Skills (1)
Research experience
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Jan 2001–
Dec 2010Research: Max-Planck-Institut für Infektionsbiologie
Max-Planck-Institut für InfektionsbiologieGermany · Berlin
Publications (23) View all
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Article: Phosphorylation of ATM/ATR substrates in eukaryotic cells after infection with Helicobacter pylori
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ABSTRACT: Phosphorylation of ATM-kinase substrates in HeLa and AGS cells in response to Helicobacter pylori infection has been characterized. Infection with wild-type (cagPAI-positive) and corresponding isogenic cagPAI negative mutant induced activation of Chk1 and Chk2 kinases. However, only Chk1 was directly activated by ATM-kinase. Using 2D-electrophoresis and mass spectrometry a group of proteins phosphorylated in AGS cells by ATM1/ATR kinases during H. pylori infection has been identified. Key words Helicobacter pylori -ATM/ATR kinases-phosphorylation-RPA32A-splicing-factorBiochemistry (Moscow) Supplement Series B Biomedical Chemistry 05/2012; -
Article: Modulation of the CD4+ T-cell response by Helicobacter pylori depends on known virulence factors and bacterial cholesterol and cholesterol α-glucoside content.
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ABSTRACT: Helicobacter pylori blocks the proliferation of human CD4(+) T cells, facilitated by vacuolating exotoxin (VacA) and γ-glutamyl transpeptidase (GGT). H. pylori-triggered T-cell reactions in mice correlate with bacterial cholesterol and cholesterol α-glucoside content but their role in human cells is unclear. We characterized the effect of VacA, GGT, and cholesterol on T-helper 1, T-helper 2, T-regulatory and T-helper 17 associated cytokines and T-cell proliferation. VacA, GGT, and bacterial cholesterol content exhibited differential and synergistic inhibitory effects on the expression of activation markers CD25 and CD69 and on interleukin 2, interleukin 4, interleukin 10, and interferon γ production. These factors did not affect the H. pylori-mediated abrogation of transforming growth factor β secretion or increased interleukin 6 production. Cholesterol α-glucosyltransferase-deficient bacteria exerted strongly reduced antiproliferative effects on primary human CD4(+) T cells. In conclusion, H. pylori shapes rather than suppresses human CD4(+) T-cell responses, and glucosylated cholesterol is a relevant bacterial component involved in this modulation.The Journal of Infectious Diseases 09/2011; 204(9):1339-48. · 6.41 Impact Factor -
Article: Bone marrow transplantation improves hepatic fibrosis in Abcb4-/- mice via Th1 response and matrix metalloproteinase activity.
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ABSTRACT: Reports on the effects of bone marrow-derived cells on hepatic fibrosis are contradictory. Impaired fibrosis but increased inflammation has recently been demonstrated 10 weeks after bone marrow transplantation (BM-Tx) in Abcb4-/- mice. It is hypothesised that BM-Tx might have long-term therapeutic potential by altering the immunological and matrix remodelling processes leading to hepatic regeneration. After lethal irradiation of recipient mice, BM cells from GFP+ donor mice (allogeneic Tx) or Abcb4-/- mice (syngeneic Tx) were transplanted via tail vein injection. Readouts were performed 2, 10 and 20 weeks after Tx. Liver integrity was assessed serologically and histologically. Surrogate markers for fibrogenesis, T helper (Th) response, inflammation, graft-versus-host disease and fibrolysis were analysed by quantitative real-time PCR, zymography and immunohistology. 20 weeks after syngeneic and allogeneic BM-Tx, hepatic grading and staging were significantly improved. In contrast, 2 weeks after BM-Tx inflammatory grading, expression of inflammatory cell markers and associated chemokines and their receptors were increased and subsequently declined. In parallel, CD8+/GFP+ donor-derived T cells infiltrated the liver 2 weeks after BM-Tx. The Th1 cyokine interferon γ was increased 2 and 10 weeks after BM-Tx whereas the Th2 associated interleukin 13 was not altered. The gene expression of matrix metalloproteinases MMP-2, MMP-7, MMP-9 and MMP-13 was transiently upregulated and MMP-9 protein remained elevated 20 weeks after BM-Tx with enhanced gelatinase activity located within the fibrotic areas. Neutrophils were identified as major sources of MMP-9. These results show that BM-Tx causes an antifibrotic Th1 response combined with transient inflammatory effects and subsequently upregulated MMP activity. Antifibrotic Th polarisation and prolonged proteolytic activity, especially of MMP-9, might be responsible for long-term amelioration of hepatic fibrosis.Gut 08/2011; 61(6):907-16. · 10.11 Impact Factor -
Article: Helicobacter pylori HP0518 affects flagellin glycosylation to alter bacterial motility.
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ABSTRACT: Helicobacter pylori is a human gastric pathogen associated with gastric and duodenal ulcers as well as gastric cancer. Mounting evidence suggests this pathogen's motility is prerequisite for successful colonization of human gastric tissues. Here, we isolated an H. pylori G27 HP0518 mutant exhibiting altered motility in comparison to its parental strain. We show that the mutant's modulated motility is linked to increased levels of O-linked glycosylation on flagellin A (FlaA) protein. Recombinant HP0518 protein decreased glycosylation levels of H. pylori flagellin in vitro, indicating that HP0518 functions in deglycosylation of FlaA protein. Furthermore, mass spectrometric analysis revealed increased glycosylation of HP0518 FlaA was due to a change in pseudaminic acid (Pse) levels on FlaA; HP0518 mutant-derived flagellin contained approximately threefold more Pse than the parental strain. Further phenotypic and molecular characterization demonstrated that the hyper-motile HP0518 mutant exhibits superior colonization capabilities and subsequently triggers enhanced CagA phosphorylation and NF-κB activation in AGS cells. Our study shows that HP0518 is involved in the deglycosylation of flagellin, thereby regulating pathogen motility. These findings corroborate the prominent function of H. pylori flagella in pathogen-host cell interactions and modulation of host cell responses, likely influencing the pathogenesis process.Molecular Microbiology 12/2010; 78(5):1130-44. · 5.01 Impact Factor -
Article: Helicobacter pylori induces miR-155 in T cells in a cAMP-Foxp3-dependent manner.
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ABSTRACT: Amongst the most severe clinical outcomes of life-long infections with Helicobacter pylori is the development of peptic ulcers and gastric adenocarcinoma--diseases often associated with an increase of regulatory T cells. Understanding H. pylori-driven regulation of T cells is therefore of crucial clinical importance. Several studies have defined mammalian microRNAs as key regulators of the immune system and of carcinogenic processes. Hence, we aimed here to identify H. pylori-regulated miRNAs, mainly in human T cells. MicroRNA profiling of non-infected and infected human T cells revealed H. pylori infection triggers miR-155 expression in vitro and in vivo. By using single and double H. pylori mutants and the corresponding purified enzymes, the bacterial vacuolating toxin A (VacA) and gamma-glutamyl transpeptidase (GGT) plus lipopolysaccharide (LPS) tested positive for their ability to regulate miR-155 and Foxp3 expression in human lymphocytes; the latter being considered as the master regulator and marker of regulatory T cells. RNAi-mediated knockdown (KD) of the Foxp3 transcription factor in T cells abolished miR-155 expression. Using adenylate cyclase inhibitors, the miR-155 induction cascade was shown to be dependent on the second messenger cyclic adenosine monophosphate (cAMP). Furthermore, we found that miR-155 directly targets the protein kinase A inhibitor alpha (PKIalpha) mRNA in its 3'UTR, indicative of a positive feedback mechanism on the cAMP pathway. Taken together, our study describes, in the context of an H. pylori infection, a direct link between Foxp3 and miR-155 in human T cells and highlights the significance of cAMP in this miR-155 induction cascade.PLoS ONE 01/2010; 5(3):e9500. · 4.09 Impact Factor
