Timing and location of Atg9 vesicle fusion during autophagosome formation

Atg23 protects Atg9 vesicles from inappropriate fusion during their movement through the cytoplasm.

• Atg9 vesicles are essential for autophagosome formation and originate from the Golgi/endosomes.
• These vesicles localize to the pre-autophagosomal structure upon induction of autophagy.
• Atg23 remains associated with Atg9 vesicles, preventing their fusion with other endomembranes while they are transported.
• Phosphorylation of Atg9 by Atg1 at the PAS leads to the dissociation of Atg23.
• This dissociation allows the recruitment of the lipid-transfer protein Atg2, facilitating autophagosome formation.

Simplified