# mTORC1 / mTORC2 (mTOR complexes)

mTOR is a master growth-control kinase, and it works inside two distinct teams. mTORC1 is built around a scaffold protein called Raptor. mTORC2 is built around a different one, Rictor. mTORC1 reads signals from amino acids, insulin, energy levels, and growth factors. It then ramps up building (mainly ribosome production, via S6K1 and 4E-BP1) and shuts off autophagy (by tagging ULK1). It is the one rapamycin quickly blocks. mTORC2 is different. Standard rapamycin does not block it. It tags AKT at a spot called Ser473 to control cell survival and shape, feeding into the PI3K/AKT/FOXO pathway. In aging, chronically overactive mTORC1 is seen as a main driver of too much building and too little autophagy. Exactly how each team affects lifespan, especially when you block mTOR everywhere at once, is still being worked out.

## Sources

- Sarbassov DD, Ali SM, Kim DH, et al.. (2004). Rictor, a novel binding partner of mTOR, defines a rapamycin-insensitive and raptor-independent pathway that regulates the cytoskeleton. Current Biology. https://doi.org/10.1016/j.cub.2004.06.054
- Saxton RA, Sabatini DM. (2017). mTOR Signaling in Growth, Metabolism, and Disease. Cell. https://doi.org/10.1016/j.cell.2017.02.004

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