Role of the dsRNA-dependent protein kinase (PKR) in the attenuation of protein loss from muscle by insulin and insulin-like growth factor-I (IGF-I)

H.L. Eley, Steve T. Russell, Michael J. Tisdale

Research output: Contribution to journalArticle

Abstract

Proteolysis-inducing factor (PIF), a tumour-produced cachectic factor, induced a dose-dependent decrease in protein synthesis in murine myotubes, together with an increase in phosphorylation of eucaryotic initiation factor 2 (eIF2) on the alpha-subunit. Both insulin (1 nM) and insulin-like growth factor I (IGF-I) (13.2 nM) attenuated the depression of protein synthesis by PIF and the increased phosphorylation of eIF2alpha, by inhibiting the activation (autophosphorylation) of the dsRNA-dependent protein kinase (PKR) by induction of protein phosphatase 1. A low-molecular weight inhibitor of PKR also reversed the depression of protein synthesis by PIF to the same extent, as did insulin and IGF-I. Both insulin and IGF-I-stimulated protein synthesis in the presence of PIF, and this was attenuated by Salubrinal, an inhibitor of phospho eIF2alpha phosphatase, suggesting that at least part of this action was due to their ability to inhibit phosphorylation of eIF2alpha. Both insulin and IGF-I also attenuated the induction of protein degradation in myotubes induced by PIF, this effect was also attenuated by Salubrinal. These results suggest an alternative mechanism involving PKR to explain the effect of insulin and IGF-I on protein synthesis and degradation in skeletal muscle in the presence of catabolic factors.
LanguageEnglish
Pages63-69
Number of pages7
JournalMolecular and Cellular Biochemistry
Volume313
Issue number1-2
DOIs
Publication statusPublished - Jun 2008

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eIF-2 Kinase
Muscle Proteins
Proteolysis
Insulin-Like Growth Factor I
Muscle
Insulin
Phosphorylation
Proteins
Skeletal Muscle Fibers
Prokaryotic Initiation Factor-2
Protein Phosphatase 1
Degradation
Phosphoric Monoester Hydrolases
Tumors
Chemical activation
Molecular weight
Skeletal Muscle
Molecular Weight

Keywords

  • muscle atrophy
  • insulin
  • IGF-I
  • PKR
  • eIF2 alpha

Cite this

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abstract = "Proteolysis-inducing factor (PIF), a tumour-produced cachectic factor, induced a dose-dependent decrease in protein synthesis in murine myotubes, together with an increase in phosphorylation of eucaryotic initiation factor 2 (eIF2) on the alpha-subunit. Both insulin (1 nM) and insulin-like growth factor I (IGF-I) (13.2 nM) attenuated the depression of protein synthesis by PIF and the increased phosphorylation of eIF2alpha, by inhibiting the activation (autophosphorylation) of the dsRNA-dependent protein kinase (PKR) by induction of protein phosphatase 1. A low-molecular weight inhibitor of PKR also reversed the depression of protein synthesis by PIF to the same extent, as did insulin and IGF-I. Both insulin and IGF-I-stimulated protein synthesis in the presence of PIF, and this was attenuated by Salubrinal, an inhibitor of phospho eIF2alpha phosphatase, suggesting that at least part of this action was due to their ability to inhibit phosphorylation of eIF2alpha. Both insulin and IGF-I also attenuated the induction of protein degradation in myotubes induced by PIF, this effect was also attenuated by Salubrinal. These results suggest an alternative mechanism involving PKR to explain the effect of insulin and IGF-I on protein synthesis and degradation in skeletal muscle in the presence of catabolic factors.",
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AU - Russell, Steve T.

AU - Tisdale, Michael J.

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AB - Proteolysis-inducing factor (PIF), a tumour-produced cachectic factor, induced a dose-dependent decrease in protein synthesis in murine myotubes, together with an increase in phosphorylation of eucaryotic initiation factor 2 (eIF2) on the alpha-subunit. Both insulin (1 nM) and insulin-like growth factor I (IGF-I) (13.2 nM) attenuated the depression of protein synthesis by PIF and the increased phosphorylation of eIF2alpha, by inhibiting the activation (autophosphorylation) of the dsRNA-dependent protein kinase (PKR) by induction of protein phosphatase 1. A low-molecular weight inhibitor of PKR also reversed the depression of protein synthesis by PIF to the same extent, as did insulin and IGF-I. Both insulin and IGF-I-stimulated protein synthesis in the presence of PIF, and this was attenuated by Salubrinal, an inhibitor of phospho eIF2alpha phosphatase, suggesting that at least part of this action was due to their ability to inhibit phosphorylation of eIF2alpha. Both insulin and IGF-I also attenuated the induction of protein degradation in myotubes induced by PIF, this effect was also attenuated by Salubrinal. These results suggest an alternative mechanism involving PKR to explain the effect of insulin and IGF-I on protein synthesis and degradation in skeletal muscle in the presence of catabolic factors.

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