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Published on: May 7, 2020
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Passive force enhancement in striated muscle.
1Human Performance Laboratory, Faculty of Kinesiology, University of Calgary , Calgary, Alberta , Canada.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|May 10, 2019
Summary
Passive force enhancement, an increase in muscle force after stretching, is linked to the protein titin. This study proposes titin binds to actin, shortening its spring length to explain this lasting muscle force increase.
Area of Science:
- Muscle physiology
- Biophysics
- Skeletal muscle research
Background:
- Passive force enhancement (PFE) is a sustained increase in passive muscle force after active stretch.
- PFE is length-dependent, contributes to residual force enhancement, and persists after deactivation.
- The underlying molecular mechanisms of PFE remain largely unknown.
Purpose of the Study:
- To propose a molecular mechanism for passive force enhancement.
- To associate PFE with the protein titin's mechanical properties.
- To elucidate the role of titin-actin interactions in PFE.
Main Methods:
- Review of experimental evidence on passive force enhancement.
- Analysis of sarcomere mechanics and protein interactions.
- Hypothesizing molecular triggers for titin-actin binding.
Main Results:
- Passive force enhancement is strongly associated with the filamentous protein titin.
- A proposed mechanism involves the shortening of titin's spring length in the I-band.
- Titin binding to actin, triggered by actin-myosin cross-bridge formation, is suggested.
Conclusions:
- Passive force enhancement may result from titin binding to actin.
- Regulatory protein movement (troponin, tropomyosin) may expose actin binding sites for titin.
- This mechanism provides insight into residual force enhancement in muscle.
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