Skeletal muscle-specific ablation of raptor, but not of rictor, causes metabolic changes and results in muscle dystrophy

Cell Metab. 2008 Nov;8(5):411-24. doi: 10.1016/j.cmet.2008.10.002.

Abstract

Mammalian target of rapamycin (mTOR) is a central controller of cell growth. mTOR assembles into two distinct multiprotein complexes called mTOR complex 1 (mTORC1) and mTORC2. Here we show that the mTORC1 component raptor is critical for muscle function and prolonged survival. In contrast, muscles lacking the mTORC2 component rictor are indistinguishable from wild-type controls. Raptor-deficient muscles become progressively dystrophic, are impaired in their oxidative capacity, and contain increased glycogen stores, but they express structural components indicative of oxidative muscle fibers. Biochemical analysis indicates that these changes are probably due to loss of activation of direct downstream targets of mTORC1, downregulation of genes involved in mitochondrial biogenesis, including PGC1alpha, and hyperactivation of PKB/Akt. Finally, we show that activation of PKB/Akt does not require mTORC2. Together, these results demonstrate that muscle mTORC1 has an unexpected role in the regulation of the metabolic properties and that its function is essential for life.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Animals
  • Carrier Proteins / genetics
  • Carrier Proteins / physiology*
  • Enzyme Activation
  • Gene Expression Regulation
  • Mechanistic Target of Rapamycin Complex 1
  • Mice
  • Mice, Knockout
  • Mitochondria / physiology*
  • Multiprotein Complexes
  • Muscle, Skeletal / metabolism*
  • Muscle, Skeletal / pathology
  • Muscular Dystrophies / metabolism*
  • Muscular Dystrophies / pathology
  • Oncogene Protein v-akt / metabolism
  • Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha
  • Phosphorylation
  • Proteins
  • Proto-Oncogene Proteins c-akt / metabolism
  • Rapamycin-Insensitive Companion of mTOR Protein
  • Regulatory-Associated Protein of mTOR
  • TOR Serine-Threonine Kinases
  • Trans-Activators / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / physiology*

Substances

  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • Multiprotein Complexes
  • Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha
  • Ppargc1a protein, mouse
  • Proteins
  • Rapamycin-Insensitive Companion of mTOR Protein
  • Regulatory-Associated Protein of mTOR
  • Rptor protein, mouse
  • Trans-Activators
  • Transcription Factors
  • rictor protein, mouse
  • TOR Serine-Threonine Kinases
  • Mechanistic Target of Rapamycin Complex 1
  • Oncogene Protein v-akt
  • Proto-Oncogene Proteins c-akt