Table 2.

Induction factors, important autophagy-related proteins, and their relevance to different stages of autophagy in mammalian cells [73,87,89,91,92,93,94].

Induction Factors	Autophagy Stages	Complex	Core Proteins of the Complex
Intrinsic cellular stress: Reactive oxygen species (ROS), damaged organelles, protein aggregates, infected pathogens, AMP/ATP, endoplasmic reticulum stress and hypoxia, etc.	Induction of autophagy	mTORC1 complex	AMPK mTOR, RAPTOR, mLST8, PRAS40, DEPTOR, CASTOR1, SLC38A9, GATOR1
	Nucleation and expansion of phagophore, Formation of autophagosomes	ULK1-FIP200-ATG13complex Beclin-1-VPS15-VPS34-ATG14 l complex	ULK1, ULK2, ATG13, ATG101, FIP200 ATG9, VPS34, VPS15, BECN1, ATG14L, AMBRA, ATG5, ATG12, ATG16
Extrinsic cellular stress: Nutrients (amino acids, glucose, and oxygen), growth factors and drugs, etc.	Fusion of autophagosome-lysosome fusion	Lipidation complex	WIPI1/2, LC3, ATG3, ATG4, ATG7, ATG12, ATG16L, GABARAP
	Degradation of autophagic substrates		syntaxin-17, SNARE, VAMP8, SNAP29, RAB7, EPG5, HOPS, PLEKHM1