Self and Nonself: How Autophagy Targets Mitochondria and Bacteria

Autophagy is an evolutionarily conserved pathway that transports cytoplasmic components for degradation into lysosomes. Selective autophagy can capture physically large objects, including cell-invading pathogens and damaged or superfluous organelles. Selectivity is achieved by cargo receptors that detect substrate-associated “eat-me” signals. In this Review, we discuss basic principles of selective autophagy and compare the “eat-me” signals and cargo receptors that mediate autophagy of bacteria and bacteria-derived endosymbionts—i.e., mitochondria. Randow and Youle compare and contrast mitophagy and xenophagy, noting similarities as well as differences in the recognition and elimination of unwanted mitochondria and invading bacteria.