Dual role of Atg1 in regulation of autophagy-specific PAS assembly in Saccharomyces cerevisiae.

Most autophagy-related (Atg) proteins are assembled at the phagophore assembly site or pre-autophagosomal structure (PAS), which is a potential site for vesicle formation during vegetative or starvation conditions. To understand the initial step of vesicle formation, it is important to know how Atg proteins are recruited to the PAS. Atg11 facilitates PAS assembly for the cytoplasm to vacuole targeting (Cvt) pathway in vegetative conditions. To examine autophagy-specific PAS formation, an ATG11 deletion mutant was used to eliminate the PAS formation that occurs in vegetative conditions. We found that Atg1, Atg13 and Atg17 play a similar role for PAS formation under autophagy-inducing conditions as seen for Atg11 during vegetative growth. In particular, Atg1 is proposed to have dual roles for autophagy-specific PAS recruitment. Atg1 plays a structural role for efficient recruitment of Atg proteins to the PAS, which is mediated by interaction with Atg13 and Atg17. In contrast, Atg1 kinase activity is needed for dissociation of Atg proteins from the PAS during autophagy inducing conditions, a function which is also critical for autophagy activity.