title: Autophagosome-lysosome fusion is independent of V-ATPase-mediated acidification.
abstract: The ATP-dependent proton pump V-ATPase ensures low intralysosomal pH, which is essential for lysosomal hydrolase activity. Based on studies with the V-ATPase inhibitor BafilomycinA1, lysosomal acidification is also thought to be required for fusion with incoming vesicles from the autophagic and endocytic pathways. Here we show that loss of V-ATPase subunits in the Drosophila fat body causes an accumulation of non-functional lysosomes, leading to a block in autophagic flux. However, V-ATPase-deficient lysosomes remain competent to fuse with autophagosomes and endosomes, resulting in a time-dependent formation of giant autolysosomes. In contrast, BafilomycinA1 prevents autophagosome-lysosome fusion in these cells, and this defect is phenocopied by depletion of the Ca(2+) pump SERCA, a secondary target of this drug. Moreover, activation of SERCA promotes fusion in a BafilomycinA1-sensitive manner. Collectively, our results indicate that lysosomal acidification is not a prerequisite for fusion, and that BafilomycinA1 inhibits fusion independent of its effect on lysosomal pH.
authors.affiliation: Department of Genetics, Cell Biology and Development, University of Minnesota, 6-160 Jackson Hall, 321 Church Street SE, Minneapolis, Minnesota 55455, USA.
authors.forename: Caroline
authors.identifier: 0000000342207272
authors.initials: C
authors.lastname: Mauvezin
authors.affiliation: Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Pazmany s. 1/C. 6.520, Budapest H-1117, Hungary.
authors.forename: Péter
authors.initials: P
authors.lastname: Nagy
authors.affiliation: Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Pazmany s. 1/C. 6.520, Budapest H-1117, Hungary.
authors.forename: Gábor
authors.initials: G
authors.lastname: Juhász
authors.affiliation: Department of Genetics, Cell Biology and Development, University of Minnesota, 6-160 Jackson Hall, 321 Church Street SE, Minneapolis, Minnesota 55455, USA.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Neufeld
mesh_terms: D000143:Acids / Q000378:metabolism*; D000818:Animals; D001343:Autophagy / Q000187:drug effects; D004331:Drosophila melanogaster / Q000187:drug effects / Q000201:enzymology*; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D018942:Macrolides / Q000494:pharmacology; D008561:Membrane Fusion / Q000187:drug effects; D008954:Models, Biological; D010588:Phagosomes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D021122:Protein Subunits / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism*
chemical_list: D000143:Acids; D018942:Macrolides; D021122:Protein Subunits; C040929:bafilomycin A1; D025262:Vacuolar Proton-Translocating ATPases; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases