PIPing on lysosome tubes.

The role of lysosomes in important cellular responses, including phagocytosis, cell surface repair, and autophagy underlies a number of human diseases. Furthermore, the role of the lysosomal surface in TORC1 signalling has revealed unexpected properties of these organelles. In this issue, Sridhar et al (2013) uncover an important role for PI(4)P for lysosome function under normal nutrient conditions and after prolonged nutrient deprivation. Ana Maria Cuervo, the late Dennis Shields, and colleagues (Sridhar et al, 2013) conclude that PI4 kinase IIIb on the surface of the lysosome controls the fidelity of sorting from the lysosome, and is required for autophagic lysosome reformation (ALR). These novel findings provide important insights into the complexities of the lipid composition of the lysosome, and how these lipids may control lysosome function. Lysosomes, traditionally thought of as inert, terminal endocytic compartments, are in fact dynamic organelles. In addition to their function in degradation of cargo ranging from small vesicles to whole phagosomes and autophago-