Nutritional control of cell growth via TOR signaling in budding yeast.

Cell growth is highly regulated and its deregulation is related to many human diseases such as cancer. Nutritional cues stimulate cell growth through modulation of TOR (target of rapamycin) signaling pathway. At the center of this pathway is a large serine/threonine protein kinase TOR, which forms two distinct functional complexes TORC1 and TORC2 in a cell. TORC1 senses the environmental nutrient quality/quantity and transmits the growth signals to multiple effectors to regulate a broad spectrum of biological processes including translation initiation, ribosome biogenesis, autophagy, nutrient uptake, and metabolism. By using budding yeast as a model, recent studies began to elucidate the complexity of the TOR signaling pathway.