O-Antigen Inhibits Internalization, Vacuole Escape, and Inflammasome Activation.

Two species, and , cause approximately 90% of bacterial dysentery worldwide. While is the dominant species in low-income countries, causes the majority of infections in middle- and high-income countries. is a prototypic cytosolic bacterium; once intracellular, it rapidly escapes the phagocytic vacuole and causes pyroptosis of macrophages, which is important for pathogenesis and bacterial spread.

Enteropathogenic Escherichia coli Stimulates Effector-Driven Rapid Caspase-4 Activation in Human Macrophages.

Microbial infections can stimulate the assembly of inflammasomes, which activate caspase-1. The gastrointestinal pathogen enteropathogenic Escherichia coli (EPEC) causes localized actin polymerization in host cells. Actin polymerization requires the binding of the bacterial adhesin intimin to Tir, which is delivered to host cells via a type 3 secretion system (T3SS).

Modulation of Host Cell Processes by T3SS Effectors.

Two of the enteric Escherichia coli pathotypes-enteropathogenic E. coli (EPEC) and enterohaemorrhagic E. coli (EHEC)-have a conserved type 3 secretion system which is essential for virulence.

The Atypical Ubiquitin E2 Conjugase UBE2L3 Is an Indirect Caspase-1 Target and Controls IL-1β Secretion by Inflammasomes.

Caspase-1 activation by inflammasome signaling scaffolds initiates inflammation and antimicrobial responses. Caspase-1 proteolytically converts newly induced pro-interleukin 1 beta (IL-1β) into its mature form and directs its secretion, triggering pyroptosis and release of non-substrate alarmins such as interleukin 1 alpha (IL-1α) and HMGB1. While some caspase-1 substrates involved in these events are known, the identities and roles of non-proteolytic targets remain unknown.