title: GABARAPs regulate PI4P-dependent autophagosome:lysosome fusion.
abstract: The Atg8 autophagy proteins are essential for autophagosome biogenesis and maturation. The γ-aminobutyric acid receptor-associated protein (GABARAP) Atg8 family is much less understood than the LC3 Atg8 family, and the relationship between the GABARAPs' previously identified roles as modulators of transmembrane protein trafficking and autophagy is not known. Here we report that GABARAPs recruit palmitoylated PI4KIIα, a lipid kinase that generates phosphatidylinositol 4-phosphate (PI4P) and binds GABARAPs, from the perinuclear Golgi region to autophagosomes to generate PI4P in situ. Depletion of either GABARAP or PI4KIIα, or overexpression of a dominant-negative kinase-dead PI4KIIα mutant, decreases autophagy flux by blocking autophagsome:lysosome fusion, resulting in the accumulation of abnormally large autophagosomes. The autophagosome defects are rescued by overexpressing PI4KIIα or by restoring intracellular PI4P through "PI4P shuttling." Importantly, PI4KIIα's role in autophagy is distinct from that of PI4KIIIβ and is independent of subsequent phosphatidylinositol 4,5 biphosphate (PIP2) generation. Thus, GABARAPs recruit PI4KIIα to autophagosomes, and PI4P generation on autophagosomes is critically important for fusion with lysosomes. Our results establish that PI4KIIα and PI4P are essential effectors of the GABARAP interactome's fusion machinery.
authors.affiliation: Department of Physiology.
authors.forename: Hanzhi
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Physiology.
authors.forename: Hui-Qiao
authors.initials: HQ
authors.lastname: Sun
authors.affiliation: Department of Physiology.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Department of Physiology.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology.
authors.forename: Joseph
authors.initials: J
authors.lastname: Albanesi
authors.affiliation: Department of Internal Medicine, Center for Autophagy Research, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390 Beth.Levine@utsouthwestern.edu Helen.Yin@UTSouthwestern.edu.
authors.forename: Beth
authors.initials: B
authors.lastname: Levine
authors.affiliation: Department of Physiology, Beth.Levine@utsouthwestern.edu Helen.Yin@UTSouthwestern.edu.
authors.forename: Helen
authors.initials: H
authors.lastname: Yin
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D051017:Apoptosis Regulatory Proteins; D002459:Cell Fusion; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D008247:Lysosomes / Q000378:metabolism*; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D015778:Minor Histocompatibility Antigens; D010588:Phagosomes / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; C116741:GABARAP protein, human; D008869:Microtubule-Associated Proteins; D015778:Minor Histocompatibility Antigens; D018129:Phosphatidylinositol Phosphates; D034741:RNA, Small Interfering; C037178:phosphatidylinositol 4-phosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C402182:phosphatidylinositol phosphate 4-kinase
keywords: GABARAP; PI4KIIα; PI4P; autophagosome:lysosome fusion; autophagy