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. 2022 Jul 14;13:930919. doi: 10.3389/fendo.2022.930919

Figure 1.

Figure 1

Autophagy Mechanism. The autophagy process involves multi-steps which are initiation, elongation, maturation, fusion and degradation. The initiation step of mammalian autophagy involves the ULK complex (consisting of ULK1/2, ATG13, FIP200, and ATG101). The ULK complex phosphorylates Beclin1 to activate PI3K complex (composed of Beclin1-VPS34-VPS15-ATG14L). The PI3K complex then induces P3P formation, which recruits DCFP1 and WIPI for autophagosome formation. During the elongation and maturation stage, ATG7 and ATG10 help to conjugate the ATG12 to ATG5, forming an ATG5-ATG12 complex. This complex then interacts with the ATG16 to form an ATG16-ATG5-ATG12 complex that is involved in elongation and maturation of the autophagosome. LC3-I is formed by the proteolysis of pro-LC3 by ATG4. The ATG3 and ATG7 conjugate LC3-I to PE to form LC3-II that inserts into the autophagosome membrane. After the elongation and maturation, autophagosome with target cargo is trafficked to the lysosome to fuse and form an autolysosome. This process is regulated by RAB protein family, SNARE protein family, and MBP. The autolysosome then releases acidic hydrolase to degrade the inner content and the degraded cargo is released back to the cytoplasm to be reused for cellular processes.