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Cardiac Myosin Filaments are Maintained by Stochastic Protein Replacement
Neil B Wood1, Colleen M Kelly1, Thomas S O'Leary1
1Department of Molecular Physiology and Biophysics, University of Vermont, Larner College of Medicine, Burlington, Vermont, USA.
Molecular & Cellular Proteomics : MCP
|August 3, 2022
Summary
Cardiac myosin filaments are dynamic, allowing new proteins to randomly mix in, ensuring muscle function. This study reveals myosin filament components are replaced stochastically, not as rigid structures.
Area of Science:
- Cardiovascular Biology
- Muscle Physiology
- Molecular Cell Biology
Background:
- Cardiac muscle sarcomeres contain myosin and myosin-binding protein C organized into large filamentous structures.
- Maintaining contractile function requires continuous replacement of these sarcomeric proteins.
Purpose of the Study:
- To investigate the dynamic nature of cardiac myosin filaments in vivo.
- To determine if individual protein components or entire filaments are replaced.
Main Methods:
- Utilized stable isotope labeling in adult mice to track newly synthesized proteins over 8 weeks.
- Employed mass spectrometry to quantify protein abundance changes.
- Used fluorescence microscopy to visualize filament dynamics and component replacement.
Main Results:
- Protein degradation followed models of stochastic molecular selection.
- Newly synthesized myosin and myosin-binding protein C molecules were randomly incorporated into existing thick filaments.
- Preferential extraction of myosin molecules from filament ends was observed.
Conclusions:
- Cardiac myosin filaments are dynamic assemblies, not rigid structures.
- Component replacement occurs randomly, supporting a model of continuous protein turnover.
- The rate of mixing may vary along the length of the thick filament.
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