Related Experiment Video

Updated: May 9, 2026

A Semi-Quantitative Drug Affinity Responsive Target Stability (DARTS) assay for studying Rapamycin/mTOR interaction
05:28

A Semi-Quantitative Drug Affinity Responsive Target Stability (DARTS) assay for studying Rapamycin/mTOR interaction

Published on: August 27, 2019

mTORC1 phosphorylation sites encode their sensitivity to starvation and rapamycin

Seong A Kang1, Michael E Pacold, Christopher L Cervantes

  • 1Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, MA 02142, USA.

Science (New York, N.Y.)
|July 27, 2013
PubMed

Insights

The mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) pathway

Area of Science:

  • Cellular signaling pathways
  • Molecular mechanisms of cell growth regulation

Background:

  • The mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) is a key regulator of cell growth.
  • Rapamycin is a drug targeting mTORC1 that extends lifespan in model organisms, but its effects on substrate phosphorylation are not fully understood.

Purpose of the Study:

  • To investigate why certain mTORC1 substrates are resistant to rapamycin.
  • To identify the determinants of substrate sensitivity to mTORC1 pathway modulators.

Main Methods:

  • In vitro kinase assays using peptides representing mTORC1 phosphorylation sites.
  • Cellular experiments assessing substrate phosphorylation sensitivity to rapamycin and starvation.

Main Results:

  • mTORC1 kinase activity varies significantly across different phosphorylation sites.
  • In vitro activity strongly correlates with in-cell resistance to rapamycin and starvation.
  • Minor modifications to phosphorylation sites alter mTORC1 activity and cellular sensitivity to pathway modulators.

Conclusions:

  • Substrate quality, defined as the intrinsic capacity of a phosphorylation site to act as an mTORC1 substrate, is a key determinant of sensitivity to rapamycin and starvation.
  • This finding reveals a mechanism for differential regulation of mTORC1 effectors by common signals.

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