mTOR (mechanistic target of rapamycin) !

A kinase that decides whether the cell grows: with enough nutrients, insulin and energy it switches on protein synthesis and stops autophagy.

Updated 2026-11-01

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Key facts

It forms two complexes: mTORC1 (with raptor, rapamycin-sensitive) and mTORC2 (with rictor, activates Akt).
mTORC1 integrates amino acids (Rag GTPases on the lysosome), insulin/growth factors (Akt → TSC2 → Rheb) and energy (AMPK holds it back).
It activates S6K1 and inhibits 4E-BP1: more protein translation; it also switches on lipid synthesis (SREBP) and stops autophagy (ULK1).
Structure 4JSV is human mTOR (catalytic region) with mLST8, ADP and Mg²⁺ in the active site.

Activation: amino acids (especially leucine), insulin and IGF-1 through Akt, Rheb-GTP.
Inhibition: the TSC1/TSC2 complex, AMPK (low energy), hypoxia, lack of amino acids.
S6K1 phosphorylates IRS-1 and dampens insulin signalling (negative feedback).

Tuberous sclerosis: loss of TSC1 or TSC2 leaves mTORC1 on and causes benign tumours in brain, skin, kidney and heart; mTOR inhibitors shrink some of them.
Sirolimus and everolimus are used as immunosuppressants in transplants and in some cancers.
Chronic activation of mTORC1 and S6K1 by nutrient excess contributes to insulin resistance.

Think of the answer, then tap the question to see it.

Which three signals does mTORC1 integrate to decide on cell growth?

Amino acids, insulin or growth factors, and energy status (through AMPK).

How does rapamycin work?

It binds FKBP12 and the complex blocks mTORC1.

Which disease does loss of the TSC1/TSC2 complex cause?

Tuberous sclerosis, from excessive mTORC1 activity.

Educational information, not medical advice. For any symptom, see a health professional.

Sources: MTOR: Serine/threonine-protein kinase mTOR (human) (UniProt, 2026); 4JSV: mTOR kinase structure, mechanism and regulation. (RCSB Protein Data Bank, 2026); MTOR gene: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Tuberous sclerosis complex: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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Representative model, for educational purposes only.