Figure 3.

Subunit composition and regulation of mTORC1. mTORC1 consists of the mTOR kinase, the complex defining subunit raptor mLST8, and the two negative regulators PRAS40 and DEPTOR. Activation of mTORC1 depends on recruiting the complex to its place of activation–the lysosomal surface–by Ras-related GTP-binding protein (Rag) GTPases. mTORC1 is fully activated by the RHEB GTPase downstream of AKT-dependent pathways. Furthermore, lysosomal PI(3)P and PI(3,5)P₂ play roles in mTORC1 activation. AMPK and PI(3,4)P₂ can inhibit mTORC1 activity by regulating the binding of raptor to inhibitory 14-3-3 proteins.