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| Title | Interactions between mTORC2 core subunits Rictor and mSin1 dictate selective and context-dependent phosphorylation of substrate kinases SGK1 and Akt. |
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| Journal, issue, pages | J Biol Chem, Vol. 298, Issue 9, Page 102288, Year 2022 |
| Publish date | Aug 1, 2022 |
 Authors | Zanlin Yu / Junliang Chen / Enzo Takagi / Feng Wang / Bidisha Saha / Xi Liu / Lydia-Marie Joubert / Catherine E Gleason / Mingliang Jin / Chengmin Li / Carlos Nowotny / David Agard / Yifan Cheng / David Pearce /  |
| PubMed Abstract | Mechanistic target of rapamycin complex 2 (mTORC2) is a multi-subunit kinase complex, central to multiple essential signaling pathways. Two core subunits, Rictor and mSin1, distinguish it from the ...Mechanistic target of rapamycin complex 2 (mTORC2) is a multi-subunit kinase complex, central to multiple essential signaling pathways. Two core subunits, Rictor and mSin1, distinguish it from the related mTORC1 and support context-dependent phosphorylation of its substrates. mTORC2 structures have been determined previously; however, important questions remain, particularly regarding the structural determinants mediating substrate specificity and context-dependent activity. Here, we used cryo-EM to obtain high-resolution structures of the human mTORC2 apo-complex in the presence of substrates Akt and SGK1. Using functional assays, we then tested predictions suggested by substrate-induced structural changes in mTORC2. For the first time, we visualized in the apo-state the side chain interactions between Rictor and mTOR that sterically occlude recruitment of mTORC1 substrates and confer resistance to the mTORC1 inhibitor rapamycin. Also in the apo-state, we observed that mSin1 formed extensive contacts with Rictor via a pair of short α-helices nestled between two Rictor helical repeat clusters, as well as by an extended strand that makes multiple weak contacts with Rictor helical cluster 1. In co-complex structures, we found that SGK1, but not Akt, markedly altered the conformation of the mSin1 N-terminal extended strand, disrupting multiple weak interactions while inducing a large rotation of mSin1 residue Arg-83, which then interacts with a patch of negatively charged residues within Rictor. Finally, we demonstrate mutation of Arg-83 to Ala selectively disrupts mTORC2-dependent phosphorylation of SGK1, but not of Akt, supporting context-dependent substrate selection. These findings provide new structural and functional insights into mTORC2 specificity and context-dependent activity. |
 External links | J Biol Chem / PubMed:35926713 / PubMed Central |
| Methods | EM (single particle) |
| Resolution | 3.28 - 3.44 Å |
| Structure data |  EMDB-26211: mTORC2 complex with SGK1  EMDB-26212: mTORC2 complex with Akt EMDB-26213, PDB-7tzo: |
| Source |
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 Keywords |  SIGNALING PROTEIN / complex |
