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. 2023 May 5;13:1150492. doi: 10.3389/fonc.2023.1150492

Figure 2.

Figure 2

Autophagy pathway is performed in five steps from initiation to fusion with lysosome. In mammalian cells, the initiation phase of autophagy consists of autophagosome formation, which is significantly dependent on the stable complex known as ULK1-Atg13-FIP200-Atg101. The activation of the ULK1 kinase launches the activity of Beclin1 (BECN1)–VPS34 complex including BECN1, VPS34, and Beclin1 regulator 1 (AMBRA-1). In the elongation phase, the WIPI2B scaffold binds to PI3P. The mentioned complex is highly essential for employing two main proteins, ATG7 and ATG10, that can couple ATG5 to ATG12, which makes a complex with ATG16L. The Atg12–Atg5–Atg16 complex positions on the outer membrane due to ATG 5 available binding sites. The next step is the fusion of autophagosome–lysosome and includes two main phases. First, the autophagosome migration to lysosomes, which is implemented by the cytoskeleton in eukaryotic cells by Rab7 and guanosine triphosphate (GTP)-binding protein to microtubules, and second, the fusion of lysosomes, with a single bilayer membrane, and mature autophagosomes, with two lipid bilayer membranes. The last step is degradation of all components in the lysosome. The lysosomal enzymes degrade autophagic cargo.