Interaction of Helicobacter pylori VacA Toxin with Its Target Cells

2018 ◽  
pp. 267-294
Author(s):  
Vittorio Ricci ◽  
Patrizia Sommi
Keyword(s):  
Helicobacter Pylori ◽  
Target Cells

scholarly journals Helicobacter pylori and Neutrophils: Sialic Acid-Dependent Binding to Various Isolated Glycoconjugates

1999 ◽  
Vol 67 (12) ◽  
pp. 6309-6313 ◽  
Author(s):  
Halina Miller-Podraza ◽  
Jörgen Bergström ◽  
Susann Teneberg ◽  
Maan Abul Milh ◽  
Marianne Longard ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Sialic Acid ◽  
Thin Layer ◽  
Inflammatory Reaction ◽  
Binding Activity ◽  
Human Stomach ◽  
Target Cells ◽  
Dependent Manner ◽  
Bacterial Cells ◽  
Slow Moving

ABSTRACT Helicobacter pylori has been shown to agglutinate erythrocytes in a sialic acid-dependent manner. However, very few studies have examined relevant target cells in the human stomach. Neutrophils are required for the onset of gastritis, and the inflammatory reaction may be induced on contact between bacteria and neutrophils. In the present work, glycolipids and glycoproteins were isolated from neutrophils and were studied for binding by overlay with radiolabeled bacteria on thin-layer chromatograms and on membrane blots. There was a complex pattern of binding bands. The only practical binding activity found was sialic acid dependent, since treatment of glycoconjugates with neuraminidase or mild periodate eliminated binding. As shown before for binding to erythrocytes and other glycoconjugates, bacterial cells grown on agar bound to many glycoconjugates, while growth in broth resulted in bacteria that would bind only to polyglycosylceramides, which are highly heterogeneous and branched poly-N-acetyllactosamine-containing glycolipids. Approximately seven positive bands were found for glycoproteins, and the traditional ganglioside fraction showed a complex, slow-moving interval with very strong sialic-acid-dependent binding, probably explained by Fuc substitutions on GlcNAc.

scholarly journals Cysteine Residues in Helicobacter pylori Adhesin HopQ are Required for CEACAM–HopQ Interaction and Subsequent CagA Translocation

2020 ◽  
Vol 8 (4) ◽  
pp. 465 ◽  
Author(s):  
Youssef Hamway ◽  
Karin Taxauer ◽  
Kristof Moonens ◽  
Victoria Neumeyer ◽  
Wolfgang Fischer ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Helicobacter Pylori ◽  
Disulfide Bonds ◽  
Binding Mode ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Cysteine Residues ◽  
Target Cells ◽  
Independent Mechanism ◽  
H Pylori

Attachment to the host gastric mucosa is a key step in Helicobacter pylori infection. Recently, a novel adhesin, HopQ, was shown to bind distinct host CEACAM proteins—an interaction that was found to be essential for the translocation of CagA, a key virulence factor of H. pylori. The HopQ–CEACAM1 co-crystal structure revealed a binding mode dependent on loops in HopQ that are clasped by disulfide bonds. In this study, we investigated the importance of these cysteine residues for CEACAM1 engagement by H. pylori. We observed a loss of CEACAM1 binding and CagA translocation upon disruption of the disulfide bond in loop CL1 (connecting C103 to C132 in HopQ). Deletion of the Dsb-like oxidoreductase HP0231 did not affect cell surface expression of HopQ or alter the interaction of H. pylori with target cells. Although HP0231 deletion was previously described to impede CagA translocation, our results indicate that this occurs through a HopQ-independent mechanism. Together, our results open up new avenues to therapeutically target the HopQ–CEACAM1 interaction and reduce the burden of pathogenic H. pylori.

scholarly journals Oligomeric and subunit structure of the Helicobacter pylori vacuolating cytotoxin.

1996 ◽  
Vol 133 (4) ◽  
pp. 801-807 ◽  
Author(s):  
P Lupetti ◽  
J E Heuser ◽  
R Manetti ◽  
P Massari ◽  
S Lanzavecchia ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Structural Similarity ◽  
Proteolytic Cleavage ◽  
Radial Symmetry ◽  
Target Cells ◽  
Subunit Structure ◽  
Vacuolar Degeneration ◽  
Vacuolating Cytotoxin ◽  
Ulcer Disease

Disease-associated strains of Helicobacter pylori produce a potent toxin that is believed to play a key role in peptic ulcer disease in man. In vitro the toxin causes severe vacuolar degeneration in target cells and has thus been termed VacA (for vacuolating cytotoxin A). Cytotoxic activity is associated with a > 600-kD protein consisting of several copies of a 95-kD polypeptide that undergoes specific proteolytic cleavage after release from the bacteria to produce 37- and 58-kD fragments. Quick freeze, deep etch electron microscopy has revealed that the native cytotoxin is formed as regular oligomers with either six- or seven-fold radial symmetry. Within each monomer, two domains can clearly be distinguished, suggesting that the 37- and 58-kD fragments derive from proteolytic cleavage between discrete subunits of the monomer. Analysis of preparations of the toxin that had undergone extensive cleavage into the 37- and 58-kD subunits supports this interpretation and reveals that after cleavage the subunits remain associated in the oligomeric structure. The data suggest a structural similarity with AB-type toxins.

scholarly journals A Helicobacter pylori Vacuolating Toxin Mutant That Fails To Oligomerize Has a Dominant Negative Phenotype

2006 ◽  
Vol 74 (3) ◽  
pp. 1786-1794 ◽  
Author(s):  
Christophe Genisset ◽  
Cesira L. Galeotti ◽  
Pietro Lupetti ◽  
David Mercati ◽  
David A. G. Skibinski ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Critical Role ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Target Cells ◽  
Amino Terminal ◽  
Negative Effect ◽  
H Pylori ◽  
Mutant Toxin

ABSTRACT Most Helicobacter pylori strains secrete a toxin (VacA) that causes massive vacuolization of target cells and which is a major virulence factor of H. pylori. The VacA amino-terminal region is required for the induction of vacuolization. The aim of the present study was a deeper understanding of the critical role of the N-terminal regions that are protected from proteolysis when VacA interacts with artificial membranes. Using a counterselection system, we constructed an H. pylori strain, SPM 326-Δ49-57, that produces a mutant toxin with a deletion of eight amino acids in one of these protected regions. VacA Δ49-57 was correctly secreted by H. pylori but failed to oligomerize and did not have any detectable vacuolating cytotoxic activity. However, the mutant toxin was internalized normally and stained the perinuclear region of HeLa cells. Moreover, the mutant toxin exhibited a dominant negative effect, completely inhibiting the vacuolating activity of wild-type VacA. This loss of activity was correlated with the disappearance of oligomers in electron microscopy. These findings indicate that the deletion in VacA Δ49-57 disrupts the intermolecular interactions required for the oligomerization of the toxin.

scholarly journals Functional and Topological Characterization of Novel Components of the comB DNA Transformation Competence System in Helicobacter pylori

2006 ◽  
Vol 188 (3) ◽  
pp. 882-893 ◽  
Author(s):  
Arno Karnholz ◽  
Claudia Hoefler ◽  
Stefan Odenbreit ◽  
Wolfgang Fischer ◽  
Dirk Hofreuter ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Target Cells ◽  
Dna Uptake ◽  
Secretion Systems ◽  
Computer Prediction ◽  
Type Iv ◽  
Essential Components ◽  
H Pylori ◽  
Transformation Competence ◽  
Competence System

ABSTRACT Helicobacter pylori is one of the most diverse bacterial species known. A rational basis for this genetic variation may be provided by its natural competence for genetic transformation and high-frequency recombination. Many bacterial competence systems have homology with proteins that are involved in the assembly of type IV pili and type II secretion systems. In H. pylori, DNA uptake relies on a transport system related to type IV secretion systems (T4SS) designated the comB system. The prototype of a T4SS in Agrobacterium tumefaciens consists of 11 VirB proteins and VirD4, which form the core unit necessary for the delivery of single proteins or large nucleoprotein complexes into target cells. In the past we identified proteins ComB4 and ComB7 through ComB10 as being involved in the process of DNA uptake in H. pylori. In this study we identified and functionally characterized further (T4SS-homologous) components of the comB transformation competence system. By combining computer prediction modeling, experimental topology determination, generation of knockout strains, and genetic complementation studies we identified ComB2, ComB3, and ComB6 as essential components of the transformation apparatus, structurally and functionally homologous to VirB2, VirB3, and VirB6, respectively. comB2, comB3, and comB4 are organized as a separate operon. Thus, for the H. pylori comB system, all T4SS core components have been identified except for homologues to VirB1, VirD4, VirB5, and VirB11.

scholarly journals Inhibition of Type IV Secretion Activity and Growth of Helicobacter pylori by Cisplatin and Other Platinum Complexes

2020 ◽  
Vol 10 ◽  
Author(s):  
Clara Lettl ◽  
Franziska Schindele ◽  
Giambattista Testolin ◽  
Alexander Bär ◽  
Tobias Rehm ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Dna Binding ◽  
Platinum Complexes ◽  
Secretion System ◽  
Type Iv Secretion ◽  
Growth Media ◽  
Target Cells ◽  
Type Iv Secretion System ◽  
Type Iv ◽  
H Pylori

Type IV secretion systems are protein secretion machineries that are frequently used by pathogenic bacteria to inject their virulence factors into target cells of their respective hosts. In the case of the human gastric pathogen Helicobacter pylori, the cytotoxin-associated gene (Cag) type IV secretion system is considered a major cause for severe disease, such as gastric cancer, and thus constitutes an attractive target for specific treatment options against H. pylori infections. Here, we have used a Cag type IV secretion reporter assay for screening a repurposing compound library for inhibitors targeting this system. We found that the antitumor agent cisplatin, a platinum coordination complex that kills target cells by formation of DNA crosslinks, is a potent inhibitor of the Cag type IV secretion system. Strikingly, we found that this inhibitory activity of cisplatin depends on a ligand exchange reaction which incorporates a solvent molecule (dimethylsulfoxide) into the complex, a modification which is known to be deleterious for DNA crosslinking, and for its anticancer activity. We extended our analysis to several analogous platinum complexes containing N-heterocyclic carbene, as well as DMSO or other ligands, and found varying inhibitory activities toward the Cag system which were not congruent with their DNA-binding properties, suggesting that protein interactions may cause the inhibitory effect. Inhibition experiments under varying conditions revealed effects on adherence and bacterial viability as well, and showed that the type IV secretion-inhibitory capacity of platinum complexes can be inactivated by sulfur-containing reagents and in complex bacterial growth media. Taken together, our results demonstrate DNA binding-independent inhibitory effects of cisplatin and other platinum complexes against different H. pylori processes including type IV secretion.

scholarly journals Binding of the Helicobacter pyloriVacuolating Cytotoxin to Target Cells

1998 ◽  
Vol 66 (8) ◽  
pp. 3981-3984 ◽  
Author(s):  
Paola Massari ◽  
Roberto Manetti ◽  
Daniela Burroni ◽  
Sandra Nuti ◽  
Nathalie Norais ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Helicobacter Pylori ◽  
Cell Surface ◽  
Indirect Immunofluorescence ◽  
Target Cells ◽  
Vacuolar Degeneration ◽  
Vacuolating Cytotoxin ◽  
Surface Receptors ◽  
High Affinity ◽  
Late Stages

ABSTRACT The vacuolating cytotoxin of Helicobacter pylori, VacA, enters the cytoplasm of target cells and causes vacuolar degeneration by interfering with late stages of endocytosis. By using indirect immunofluorescence and flow cytometry, we have demonstrated that VacA binds to specific high-affinity cell surface receptors and that this interaction is necessary for cell intoxication.

Ultrastructural Changes in Tumor Cells During Human Peripheral Blood Monocyte-Mediated Cytotoxicity

1981 ◽  
Vol 39 ◽  
pp. 452-453
Author(s):  
K. E. Muse ◽  
D. G. Fischer ◽  
H. S. Koren
Keyword(s):  
Target Cell ◽  
Human Peripheral Blood ◽  
Mononuclear Phagocytes ◽  
Ultrastructural Changes ◽  
Target Cells ◽  
Limited Information ◽  
Blood Monocytes ◽  
Tumoricidal Activity ◽  
Activated State

Mononuclear phagocytes, a pluripotential cell line, manifest an array of basic extracellular functions. Among these physiological regulatory functions is the expression of spontaneous cytolytic potential against tumor cell targets.The limited observations on human cells, almost exclusively blood monocytes, initially reported limited or a lack of tumoricidal activity in the absence of antibody. More recently, freshly obtained monocytes have been reported to spontaneously impair the biability of tumor target cells in vitro (Harowitz et al., 1979; Montavani et al., 1979; Hammerstrom, 1979). Although the mechanism by which effector cells express cytotoxicity is poorly understood, discrete steps can be distinguished in the process of cell mediated cytotoxicity: recognition and binding of effector to target cells,a lethal-hit stage, and subsequent lysis of the target cell. Other important parameters in monocyte-mediated cytotoxicity include, activated state of the monocyte, effector cell concentrations, and target cell suseptibility. However, limited information is available with regard to the ultrastructural changes accompanying monocyte-mediated cytotoxicity.

The Effect of Androgen Depletion and Replacement on the Epithelium of the Seminal Vesicle of the Aging Rat

1975 ◽  
Vol 33 ◽  
pp. 590-591
Author(s):  
Venita F. Allison
Keyword(s):  
Cell Proliferation ◽  
Seminal Vesicle ◽  
Male Rats ◽  
Target Cells ◽  
Cell Regeneration ◽  
Secretory Function ◽  
Electron Microscopic ◽  
Aging Rat ◽  
Microscopic Studies ◽  
Androgen Depletion

In 1930, Moore, Hughes and Gallager reported that after castration seminal vesicle epithelial cell atrophy occurred and that cell regeneration could be achieved with daily injections of testis extract. Electron microscopic studies have confirmed those observations and have shown that testosterone injections restore the epithelium of the seminal vesicle in adult castrated male rats. Studies concerned with the metabolism of androgens point out that dihydrotestosterone stimulates cell proliferation and that other metabolites of testosterone probably influence secretory function in certain target cells.Although the influence of androgens on adult seminal vesicle epithelial cytology is well documented, little is known of the effect of androgen depletion and replacement on those cells in aging animals. The present study is concerned with the effect of castration and testosterone injection on the epithelium of the seminal vesicle of aging rats.

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