To die or not to die: Shigella has an answer.

Invasion of epithelial cells by Shigella is a critical step in the pathogenesis of bacillary dysentery. In this issue of Cell Host & Microbe, Bergounioux et al. (2012) uncover a complex interplay of proinvasion, prosurvival, and prodeath signals centered on the activation of calpain protease by the Shigella VirA protein.