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A PI3K-WIPI2 positive feedback loop allosterically activates LC3 lipidation in autophagy.

Authors
  • Fracchiolla, Dorotea1
  • Chang, Chunmei2
  • Hurley, James H2
  • Martens, Sascha1
  • 1 Department of Biochemistry and Cell Biology, Vienna BioCenter, Vienna, Austria. , (Austria)
  • 2 Department of Molecular and Cell Biology, California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA.
Type
Published Article
Journal
The Journal of Cell Biology
Publisher
The Rockefeller University Press
Publication Date
Jul 06, 2020
Volume
219
Issue
7
Identifiers
DOI: 10.1083/jcb.201912098
PMID: 32437499
Source
Medline
Language
English
License
Unknown

Abstract

Autophagy degrades cytoplasmic cargo by its delivery to lysosomes within double membrane autophagosomes. Synthesis of the phosphoinositide PI(3)P by the autophagic class III phosphatidylinositol-3 kinase complex I (PI3KC3-C1) and conjugation of ATG8/LC3 proteins to phagophore membranes by the ATG12-ATG5-ATG16L1 (E3) complex are two critical steps in autophagosome biogenesis, connected by WIPI2. Here, we present a complete reconstitution of these events. On giant unilamellar vesicles (GUVs), LC3 lipidation is strictly dependent on the recruitment of WIPI2 that in turn depends on PI(3)P. Ectopically targeting E3 to membranes in the absence of WIPI2 is insufficient to support LC3 lipidation, demonstrating that WIPI2 allosterically activates the E3 complex. PI3KC3-C1 and WIPI2 mutually promote the recruitment of each other in a positive feedback loop. When both PI 3-kinase and LC3 lipidation reactions were performed simultaneously, positive feedback between PI3KC3-C1 and WIPI2 led to rapid LC3 lipidation with kinetics similar to that seen in cellular autophagosome formation. © 2020 Fracchiolla et al.

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