Ramping up the autophagy-lysosome system to cope with osmotic stress.

Osmotic stress is a critical challenge for mammalian cells as loss of water triggered by a hyperosmotic environment promotes harmful protein aggregation and impairs cell survival. How the degradative capacity of cells, in particular the macroautophagy/autophagy-lysosome system, is adapted to meet the proteolytic demands induced by osmotic challenge remains poorly understood. We have identified a hitherto unknown pathway that is activated by hyperosmotic stress and serves to link alterations in cellular ion homeostasis to the induction of autophagy and lysosomal gene expression and, thereby, to lysosome biogenesis.