ATG2A-WDR45/WIPI4-ATG9A complex-mediated lipid transfer and equilibration during autophagosome formation.

Macroautophagy/autophagy is a highly conserved cellular process, spanning from yeast to humans, and plays a vital role in maintaining cellular homeostasis. Dysregulation of autophagy has been linked to a wide range of diseases. A hallmark of autophagy is the formation of double-membrane vesicles called autophagosomes. Autophagosome biogenesis requires a large number of phospholipids, with the endoplasmic reticulum (ER) being the main lipid source. The ATG2A-WDR45/WIPI4-ATG9A complex serves as the core machinery responsible for lipid transfer and equilibration during this process. In our recent study, we resolved the cryo-electron microscopy (cryo-EM) structures of the ATG2A-WDR45/WIPI4 and ATG2A-WDR45/WIPI4-ATG9A complexes, providing critical insights into their architecture and function. Additionally, molecular dynamics simulations were employed to investigate the mechanism by which ATG2A mediates lipid extraction from donor membranes. Our findings offer structural and mechanistic insights into the spatially coupled processes of lipid transfer and re-equilibration, which are essential for phagophore membrane expansion. ATG: autophagy related; ATG2A: autophagy related 2A; ATG2A[NR]: ATG2A N-terminal region; ATG9A: autophagy related 9A; cryo-EM: cryo-electron microscopy; cryo-ET: cryo-electron tomography; ER: endoplasmic reticulum; PtdIns3P: phosphatidylinositol-3-phosphate; Atg2[NR]: Atg2 N-terminal region; SUVs: small unilamellar vesicles; TGN: trans-Golgi network; TMEM41B: transmembrane protein 41B; VMP1: vacuole membrane protein 1; WDR45/WIPI4: WD repeat domain 45.