An Atg9 vesicle serves as a platform for the recruitment of the autophagic machinery. It thereby forms a seed for the formation of an autophagosome around the cargo by accepting lipids that are transferred by the Atg2 protein from the neighbouring endoplasmic reticulum (ER). (c) Verena Baumann, Max Perutz Labs
Autophagy, from the Greek for ‘self-eating’, is an essential process that isolates and recycles cellular components under conditions of stress or when resources are limited. Cargoes such as misfolded proteins or damaged organelles are captured in a double membrane-bound compartment called the autophagosome and targeted for degradation. A fundamental question concerns precisely how these “garbage bags” form in the cell. Scientists led by Sascha Martens from the Max Perutz Labs, a joint venture of the University of Vienna and the Medical University of Vienna, have now reconstructed the first steps in the formation of autophagosomes. They show that tiny vesicles loaded with the protein Atg9 act as the seed from which the autophagosome emerges. The study is published in Science.