Bateer, Eshita Y, Chi B, Zhao L, Fang X, Hao W, Wu S, Bian J, Chen J, Ouyang X. The role of small molecular weight compounds to increase vacuolation induced by VacA toxin in vitro. Toxicol In Vitro 2010; 24:1373-8. [DOI: 10.1016/j.tiv.2010.04.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2009] [Revised: 03/05/2010] [Accepted: 04/13/2010] [Indexed: 02/06/2023]
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Domańska G, Motz C, Meinecke M, Harsman A, Papatheodorou P, Reljic B, Dian-Lothrop EA, Galmiche A, Kepp O, Becker L, Günnewig K, Wagner R, Rassow J. Helicobacter pylori VacA toxin/subunit p34: targeting of an anion channel to the inner mitochondrial membrane. PLoS Pathog 2010; 6:e1000878. [PMID: 20442789 PMCID: PMC2861713 DOI: 10.1371/journal.ppat.1000878] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2009] [Accepted: 03/25/2010] [Indexed: 12/13/2022] Open
Abstract
The vacuolating toxin VacA, released by Helicobacter pylori, is an important virulence factor in the pathogenesis of gastritis and gastroduodenal ulcers. VacA contains two subunits: The p58 subunit mediates entry into target cells, and the p34 subunit mediates targeting to mitochondria and is essential for toxicity. In this study we found that targeting to mitochondria is dependent on a unique signal sequence of 32 uncharged amino acid residues at the p34 N-terminus. Mitochondrial import of p34 is mediated by the import receptor Tom20 and the import channel of the outer membrane TOM complex, leading to insertion of p34 into the mitochondrial inner membrane. p34 assembles in homo-hexamers of extraordinary high stability. CD spectra of the purified protein indicate a content of >40% beta-strands, similar to pore-forming beta-barrel proteins. p34 forms an anion channel with a conductivity of about 12 pS in 1.5 M KCl buffer. Oligomerization and channel formation are independent both of the 32 uncharged N-terminal residues and of the p58 subunit of the toxin. The conductivity is efficiently blocked by 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), a reagent known to inhibit VacA-mediated apoptosis. We conclude that p34 essentially acts as a small pore-forming toxin, targeted to the mitochondrial inner membrane by a special hydrophobic N-terminal signal.
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Affiliation(s)
- Grażyna Domańska
- Institut für Physiologische Chemie, Ruhr-Universität Bochum, Bochum, Germany
| | - Christian Motz
- Institut für Physiologische Chemie, Ruhr-Universität Bochum, Bochum, Germany
| | - Michael Meinecke
- Institut für Biophysik, Universität Osnabrück, Osnabrück, Germany
| | - Anke Harsman
- Institut für Biophysik, Universität Osnabrück, Osnabrück, Germany
| | | | - Boris Reljic
- Institut für Physiologische Chemie, Ruhr-Universität Bochum, Bochum, Germany
| | | | - Antoine Galmiche
- Laboratoire de Biochimie, INSERM ERI12, Hopital Nord, CHU Amiens Picardie, Amiens, France
| | - Oliver Kepp
- INSERM U848, Institute Gustave Roussy, Université Paris Sud, Villejuif, France
| | - Lars Becker
- Institut für Biophysik, Universität Osnabrück, Osnabrück, Germany
| | - Kathrin Günnewig
- Institut für Physiologische Chemie, Ruhr-Universität Bochum, Bochum, Germany
| | - Richard Wagner
- Institut für Biophysik, Universität Osnabrück, Osnabrück, Germany
| | - Joachim Rassow
- Institut für Physiologische Chemie, Ruhr-Universität Bochum, Bochum, Germany
- * E-mail:
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El Kirat K, Morandat S, Dufrêne YF. Nanoscale analysis of supported lipid bilayers using atomic force microscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:750-65. [DOI: 10.1016/j.bbamem.2009.07.026] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 07/17/2009] [Accepted: 07/23/2009] [Indexed: 12/11/2022]
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Backert S, Tegtmeyer N. the versatility of the Helicobacter pylori vacuolating cytotoxin vacA in signal transduction and molecular crosstalk. Toxins (Basel) 2010; 2:69-92. [PMID: 22069547 PMCID: PMC3206623 DOI: 10.3390/toxins2010069] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Revised: 12/31/2009] [Accepted: 01/14/2010] [Indexed: 12/13/2022] Open
Abstract
By modulating important properties of eukaryotic cells, many bacterial protein toxins highjack host signalling pathways to create a suitable niche for the pathogen to colonize and persist. Helicobacter pylori VacA is paradigm of pore-forming toxins which contributes to the pathogenesis of peptic ulceration. Several cellular receptors have been described for VacA, which exert different effects on epithelial and immune cells. The crystal structure of VacA p55 subunit might be important for elucidating details of receptor interaction and pore formation. Here we discuss the multiple signalling activities of this important toxin and the molecular crosstalk between VacA and other virulence factors.
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Affiliation(s)
- Steffen Backert
- Ardmore House, School of Biomolecular and Biomedical Sciences, Belfield Campus, University College Dublin, Dublin-4, Ireland.
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Abstract
Microbial pathogens contribute to the development of more than 1 million cases of cancer per year. Gastric adenocarcinoma is the second leading cause of cancer-related death in the world, and gastritis induced by Helicobacter pylori is the strongest known risk factor for this malignancy. H. pylori colonizes the stomach for years, not days or weeks, as is usually the case for bacterial pathogens and it always induces inflammation; however, only a fraction of colonized individuals ever develop disease. Identification of mechanisms through which H. pylori co-opts host defenses to facilitate its own persistence will not only improve diagnostic and therapeutic modalities, but may also provide insights into other diseases that arise within the context of long-term pathogen-initiated inflammatory states, such as chronic viral hepatitis and hepatocellular carcinoma.
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Affiliation(s)
- Dawn A Israel
- Department of Medicine; Division of Gastroenterology; Vanderbilt University Medical Center; Nashville, TN USA
| | - Richard M Peek
- Department of Medicine; Division of Gastroenterology; Vanderbilt University Medical Center; Nashville, TN USA,Department of Cancer Biology; Vanderbilt University Medical Center; Nashville, TN USA,Department of Veterans Affairs Medical Center; Nashville, TN USA
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Galmiche A, Rassow J. Targeting of Helicobacter pylori VacA to mitochondria. Gut Microbes 2010; 1:392-5. [PMID: 21468222 PMCID: PMC3056105 DOI: 10.4161/gmic.1.6.13894] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Revised: 10/04/2010] [Accepted: 10/08/2010] [Indexed: 02/03/2023] Open
Abstract
One of the major virulence factors of Helicobacter pylori is the vacuolating toxin vaca. It has been known for a long time that the toxin enters host cells by endocytosis. On the other hand there is ample evidence that vaca is able to trigger apoptosis and this effect has been attributed in part to interactions with mitochondria. However, for 10 years it was difficult to reconcile the obvious accumulation of vaca in endosomes with mitochondrial targeting. The accessibility of the mitochondria to the toxin was enigmatic. In our new study, we investigated the activities of p34, the toxic subunit of vaca, in more detail. We found that the p34 N-terminus carries a unique targeting sequence for import into mitochondria and for insertion into the mitochondrial inner membrane. By forming an anion channel in this membrane, the toxin has the ability to interfere directly with mitochondrial functions. Taking into account additional results from independent studies, we discuss the implications of our findings with respect to intracellular traffic, the remarkable possibility of a direct transfer of VacA from endosomes to mitochondria and vaca-dependent cell death.
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Affiliation(s)
- Antoine Galmiche
- Laboratoire de Biochimie Inserm ERI12; Hopital Nord; CHU Amiens Picardie; Amiens Cedex 1, France
| | - Joachim Rassow
- Institut für Physiologische Chemie; Ruhr-Universität Bochum; Bochum, Germany
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40
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Atherton JC, Blaser MJ. Coadaptation of Helicobacter pylori and humans: ancient history, modern implications. J Clin Invest 2009. [PMID: 19729845 DOI: 10.1172/jci38605.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Humans have been colonized by Helicobacter pylori for at least 50,000 years and probably throughout their evolution. H. pylori has adapted to humans, colonizing children and persisting throughout life. Most strains possess factors that subtly modulate the host environment, increasing the risk of peptic ulceration, gastric adenocarcinoma, and possibly other diseases. H. pylori genes encoding these and other factors rapidly evolve through mutation and recombination, changing the bacteria-host interaction. Although immune and physiologic responses to H. pylori also contribute to pathogenesis, humans have evolved in concert with the bacterium, and its recent absence throughout the life of many individuals has led to new human physiological changes. These may have contributed to recent increases in esophageal adenocarcinoma and, more speculatively, other modern diseases.
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Affiliation(s)
- John C Atherton
- Nottingham Digestive Diseases Centre Biomedical Research Unit and Institute of Infection, Immunity and Inflammation, Centre for Biomolecular Sciences, University of Nottingham, Nottingham, United Kingdom.
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41
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Atherton JC, Blaser MJ. Coadaptation of Helicobacter pylori and humans: ancient history, modern implications. J Clin Invest 2009; 119:2475-87. [PMID: 19729845 DOI: 10.1172/jci38605] [Citation(s) in RCA: 378] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Humans have been colonized by Helicobacter pylori for at least 50,000 years and probably throughout their evolution. H. pylori has adapted to humans, colonizing children and persisting throughout life. Most strains possess factors that subtly modulate the host environment, increasing the risk of peptic ulceration, gastric adenocarcinoma, and possibly other diseases. H. pylori genes encoding these and other factors rapidly evolve through mutation and recombination, changing the bacteria-host interaction. Although immune and physiologic responses to H. pylori also contribute to pathogenesis, humans have evolved in concert with the bacterium, and its recent absence throughout the life of many individuals has led to new human physiological changes. These may have contributed to recent increases in esophageal adenocarcinoma and, more speculatively, other modern diseases.
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Affiliation(s)
- John C Atherton
- Nottingham Digestive Diseases Centre Biomedical Research Unit and Institute of Infection, Immunity and Inflammation, Centre for Biomolecular Sciences, University of Nottingham, Nottingham, United Kingdom.
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Role of deletion located between the intermediate and middle regions of the Helicobacter pylori vacA gene in cases of gastroduodenal diseases. J Clin Microbiol 2009; 47:3493-500. [PMID: 19726606 DOI: 10.1128/jcm.00887-09] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The vacuolating cytotoxin gene of Helicobacter pylori, vacA, induces cytoplasmic vacuolation in gastric epithelial cells. Recently, the vacA intermediate (i) region, which is located between the signal (s) and middle (m) regions, was identified as a third polymorphic determinant of vacA activity. In vacA, there are approximately 81-bp deletions between the vacA i and m regions (denoted the d region). The aim was to clarify the roles of the vacA d region in relation to H. pylori-related diseases and histopathological gastric mucosal changes. We assessed the vacA signal s-, m-, i-, and d-region genotypes and cagA status in H. pylori isolates recovered from Western countries (n = 266) and East Asian countries (n = 244) by PCR. In East Asian countries, there were no relationships between the vacA genotypes and the clinical outcomes and histopathological changes. In Western countries, strains with the vacA s1, m1, i1, or d1 (no deletion) genotype significantly increased the risk for the development of gastric cancer compared with the risk from strains with the s2, m2, i2, or d2 genotype (adjusted odd ratios, 3.17 [95% confidence interval {CI}, 1.07 to 9.45] for s1, 10.65 [95% CI, 3.36 to 31.35] for m1, 8.57 [95% CI, 2.85 to 25.81] for i1, and 8.04 [95% CI, 2.67 to 24.16] for d1). The highly virulent vacA genotypes significantly enhanced neutrophil infiltration and gastric atrophy in univariant analysis, whereas only the vacA d-region genotype was significantly associated with neutrophil infiltration and gastric atrophy in both the antrum and the corpus by multiple linear regression analysis. The presence of the vacA d1 genotype in H. pylori strains could be an improved predictor of histological inflammation and the potential for atrophy compared with the presence of the vacA s-, m-, and i-region genotypes in Western countries.
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Helsel AJ, Brown AL, Yamato K, Feng W, Yuan L, Clements AJ, Harding SV, Szabo G, Shao Z, Gong B. Highly conducting transmembrane pores formed by aromatic oligoamide macrocycles. J Am Chem Soc 2009; 130:15784-5. [PMID: 18973294 DOI: 10.1021/ja807078y] [Citation(s) in RCA: 126] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Oligoamide macrocycles 1d and 1e, which carry membrane-compatible side chains and contain a hydrophilic, noncollapsible cavity, were found to mediate high ion flux across a lipid bilayer, as demonstrated by results from (23)Na NMR and planar bilayer conductance measurements. The measured transmembrane single channel currents are very high, rivaling those typically associated with pore-forming protein toxins. The obtained results have demonstrated the promise of developing large, highly conducting channels based on nanopores formed by oligoamide macrocycles.
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Affiliation(s)
- Amber Jade Helsel
- Department of Chemistry, Natural Sciences Complex, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA
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Gupta VR, Patel HK, Kostolansky SS, Ballivian RA, Eichberg J, Blanke SR. Sphingomyelin functions as a novel receptor for Helicobacter pylori VacA. PLoS Pathog 2008; 4:e1000073. [PMID: 18497859 PMCID: PMC2374909 DOI: 10.1371/journal.ppat.1000073] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Accepted: 04/15/2008] [Indexed: 12/18/2022] Open
Abstract
The vacuolating cytotoxin (VacA) of the gastric pathogen Helicobacter pylori binds and enters epithelial cells, ultimately resulting in cellular vacuolation. Several host factors have been reported to be important for VacA function, but none of these have been demonstrated to be essential for toxin binding to the plasma membrane. Thus, the identity of cell surface receptors critical for both toxin binding and function has remained elusive. Here, we identify VacA as the first bacterial virulence factor that exploits the important plasma membrane sphingolipid, sphingomyelin (SM), as a cellular receptor. Depletion of plasma membrane SM with sphingomyelinase inhibited VacA-mediated vacuolation and significantly reduced the sensitivity of HeLa cells, as well as several other cell lines, to VacA. Further analysis revealed that SM is critical for VacA interactions with the plasma membrane. Restoring plasma membrane SM in cells previously depleted of SM was sufficient to rescue both toxin vacuolation activity and plasma membrane binding. VacA association with detergent-resistant membranes was inhibited in cells pretreated with SMase C, indicating the importance of SM for VacA association with lipid raft microdomains. Finally, VacA bound to SM in an in vitro ELISA assay in a manner competitively inhibited by lysenin, a known SM-binding protein. Our results suggest a model where VacA may exploit the capacity of SM to preferentially partition into lipid rafts in order to access the raft-associated cellular machinery previously shown to be required for toxin entry into host cells. Sensitivity to toxins produced by pathogenic bacteria is largely dictated by the presence or absence of toxin receptors on the plasma membrane of host cells. VacA is an important toxin produced by the pathogenic bacterium Helicobacter pylori, which infects the human stomach and causes gastric ulcer disease and stomach cancer. VacA binds and enters human cells, and induces several changes resulting ultimately in the death of the intoxicated cells. However, the identity of the VacA receptor responsible for toxin binding and function has remained a topic of debate. In this paper, we demonstrate that sphingomyelin, a lipid on the surface of cells with important membrane structural and signaling properties, functions as a VacA receptor. We demonstrate that VacA binds to sphingomyelin, and that presence or absence of sphingomyelin on the plasma membrane dictates how much VacA binds to the cell surface, and therefore, how sensitive cells are to the toxin. The identification of sphingomyelin also provides a conceptual framework for how VacA may enter cells through specialized functional domains on the surface of cells. This is the first example of a bacterial toxin that exploits sphingomyelin as a receptor, and future work will focus on developing strategies to block VacA interactions with sphingomyelin, thereby protecting cells from the downstream consequences of toxin action.
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Affiliation(s)
- Vijay R. Gupta
- Department of Microbiology, Institute for Genomic Biology, University of Illinois, Urbana, Illinois, United States of America
| | - Hetal K. Patel
- Department of Microbiology, Institute for Genomic Biology, University of Illinois, Urbana, Illinois, United States of America
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Sean S. Kostolansky
- Department of Microbiology, Institute for Genomic Biology, University of Illinois, Urbana, Illinois, United States of America
| | - Roberto A. Ballivian
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Joseph Eichberg
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Steven R. Blanke
- Department of Microbiology, Institute for Genomic Biology, University of Illinois, Urbana, Illinois, United States of America
- * E-mail:
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46
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Differences in virulence markers between Helicobacter pylori strains from Iraq and those from Iran: potential importance of regional differences in H. pylori-associated disease. J Clin Microbiol 2008; 46:1774-9. [PMID: 18353934 DOI: 10.1128/jcm.01737-07] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Helicobacter pylori causes peptic ulceration and gastric adenocarcinoma; the latter is common in Iran but not in Iraq. We hypothesized that more virulent H. pylori strains may be found in Iran than in Iraq and so compared established and newly described virulence factors in strains from these countries. We studied 59 unselected dyspeptic patients from Iran and 49 from Iraq. cagA was found in similar proportions of strains from both countries (76% in Iran versus 71% in Iraq) and was significantly associated with peptic ulcer disease in Iraq (P <or= 0.01) but not in Iran. cagA alleles encoding four or more tyrosine phosphorylation motifs were found in 12% of the Iranian strains but none of the Iraqi strains (P = 0.02). There were no significant differences in the vacA signal-, middle-, or intermediate-region types between Iranian and Iraqi strains. Among the strains from Iran, vacA genotypes showed no specific peptic ulcer associations, but among the strains from Iraq, vacA i1 strains were associated with gastric ulcer (P <or= 0.02), mimicking their previously demonstrated association with gastric cancer in Iran. dupA was found in similar proportions of Iranian and Iraqi strains (38% and 32%, respectively) and was associated with peptic ulceration in Iraqi patients (P <or= 0.01) but not Iranian patients. H. pylori strains from Iraq and Iran possess virulence factors similar to those in Western countries. The presence of cagA with more phosphorylation motifs in Iranian strains may contribute to the higher incidence of gastric cancer. However, the association between strain virulence markers and disease in Iraq but not Iran suggests that other host and environmental factors may be more important in the disease-prone Iranian population.
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47
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Amieva MR, El-Omar EM. Host-bacterial interactions in Helicobacter pylori infection. Gastroenterology 2008; 134:306-23. [PMID: 18166359 DOI: 10.1053/j.gastro.2007.11.009] [Citation(s) in RCA: 370] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2007] [Accepted: 10/21/2007] [Indexed: 02/07/2023]
Abstract
Helicobacter pylori are spiral-shaped gram-negative bacteria with polar flagella that live near the surface of the human gastric mucosa. They have evolved intricate mechanisms to avoid the bactericidal acid in the gastric lumen and to survive near, to attach to, and to communicate with the human gastric epithelium and host immune system. This interaction sometimes results in severe gastric pathology. H pylori infection is the strongest known risk factor for the development of gastroduodenal ulcers, with infection being present in 60%-80% of gastric and 95% of duodenal ulcers.(1)H pylori is also the first bacterium to be classified as a definite carcinogen by the World Health Organization's International Agency for Research on Cancer because of its epidemiologic relationship to gastric adenocarcinoma and gastric mucosa-associated lymphoid tissue lymphoma.(2) In the last 25 years, since H pylori was first described and cultured, a complete paradigm shift has occurred in our clinical approach to these gastric diseases, and more than 20,000 scientific publications have appeared on the subject. From the medical point of view, H pylori is a formidable pathogen responsible for much morbidity and mortality worldwide. However, H pylori infection occurs in approximately half of the world population, with disease being an exception rather than the rule. Understanding how this organism interacts with its host is essential for formulating an intelligent strategy for dealing with its most important clinical consequences. This review offers an insight into H pylori host-bacterial interactions.
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Affiliation(s)
- Manuel R Amieva
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
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Dautin N, Bernstein HD. Protein secretion in gram-negative bacteria via the autotransporter pathway. Annu Rev Microbiol 2007; 61:89-112. [PMID: 17506669 DOI: 10.1146/annurev.micro.61.080706.093233] [Citation(s) in RCA: 219] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Autotransporters are a large and diverse superfamily of proteins produced by pathogenic gram-negative bacteria that are composed of an N-terminal passenger domain, which typically harbors a virulence function, and a C-terminal beta domain. It has long been known that the beta domain anchors the protein to the outer membrane and facilitates transport of the passenger domain into the extracellular space. Despite the apparent simplicity of the autotransporter pathway, several aspects of autotransporter biogenesis remain poorly understood, most notably the mechanism by which the passenger domain is translocated across the outer membrane. Here we review recent evidence that the enormous sequence diversity of both passenger and beta domains belies a remarkable conservation of structure. We also discuss insights into each stage of autotransporter biogenesis that have emerged from recent structural, biochemical, and imaging studies.
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Affiliation(s)
- Nathalie Dautin
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0538, USA.
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Gangwer KA, Mushrush DJ, Stauff DL, Spiller B, McClain MS, Cover TL, Lacy DB. Crystal structure of the Helicobacter pylori vacuolating toxin p55 domain. Proc Natl Acad Sci U S A 2007; 104:16293-8. [PMID: 17911250 PMCID: PMC2042200 DOI: 10.1073/pnas.0707447104] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Helicobacter pylori VacA, a pore-forming toxin secreted by an autotransporter pathway, causes multiple alterations in human cells, contributes to the pathogenesis of peptic ulcer disease and gastric cancer, and is a candidate antigen for inclusion in an H. pylori vaccine. Here, we present a 2.4-A crystal structure of the VacA p55 domain, which has an important role in mediating VacA binding to host cells. The structure is predominantly a right-handed parallel beta-helix, a feature that is characteristic of autotransporter passenger domains but unique among known bacterial protein toxins. Notable features of VacA p55 include disruptions in beta-sheet contacts that result in five beta-helix subdomains and a C-terminal domain that contains a disulfide bond. Analysis of VacA protein sequences from unrelated H. pylori strains, including m1 and m2 forms of VacA, allows us to identify structural features of the VacA surface that may be important for interactions with host receptors. Docking of the p55 structure into a 19-A cryo-EM map of a VacA dodecamer allows us to propose a model for how VacA monomers assemble into oligomeric structures capable of membrane channel formation.
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Affiliation(s)
- Kelly A. Gangwer
- Departments of *Microbiology and Immunology
- Center for Structural Biology, Vanderbilt University Medical Center, Nashville, TN 37232; and
| | - Darren J. Mushrush
- Biochemistry
- Center for Structural Biology, Vanderbilt University Medical Center, Nashville, TN 37232; and
| | | | - Ben Spiller
- Departments of *Microbiology and Immunology
- Pharmacology, and
- Center for Structural Biology, Vanderbilt University Medical Center, Nashville, TN 37232; and
| | | | - Timothy L. Cover
- Departments of *Microbiology and Immunology
- Medicine and
- Veterans Affairs Tennessee Valley Healthcare System, Nashville, TN 37212
| | - D. Borden Lacy
- Departments of *Microbiology and Immunology
- Biochemistry
- Center for Structural Biology, Vanderbilt University Medical Center, Nashville, TN 37232; and
- **To whom correspondence should be addressed. E-mail:
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Bode BE, Margraf D, Plackmeyer J, Dürner G, Prisner TF, Schiemann O. Counting the Monomers in Nanometer-Sized Oligomers by Pulsed Electron−Electron Double Resonance. J Am Chem Soc 2007; 129:6736-45. [PMID: 17487970 DOI: 10.1021/ja065787t] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In a lot of cases active biomolecules are complexes of higher order, thus methods capable of counting the number of building blocks and elucidating their geometric arrangement are needed. Therefore, we experimentally validate here spin-counting via 4-pulse electron-electron double resonance (PELDOR) on well-defined test samples. Two biradicals, a symmetric and an asymmetric triradical, and a tetraradical were synthesized in a convergent reaction scheme via palladium-catalyzed cross-coupling reactions. PELDOR was then used to obtain geometric information and the number of spin centers per molecule in a single experiment. The measurement yielded the expected distances (2.2-3.8 nm) and showed that different spin-spin distances in one molecule can be resolved even if the difference amounts to only 5 A. The number of spins n has been determined to be 2.1 in both biradicals, to 3.1 and 3.0 in the symmetric and asymmetric triradicals, respectively, and to 3.9 in the tetraradical. The overall error of PELDOR spin-counting was found to be 5% for up to four spins. Thus, this method is a valuable tool to determine the number of constituting spin-bearing monomers in biologically relevant homo- and heterooligomers and how their oligomerization state and geometric arrangement changes during function.
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Affiliation(s)
- Bela E Bode
- Institute of Physical and Theoretical Chemistry, Center for Biomolecular Magnetic Resonance, J. W. Goethe-University, Frankfurt am Main, Germany
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