Frank-Starling's Law of the Heart: Cellular Mechanisms

描述(由申请人提供)：弗兰克-斯塔林心脏定律描述了舒张末容量和心脏射血量之间的相互关系，这是一种以节拍为基础运行的调节系统。在细胞水平上，肌节长度(SL)依赖的肌丝钙敏感性是这种现象(长度依赖的激活-LDA)的基础。收缩装置如何传递关于SL的信息尚不清楚。我们研究的总体目标是阐明LDA背后的分子机制。在上一个供资周期中，我们发现细丝间距的变化并不是LDA的基础机制。此外，我们发现心肌肌钙蛋白-I对LDA是必不可少的。目前的初步研究表明，沿细丝协同激活的中断显著增强了LDA，而跨桥活跃循环的减少并不影响LDA。综上所述，我们的发现表明，肌肉长度依赖的分子机制是肌节长度直接调节细丝系统、肌球蛋白和/或粗丝系统的结构/功能的结果，或者是肌动蛋白和肌球蛋白相互作用的动力学/结构的结果。拟议的研究项目围绕三个具体目标来测试LDA是否是细丝、粗丝或肌动蛋白-肌球蛋白相互作用动力学水平上的调制结果。总体而言，我们已经获得了初步数据，证明了我们的假设的可行性，以及我们进行拟议实验的技术专长。尽管弗兰克-斯塔林心脏定律构成了心脏的一个基本性质，它已经被认识了一个多世纪，但这种现象背后的分子机制仍然没有完全理解。我们的研究建议旨在加强我们对这一重要的生理过程的理解，这一过程在节拍的基础上控制着心脏的性能。与公共健康相关：弗兰克-斯塔林定律描述了心脏的基本性质，即随着充盈量的增加而增加心脏力量。这种现象的细胞机制是肌节伸展后肌丝钙反应性的增加，其机制尚不完全清楚。我们将使用分离的心肌进行生物物理测量，使用收缩蛋白交换、转基因小鼠模型、荧光探针以及X射线衍射来探测细丝和粗丝结构。总体目标是解开在心脏中以节拍为基础运行的这一重要的生理调节系统背后的分子机制。

DESCRIPTION (provided by applicant): The Frank-Starling law of the heart describes the interrelationship between end-diastolic volume and cardiac ejection volume, a regulatory system that operates on a beat-to-beat basis. At the cellular level, sarcomere length (SL) dependent myofilament Ca2+ sensitivity underlies this phenomenon (length dependent activation-LDA). How the contractile apparatus transduces the information concerning SL is not known. The overall goal of our research is to elucidate the molecular mechanisms that underlie LDA. During the previous funding cycle we have found that changes in inter-filament spacing is not the mechanism that underlies LDA. Furthermore, we discovered that cardiac troponin-I is essential for LDA. Preliminary studies now show that interruption of cooperative activation along the thin filament markedly enhances LDA, while a reduction in active cycling cross-bridges does not affect LDA. Together, our findings suggest that the molecular mechanisms that underlie length dependency in muscle are the result of a direct sarcomere length mediated modulation of the structure/function of the thin filament system, myosin and/or thick filament system, or the kinetics/structure of the interaction between actin and myosin. The proposed research project is focused around three specific aims to test whether LDA is the result of modulation at the level of the thin filament, the thick filament or the kinetics of actin-myosin interaction. Overall, we have obtained preliminary data that demonstrate the feasibility of our hypotheses as well as our technical expertise to conduct the proposed experiments. Although the Frank- Starling Law of the Heart constitutes a fundamental property of the heart that has been appreciated for well over a century, the molecular mechanisms that underlie this phenomenon are still incompletely understood. Our research proposal is aimed to enhance our understanding of this important physiological process that controls cardiac performance on a beat-to-beat basis. PUBLIC HEALTH RELEVANCE: The Frank-Starling Law describes the fundamental property of the heart to increase cardiac strength in response to increased filling volume. The cellular mechanism for this phenomenon is an increase in myofilament Ca2+ responsiveness in response to sarcomere stretch via mechanisms that are incompletely understood. We will employ isolated myocardium for biophysical measurements probing at thin and thick filament structure using contractile protein exchange, transgenic murine models, fluorescent probes, as well as x-ray diffraction. The overall aim is to unravel the molecular mechanisms that underlie this important physiological regulatory system operating in the heart on a beat-to- beat basis.