[HTML][HTML] Autophagosome–lysosome fusion is independent of V-ATPase-mediated acidification

C Mauvezin, P Nagy, G Juhász, TP Neufeld - Nature communications, 2015 - nature.com
Nature communications, 2015nature.com
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 …
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 Ca2+ 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.
nature.com