Fig. 1.

Autophagosome formation in yeast. A membrane precursor enwraps cargo material (not shown) by elongating into a closed double membrane vesicle, which finally fuses with the vacuole. The process of autophagosome formation is tightly regulated by an orchestrated Atg machinery (different blue/green shades) including the Atg1 kinase complex (composed of Atg1, Atg13, Atg17, Atg29, Atg31), Atg9 vesicles, the core PIK3C3-CI (composed of Vps34, Vps15, Vps30, Atg14), the Atg2-Atg18 module, and the Atg8 conjugation system including Atg4 (CS), which promotes Atg8 lipidation to PE. Some early Atg members also play a role during late autophagy steps such as the Atg8 conjugation system in autophagosome closure. This scission step is also facilitated by the ESCRT machinery (turquoise). Autophagosome-vacuole fusion is promoted by the SNARE proteins (light purple) Ykt6, Vti1, Vam7 and Vam3, the tethering complex HOPS (purple), and the Rab GTPase Ypt7 (dark purple). Lipidated Atg8 (green) is implicated in various steps throughout autophagosome biogenesis.