AMP-activated Protein Kinase (AMPK) Control of mTORC1 Is p53- and TSC2-independent in Pemetrexed-treated Carcinoma Cells

J Biol Chem. 2015 Nov 13;290(46):27473-86. doi: 10.1074/jbc.M115.665133. Epub 2015 Sep 21.


The key sensor of energy status in mammalian cells, AMP-activated protein kinase (AMPK), can also be activated by the AMP analog aminoimidazolecarboxamide nucleoside monophosphate (ZMP) generated directly from aminoimidazolecarboxamide ribonucleoside (AICAR) or from inhibition of purine synthesis by the antifolate pemetrexed (PTX), a drug used extensively in the treatment of lung cancers. Despite this common mechanism, signaling downstream of AMPK activated by PTX or AICAR differed. AICAR-activated AMPK inhibited mTORC1 both directly by phosphorylation of the mTORC1 subunit Raptor and indirectly by phosphorylation of the regulator TSC2. In contrast, PTX-activated AMPK inhibited mTORC1 solely through Raptor phosphorylation. This dichotomy was due to p53 function. Transcription of p53 target genes, including TSC2, was activated by AICAR but not by PTX. Although both PTX and AICAR stabilized p53, only AICAR activated Chk2 phosphorylation, stimulating p53-dependent transcription. However, Raptor phosphorylation by AMPK was independent of p53 and was sufficient, after PTX treatment, to inhibit mTORC1. We concluded that PTX effects on mTORC1 were independent of TSC2 and p53 and that the activation of a p53 transcriptional response by AICAR was due to an activation of Chk2 that was not elicited by PTX.

Keywords: AMP-activated kinase (AMPK); TSC2; lung cancer; mTOR complex (mTORC); p53; pemetrexed; raptor; signal transduction.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • AMP-Activated Protein Kinases / metabolism*
  • Adaptor Proteins, Signal Transducing / metabolism
  • Aminoimidazole Carboxamide / analogs & derivatives
  • Aminoimidazole Carboxamide / pharmacology
  • Antineoplastic Agents / pharmacology*
  • Checkpoint Kinase 2 / genetics
  • Enzyme Activation / drug effects
  • Folic Acid Antagonists / pharmacology*
  • HCT116 Cells
  • Humans
  • Mechanistic Target of Rapamycin Complex 1
  • Multiprotein Complexes / metabolism*
  • Pemetrexed / pharmacology*
  • Phosphorylation
  • Regulatory-Associated Protein of mTOR
  • Ribonucleotides / pharmacology
  • Signal Transduction / drug effects
  • TOR Serine-Threonine Kinases / metabolism*
  • Transcription, Genetic / drug effects
  • Tuberous Sclerosis Complex 2 Protein
  • Tumor Suppressor Protein p53 / genetics
  • Tumor Suppressor Protein p53 / metabolism*
  • Tumor Suppressor Proteins / genetics


  • Adaptor Proteins, Signal Transducing
  • Antineoplastic Agents
  • Folic Acid Antagonists
  • Multiprotein Complexes
  • RPTOR protein, human
  • Regulatory-Associated Protein of mTOR
  • Ribonucleotides
  • TSC2 protein, human
  • Tuberous Sclerosis Complex 2 Protein
  • Tumor Suppressor Protein p53
  • Tumor Suppressor Proteins
  • Pemetrexed
  • Aminoimidazole Carboxamide
  • Checkpoint Kinase 2
  • CHEK2 protein, human
  • Mechanistic Target of Rapamycin Complex 1
  • TOR Serine-Threonine Kinases
  • AMP-Activated Protein Kinases
  • AICA ribonucleotide