Fig. 8.

Vac8 confines autophagosome formation between the vacuole and the ER by tethering the PAS to the vacuole. Vac8 tethers the early PAS to the vacuole via interaction with Atg13. Maturation of the PAS by recruitment of downstream Atg factors, including Atg2, results in establishment of an ER–PAS–vacuole connection. Consequently, autophagosome formation takes place in a confined space between the ER and the vacuole. This allows autophagosome formation to be spatially coordinated with autophagosome–vacuole fusion. In a VAC8 deletion mutant, the connection between PAS and vacuole is lost and the site of autophagosome formation remains only at the ER. As a consequence, PAS initiation is decreased, autophagosomes form with a reduced size and are ultimately released into the cytosol, which makes the autophagosome–vacuole fusion process inefficient.