mTOR signaling: RAG GTPases transmit the amino acid signal

Trends Biochem Sci. 2008 Dec;33(12):565-8. doi: 10.1016/j.tibs.2008.09.005. Epub 2008 Oct 15.


mTOR (mammalian target of rapamycin) is a highly conserved nutrient-responsive regulator of cell growth that is found in all eukaryotes. The mechanism by which amino acids signal to mTOR has remained one of the largest outstanding questions in the field. Two recent complimentary studies provide compelling evidence that the Rag family of small GTPases is both necessary and sufficient to transmit a positive signal from amino acids to mTOR.

MeSH terms

  • Amino Acids / physiology*
  • Animals
  • Guanine Nucleotide Exchange Factors / metabolism
  • Guanosine Triphosphate / metabolism
  • Humans
  • Monomeric GTP-Binding Proteins / metabolism
  • Monomeric GTP-Binding Proteins / physiology*
  • Neuropeptides / metabolism
  • Protein Kinases / physiology*
  • Ras Homolog Enriched in Brain Protein
  • Signal Transduction / physiology*
  • TOR Serine-Threonine Kinases


  • Amino Acids
  • Guanine Nucleotide Exchange Factors
  • Neuropeptides
  • RHEB protein, human
  • Ras Homolog Enriched in Brain Protein
  • Guanosine Triphosphate
  • Protein Kinases
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • Monomeric GTP-Binding Proteins