PerspectiveCell Biology

Why Starving Cells Eat Themselves

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Science  28 Jan 2011:
Vol. 331, Issue 6016, pp. 410-411
DOI: 10.1126/science.1201691

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In the 1950s, electron microscopists observed regions of cytoplasm and organelles being engulfed by a double membrane to form vesicles that then fused with lysosomes (1). This process, called autophagy (“self-eating”), was correctly deduced to be a mechanism to degrade and recycle the contents of nutrient-starved cells (2). Since then, signaling pathways that sense nutrient deprivation and energy stress have been identified, but how these interact with autophagy has not been clear. On page 456 in this issue, Egan et al. (3) show that the adenosine monophosphate–activated protein kinase (AMPK), an energy sensor that is also activated by glucose starvation, triggers autophagy by phosphorylating ULK1, establishing a direct molecular link between the two processes.