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. 2021 Apr 20;53(4):548–559. doi: 10.1038/s12276-021-00611-0

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© The Author(s) 2021

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

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Fig. 1 — a When autophagy is induced by various stress factors, the Unc-51-like autophagy activating kinase (ULK) complex is activated and initiates autophagy. b Activated ULK triggers phosphatidylinositol 3-kinase complex III (VPS34) to form the phagophore at omegasomes. c The phagophore is elongated by two ubiquitin-like conjugation systems to form an autophagosome. The first system involves conjugation of autophagy-related protein (ATG)12 to ATG5 in a reaction that requires the E1-like enzyme ATG7 and E2-like enzyme ATG10. The second system involves the conjugation of C-type lectin 3 (LC3) to phosphatidylethanolamine (PE). d The mature autophagosome or amphisome binds a lysosome, and the autophagic cargo is degraded by acidic hydrolases in the lysosome and is recycled in the cell as nutrients.