title: CapZ regulates autophagosomal membrane shaping by promoting actin assembly inside the isolation membrane.
abstract: A fundamental question regarding autophagosome formation is how the shape of the double-membrane autophagosomal vesicle is generated. Here we show that in mammalian cells assembly of an actin scaffold inside the isolation membrane (the autophagosomal precursor) is essential for autophagosomal membrane shaping. Actin filaments are depolymerized shortly after starvation and actin is assembled into a network within the isolation membrane. When formation of actin puncta is disrupted by an actin polymerization inhibitor or by knocking down the actin-capping protein CapZβ, isolation membranes and omegasomes collapse into mixed-membrane bundles. Formation of actin puncta is PtdIns(3)P dependent, and inhibition of PtdIns(3)P formation by treating cells with the PI(3)K inhibitor 3-MA, or by knocking down Beclin-1, abolishes the formation of actin puncta. Binding of CapZ to PtdIns(3)P, which is enriched in omegasomes, stimulates actin polymerization. Our findings illuminate the mechanism underlying autophagosomal membrane shaping and provide key insights into how autophagosomes are formed.
authors.affiliation: The State Key Laboratory of Membrane Biology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Na
authors.initials: N
authors.lastname: Mi
authors.affiliation: The State Key Laboratory of Membrane Biology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Center for Structural Biology, Tsinghua University, Beijing 100084, China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Wang
authors.affiliation: Center for Structural Biology, Tsinghua University, Beijing 100084, China.
authors.forename: Mengran
authors.initials: M
authors.lastname: Chen
authors.affiliation: The State Key Laboratory of Membrane Biology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Mingkun
authors.initials: M
authors.lastname: Zhao
authors.affiliation: The State Key Laboratory of Membrane Biology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Guang
authors.initials: G
authors.lastname: Yang
authors.affiliation: The State Key Laboratory of Membrane Biology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Meisheng
authors.initials: M
authors.lastname: Ma
authors.affiliation: The State Key Laboratory of Membrane Biology, Biodynamic Optical Imaging Center, School of Life Sciences, Peking University, Beijing 100871, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Su
authors.affiliation: The State Key Laboratory of Membrane Biology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Sai
authors.initials: S
authors.lastname: Luo
authors.affiliation: The State Key Laboratory of Membrane Biology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Jingwen
authors.initials: J
authors.lastname: Shi
authors.affiliation: The State Key Laboratory of Membrane Biology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Xu
authors.affiliation: Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Guo
authors.affiliation: Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Gao
authors.affiliation: The State Key Laboratory of Membrane Biology, Biodynamic Optical Imaging Center, School of Life Sciences, Peking University, Beijing 100871, China.
authors.forename: Yujie
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Center for Structural Biology, Tsinghua University, Beijing 100084, China.
authors.forename: Zhucheng
authors.initials: Z
authors.lastname: Chen
authors.affiliation: The State Key Laboratory of Membrane Biology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Li
authors.initials: L
authors.lastname: Yu
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D001343:Autophagy; D051347:CapZ Actin Capping Protein / Q000502:physiology*; D002478:Cells, Cultured; D007425:Intracellular Membranes / Q000378:metabolism* / Q000648:ultrastructure; D010588:Phagosomes / Q000378:metabolism* / Q000648:ultrastructure; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D011485:Protein Binding; D055503:Protein Multimerization; D021381:Protein Transport; D051381:Rats
chemical_list: D051347:CapZ Actin Capping Protein; D018129:Phosphatidylinositol Phosphates; C060974:phosphatidylinositol 3,4,5-triphosphate