title: ATG14 promotes membrane tethering and fusion of autophagosomes to endolysosomes.
abstract: Autophagy, an important catabolic pathway implicated in a broad spectrum of human diseases, begins by forming double membrane autophagosomes that engulf cytosolic cargo and ends by fusing autophagosomes with lysosomes for degradation. Membrane fusion activity is required for early biogenesis of autophagosomes and late degradation in lysosomes. However, the key regulatory mechanisms of autophagic membrane tethering and fusion remain largely unknown. Here we report that ATG14 (also known as beclin-1-associated autophagy-related key regulator (Barkor) or ATG14L), an essential autophagy-specific regulator of the class III phosphatidylinositol 3-kinase complex, promotes membrane tethering of protein-free liposomes, and enhances hemifusion and full fusion of proteoliposomes reconstituted with the target (t)-SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) syntaxin 17 (STX17) and SNAP29, and the vesicle (v)-SNARE VAMP8 (vesicle-associated membrane protein 8). ATG14 binds to the SNARE core domain of STX17 through its coiled-coil domain, and stabilizes the STX17-SNAP29 binary t-SNARE complex on autophagosomes. The STX17 binding, membrane tethering and fusion-enhancing activities of ATG14 require its homo-oligomerization by cysteine repeats. In ATG14 homo-oligomerization-defective cells, autophagosomes still efficiently form but their fusion with endolysosomes is blocked. Recombinant ATG14 homo-oligomerization mutants also completely lose their ability to promote membrane tethering and to enhance SNARE-mediated fusion in vitro. Taken together, our data suggest an autophagy-specific membrane fusion mechanism in which oligomeric ATG14 directly binds to STX17-SNAP29 binary t-SNARE complex on autophagosomes and primes it for VAMP8 interaction to promote autophagosome-endolysosome fusion.
authors: 1] Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305, USA [2] Department of Structural Biology, Stanford University, Stanford, California 94305, USA [3] Department of Photon Science, Stanford University, Stanford, California 94305, USA [4] Department of Neurology and Neurological Sciences, Stanford University, Stanford, California 94305, USA [5] Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA.
authors: Jiajie
authors: J
authors: Diao
authors: 1] Center for Autophagy Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA [2] Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA [3] College of Food Science &Nutritional Engineering, China Agricultural University, Beijing 100083, China.
authors: Rong
authors: R
authors: Liu
authors: 1] Center for Autophagy Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA [2] Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
authors: Yueguang
authors: Y
authors: Rong
authors: 1] Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305, USA [2] Department of Structural Biology, Stanford University, Stanford, California 94305, USA [3] Department of Photon Science, Stanford University, Stanford, California 94305, USA [4] Department of Neurology and Neurological Sciences, Stanford University, Stanford, California 94305, USA [5] Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA.
authors: Minglei
authors: M
authors: Zhao
authors: 1] Center for Autophagy Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA [2] Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
authors: Jing
authors: J
authors: Zhang
authors: 1] Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305, USA [2] Department of Structural Biology, Stanford University, Stanford, California 94305, USA [3] Department of Photon Science, Stanford University, Stanford, California 94305, USA [4] Department of Neurology and Neurological Sciences, Stanford University, Stanford, California 94305, USA [5] Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA.
authors: Ying
authors: Y
authors: Lai
authors: 1] Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305, USA [2] Department of Structural Biology, Stanford University, Stanford, California 94305, USA [3] Department of Photon Science, Stanford University, Stanford, California 94305, USA [4] Department of Neurology and Neurological Sciences, Stanford University, Stanford, California 94305, USA [5] Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA.
authors: Qiangjun
authors: Q
authors: Zhou
authors: Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA.
authors: Livia M
authors: LM
authors: Wilz
authors: Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA.
authors: Jianxu
authors: J
authors: Li
authors: 1] Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305, USA [2] Department of Structural Biology, Stanford University, Stanford, California 94305, USA [3] Department of Photon Science, Stanford University, Stanford, California 94305, USA [4] Department of Neurology and Neurological Sciences, Stanford University, Stanford, California 94305, USA [5] Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA.
authors: Sandro
authors: S
authors: Vivona
authors: 1] Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305, USA [2] Department of Structural Biology, Stanford University, Stanford, California 94305, USA [3] Department of Photon Science, Stanford University, Stanford, California 94305, USA [4] Department of Neurology and Neurological Sciences, Stanford University, Stanford, California 94305, USA [5] Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA.
authors: Richard A
authors: RA
authors: Pfuetzner
authors: 1] Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305, USA [2] Department of Structural Biology, Stanford University, Stanford, California 94305, USA [3] Department of Photon Science, Stanford University, Stanford, California 94305, USA [4] Department of Neurology and Neurological Sciences, Stanford University, Stanford, California 94305, USA [5] Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA.
authors: Axel T
authors: AT
authors: Brunger
authors: 1] Center for Autophagy Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA [2] Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
authors: Qing
authors: Q
authors: Zhong
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000737:chemistry* / Q000378:metabolism*; D001343:Autophagy; D000071183:Autophagy-Related Proteins; D011992:Endosomes / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008247:Lysosomes / Q000378:metabolism*; D008561:Membrane Fusion; D010588:Phagosomes / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D050765:Qa-SNARE Proteins / Q000378:metabolism; D050766:Qb-SNARE Proteins / Q000378:metabolism; D050767:Qc-SNARE Proteins / Q000378:metabolism; D050683:R-SNARE Proteins / Q000378:metabolism; D050600:SNARE Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: C539000:ATG14 protein, human; D033942:Adaptor Proteins, Vesicular Transport; D000071183:Autophagy-Related Proteins; D050765:Qa-SNARE Proteins; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; D050683:R-SNARE Proteins; C432420:SNAP29 protein, human; D050600:SNARE Proteins; C551267:STX17 protein, human; C112938:VAMP8 protein, human