Effects of contraction and insulin on protein synthesis, AMP-activated protein kinase and phosphorylation state of translation factors in rat skeletal muscle.

Miranda, Lisa;Horman, Sandrine;De Potter, Isabelle;Hue, Louis;Rider, Mark H.;et.al.
(2008) Pflügers Archiv - European journal of physiology — Vol. 455, n° 6, p. 1129-1140 (2008)

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Authors
  • Miranda, Lisa
    Author
  • Horman, Sandrineorcid-logoUCLouvain
    Author
  • De Potter, Isabelle
    Author
  • Hue, LouisUCLouvain
    Author
  • Rider, Mark H.UCLouvain
    Author
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Abstract
In rat epitrochlearis skeletal muscle, contraction inhibited the basal and insulin-stimulated rates of protein synthesis by 75 and 70%, respectively, while increasing adenosine monophosphate-activated protein kinase (AMPK) activity. Insulin, on the other hand, stimulated protein synthesis (by 30%) and increased p70 ribosomal protein S6 kinase (p70S6K) Thr389, 40S ribosomal protein S6 (rpS6) Ser235/236, rpS6 Ser240/244 and eukaryotic initiation factor-4E-binding protein-1 (4E-BP1) Thr37/46 phosphorylation over basal values. Electrical stimulation had no effect on mammalian target of rapamycin complex 1 (mTORC1) signalling, as reflected by the lack of reduction in basal levels of p70S6K, rpS6 Ser235/236, rpS6 Ser240/244 and 4E-BP1 phosphorylation, but did antagonize mTORC1 signalling after stimulation of the pathway by insulin. Eukaryotic elongation factor-2 (eEF2) Thr56 phosphorylation increased rapidly on electrical stimulation reaching a maximum at 1 min, whereas AMPK Thr172 phosphorylation slowly increased to reach threefold after 30 min. Eukaryotic elongation factor-2 kinase (eEF2K) was not activated after 30 min of contraction when AMPK was activated. This could not be explained by the expression of a tissue-specific isoform of eEF2K in skeletal muscle lacking the Ser398 AMPK phosphorylation site. Therefore, in this skeletal muscle system, the contraction-induced inhibition of protein synthesis could not be attributed to a reduction in mTORC1 signalling but could be due to an increase in eEF2 phosphorylation independent of AMPK activation.
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Miranda, L., Horman, S., De Potter, I., Hue, L., Jensen, J., & Rider, M. H. (2008). Effects of contraction and insulin on protein synthesis, AMP-activated protein kinase and phosphorylation state of translation factors in rat skeletal muscle. Pflügers Archiv - European journal of physiology, 455(6), 1129-1140. https://doi.org/10.1007/s00424-007-0368-2 (Original work published 2008)