Rheb GTPase is a direct target of TSC2 GAP activity and regulates mTOR signaling

TLDR

Tuberous sclerosis complex, caused by mutations in TSC1 or TSC2, encodes a complex that suppresses mTOR signaling to S6K and 4EBP1, while the Ras‑like GTPase Rheb activates this pathway and is inhibited by rapamycin. The study demonstrates that TSC2 functions as a GTPase‑activating protein for Rheb. Data show that Rheb lies downstream of the TSC1/TSC2 complex and upstream of mTOR, thereby controlling cell growth.

Abstract

Tuberous sclerosis complex (TSC) is a genetic disease caused by mutation in either TSC1 or TSC2 . The TSC1 and TSC2 gene products form a functional complex and inhibit phosphorylation of S6K and 4EBP1. These functions of TSC1/TSC2 are likely mediated by mTOR. Here we report that TSC2 is a GTPase-activating protein (GAP) toward Rheb, a Ras family GTPase. Rheb stimulates phosphorylation of S6K and 4EBP1. This function of Rheb is blocked by rapamycin and dominant-negative mTOR. Rheb stimulates the phosphorylation of mTOR and plays an essential role in regulation of S6K and 4EBP1 in response to nutrients and cellular energy status. Our data demonstrate that Rheb acts downstream of TSC1/TSC2 and upstream of mTOR to regulate cell growth.