What is it about?
The control scheme for lengthdependent activation (LDA), a fundamental, striated muscle property where submaximal contraction is improved at longer compared to shorter lengths, is poorly understood. We demonstrate that 50% titin cleavage in passive sarcomeres attenuates all measured structural markers of LDA for thick (e.g., myosin) and thin (e.g., actin, troponin) filaments, as well as a functionally required thick-thin filament bridge in the A-band. These culminate to attenuate LDA in contracting fibers. The identified regulatory role of titin to LDA structural features is critical to the future study of many myo- and cardiomyopathies, of which LDA impairment is a hallmark.
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Why is it important?
The identified regulatory role of titin to muscle function and performance is critical to the future study of many myo- and cardiomyopathies.
Perspectives
The titin protein is the biggest protein known but was discovered relatively late, and so muscle contraction theory was based solely on other proteins. These current theories fail to predict muscle function well, but are drastically improved when the uncovered functional roles of titin are incorporated. As we learn more about titin, we are better able to understand how muscles work, and so gives us a better change to understand them when they become disfunctional, like during disease or after a hard gym workout.
Anthony Hessel
University of Muenster
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This page is a summary of: Titin force in muscle cells alters lattice order, thick and thin filament protein formation, Proceedings of the National Academy of Sciences, November 2022, Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.2209441119.
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