title: The HOPS complex mediates autophagosome-lysosome fusion through interaction with syntaxin 17.
abstract: Membrane fusion is generally controlled by Rabs, soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), and tethering complexes. Syntaxin 17 (STX17) was recently identified as the autophagosomal SNARE required for autophagosome-lysosome fusion in mammals and Drosophila. In this study, to better understand the mechanism of autophagosome-lysosome fusion, we searched for STX17-interacting proteins. Immunoprecipitation and mass spectrometry analysis identified vacuolar protein sorting 33A (VPS33A) and VPS16, which are components of the homotypic fusion and protein sorting (HOPS)-tethering complex. We further confirmed that all HOPS components were coprecipitated with STX17. Knockdown of VPS33A, VPS16, or VPS39 blocked autophagic flux and caused accumulation of STX17- and microtubule-associated protein light chain (LC3)-positive autophagosomes. The endocytic pathway was also affected by knockdown of VPS33A, as previously reported, but not by knockdown of STX17. By contrast, ultraviolet irradiation resistance-associated gene (UVRAG), a known HOPS-interacting protein, did not interact with the STX17-HOPS complex and may not be directly involved in autophagosome-lysosome fusion. Collectively these results suggest that, in addition to its well-established function in the endocytic pathway, HOPS promotes autophagosome-lysosome fusion through interaction with STX17.
authors.affiliation: Department of Biochemistry and Molecular Biology, Graduate School, and Faculty of Medicine, University of Tokyo, Tokyo 113-0033, Japan Department of Physiology and Cell Biology, Tokyo Medical and Dental University, Tokyo 113-8519, Japan Research Center for Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo 113-8519, Japan Molecular Profiling Research Center for Drug Discovery, National Institute of Advanced Industrial Science and Technology, Tokyo 135-0064, Japan.
authors.forename: Peidu
authors.initials: P
authors.lastname: Jiang
authors.forename: Taki
authors.initials: T
authors.lastname: Nishimura
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Sakamaki
authors.forename: Eisuke
authors.initials: E
authors.lastname: Itakura
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Hatta
authors.forename: Tohru
authors.initials: T
authors.lastname: Natsume
authors.forename: Noboru
authors.initials: N
authors.lastname: Mizushima
mesh_terms: D000818:Animals; D000071183:Autophagy-Related Proteins; D002459:Cell Fusion; D049452:Green Fluorescent Proteins / Q000235:genetics; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics; D008247:Lysosomes / Q000276:immunology*; D008561:Membrane Fusion / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009842:Oligopeptides / Q000276:immunology; D010588:Phagosomes / Q000276:immunology*; D011485:Protein Binding; D050765:Qa-SNARE Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000071183:Autophagy-Related Proteins; D047908:Intracellular Signaling Peptides and Proteins; C480860:Map1lc3b protein, mouse; D008869:Microtubule-Associated Proteins; D009842:Oligopeptides; D050765:Qa-SNARE Proteins; D034741:RNA, Small Interfering; C551267:STX17 protein, human; D025521:Tumor Suppressor Proteins; C408122:UVRAG protein, human; C424439:VPS16 protein, human; C424440:VPS33A protein, human; C485791:VPS39 protein, human; D033921:Vesicular Transport Proteins; D049452:Green Fluorescent Proteins; C085706:FLAG peptide