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Insulin-like growth factor-mediated muscle differentiation: collaboration between phosphatidylinositol

J Tureckova1, E M Wilson, J L Cappalonga

  • 1Oregon Health and Science University, Molecular Medicine Division, Department of Medicine, Portland, Oregon 97201-3098, USA.

The Journal of Biological Chemistry
|August 14, 2001
PubMed

Insights

Insulin-like growth factors (IGFs) regulate muscle differentiation via the PI 3-kinase-Akt pathway. This pathway controls myogenin expression and myotube formation, crucial for skeletal muscle development and regeneration.

Area of Science:

  • Muscle biology
  • Cell signaling
  • Molecular endocrinology

Background:

  • Skeletal muscle differentiation requires coordinated signaling pathways and myogenic transcription factors.
  • Insulin-like growth factors (IGFs) are critical for embryonic muscle development and adult muscle regeneration.
  • A novel myogenic cell line overexpressing IGF-binding protein-5 (C2BP5) was developed to study IGF action.

Purpose of the Study:

  • To elucidate the specific signaling pathways mediating IGF-I-induced muscle differentiation.
  • To identify the role of phosphatidylinositol 3-kinase (PI 3-kinase) and Akt in IGF-I signaling.
  • To investigate the relationship between IGF-I, PI 3-kinase-Akt pathway, and myogenin in muscle differentiation.

Main Methods:

  • Utilized a C2BP5 myogenic cell line that requires IGF-I for differentiation.
  • Employed the PI 3-kinase inhibitor LY294002 to block signaling pathways.
  • Expressed active PI 3-kinase and a modified Akt-1 (iAkt) to assess their effects on differentiation.
  • Studied the induction of myogenin and myotube formation.

Main Results:

  • IGF-I-induced myogenin expression and myotube formation were blocked by LY294002, even with delayed addition.
  • Active PI 3-kinase promoted differentiation independently of IGF-I.
  • Myogenin-induced differentiation was also inhibited by LY294002.
  • iAkt mimicked IGF-I's differentiation effects and rescued differentiation inhibited by LY294002.

Conclusions:

  • The PI 3-kinase-Akt pathway is essential for IGF-I-mediated skeletal muscle differentiation.
  • This pathway acts both upstream and downstream of myogenin.
  • IGF-I signaling converges on the PI 3-kinase-Akt pathway to regulate muscle development and regeneration.

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