VAMP8 phosphorylation regulates lysosome dynamics during autophagy.

In the final critical step for autophagic degradation, lysosomes fuse with autophagosomes to form autolysosomes. Although recent research has suggested that soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins are important for lysosome-autophagosome fusion, neither the architecture of the prefusion state nor the regulatory mechanisms have been identified. In our study, using structured illumination microscopy, we observed that lysosomes formed clusters around individual autophagosomes, thereby setting the stage for membrane fusion. Moreover, VAMP8 (vesicle-associated membrane protein 8) assists in forming the prefusion state of these clusters. We also found that VAMP8 phosphorylation reduces spontaneous lysosome-autophagosome fusion, whereas its dephosphorylation promotes fusion events between lysosomes and autophagosomes in both normal and autophagy-induced conditions. Our data thus suggest a key role of VAMP8 phosphorylation in the regulation of lysosome-autophagosome fusion.