Localization of the enteropathogenic E. coli EspZ effector at infection sites is essential for exerting its anti-host cell death function

While most of our gut Escherichia coli live there peacefully, there are few E. coli that are virulent to humans. One of them is enteropathogenic E. coli (EPEC). EPEC is a diarrheagenic Gram-negative bacterium expressing a protein complex named: type 3 secretion system, which allows the injection of bacterial proteins (termed effectors) from the bacterial cell cytoplasm into the host cell. EPEC and its close relatives, enterohemorrhagic E. coli and Citrobacter rodentium, are characterized by their ability to attach to the intestinal epithelia and cause microvilli effacement, thereby called ‘attaching and effacing (A/E)’ pathogens. The A/E effect is crucial for inducing pathogenesis. Despite extensive knowledge, the mechanisms by which these effectors act within the host cells remain largely unknown. One of these effectors is EspZ, shown to be critical for eliciting the EPEC disease. Studies have shown that EspZ, which harbors two predicted transmembrane domains and an extracellular loop, is localized at infection sites, and protects against host cell death.