mTOR Signaling

The scarcity of nutrients/energy interspersed with sporadic periods of abundance means that cells must transition between anabolic and catabolic states. An important protein that has evolved to respond to this need is the target of rapamycin (TOR). TOR is a well-conserved serine/ threonine kinase that plays an important role in the signaling network that controls growth and metabolism in response to environmental cues. As its name indicates, TOR is the target of a molecule named rapamycin, an anti-fungal macrolide produced by the bacterial species Streptomyces hygroscopicus, which was isolated from a soil sample from the Eastern Islands in the 1970s (Vezina et al. 1975). In addition to its anti-fungal properties, rapamycin strongly inhibits cell growth and proliferation, making this molecule a valuable tool to study cell growth control. In the early 1990s, yeast genetic screens led to the identification of