In situ structural analysis reveals membrane shape transitions during autophagosome formation
Journal
Proceedings of the National Academy of Sciences
Journal Volume
119
Journal Issue
39
Pages
e2209823119
Date Issued
2022-09-19
Author(s)
Anna Bieber
Cristina Capitanio
Philipp S. Erdmann
Fabian Fiedler
Florian Beck
Delong Li
Gerhard Hummer
Brenda Schulman
Wolfgang Baumeister
Florian Wilfling
Abstract
Autophagosomes are unique organelles that form de novo as double-membrane vesicles engulfing cytosolic material for destruction. Their biogenesis involves membrane transformations of distinctly shaped intermediates whose ultrastructure is poorly understood. Here, we combine cell biology, correlative cryo-electron tomography (cryo-ET), and extensive data analysis to reveal the step-by-step structural progression of autophagosome biogenesis at high resolution directly within yeast cells. The analysis uncovers an unexpectedly thin intermembrane distance that is dilated at the phagophore rim. Mapping of individual autophagic structures onto a timeline based on geometric features reveals a dynamical change of membrane shape and curvature in growing phagophores. Moreover, our tomograms show the organelle interactome of growing autophagosomes, highlighting a polar organization of contact sites between the phagophore and organelles, such as the vacuole and the endoplasmic reticulum (ER). Collectively, these findings have important implications for the contribution of different membrane sources during autophagy and for the forces shaping and driving phagophores toward closure without a templating cargo.
Subjects
autophagosome biogenesis; autophagy; cryo-electron tomography; membrane structure; organelle contact sites
SDGs
Publisher
National Academy of Science.
Type
journal article