Target of Rapamycin (TOR)Regulates Growth inResponse to Nutritional Signals

摘要

All organisms can respond to the availability ofnutrients by regulating their metabolism, growth, and celldivision. Central to the regulation of growth in response tonutrient availability is the target of rapamycin (TOR) signalingthat is composed of two structurally distinct complexes:TOR complex 1 (TORC1) and TOR complex 2 (TORC2).The TOR genes were first identified in yeast as target ofrapamycin, a natural product of a soil bacterium,which proved beneficial as an immunosuppressive andanticancer drug and is currently being tested for a handfulof other pathological conditions including diabetes,neurodegeneration, and age-related diseases. Studies of theTOR pathway unraveled a complex growth-regulating network.TOR regulates nutrient uptake, transcription, protein synthesisand degradation, as well as metabolic pathways, in a coordinatedmanner that ensures that cells grow or cease growth in responseto nutrient availability. The identification of specific signalsand mechanisms that stimulate TOR signaling is an active andexciting field of research that has already identified nitrogen andamino acids as key regulators of TORC1 activity. The signals,as well as the cellular functions of TORC2, are far less wellunderstood. Additional open questions in the field concern therelationships between TORC1 and TORC2, as well as the linkswith other nutrient-responsive pathways. Here I review the mainfeatures of TORC1 and TORC2, with a particular focus on yeastsas model organisms.