Medizinische Mikrobiologie & Krankenhaushygiene

Arbeitsgruppe Prof. Dr. rer. nat. Rainer Haas

Helicobacter pylori ist ein äußerst erfolgreicher bakterieller Krankheitserreger, der die Magenschleimhaut von etwa 50% der Menschheit infiziert, zu chronischer Gastritis oder Magengeschwüren führt, und das Risiko von Magenkrebs erhöht. Wir untersuchen die Wirkungsweise spezifischer Bakterien-Wirt-Interaktionen und die Art und Weise, wie die Bakterien Epithelzellen oder die Einwanderung von Immunzellen beeinflussen und dadurch möglicherweise eine Erkrankung des Magens verursachen. Unsere Gruppe konzentriert sich auf das Cag-Typ-4-Sekretionssystem (cag-T4SS), seine Struktur und Funktion sowie den molekularen Mechanismus der CagA-Translokation. Bakterielle Adhäsine der äußeren Membran und ihre Rezeptoren auf den Wirtszellen, wie die carcinoembryonic antigen-related cell adhesion molecules (CEACAMs) oder Integrine, werden unter in vitro- und in vivo-Bedingungen mit geeigneten Zelllinien und einem CEACAM-humanisierten Mausmodell untersucht. Außerdem identifizieren und charakterisieren wir niedermolekulare Inhibitoren (SMI), die das cag-T4SS und/oder andere lebenswichtige Funktionen des bakteriellen Erregers hemmen können.

Kontakt

Professor Dr. rer. nat. Rainer Haas

Max von Pettenkofer-Institut
Pettenkoferstrasse 9a
80336 München
+49 89 2180-72855

Zur Arbeitsgruppe

Leitung

Prof. Dr. rer. nat. Rainer Haas

Rainer Haas is Professor of Medical Microbiology and Hospital Epidemiology at the Max von Pettenkofer Institute of the Ludwig Maximilian University (LMU) Munich, Germany. He studied biology in Frankfurt, Heidelberg and Tübingen. After postdoctoral positions at the Max Planck Institute for Biology in Tübingen as well as at the Centre Hospitalier Universitaire Vaudois (CHUV) and the Swiss Institute for Experimental Cancer Research (ISREC) at the University of Lausanne, he habilitated at the University of Tübingen. In 1997, he became an associate professor at the Ludwig Maximilian University of Munich. From 2005 to 2015, he was Speaker of the Gastrointestinal Infections Section of the German Society for Hygiene and Microbiology (DGHM). He received the Raine Visiting Professorship at the University of Western Australia in 2011 and was acting director of the Department of Bacteriology at the Max von Pettenkofer Institute from 2014 to 2016. Prof. Haas has received several awards for his research, including the Young Investigator Award of the Society for the Advancement of Molecular Biology, Heidelberg, the Otto Hahn Medal of the Max Planck Society, Munich, and the DGHM Main Award.

Prof. Dr. rer. nat. Rainer Haas

AG-Mitglieder

Aktuelle Gruppenmitglieder

Rainer Haas, Dr. rer. nat., Professor
E-Mail: haas@mvp.uni-muenchen.de
Phone: +49 89 2180-72855

Sukumar Namineni, PhD, postdoc
E-Mail: namineni@mvp.lmu.de
Phone: +49 89 2180-72936

Evelyn Weiss, technician
E-Mail: Weiss_e@mvp.lmu.de
Phone: +49 89 2180-72877

Dr. rer. nat. Studierende

  • Stefan Odenbreit
  • Dirk Hofreuter
  • Klaus Panthel
  • Jürgen Püls
  • Holger Kavermann
  • Bettina Gebert
  • Renate Buhrdorf
  • Kirsten Engel
  • Arno Karnholz
  • Isabelle Pattis
  • Xaver Sewald
  • Stefan Kutter
  • Iris Barwig
  • Stefanie Rohrer
  • Claudia Ertl
  • Beate Kern
  • Lea Holsten
  • Verena Königer
  • Thuy Pham
  • Franziska Schindele
  • Quing Zhao
  • Ina-Kristin Behrens
  • Clara Lettl
  • Barbara Schmidinger

Dr. biol. Hum Studierende

  • Luisa Jiménez-Soto
  • Utkarsh Jain

Dr. med. Studierende

  • Sabine Hohlfeld
  • Barbara Eberle
  • Kristina Petri

Postdocs

  • Gabriele Rieder
  • Benjamin Busch
  • Ute Breithaupt
  • Pia Palamides
  • Sukumar Namineni

Forschung

Helicobacter pylori adherence and signal transduction mechanisms in gastric epithelial cells.

Helicobacter pylori shows remarkably specific adherence to gastric epithelial cells in vivo. A variety of adhesins play a role, such as BabA, SabA, AlpAB, OipA, etc. all of which belong to the large group of H. pylori outer membrane proteins (OMPs). BabA binds to Lewis b blood group antigen (Leb), while SabA binds to sialylated glycoproteins. No definite receptors are known for OipA, HopZ and AlpAB. We are investigating the role of adhesins and other OMPs in the establishment and persistence of gastrointestinal tract infection. We study the processes of signal transduction induced by bacterial binding to gastric epithelial cells and identify the receptors involved. We use in vitro and in vivo adherence models, such as gastric epithelial cell lines, human gastric epithelial tissue sections, and the newly established CEACAM-humanized mouse model.

H. pylori (red) binding gastric epithelial cells in vitro (electron micrograph: M. Rohde)
H. pylori (red) binding gastric epithelial cells in vitro (electron micrograph: M. Rohde)
Phylogenetic tree of the Helicobacter outer membrane (Hop, red dots) and Hop-related (Hor, blue dots) gene family. BabA, SabA, HopQ HopZ and AlpAB have been identified as bacterial adhesins.
Phylogenetic tree of the Helicobacter outer membrane (Hop, red dots) and Hop-related (Hor, blue dots) gene family. BabA, SabA, HopQ HopZ and AlpAB have been identified as bacterial adhesins.

Mechanisms of protein translocation by the H. pylori cag-T4SS

The H. pylori cag type IV secretion system (cag-T4SS) is a complex molecular machinery consisting of a membrane-spanning transport channel and a surface pilus designed to transport the bacterial protein CagA into gastric cells.

Translocation of CagA is dependent on the interaction of components of the cag-T4SS with the carcinoembryonic antigen-related cell adhesion molecule (CEACAM) receptor family on the cell surface. In this project, we seek to elucidate the unique, complex interaction between components of the H. pylori cag-T4SS with the CEACAM receptor to understand the molecular mechanism of protein translocation. We are using specific H. pylori mutants, protein-protein interaction methods, other biochemical methods, and novel microscopic techniques.

Scanning electron micrograph showing the interaction of H. pylori (yellow) with human gastric epithelial cells (AGS, red) via the formation of surface appendages, which are part of the bacterial cag-T4SS. (electron micrograph: M. Rohde)
Scanning electron micrograph showing the interaction of H. pylori (yellow) with human gastric epithelial cells (AGS, red) via the formation of surface appendages, which are part of the bacterial cag-T4SS. (electron micrograph: M. Rohde)
The outer membrane protein HopQ of H. pylori interacts with diverse CEACAMs, including CEACAM1 carrying an immunoreceptor tyrosine-based inhibitory motif (ITIM), or CEACAM3 with an immuno-receptor tyrosine-based activation motif (ITAM), whereas the cag-T4SS appendages can bind human integrins.
The outer membrane protein HopQ of H. pylori interacts with diverse CEACAMs, including CEACAM1 carrying an immunoreceptor tyrosine-based inhibitory motif (ITIM), or CEACAM3 with an immuno-receptor tyrosine-based activation motif (ITAM), whereas the cag-T4SS appendages can bind human integrins.

Helicobacter pylori – CEACAM interaction, gastric leukocyte recruitment and local immune-modulation

Gastric inflammation is often asymptomatic but can also give rise to more severe gastric diseases, like peptic ulcer disease or gastric cancer. For a successful stomach mucosa colonization, H. pylori has to cope with the host immune system. The bacteria apply immune evasion strategies. We previously demonstrated that H. pylori interferes with leukocyte migration in vitro, using its major virulence factor CagA. Recent findings suggest that H. pylori manipulates its host via the CEACAM family of host cell receptors. The H. pylori protein HopQ, a specialized adhesin, binds human, but not murine CEACAMs. The H. pylori mouse model permits gastric colonization but does not adequately reproduce severe inflammation or malignant disease. The inability of H. pylori to interact with murine CEACAMs probably prevents cellular signaling and subsequent chemokine release, responsible for a strong recruitment of immune cells in the gastric mucosa. We functionally characterize human CEACAM expressing (humanized) murine leukocytes and investigate their interaction with H. pylori in vitro. Using various types of CEACAM-humanized mice, we study the HopQ-CEACAM interactions from isolated neutrophils, macrophages and dendritic cells (DCs). Hoxb8 cells are used to unravel the underlying biochemical mechanisms and signaling events of bacteria-induced leukocyte responses, to better understand immune cell migration into the stomach mucosa and phagocytosis events in vivo. These immune cell dynamics of CEACAM-humanized neutrophils, macrophages and DCs in the stomach mucosa in vivo are studied in a novel murine open stomach model using multiphoton intravital microscopy (MP-IVM). The central focus is to understand the failure of the infected host to mount an immune response adequate for H. pylori eradication.

HoxB8 cells generated from murine neutrophils interact with H. pylori (red) and are able to efficiently phagocytose H. pylori in vitro. (micrograph: Almke Bader)

Development of small-molecule inhibitors against H. pylori and the cag-type IV secretion system

The pathogenic potential of H. pylori is mainly dependent its type IV secretion system (cag-T4SS), which is responsible for the induction for release of the chemoattractant Interleukin-8 (IL-8) and the translocation of CagA into different types of host cells. Antibiotic treatment of H. pylori infection requires a combination therapy for several days, which is cumbersome, expensive and associated with frequent side effects. Furthermore, bacteria become more and more resistant against antibiotic treatment. In this project, we screen for and develop further specific small molecule inhibitors (SMI) directed against the cag-T4SS as the major bacterial pathogenicity factor (pathoblocker approach), as well as SMIs active against H. pylori itself (pathogen-blocker).

We therefore developed a high throughput screening assay based on specific CagA translocation reporters (TEM1 beta lactamase reporter assay, HiBiT CagA reporter assay) and screened different compound libraries to identify corresponding inhibitors. Suitable SMI inhibitor candidate are further characterized by ADME/PK studies.

Publikationen

Top 10 Publikationen

Behrens I-K, Busch B, Ishikawa-Ankerhold H, Palamides P, Shively JE, Stanners C, Chan C, Leung N, Gray-Owen S, Haas R. (2020) The HopQ-CEACAM interaction controls CagA translocation, phosphorylation and phagocytosis of Helicobacter pylori in neutrophils. mBio. 11(1). pii: e03256-19. doi: 10.1128/. mBio.03256-19.
Zhao Q, Busch B, Jiménez-Soto L-F, Ishikawa-Ankerhold H, Massberg S, Terradot L, Fischer W, Haas, R. (2018) Integrin but not CEACAM receptors are dispensable for Helicobacter pylori CagA translocation. PLoS Pathogens 14(10):e1007359. doi: 10.1371/journal.ppat.1007359
Königer V, Holsten L, Harrison U, Busch B, Loell E, Zhao Q, Bonsor DA, Roth A, Kengmo-Tchoupa A, Smith SI, Mueller S, Sundberg SJ, Zimmermann W, Fischer W, Hauck CR and Haas R. (2016) Helicobacter pylori exploits human CEACAMs via HopQ for adherence and translocation of CagA. Nature Microbiol. ARTICLE NUMBER: 16188 | DOI: 10.1038/NMICROBIOL.2016.188.
Kaplan-Türköz B, Jiménez-Soto LF, Dian C, Ertl C, Remaut H, Louche A, Tosi T, Haas R, Terradot L. (2012) Structural insights into Helicobacter pylori oncoprotein CagA interaction with beta1 integrin. Proc Natl Acad Sci U S A. 109(36):14640-5.
Fischer W, Windhager L, Rohrer S, Zeiller M, Karnholz A, Hoffmann R, Zimmer R, Haas R. (2010) Strain-specific genes of Helicobacter pylori: genome evolution driven by a novel type IV secretion system and genomic island transfer. Nucleic Acids Res 38(18):6089-101.
Jiménez-Soto LF, Kutter S, Sewald X, Ertl C, Weiss E, Kapp U, Rohde M, Pirch T, Jung K, Retta SF, Terradot L, Fischer W, Haas R. (2009) Helicobacter pylori type IV secretion apparatus exploits beta1 integrin in a novel RGD-independent manner. PLoS Pathog 5(12):e1000684
Sewald X, Gebert-Vogl B, Prassl S, Barwig I, Weiss E, Fabbri M, Osicka R, Schiemann M, Busch DH, Semmrich M, Holzmann B, Sebo P, Haas R. (2008) Integrin subunit CD18 Is the T-lymphocyte receptor for the Helicobacter pylori vacuolating cytotoxin. Cell Host Microbe 3(1):20-9.
Rieder G, Merchant JL, Haas R. (2005) Helicobacter pylori cag-type IV secretion system facilitates corpus colonization to induce precancerous conditions in Mongolian gerbils. Gastroenterology 128(5):1229-42.
Gebert B, Fischer W, Weiss E, Hoffmann R, Haas R. (2003) Helicobacter pylori vacuolating cytotoxin inhibits T lymphocyte activation. Science 301(5636):1099-102.
Odenbreit S, Puls J, Sedlmaier B, Gerland E, Fischer W, Haas R. (2000) Translocation of Helicobacter pylori CagA into gastric epithelial cells by type IV secretion. Science 287(5457):1497-500.

Auszeichnungen

  • 1987 Young Investigator Award from the Society for the Advancement of Molecular Biology, Heidelberg
  • 1987 Otto Hahn Medal of Max Planck Society, Munich
  • 2001 Main Award from the German Society for Hygiene and Microbiology (DGHM), Aachen
  • 2011 Raine Visiting Professorship from the University of Western Australia, Perth