Adenosine triphosphate (ATP) is not only the most important energy carrier inside the cell, but also a universal extracellular signaling molecule. Astrocytes, the most abundant glial cell type in the brain, have been found to release signaling molecules, including ATP, which mediates inter-astrocytic as well as neuronal-astrocytic interactions. Unlike in neurons and secretory cells, however, the mechanisms of ATP release in glial cells are unknown. Dr Shumin Duan and graduate students Zhijun Zhang, Gang Chen, and Wei Zhou from the Laboratory of Synapse Development and Plasticity found that lysosomes in astrocytes contains abundant ATP and exhibit different modes of exocytosis in response to physiological and pathological stimulations. Lysosomes have been regarded as “digestion organelles” of the cell for degrading “waste proteins”. This present finding indicates that regulated lysosomal exocytosis of ATP from astrocytes may have important physiological functions. This work was published online on July 8 in Nature Cell Biology.