Model of the Akt–TOR signaling transduction network in vivo.
Under wild-type conditions, negative feedback to the PI3K/Akt signaling branch is mediated by TORC1 (containing TOR, Lst8 and Raptor), independently of S6K. Under conditions of high TORC1 signaling load, induced e.g. by mutations in tsc1 or tsc2, negative feedback becomes S6K dependent. See discussion for details.