How to shape mitochondrial networks Mitochondria undergo fragmentation or fusion in response to changes in cellular metabolism. Toyama et al. report that adenosine monophosphate-activated protein kinase (AMPK) is both necessary and sufficient to control mitochondrial fragmentation. AMPK functions as a sensor to monitor the energy status of the cell by phosphorylating mitochondrial fission factor (MFF), a protein of the mitochondrial outer membrane. MFF then acts to recruit a cytoplasmic guanosine triphosphatase that promotes mitochondrial fission. Science , this issue p. 275

AMP-activated protein kinase mediates mitochondrial fission in response to energy stress