4E-BP1
Translational repressor; the master effector through which mTORC1 controls protein synthesis. mTORC1 phosphorylates 4E-BP1 to release eIF4E and switch translation ON.
A cap on protein-making that mTORC1 removes.
Only partially rapamycin-sensitive. This single fact explains the rapalog/Torin discrepancy and drove the whole ATP-competitive inhibitor programme.
Evidence at a glance
| Evidence | What it means | Studies |
|---|---|---|
| H | Human study | 1 |
| A | Animal model | 2 |
| M | Molecular — cells, biochemistry, structure | 4 |
Studies
| Year | Evidence | Study |
|---|---|---|
| 2025 | H | The Bi-steric, mTORC1-Selective Inhibitor, RMC-5552, in Advanced Solid Tumors: A Phase 1 Trial SCH2025 First-in-human, open-label dose-escalation trial (n=57, advanced solid tumors, no comparator arm) of a bi-steric mTORC1-selective inhibitor. Treatment-related hyperglycemia was low (4%) and not dose-limiting, alongside a 64% disease control rate. Because the trial was uncontrolled and made no head-to-head comparison against rapamycin or an ATP-site inhibitor, this is encouraging early clinical evidence consistent with the hypothesis that sparing mTORC2 reduces metabolic toxicity -- it does not establish mTORC2 sparing as the cause. |
| 2023 | A | A bi-steric mTORC1-selective inhibitor overcomes drug resistance in breast cancer MEN2023 RMC-6272, a bi-steric molecule with >25-fold selectivity for mTORC1 over mTORC2, completely suppresses mTORC1 (hitting the rapamycin-resistant substrate 4E-BP1) and overcomes hormone- and CDK4/6-inhibitor resistance in breast cancer cell lines and PDX -- the preclinical basis for the RMC-5552 selective-inhibitor clinical program. |
| 2009 | A | 4E-BP extends lifespan upon dietary restriction by enhancing mitochondrial activity in Drosophila ZID2009 Connected the dots between diet, mTOR, and lifespan. Dietary restriction lowers mTOR activity, which frees up 4E-BP - and here 4E-BP was shown to be REQUIRED for the lifespan boost, working by selectively boosting translation of mitochondrial genes. A rare case pinning a specific mTOR effector to the longevity benefit of eating less. |
| 2015 | M | mTOR regulates the pro-tumorigenic senescence-associated secretory phenotype by promoting IL1A translation LAB2015 Explained HOW rapamycin calms 'inflammaging'. Senescent cells spew inflammatory signals (the SASP) that damage surrounding tissue and even feed tumors. mTOR powers this by translating IL1A, the cytokine at the top of the cascade. Rapamycin selectively shuts it down - and blocked senescent cells from fueling prostate tumor growth in mice. |
| 2012 | M | A unifying model for mTORC1-mediated regulation of mRNA translation THO2012 Used ribosome profiling with the complete inhibitor Torin1 to address a long-standing debate: in these cells, mTORC1's translational control runs largely through the 4E-BP family acting on a specific class of mRNAs (TOP motifs). Losing just the 4E-BPs makes translation resistant to mTOR inhibition - naming them the master effectors. |
| 2012 | M | The translational landscape of mTOR signalling steers cancer initiation and metastasis HSI2012 Showed WHY mTOR-driven translation matters for cancer: in prostate cancer, oncogenic mTOR selectively translates a specific set of pro-invasion mRNAs that drive metastasis. An ATP-competitive mTOR inhibitor (INK128) reversed that signature - an early preclinical rationale from mouse models and cell lines, not a clinical result. |
| 2009 | M | An ATP-competitive mammalian target of rapamycin inhibitor reveals rapamycin-resistant functions of mTORC1 THO2009 Dropped a bombshell: rapamycin does NOT fully block mTORC1. Using Torin1 (which jams the active site directly), the authors showed rapamycin leaves important mTORC1 jobs running - notably 4E-BP1 phosphorylation and autophagy suppression. This reframed a decade of rapamycin experiments and launched the search for complete inhibitors. |