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Differential effects of Hsp90 inhibition on protein kinases regulating signal transduction pathways required for

Bo-Geon Yun1, Robert L Matts

  • 1Department of Biochemistry and Molecular Biology, 246 NRC, Oklahoma State University, Stillwater, OK 74078-3035, USA.

Experimental Cell Research
|June 1, 2005
PubMed

Insights

Geldanamycin, an Hsp90 inhibitor, disrupts muscle cell differentiation and survival by depleting key proteins. This suggests potential adverse effects of geldanamycin derivatives on sensitive muscle populations in vivo.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Pharmacology

Background:

  • Geldanamycin is an Hsp90 inhibitor with tumoricidal properties.
  • Its derivatives are entering clinical trials, necessitating investigation into non-tumor cell effects.
  • The impact of geldanamycin on muscle cell differentiation and survival requires examination.

Purpose of the Study:

  • To investigate the effects of geldanamycin on C2C12 myoblast differentiation and survival.
  • To identify Hsp90-dependent proteins affected by geldanamycin in muscle cells.
  • To elucidate the mechanisms underlying geldanamycin-induced myoblast apoptosis.

Main Methods:

  • Treatment of C2C12 myoblasts with geldanamycin.
  • Analysis of myogenin expression and myotubule formation.
  • Western blotting to assess protein levels (ErbB2, Fyn, Akt, c-Src, MyoD).
  • Co-immunoprecipitation to study protein interactions (Hsp90, Cdc37).
  • Pulse-chase experiments to evaluate protein turnover rates.

Main Results:

  • Geldanamycin inhibited myogenin expression and myotubule formation.
  • It led to depletion of Hsp90-dependent kinases ErbB2, Fyn, and Akt, inducing apoptosis.
  • Geldanamycin disrupted Hsp90/Cdc37 interaction with Fyn and Cdc37 interaction with MyoD.
  • Newly synthesized Akt and Fyn showed rapid degradation, while mature protein turnover was less affected.
  • c-Src levels and turnover, and MyoD levels, were unaffected.

Conclusions:

  • Hsp90 inhibition by geldanamycin depletes essential signal transduction proteins in C2C12 myoblasts.
  • This depletion impairs myoblast differentiation and muscle cell survival.
  • Geldanamycin derivatives may adversely affect sensitive muscle cell populations in vivo.

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