ATG5,also named as APG5L and ASP,belongs to the ATG5 family. It is required for autophagy. It plays an important role in the apoptotic process,possibly within the modified cytoskeleton. Its expression is a relatively late event in the apoptotic process,occurring downstream of caspase activity. Autophagy is a catabolic process for the autophagosomic-lysosomal degradation of bulk cytoplasmic contents. Formation of the autophagosome involves a ubiquitin-like conjugation system in which Atg12 is covalently bound to Atg5 and targeted to autophagosome vesicles. It mediates autophagosome-independent host protection.