Fig. 1

Autophagy is classified into three types based on the route of delivery. Microautophagy refers to the sequestration of misfunction proteins or whole organelles such as mitochondria (named mitophagy) directly by lysosomes. Chaperone-mediated autophagy (CMA) involves direct translocation of misfolded substrates across the lysosome membrane through the action of a cytosolic and lysosomal chaperone hsc70, and the integral membrane receptor LAMP-2A (lysosome-associated membrane protein type 2A). In the case of macroautophagy, the cargoes are sequestered within a unique double-membrane cytosolic vesicle, named autophagosome. This type of autophagy is initiated by the nucleation of an isolation membrane or phagophore. ULK, ATG 13, FIP200, and ATG101 are involved in this stage. Then, the Beclin-1 and ATG14L complex contributes to the nucleation of the phagophore. This membrane then elongates and closes on itself to form an autophagosome. Elongation of the phagophore membrane is dependent on the Atg12 and LC3 conjugation systems. Closure of the autophagosome is dependent on the activity of the LC3-conjugation system. The autophagosome matures by fusing with endosomes and lysosomes, finally forming the autophagolysosome where the cargo degradation occurs