title: Phosphatidylinositol 3-kinase and COPII generate LC3 lipidation vesicles from the ER-Golgi intermediate compartment.
abstract: Formation of the autophagosome requires significant membrane input from cellular organelles. However, no direct evidence has been developed to link autophagic factors and the mobilization of membranes to generate the phagophore. Previously, we established a cell-free LC3 lipidation reaction to identify the ER-Golgi intermediate compartment (ERGIC) as a membrane source for LC3 lipidation, a key step of autophagosome biogenesis (Ge et al., eLife 2013; 2:e00947). We now report that starvation activation of autophagic phosphotidylinositol-3 kinase (PI3K) induces the generation of small vesicles active in LC3 lipidation. Subcellular fractionation studies identified the ERGIC as the donor membrane in the generation of small lipidation-active vesicles. COPII proteins are recruited to the ERGIC membrane in starved cells, dependent on active PI3K. We conclude that starvation activates the autophagic PI3K, which in turn induces the recruitment of COPII to the ERGIC to bud LC3 lipidation-active vesicles as one potential membrane source of the autophagosome.
authors.affiliation: Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States.
authors.forename: Liang
authors.initials: L
authors.lastname: Ge
authors.affiliation: Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States.
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States.
authors.forename: Randy
authors.initials: R
authors.lastname: Schekman
mesh_terms: D000818:Animals; D022181:COP-Coated Vesicles / Q000378:metabolism*; D002451:Cell Compartmentation; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008055:Lipids / Q000737:chemistry*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism*; D022142:Secretory Vesicles / Q000378:metabolism*
chemical_list: D008055:Lipids; C480860:Map1lc3b protein, mouse; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D058539:Phosphatidylinositol 3-Kinase
keywords: COPII; ER-Golgi intermediate compartment; LC3 lipidation; Phosphatidylinositol 3-kinase; autophagosome; autophagy; biochemistry; cell biology; human; mouse