Mammalian target of rapamycin-independent S6K1 and 4E-BP1 phosphorylation during contraction in rat skeletal muscle

Yang Liu, Yu Chiang Lai*, Didier Vertommen, Mark H. Rider

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)


Muscle protein synthesis rates decrease during contraction/exercise, but rapidly increase post-exercise. Previous studies mainly focused on signaling pathways that control protein synthesis during post-exercise recovery, such as mTOR and its downstream targets S6K1 and 4E-BP1. In this study, we investigated the effect of high-frequency electrical stimulation on the phosphorylation state of signaling components controlling protein synthesis in rat skeletal muscle. Electrical stimulation increased S6K1 Thr389 phosphorylation, which was unaffected by Torin1, a selective mTOR inhibitor, suggesting that S6K1 phosphorylation by contraction was mTOR-independent. Phosphorylation of eIF4B Ser422 was also increased during electrical stimulation, which was abrogated by inhibition of MEK/ERK/RSK1 activation. Moreover, although phosphorylation of conventional mTOR sites in 4E-BP1 decreased during contraction, mTOR-independent phosphorylation was also apparent, which was associated with the release of 4E-BP1 from eIF4E. The results indicate mTOR-independent phosphorylation of S6K1 and 4E-BP1 and suggest MEK/ERK/RSK1-dependent phosphorylation of eIF4B during skeletal muscle contraction. These phosphorylation events would keep the translation initiation machinery "primed" in an active state so that protein synthesis could quickly resume post-exercise.

Original languageEnglish
Pages (from-to)1877-1886
Number of pages10
JournalCellular Signalling
Issue number9
Early online date21 May 2013
Publication statusPublished - 1 Sept 2013


  • 4E-BP1
  • AMPK
  • Contraction
  • EIF4B
  • Protein synthesis
  • S6K1

ASJC Scopus subject areas

  • Cell Biology


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