Structural basis for a phosphoinositide-driven mTORC2-AKT positive feedback loop

Authors

Hay, I. M., Bourguet, M., Ahsan, B., Perisic, O., Anandapadamanaban, M., Williams, R. L.

Abstract

The mammalian target of rapamycin complex 2 (mTORC2) regulates metabolism, growth, survival and cytoskeletal organization, yet its activation mechanism is poorly understood. We show that mTORC2 is directly activated by membranes and our cryo-electron tomography structure of membrane-bound mTORC2 reveals the N-HEAT region of mTOR is at the major membrane interface. mTORC2 is further potently activated by a positive feedback loop involving reciprocal phosphorylation of mTORC2 and its substrate kinase AKT. Cryo-EM structures of dephosphorylated, autophosphorylated and AKT-phosphorylated mTORC2 reveal structural changes in the SIN1 subunit, regulating an autoinhibitory anchor. Reconstitution of the PDK1-AKT-mTORC2 hub on PIP3-containing membranes shows that PDK1/PIP3-dependent AKT activation drives SIN1-T86 phosphorylation, enabling mTORC2 to phosphorylate S473 of AKT's hydrophobic motif, establishing a PI3K-dependent, phosphorylation-driven positive feedback loop at the membrane.

Preprint server: bioRxiv
The authors list and abstract were imported from bioRxiv on 10 Jan 2026.

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