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

描述（由申请人提供）：心脏的Frank-Starling定律描述了舒张末期容积和心脏射血量之间的相互关系，这是一个以搏动为基础的调节系统。在细胞水平上，肌节长度（SL）依赖性肌丝Ca2+敏感性是这种现象（长度依赖性激活- lda）的基础。收缩器官如何传导有关SL的信息尚不清楚。我们研究的总体目标是阐明LDA的分子机制。在之前的融资周期中，我们发现丝间间距的变化并不是LDA的机制。此外，我们发现心肌肌钙蛋白- 1对LDA至关重要。目前的初步研究表明，沿细丝的协同激活的中断显著提高LDA，而主动循环交叉桥的减少不影响LDA。总之，我们的研究结果表明，肌肉中长度依赖的分子机制是肌节长度直接介导的细丝系统、肌凝蛋白和/或粗丝系统的结构/功能调节的结果，或者是肌动蛋白和肌凝蛋白相互作用的动力学/结构的结果。拟议的研究项目主要围绕三个具体目标来测试LDA是在细丝，粗丝或肌动蛋白-肌球蛋白相互作用的动力学水平上调制的结果。总的来说，我们已经获得了初步的数据，证明了我们的假设的可行性，以及我们的技术专长来进行拟议的实验。尽管弗兰克-斯特林心脏定律构成了心脏的基本属性，已经被人们欣赏了一个多世纪，但这一现象背后的分子机制仍然没有完全被理解。我们的研究计划旨在加强我们对这一重要生理过程的理解，这一生理过程控制着心脏搏动的表现。公共卫生相关性：弗兰克-斯塔林定律描述了心脏的基本特性，即随着充盈量的增加而增加心脏强度。这种现象的细胞机制是肌丝Ca2+响应肌节拉伸的反应增加，其机制尚不完全清楚。我们将采用分离心肌进行生物物理测量，利用收缩蛋白交换、转基因小鼠模型、荧光探针和x射线衍射探测细纤维和粗纤维结构。总的目标是解开这个重要的生理调节系统的分子机制，该系统在心脏中以心跳为基础运作。

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.