Myofilaments as regulators of heart function in disease

摘要 缺血性心肌病和心力衰竭是老年人合并发病率和死亡率的主要原因。 人类在此，肌节功能障碍在疾病发病机制中具有中心作用。肌节是 心肌的基本功能单位，直接负责心脏的泵血作用。心脏 肌节是一种多聚体收缩装置，由一个薄的基于肌原性的变构调节蛋白组成。 复合物与产生力的基于肌球蛋白的粗肌丝一起。交织肌丝 同步操作以调节和产生心脏性能所需的力。逐拍控制 心肌肌节激活的程度是指细丝调节系统在控制心肌肌节激活程度中的地位。 在抽搐期间收缩被打开和关闭。肌节功能的破坏是 许多形式的后天性和遗传性心脏病影响着这个国家的数百万人。因此，Focus 在这里，对肌节调节的机械见解强调了这一建议的主要健康相关性。 最近，新的研究结果已经走到了前面，提出协同肌丝间调节信号 机制，包括肌球蛋白跨桥ON/OFF状态在控制肌肉收缩中的新作用。 基于我们的肌节激活创新，以单个未加载的心肌细胞为特征，我们制作了一个 突破性的方法学进展，允许实时记录完整心脏中的肌节激活 生理负荷下的肌肉。该系统能够通过分子内FRET检测多个 完整心脏单次抽动收缩生理时程中肌丝激活配体的变化 肌肉负荷。指导假设：在负荷下生理相关的抽搐收缩期间， 肌丝激活由多个协同肌丝间调节输入动态控制，包括 TnC结合Ca ~（2+）、TnI开关结构域-TnC相互作用、OFF到ON状态肌球蛋白跨桥和MyBP-C在活体中的作用 心肌本研究旨在通过改变肌钙蛋白I分子开关来研究肌丝间信号传导 在负荷下活心肌中单个心脏抽搐的生理时间过程期间的机制; 探讨心肌收缩过程中肌丝间信号转导机制 通过修饰肌球蛋白跨桥，研究MyBP-C在肌丝间的作用， 在完整的心肌中生理性抽搐收缩期间的信号传导。通过我们的创新方法， 对肌丝间信号传导机制的新认识将对我们的研究产生重大影响。 了解心脏功能。反过来，这为指导新的治疗方法提供了必要的基础。 通过利用肌节作为开发新的 治疗和疗法的心脏病。

Abstract Ischemic cardiomyopathy and heart failure are the leading causes of combined morbidity and mortality in humans. Herein, sarcomere dysfunction has a central role in disease pathogenesis. The sarcomere is the essential functional unit of cardiac muscle, directly responsible for the pumping action of the heart. The cardiac sarcomere is a multimeric contractile apparatus consisting of a thin myofilament-based allosteric regulatory complex together with the myosin-based thick myofilament that generates force. Interlacing myofilaments operate in synchrony to regulate and generate the forces necessary for heart performance. Beat-to-beat control of cardiac sarcomere activation refers to the status of the thin filament regulatory system in controlling the degree to which contraction is turned on and off during a twitch. Disruption in sarcomere function underlies the basis for numerous forms of acquired and inherited heart diseases affecting millions of people in this country. Thus, focus here on mechanistic insights into sarcomere regulation underscores the major health relevance of this proposal. Recently, emerging results have come to the fore positing synergistic inter-myofilament regulatory signaling mechanisms, including a new role of myosin cross-bridge ON/OFF states in controlling muscle contraction. Building on our sarcomere activation innovations featuring single unloaded cardiac myocytes, we have made a breakthrough methodological advance, permitting real-time recordings of sarcomere activation in intact cardiac muscle under physiological load. This system is capable of detecting, by intramolecular FRET, multiple myofilament activating ligands during the physiological time course of a single twitch contraction in intact cardiac muscle under load. Guiding hypothesis: During physiologically relevant twitch contractions under load, thin filament activation is controlled dynamically by multiple synergistic inter-myofilament regulatory inputs, including TnC bound Ca2+, TnI switch domain-TnC interaction, OFF to ON state myosin cross-bridges, and MyBP-C in live cardiac muscle. This proposal aims to investigate inter-myofilament signaling by altering the TnI molecular switch mechanism during the physiological time-course of a single cardiac twitch in live cardiac muscles under load; to investigate the mechanism of inter-myofilament signaling during the cardiac twitch contraction in live intact cardiac muscles by modification in myosin cross-bridges; and to investigate the role MyBP-C in inter-myofilament signaling during physiological twitch contractions in intact cardiac muscles. Enabled by our innovative approach, the new insights into inter-myofilament signaling mechanisms gained here will significantly impact our understanding of cardiac function. In turn, this provides the essential foundation to guide new therapeutic discovery for the diseased heart by leveraging the sarcomere as an excellent target for developing new treatments and therapies for the diseased heart.