A table for two

Abstract

Autophagy, the process of cellular self-cannibalism, comes in various forms. It now emerges that two of these — mitophagy and xenophagy — share a common initiator protein, Parkin. See Article p.512 The ubiquitin ligase parkin is required for ubiquitination and for mitophagy — the type of autophagy involved in the clearance of damaged mitochondria. This study demonstrates that parkin also acts in innate immune defence, marking Mycobacterium tuberculosis-containing phagosomes with ubiquitin chains and targeting them for xenophagy, the autophagic degradation process that deals with intracellular bacterial pathogens. The fact that parkin regulates a common cellular program for the quality control of endogenous mitochondria (self) and the eradication of harmful bacterial pathogens (non-self) is intriguing in light of the presumed evolutionary origin of mitochondria from a bacterial endosymbiont.