Coordinated regulation of protein synthesis and degradation by mTORC1

Nature. 2014 Sep 18;513(7518):440-3. doi: 10.1038/nature13492. Epub 2014 Jul 13.

Abstract

Eukaryotic cells coordinately control anabolic and catabolic processes to maintain cell and tissue homeostasis. Mechanistic target of rapamycin complex 1 (mTORC1) promotes nutrient-consuming anabolic processes, such as protein synthesis. Here we show that as well as increasing protein synthesis, mTORC1 activation in mouse and human cells also promotes an increased capacity for protein degradation. Cells with activated mTORC1 exhibited elevated levels of intact and active proteasomes through a global increase in the expression of genes encoding proteasome subunits. The increase in proteasome gene expression, cellular proteasome content, and rates of protein turnover downstream of mTORC1 were all dependent on induction of the transcription factor nuclear factor erythroid-derived 2-related factor 1 (NRF1; also known as NFE2L1). Genetic activation of mTORC1 through loss of the tuberous sclerosis complex tumour suppressors, TSC1 or TSC2, or physiological activation of mTORC1 in response to growth factors or feeding resulted in increased NRF1 expression in cells and tissues. We find that this NRF1-dependent elevation in proteasome levels serves to increase the intracellular pool of amino acids, which thereby influences rates of new protein synthesis. Therefore, mTORC1 signalling increases the efficiency of proteasome-mediated protein degradation for both quality control and as a mechanism to supply substrate for sustained protein synthesis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acids / metabolism
  • Animals
  • Humans
  • Male
  • Mechanistic Target of Rapamycin Complex 1
  • Mice
  • Mice, Inbred C57BL
  • Multiprotein Complexes / metabolism*
  • Nuclear Respiratory Factor 1 / genetics
  • Nuclear Respiratory Factor 1 / metabolism
  • Proteasome Endopeptidase Complex / genetics
  • Proteasome Endopeptidase Complex / metabolism
  • Protein Biosynthesis*
  • Proteins / chemistry
  • Proteins / metabolism*
  • Proteolysis*
  • Signal Transduction
  • Sterol Regulatory Element Binding Protein 1 / metabolism
  • TOR Serine-Threonine Kinases / metabolism*
  • Transcription, Genetic

Substances

  • Amino Acids
  • Multiprotein Complexes
  • Nuclear Respiratory Factor 1
  • Proteins
  • Sterol Regulatory Element Binding Protein 1
  • TOR Serine-Threonine Kinases
  • Mechanistic Target of Rapamycin Complex 1
  • Proteasome Endopeptidase Complex