Fig. 1

Induction and mechanisms of autophagy in mammalian cells. The process of autophagy involves two major steps: induction of autophagosome and fusion of autophagosome with lysosome. The ULK/Atg1 kinase complex, the autophagy-specific PI3-kinase complex, and PI(3)P effectors and their related proteins are important for the nucleation step, whereas the Atg12- and LC3/Atg8-conjugation systems are important for the elongation step. In addition, other proteins required for autophagosome-lysosomal fusion, lysosomal acidification, and lysosomal digestion, and regulatory signals that integrate environmental cues with the autophagic machinery are involved in autophagy