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Grb2 is a key mediator of helicobacter pylori CagA protein activities
Hitomi Mimuro1, Toshihiko Suzuki, Jiro Tanaka
1Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
Abstract:
CagA delivered from Helicobacter pylori into gastric epithelial cells undergoes tyrosine phosphorylation and induces host cell morphological changes. Here we show that CagA can interact with Grb2 both in vitro and in vivo, which results in the activation of the Ras/MEK/ERK pathway and leads to cell scattering as well as proliferation. Importantly, this ability of CagA is independent from the tyrosine phosphorylation, which occurs within the five repeated EPIYA sequences (PY region) of CagA. However, the PY region appears to be indispensable for the Grb2 binding and induction of the cellular responses. Thus, intracellular CagA via its binding to Grb2 may act as a transducer for stimulating growth factor-like downstream signals which lead to cell morphological changes and proliferation, the causes of H. pylori-induced gastric hyperplasia.
Insights
Helicobacter pylori CagA protein binds to Grb2, activating cell growth pathways. This interaction, independent of tyrosine phosphorylation, causes cell scattering and proliferation, contributing to gastric hyperplasia.
Area of Science:
- Microbiology and Molecular Biology
- Cell Biology
- Oncology
Background:
- Helicobacter pylori infection is a major cause of gastric diseases, including cancer.
- The bacterial effector protein CagA plays a key role in H. pylori pathogenesis.
- CagA is translocated into gastric epithelial cells, where it induces significant cellular changes.
Purpose of the Study:
- To investigate the interaction between CagA and host cell proteins.
- To elucidate the mechanism by which CagA induces gastric epithelial cell morphological changes and proliferation.
- To determine the role of CagA's EPIYA motifs in these cellular responses.
Main Methods:
- In vitro and in vivo binding assays to assess CagA-Grb2 interaction.
- Analysis of the Ras/MEK/ERK signaling pathway activation.
- Cell scattering and proliferation assays.
- Mutational analysis of CagA's EPIYA region.
Main Results:
- CagA directly interacts with Grb2 both in vitro and in vivo.
- This interaction leads to the activation of the Ras/MEK/ERK signaling pathway.
- CagA-induced cell scattering and proliferation are independent of CagA tyrosine phosphorylation but dependent on the EPIYA region for Grb2 binding.
- The PY region of CagA is crucial for Grb2 binding and subsequent cellular responses.
Conclusions:
- Intracellular CagA binds to Grb2, acting as a signaling transducer.
- This CagA-Grb2 interaction stimulates growth factor-like downstream signals, promoting cell proliferation and morphological changes.
- The findings provide a mechanism for H. pylori-induced gastric hyperplasia, highlighting CagA's role in oncogenesis.