HSP90 modulates the myosin replacement rate in myofibrils
Koichi Ojima1, Emi Ichimura2, Takahiro Suzuki2
1Division of Animal Products Research, Institute of Livestock and Grassland Science, NARO, Tsukuba , Japan.
American Journal of Physiology. Cell Physiology
|March 22, 2018
Summary
Heat shock protein 90 (HSP90) activity is crucial for rapid myosin replacement in skeletal muscle thick filaments. HSP90 promotes myosin incorporation by increasing myosin heavy chain (MYH) gene expression and cytosolic myosin levels.
Area of Science:
- Muscle physiology
- Molecular biology
- Protein dynamics
Background:
- Myosin is a key protein in skeletal muscle thick filaments, undergoing continuous turnover.
- Previous research indicated protein synthesis inhibition reduces myosin replacement rate.
- Factors regulating myosin replacement beyond protein synthesis were unknown.
Purpose of the Study:
- To investigate the role of heat shock protein 90 (HSP90) in regulating myosin replacement in skeletal muscle.
- To elucidate the mechanism by which HSP90 influences myosin turnover.
Main Methods:
- Utilized fluorescence recovery after photobleaching (FRAP) to quantify myosin replacement rate.
- Measured myosin heavy chain (MYH) gene expression levels.
- Assessed cytosolic myosin content in myotubes.
Main Results:
- HSP90 overexpression significantly increased myosin replacement rate in myotubes.
- Inhibition of HSP90 activity markedly slowed myosin replacement.
- HSP90 activity upregulated MYH gene expression and increased cytosolic myosin content.
Conclusions:
- HSP90 activity is essential for efficient myosin replacement in skeletal muscle.
- HSP90 promotes myosin incorporation by enhancing MYH gene expression and cytosolic myosin availability.
- This mechanism highlights HSP90's role in maintaining myofibril integrity and function.
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