mTOR activity is regulated by various upstream signals, including growth factors, nutrients, energy status, and stress conditions. The PI3K/AKT pathway is a significant regulator, where AKT activation leads to the inhibition of the TSC1/2 complex, thus activating mTORC1. Amino acids activate mTORC1 through the Rag GTPases, while energy status is sensed through AMP-activated protein kinase (AMPK), which inhibits mTORC1 under low energy conditions.
