Autophagy, a process that results in the degradation of intracellular proteins, is initiated by amino-acid starvation but is also negatively regulated by the metabolic-checkpoint kinase mTOR. In Cell Host and Microbe, Giradin and colleagues examine the initiation and control of xenophagy, a specialized form of autophagy used for the destruction of intracellular pathogens. Epithelial cells infected by the pathogenic bacterium Shigella trigger endomembrane damage, which results in a general amino-acid-starvation response and consequently lower activity of mTOR—a 'double-whammy' that initiates xenophagy and potentially control of this pathogen. In contrast, infection by Salmonella is characterized by only transient disruption of endomembrane integrity and consequent rapid normalization of amino acid concentrations and mTOR activity. By minimally perturbing these stress-related pathways, Salmonella is therefore able to circumvent this cell-intrinsic defense pathway.

Cell Host Microbe (14 June 2012) doi:10.1016/j.chom.2012.04.012