Table 1.
Major key players in the maturation and degradation of autophagosomes
| Names | Functions | Refs |
|---|---|---|
| Small GTPase RAB7 | RAB7 is required for the fusion of autophagosomes and amphisomes (compartments resulting from the fusion of autophagosomes with endosomes) with lysosomes | 221,222 |
| Small GTPase RAB11 | RAB11 is required for the fusion of autophagosomes with multivesicular bodies | 223 |
| Small GTPase RAB33B | RAB33B is localized in the Golgi; it regulates autophagosome maturation by controlling their fusion with lysosomes | 224 |
| PIK3C3 complex; UVRAG | UVRAG in the PI3K complex interacts with beclin 1 to upregulate the maturation of autophagosomes | 225 |
| Rubicon | Rubicon interacts with UVRAG to downregulate the maturation of autophagosomes | 226, 227 |
| SNAREs: VAMP3, VAMP8 and VTI1B | VAMP3 controls the fusion of autophagosomes with multivesicular bodies; VAMP8 and VTI1B control the fusion of autophagosomes with lysosomes | 228–230 |
| Syntaxin 5 | Syntaxin 5 is required for the late stage of autophagy | 231 |
| ESCRTs | ESCRT proteins mediate the biogenesis of multivesicular bodies and the endocytic sorting of proteins; ESCRT-I, ESCRT-II and ESCRT-III are most likely to be involved in the fusion of autophagosomes with the endolysosomal system | 232–234 |
| DRAM | DRAM is a direct target of p53 and is located in the lysosomal membrane; it may regulate the late stage of autophagy | 235 |
| TFEB | TFEB controls the expression of genes involved in lysosomal biogenesis and in different steps of autophagy; its nuclear transport is controlled by mTORC1 | 213, 218 |
| Microtubules | Microtubules are cytoskeletal elements that are used by autophagosomes to move towards lysosomes | 236–241 |
| V-ATPase | V-ATPase is located in the membrane of acidic compartments; inhibition of V-ATPase by bafilomycin A1 blocks the maturation of autophagosomes; V-ATPase is involved in the amino acid signalling that activates mTORC1 | 219, 242, 243 |
| ATG22 | ATG22 is a permease in yeast that is required for the lysosomal efflux of amino acids | 244 |
| Spinster | Spinster is a putative lysosomal permease that is required for lysosomal reformation | 245 |
ATG22, autophagy-regulated protein 22; DRAM, damage-regulated autophagy modulator; ESCRT, endosomal sorting complex required for transport; mTORC1, mammalian target of rapamycin complex 1; p53, cellular tumour antigen p53; PI3K, phosphoinositide 3-kinase; SNARE, soluble NSF (N-ethylmaleimide-sensitive factor) attachment protein (SNAP) receptor; TFEB, transcription factor EB; UVRAG, UV irradiation resistance-associated gene; VAMP3, vesicle-associated membrane protein 3; V-ATPase, vacuolar ATPase; VTI1B, vesicle transport through interaction with t-SNARE homolog 1B.