Who plays the ferryman: ATG2 channels lipids into the forming autophagosome

Abstract

Expansion of the autophagosomal membrane requires a mechanism to supply lipids while excluding most membrane proteins. In this issue, Valverde et al. (2019. J. Cell Biol. https://doi.org/10.1083/jcb.201811139) identify ATG2, a member of the autophagy-related protein family, as a lipid transfer protein and provide important novel insights on how autophagosomes grow.

Figure 1.

ATG2 bridges the forming autophagosome with the ER. (A) Superresolution imaging of starvation-induced ATG13 pre-autophagosomal structures in association with ER strands. Two examples are shown. Bars, 5 µM. (B) Drawing showing an isolation membrane (IM) forming within an omegasome intermediate, both connected to the ER via ATG2. In this drawing, ATG2 is tethered to the omegasome via WIPI2, and it transports lipid molecules from the ER to the expanding autophagosome.