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

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

Author information

1
From the Department of Pharmacology and Toxicology and the Massey Cancer Center, Virginia Commonwealth University, Richmond, Virginia 23298 and.
2
the Center for Epigenetics, Van Andel Research Institute, Grand Rapids, Michigan 49503.
3
From the Department of Pharmacology and Toxicology and the Massey Cancer Center, Virginia Commonwealth University, Richmond, Virginia 23298 and rmoran@vcu.edu.

Abstract

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

PMID:
26391395
PMCID:
PMC4646000
DOI:
10.1074/jbc.M115.665133
[Indexed for MEDLINE]
Free PMC Article

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