Nutrient signals driving cell growth.

Regulation of cell growth in response to nutrients is crucial for the survival of all organisms. In yeast, cell growth and division require two signaling pathways, TORC1 and PKA. Activation of these pathways crucially depends on intracellular metabolic signals, but the mechanisms remain elusive. Recent studies have identified potential activators of TORC1 and have highlighted a crucial role for the endomembrane system. Moreover, calcium was recognized as an important second messenger for TORC1 activation in response to amino acid levels. On the contrary, genetic analysis indicates that PKA activation depends on an intracellular glucose metabolite. Together with novel quantitative approaches, these findings provide important groundwork in our understanding of the molecular mechanisms for nutrient sensing in yeast and humans.