Focus issue: metabolic signals.

This Focus Issue of Science Signaling complements the Science Special Issue on Metabolism (http://www.sciencemag.org/special/metabolism) by turning attention to the pathways and molecules involved in controlling cellular metabolic processes. Highlights include an unexpected role in triggering apoptosis for the insulin receptor and the related IGF-1 receptor (known for their roles in metabolism and growth), a role for lipids as cellular sensors of glucose metabolism, and a mechanism whereby cells can survive oxidative stress by shifting the activity of the cell's protein degradation complex.