Table 1.

Classification of autophagy from the view of inducers and substrates.

	Bulk autophagy (non-specific degradation)	Selective autophagy (specific degradation)
Constitutive autophagy (maintain homeostasis)	Cellular metabolism Replace old proteins/organelles with new ones	Cell protection Degrade unfavorable, damaged proteins, and organelles
Inducible autophagy (response to various stimuli)	Nutrient supply Starvation-induced Rapamycin-activated	Cellular adaptation Cellular stress (DNA damage, etc.) Differentiation