Introduction
Most organisms have evolved mechanisms for efficiently transitioning between anabolic and catabolic states, allowing them to survive and grow in environments in which nutrient availability is variable. In mammals, an example of such a mechanism is the signaling network anchored by the protein kinase mTOR (originally ‘mammalian TOR’, but now officially ‘mechanistic TOR’). This pathway, which responds to diverse environmental cues, controls many processes that generate or use large amounts of energy and nutrients. It is increasingly apparent that mTOR signaling impacts most major cellular functions, giving it an outsized role in regulating basic cell behaviors like growth (mass accumulation) and proliferation. Because mTOR deregulation occurs in human disease, including cancer, obesity, type 2 diabetes, and neurodegeneration, there are significant ongoing efforts to pharmacologically target the pathway. Here, we review our current understanding of the mTOR pathway and its role in health and disease, as well as discuss pharmacological approaches for modulating mTOR activity.