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bioRxiv · 10.1101/2023.07.08.548186

Structural basis for lipid transfer by the ATG2A-ATG9A complex

Wang, Y.·Dahmane, S.·Ti, R.·Mai, X.·Zhu, L.·Carlson, L.-A.·Stjepanovic, G.
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Abstract

Autophagy is characterized by the formation of double-membrane vesicles called autophagosomes. ATG2A and ATG9A play an essential role in autophagy by mediating lipid transfer and re-equilibration between membranes for autophagosome formation. Here we report the cryo-EM structures of human ATG2A-WIPI4 complex at 3.2 [A], and ATG2A-WIPI4-ATG9A complex at 7 [A] resolution. The ATG2A structure is characterized by a central hydrophobic cavity formed by a network of {beta}-strands that facilitates lipid transfer, and highly flexible N- and C-terminal domains. Molecular dynamics simulations of the ATG2A N-terminal domain revealed the mechanism of lipid-extraction from the donor membranes while the ATG2A-ATG9A complex structure provides insights into the later stages of the lipid transfer reaction. ATG9A-ATG2A structural analysis revealed a 1:1 stoichiometry, directly aligning the ATG9A lateral pore with ATG2A lipid transfer cavity, hence allowing for a direct transfer of lipids from ATG2A. The ATG9A trimer can interact with both N- and C-terminal tip of rod-shaped ATG2A. Cryo-electron tomography of ATG2A-liposome binding states shows that ATG2A tethers lipid vesicles at different orientations. In summary, this study provides a molecular basis for the growth of the phagophore membrane, and lends structural insights into spatially coupled lipid transport and re-equilibration during autophagosome formation.

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Wang, Y., Dahmane, S., Ti, R., Mai, X., Zhu, L., Carlson, L.-A., Stjepanovic, G.. 2023-07-08. Structural basis for lipid transfer by the ATG2A-ATG9A complex. https://doi.org/10.1101/2023.07.08.548186

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