title: Impairment of autophagosome-lysosome fusion in the buff mutant mice with the VPS33A(D251E) mutation.
abstract: The HOPS (homotypic fusion and protein sorting) complex functions in endocytic and autophagic pathways in both lower eukaryotes and mammalian cells through its involvement in fusion events between endosomes and lysosomes or autophagosomes and lysosomes. However, the differential molecular mechanisms underlying these fusion processes are largely unknown. Buff (bf) is a mouse mutant that carries an Asp251-to-Glu point mutation (D251E) in the VPS33A protein, a tethering protein and a core subunit of the HOPS complex. Bf mice showed impaired spontaneous locomotor activity, motor learning, and autophagic activity. Although the gross anatomy of the brain was apparently normal, the number of Purkinje cells was significantly reduced. Furthermore, we found that fusion between autophagosomes and lysosomes was defective in bf cells without compromising the endocytic pathway. The direct association of mutant VPS33A(D251E) with the autophagic SNARE complex, STX17 (syntaxin 17)-VAMP8-SNAP29, was enhanced. In addition, the VPS33A(D251E) mutation enhanced interactions with other HOPS subunits, namely VPS41, VPS39, VPS18, and VPS11, except for VPS16. Reduction of the interactions between VPS33A(Y440D) and several other HOPS subunits led to decreased association with STX17. These results suggest that the VPS33A(D251E) mutation plays dual roles by increasing the HOPS complex assembly and its association with the autophagic SNARE complex, which selectively affects the autophagosome-lysosome fusion that impairs basal autophagic activity and induces Purkinje cell loss.
authors.affiliation: a State Key Laboratory of Molecular Developmental Biology; Institute of Genetics & Developmental Biology; Chinese Academy of Sciences ; Beijing , China.|b University of Chinese Academy of Sciences ; Beijing , China.
authors.forename: Yuanli
authors.initials: Y
authors.lastname: Zhen
authors.affiliation: a State Key Laboratory of Molecular Developmental Biology; Institute of Genetics & Developmental Biology; Chinese Academy of Sciences ; Beijing , China.|c Center of Alzheimer Disease; Beijing Institute for Brain Disorders ; Beijing China.|d Beijing Children's Hospital; Capital Medical University ; Beijing , China.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
mesh_terms: D000818:Animals; D001343:Autophagy; D004705:Endocytosis; D005347:Fibroblasts / Q000378:metabolism / Q000648:ultrastructure; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008247:Lysosomes / Q000378:metabolism*; D008561:Membrane Fusion; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D009043:Motor Activity; D050505:Mutant Proteins / Q000378:metabolism; D010588:Phagosomes / Q000378:metabolism*; D017354:Point Mutation / Q000235:genetics*; D011485:Protein Binding; D055550:Protein Stability; D021122:Protein Subunits / Q000378:metabolism; D011689:Purkinje Cells / Q000378:metabolism / Q000473:pathology; D050600:SNARE Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D050505:Mutant Proteins; D021122:Protein Subunits; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins; C472129:Vps33a protein, mouse
keywords: HOPS complex; Hermansky-Pudlak syndrome; Purkinje cell loss; VPS33A; autophagic SNARE complex; autophagy