Autophagy pathway. Autophagy is a membrane-dependent pathway that involves a defined series of steps. The pathway is initiated by the autophagosome nucleation step (formation of a preautophagosomal structure leading to an isolation membrane or phagophore). This is followed by autophagosome membrane elongation. The next steps involve the formation of the mature autophagosome, which engulphs cytosol or specific substrates such as mitochondria or ubiquitinated proteins. Subsequently, the autophagosome containing its cargo fuses with the lysosome. In the autolysosome, the autophagosomal cargoes are digested by lysosomal hydrolases and the contents released for metabolic recycling.
