TY - JOUR T1 - Insights into autophagosome biogenesis from structural and biochemical analyses of the ATG2AWIPI4 complex JF - bioRxiv DO - 10.1101/180315 SP - 180315 AU - Saikat Chowdhury AU - Chinatsu Otomo AU - Alexander Leitner AU - Kazuto Ohashi AU - Ruedi Aebersold AU - Gabriel C. Lander AU - Takanori Otomo Y1 - 2018/01/01 UR - http://biorxiv.org/content/early/2018/08/09/180315.abstract N2 - Autophagy is an enigmatic cellular process in which double-membrane compartments, called autophagosomes, form de novo adjacent to the endoplasmic reticulum (ER) and package cytoplasmic contents for delivery to lysosomes. Expansion of the precursor membrane phagophore requires autophagy-related 2 (ATG2), which localizes to the phosphatidylinositol-3-phosphate (PI3P)-enriched ER-phagophore junction. We combined single-particle electron microscopy, chemical cross-linking coupled with mass spectrometry, and biochemical analyses to characterize human ATG2A in complex with the PI3P effector WIPI4. ATG2A is a rod-shaped protein that can bridge neighboring vesicles through interactions at each of its tips. WIPI4 binds to one of the tips, enabling the ATG2A-WIPI4 complex to tether a PI3P-containing vesicle to another PI3P-free vesicle. These data suggest that the ATG2A-WIPI4 complex mediates ER-phagophore association and/or tethers vesicles to the ER-phagophore junction, establishing the required organization for phagophore expansion via the transfer of lipid membranes from the ER and/or the vesicles to the phagophore. ER -