Simplified schema showing the interactions between mTORC1 and mTORC2, and associated pathways. The downstream effectors of mTORC1 include S6K and 4EBP1. When phosphorylated, 4EBP1 releases eIF4E, which then facilitates messenger RNA translation and contributes to cell growth. Activation of eIF4E also occurs via the ras/MAPK pathway. Among the key downstream effectors of mTORC2 is Akt, which suppresses apoptosis by inhibiting pro-apoptotic proteins and further promotes cell growth through activation of mTORC1 (via inhibition of TSC 1/2). The activation of mTORC1 also causes downregulation of mTORC2 by inhibition of IRS1 by S6K. 4EBP1, eukaryotic translation initiation factor 4E–binding protein 1; eIF4E, eukaryotic translation initiation factor 4E; IRS1, insulin receptor substrate 1; Rheb, ras homolog enriched in brain; S6K, ribosomal S6 kinase; TSC 1/2, tuberous sclerosis 1/2; PI3K, phosphatidylinositol 3-kinase.