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Helicobacter pylori CagA targets gastric tumor suppressor RUNX3 for proteasome-mediated degradation

Y H Tsang1, A Lamb, J Romero-Gallo

  • 1Department of Biochemistry, College of Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.

Oncogene
|August 3, 2010
PubMed

Insights

Helicobacter pylori infection inactivates the gastric tumor suppressor RUNX3 via its CagA protein. This interaction blocks RUNX3

Area of Science:

  • Oncology
  • Microbiology
  • Molecular Biology

Background:

  • Chronic Helicobacter pylori infection is a major risk factor for gastric cancer.
  • The cagA-positive strain of H. pylori injects the CagA protein into gastric cells, disrupting cellular functions.
  • RUNX3 is a known tumor suppressor frequently inactivated in gastric cancer.

Purpose of the Study:

  • To investigate the mechanism by which H. pylori infection inactivates the gastric tumor suppressor RUNX3.
  • To identify RUNX3 as a novel cellular target of H. pylori CagA.
  • To elucidate how CagA functions as an oncoprotein by targeting RUNX3.

Main Methods:

  • Investigated the interaction between H. pylori CagA and RUNX3 in gastric epithelial cells.
  • Utilized deletion mutants of CagA and mutated RUNX3 to study the CagA-RUNX3 interaction.
  • Assessed the effects of CagA on RUNX3 ubiquitination, degradation, and transcriptional activity.

Main Results:

  • H. pylori infection inactivates RUNX3 in a CagA-dependent manner.
  • CagA directly binds to RUNX3 via its WW domain recognizing RUNX3's PY motif.
  • CagA promotes RUNX3 ubiquitination and degradation, inhibiting its transcriptional activity.

Conclusions:

  • RUNX3 is a novel cellular target of H. pylori CagA.
  • CagA acts as an oncoprotein by blocking the activity of the gastric tumor suppressor RUNX3.
  • This mechanism contributes to the development of gastric adenocarcinoma.

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