The REAL Mechanism of Rapamycin: MTOR Inhibition Explained

25 Jan 2025 · 1 min

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In this segment, the presenter clarifies how rapamycin interacts with the mTOR signaling pathway. Rather than fully shutting down the two major mTOR complexes (mTORC1 and mTORC2), rapamycin acts as a non‑uniform, steric inhibitor that partially blocks each complex in a nonlinear fashion. This incomplete inhibition reduces the activity of both complexes enough to modulate cell maintenance and growth without causing lethal shutdown of essential cellular functions, explaining why rapamycin can be used therapeutically without killing the organism.

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And here's the thing. If you think of the pathway coming in and then you have the mTOR complex of mTOR1 and 2 modulating cell maintenance, cell growth, stuff like that, what rapamycin does is in a non-uniform manner, meaning it hits the 2 points differently, it causes what's called a steric block, which means it doesn't shut them down. If it did, you would die, basically, but it modulates them downward. So it's an incomplete block of mTOR. So when we say rapamycin is an mTOR inhibitor, yes, but it's a steric inhibitor that hits in a nonlinear fashion at the 2 points and doesn't block them totally, which is great because then it doesn't wind up killing the organism or the human.