Single sarcomere and Structural Protein Mechanics Measurement System

单肌节和结构蛋白力学测量系统

• 批准号: RTI-2023-00055
• 负责人: Herzog, Walter
• 金额: $ 10.62万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Research Tools and Instruments
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=757897
• 关键词: Single; sarcomere; Structural; Protein; Mechanics

The way striated muscles contract and produce force, and so allow for human movement, is described by a theory developed in 1957 by Nobel Prize Winner AF Huxley. Huxley proposed that muscle contraction occurs through the sliding of two filamentous proteins called actin and myosin, and that this sliding is produced by small molecular motors called cross-bridges. This so-called cross-bridge theory of muscle contraction is described in textbooks of muscle physiology and is taught across the globe. This theory is excellent in describing the mechanics of contraction for muscles that either remain at a constant length (isometric contraction) or shorten (concentric contraction). However, the cross-bridge theory was never able to predict the mechanics of contraction when a muscle is stretched (a so-called eccentric contraction). Eccentric contractions occur during every movement, for example when we walk or run. In 2002, we discovered that there must be a "passive" structural element that also contributes to active force production. Using careful experiments at different structural levels, we identified that the force beyond that caused by actin and myosin comes from a structural protein called titin. However, despite this discovery 15 years ago, the molecular mechanism by which titin contributes to active force remains unknown, although ample theories have been proposed. The primary reason for this lack in progress has been because even though actin, myosin and cross-bridges can be seen using sophisticated imaging and diffraction techniques, titin does not provide a diffraction pattern, and thus cannot be seen using even the most sophisticated imaging techniques available today. Ten years ago, we proposed the theory that titin changes its inherent stiffness when a muscle is activated and does so by binding to the actin filament. Currently, this is the most accepted theory, but there is no direct experimental proof supporting the theory. In the current NSERC RTI application, we request the components for an equipment system that will allow us to probe our theory directly. In contrast to other equipment systems, the proposed system has unique features that allow for gaining unprecedented insights into the molecular interaction of actin, myosin, and titin: -It allows for mechanical testing of single sarcomeres (the smallest contractile unit of muscle) -It allows for controlled activation of any number of sarcomeres within a myofibril -It allows for measuring sarcomere mechanics with unprecedented accuracy -And it allows for visualizing titin-actin interactions in activated sarcomeres If our theory was proven correct with this new equipment system, it would fundamentally change how scientists view muscle contraction, it would produce a change in our textbooks and our teachings of muscle physiology: It would be the greatest paradigm shift in the field of muscle contraction and function since Huxley's 1957 proposal of the cross-bridge paradigm.

诺贝尔奖获得者 AF Huxley 于 1957 年提出的理论描述了横纹肌收缩和产生力的方式，从而允许人体运动。赫胥黎提出，肌肉收缩是通过称为肌动蛋白和肌球蛋白的两种丝状蛋白的滑动而发生的，并且这种滑动是由称为跨桥的小分子马达产生的。这种所谓的肌肉收缩跨桥理论在肌肉生理学教科书中有所描述，并在全球范围内教授。该理论非常适合描述保持恒定长度（等长收缩）或缩短（同心收缩）的肌肉收缩机制。然而，跨桥理论始终无法预测肌肉拉伸时的收缩机制（所谓的偏心收缩）。每次运动时都会发生离心收缩，例如当我们走路或跑步时。 2002年，我们发现一定有一个“被动”结构元素也有助于产生主动力。通过在不同结构水平上进行仔细的实验​​，我们发现除了肌动蛋白和肌球蛋白引起的力之外，来自一种称为肌联蛋白的结构蛋白。然而，尽管 15 年前就有了这一发现，但肌动蛋白产生主动力的分子机制仍然未知，尽管人们已经提出了充足的理论。缺乏进展的主要原因是，尽管使用复杂的成像和衍射技术可以看到肌动蛋白、肌球蛋白和跨桥，但肌动蛋白不提供衍射图样，因此即使使用当今最复杂的成像技术也无法看到。十年前，我们提出了这样的理论：当肌肉被激活时，肌动蛋白会通过与肌动蛋白丝结合来改变其固有的硬度。目前，这是最被接受的理论，但没有直接的实验证据支持该理论。在当前的 NSERC RTI 应用程序中，我们请求设备系统的组件，以便我们能够直接探索我们的理论。与其他设备系统相比，所提出的系统具有独特的功能，可以对肌动蛋白、肌球蛋白和肌联蛋白的分子相互作用获得前所未有的了解：-它允许对单个肌节（肌肉的最小收缩单位）进行机械测试-它允许控制肌原纤维内任意数量的肌节的激活-它允许以前所未有的精度测量肌节力学-而且它 允许可视化激活肌节中的肌动蛋白-肌动蛋白相互作用如果我们的理论被证明是正确的，这个新的设备系统，它将从根本上改变科学家对肌肉收缩的看法，它将改变我们的教科书和我们的肌肉生理学教学：这将是自赫胥黎1957年提出跨桥范式以来肌肉收缩和功能领域最大的范式转变。