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Protein Trio Ups Gastric Cancer Risk

September 23, 2011 | Leigh MacMillan

The bacterium Helicobacter pylori colonizes the stomachs of about half of the world’s population and increases the risk of gastric cancer. Individuals infected with H. pylori strains that have the cag pathogenicity island (cag PAI) – a group of genes that encodes the bacterial toxin CagA and a secretion system to inject it into gastric cells – are at higher risk of developing gastric cancer.

Timothy Cover, M.D., and colleagues used mass spectrometry and electron microscopy tools to reveal that three cag PAI proteins (CagH, CagI and CagL) are involved in the formation of hair-like structures called pili on the bacterial surface. These proteins – and the pili they produce – are essential for moving CagA into the gastric epithelial cells, where it promotes cellular changes that can lead to the development of cancer.

The findings in the September issue of PLoS Pathogens reveal unique components of the H. pylori secretion system and demonstrate that this system varies from previously characterized bacterial secretion systems.