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Assessment of Myofilament Ca2+ Sensitivity Underlying Cardiac Excitation-contraction Coupling
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Multiple forms of cardiac myosin-binding protein C exist and can regulate thick filament stability

Irina Kulikovskaya1, George B McClellan, Rhea Levine

  • 1Department of Physiology, University of Philadelphia School of Medicine, Philadelphia, PA 19104, USA. bsg@mail.med.upenn.edu

The Journal of General Physiology
|May 2, 2007
PubMed

Insights

Cardiac myosin binding protein C (cMyBP-C) phosphorylation regulates cardiac contractile filament stability. This phosphorylation determines filament structure, impacting heart function and contraction strength.

Area of Science:

  • Cardiology
  • Molecular Biology
  • Biochemistry

Background:

  • Absence or abnormality of cardiac myosin binding protein C (cMyBP-C) leads to severe cardiac structural and functional issues.
  • The precise function of cMyBP-C and the mechanisms behind these cardiac abnormalities remain unclear.

Purpose of the Study:

  • To investigate the role of cMyBP-C in regulating the stability of cardiac myosin-containing contractile filaments.
  • To explore the influence of cMyBP-C phosphorylation on filament structure and cardiac function.

Main Methods:

  • Antibodies were generated against three distinct regions of cMyBP-C to assess structural changes.
  • Western blotting and polyacrylamide gel electrophoresis were employed to analyze cMyBP-C forms and myosin heavy chain degradation.
  • Thick filament stability was evaluated under varying conditions, including shear force.

Main Results:

  • cMyBP-C exists in two forms: a stable, phosphorylated form with ordered myosin heads, and an unstable, unphosphorylated form with disordered myosin heads.
  • The unstable, unphosphorylated cMyBP-C is susceptible to proteolysis, leading to thick filament degradation and myosin release.
  • Filaments lacking cMyBP-C showed fragmentation under shear force, unlike the stable form.

Conclusions:

  • Phosphorylation of cMyBP-C is crucial for maintaining stable cardiac contractile filaments.
  • Modulation of filament stability by cMyBP-C may be linked to contraction strength via calcium ion sensitivity.

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