Biomedical subjects

Thomas F Meyer

Publications and source records attributed to Thomas F Meyer.

59 records · Page 4Linked to original sources

PubMed2002

Specific entry of Helicobacter pylori into cultured gastric epithelial cells via a zipper-like mechanism.

Although Helicobacter pylori has generally been considered an extracellular pathogen, a number of in vitro infection experiments and biopsy examinations have shown that it is capable of occasionally entering mammalian host cells. Here, we characterized this entry process by using AGS cells as a host cell model. In gentamicin protection-invasion assays, the number of H. pylori colonies recovered was lower than that for Salmonella enterica serovar Typhimurium X22, Escherichia coli expressing InvA, and Yersinia enterocolitica YO:9 grown at 25 degrees C but higher than that for Neisseria gonorrhoeae VP1 and Y. enterocolitica YO:9 grown at 37 degrees C. At the ultrastructural level, the entry process was observed to occur via a zipper-like mechanism. Internalized H. pylori was bound in tight LAMP-1-containing vacuoles in close association with condensed filamentous actin and tyrosine phosphorylation signals. Wortmannin, a potent inhibitor of phosphatidylinositol 3-kinase, and calphostin C, an inhibitor of protein kinase C, both inhibited the entry of H. pylori in a sensitive and dose-dependent manner; however, the level of entry was enhanced by sodium vanadate, an inhibitor of tyrosine phosphatases and ATPases. Furthermore, the cytokine tumor necrosis factor alpha antagonized the entry of H. pylori into AGS cells. Collectively, these results demonstrate that the entry of H. pylori into AGS cells occurs via a zipper-like mechanism which involves various host signal transduction events.

Actins↗

PubMed2002

Proteome analysis of secreted proteins of the gastric pathogen Helicobacter pylori.

Secreted proteins (the secretome) of the human pathogen Helicobacter pylori may mediate important pathogen-host interactions, but such proteins are technically difficult to analyze. Here, we report on a comprehensive secretome analysis that uses protein-free culture conditions to minimize autolysis, an efficient recovery method for extracellular proteins, and two-dimensional gel electrophoresis followed by peptide mass fingerprinting for protein resolution and identification. Twenty-six of the 33 separated secreted proteins were identified. Among them were six putative oxidoreductases that may be involved in the modification of protein-disulfide bonds, three flagellar proteins, three defined fragments of the vacuolating toxin VacA, the serine protease HtrA, and eight proteins of unknown function. A cleavage site for the amino-terminal passenger domain of VacA between amino acids 991 and 992 was determined by collision-induced dissociation mass spectrometry. Several of the secreted proteins are interesting targets for antimicrobial chemotherapy and vaccine development.

Bacterial Proteins↗

PubMed2002

cag+ Helicobacter pylori induces homotypic aggregation of macrophage-like cells by up-regulation and recruitment of intracellular adhesion molecule 1 to the cell surface.

Infection with cag+ but not cag-negative Helicobacter pylori leads to the formation of large homotypic aggregates of macrophage-like cells. Intracellular adhesion molecule 1 is up-regulated and recruited to the cell surface of infected cells and mediates the aggregation via lymphocyte function-associated molecule 1. This signaling may regulate cell-cell interactions and inflammatory responses.

Antigens, Bacterial↗

PubMed2002

Helicobacter pylori type IV secretion, host cell signalling and vaccine development.

Helicobacter pylori is a bacterial pathogen specialised to colonise and persist the gastric mucosa and to cause severe gastroduodenal disease. A major disease-associated bacterial component is a type IV secretion system (TFSS) encoded by the cytotoxin-associated genes pathogenicity island (cagPAI). Among the multiple responses in H. pylori-infected epithelial cells, the induction of proinflammatory cytokines and chemokines, cell spreading and motility associated with the "hum mingbird" phenotype appear strictly dependent on the functional transporter complex in the cagPAI. H. pylori is also capable of occasionally entering epithelial cells and manipulates the host immune system for immune evasion. Attached bacteria actively translocate the CagA protein into epithelial cells by a TFSS-dependent process and translocated CagA undergoes tyrosine phosphorylation in the carboxy terminal EPIYA sequence repeat motif (Y-972) by kinases of the Src family. Furthermore, we have identified a novel TFSS in H. pylori involved in horizontal DNA-transfer. Host cell signalling events and cellular phenotypes provoked by the cagPAI, the investigation of mechanisms related to gastric cancer as well as the development of a Salmonella based live recombinant vaccine are in the focus of additional departmental activities.

Amino Acid Motifs↗

PubMed2001

Nuclear factor-kappa B directs carcinoembryonic antigen-related cellular adhesion molecule 1 receptor expression in Neisseria gonorrhoeae-infected epithelial cells.

The human-specific pathogen Neisseria gonorrhoeae expresses opacity-associated (Opa) protein adhesins that bind to various members of the carcinoembryonic antigen-related cellular adhesion molecule (CEACAM) family. In this study, we have analyzed the mechanism underlying N. gonorrhoeae-induced CEACAM up-regulation in epithelial cells. Epithelial cells represent the first barrier for the microbial pathogen. We therefore characterized CEACAM expression in primary human ovarian surface epithelial (HOSE) cells and found that CEACAM1-3 (L, S) and CEACAM1-4 (L, S) splice variants mediate an increased Opa(52)-dependent gonoccocal binding to HOSE cells. Up-regulation of these CEACAM molecules in HOSE cells is a direct process that takes place within 2 h postinfection and depends on close contact between microbial pathogen and HOSE cells. N. gonorrhoeae-triggered CEACAM1 up-regulation involves activation of the transcription factor nuclear factor kappaB (NF-kappaB), which translocates as a p50/p65 heterodimer into the nucleus, and an NF-kappaB-specific inhibitory peptide inhibited CEACAM1-receptor up-regulation in N. gonorrhoeae-infected HOSE cells. Bacterial lipopolysaccharides did not induce NF-kappaB and CEACAM up-regulation, which corresponds to our findings that HOSE cells do not express toll-like receptor 4. The ability of N. gonorrhoeae to up-regulate its epithelial receptor CEACAM1 through NF-kappaB suggests an important mechanism allowing efficient bacterial colonization during the initial infection process.

Alternative Splicing↗