Fig. 1

The mechanism of the autophagy pathway in mammalian cells. The autophagy process includes four main steps: induction, phagophore formation, phagophore elongation, and fusion with the lysosome. In the first step, different signals, such as starvation, rapamycin, and similar factors, inhibit mTOR and activate the ULK complex, thereby inducing autophagy. Active ULK stimulates the Vps34 complex to produce PI3P, which is needed for phagophore formation. In the following step, the phagophore expands, engulfs cytoplasmic constituents, and finally fuses with the lysosome to degrade their contents