Role of Myosin Binding Protein-C in the Regulation of Myocardial Contraction

描述(申请人提供)：拟议实验的长期目标是了解心肌肌球蛋白结合蛋白-C(cMyBP-C)在调节心肌收缩中的功能。CMyBP-C的突变导致全球数百万人患有肥厚性心肌病和心力衰竭，在正常情况下，cMyBP-C以节拍为基础调节收缩。然而，cMyBP-C突变致病的机制和cMyBP-C影响收缩的机制都不完全清楚。到目前为止，流行的假说一直是MyBP-C通过与肌球蛋白结合来可逆地限制收缩速度，并限制肌球蛋白头从粗丝向外延伸的能力，以及与细丝上的肌动蛋白相互作用的周期。然而，我们实验室在这笔赠款的第一阶段所做的发现挑战了这一观点，并表明cMyBP-C本身可以与肌动蛋白或其他配体结合来影响收缩。本文旨在通过探讨cMyBP-C调控M区中新的分子识别特征(Morf)的功能意义来测试cMyBP-C介导的配体结合作用，该功能赋予cMyBP-C N端与肌动蛋白的特异性结合或在体外介导N端的其他功能效应。了解Morf片段的功能将进一步提供对疾病的新见解，因为HCM错义突变聚集在该片段中。特定的目标将1)利用新的转基因小鼠来定位M-结构域中介导肌动蛋白结合和其他功能效应的M-结构域的残基；2)使用新的和现有的转基因小鼠来确定M-结构域之外的cMyBP-C的Pro-丙氨酸和C1结构域是否有助于cMyBP-C的功能；以及3)确定cMyBP-C与细丝和粗丝的结构相互作用。拟议中的实验结果将为了解MyBP-C的功能以及健康和疾病中心肌收缩的调节机制提供新的见解。 与公共健康相关：拟议的实验将研究心肌肌球蛋白结合蛋白-C(cMyBP-C)调节心肌收缩强度和速度的基本分子机制。CMyBP-C突变是肥厚型心肌病(HCM)的重要原因，这种临床疾病的发病率为每500人中就有一例。由于HCM是青少年心源性猝死和老年人群心力衰竭的常见原因，提高我们对cMyBP-C影响健康和疾病心脏功能的机制的理解最终有望有助于疾病诊断、预后和治疗的进步。拟议的实验将通过研究cMyBP-C与肌肉肌节细丝和粗丝结合所产生的功能影响，来研究cMyBP-C调节心脏收缩的能力。

DESCRIPTION (provided by applicant): The long-range goal of the proposed experiments is to understand the function of cardiac myosin binding protein-C (cMyBP-C) in the regulation of myocardial contraction. Mutations in cMyBP-C cause hypertrophic cardiomyopathy and heart failure in millions of people worldwide and under normal conditions cMyBP-C regulates contraction on a beat-to- beat basis. However, neither the mechanisms by which cMyBP-C mutations cause disease nor the mechanisms by which cMyBP-C affects contraction are completely understood. Until now the prevailing hypothesis has been that MyBP-C reversibly limits the speed of contraction by binding to myosin and restricting the ability of myosin heads to extend away from thick filaments and to undergo cycles of interaction with actin on the thin filaments. However, discoveries made by our lab during the first period of this grant challenged this idea and suggest that cMyBP-C itself can bind to actin or other ligands to influence contraction. Aims here will test the role of ligand binding interactions mediated by cMyBP-C by probing the functional significance of novel Molecular Recognition Features (MoRFs) in the regulatory M- domain of cMyBP-C that confer specific binding of the cMyBP-C N-terminus to actin or that mediate other functional effects of the N-terminus in vitro. Understanding the function of the MoRF segment will further provide new insights into disease since HCM missense mutations are clustered within this segment. Specific Aims will 1) map residues in the M-domain MoRFs that mediate actin binding and other functional effects of the M-domain in vitro and in vivo using novel transgenic mice; 2) determine whether the proline-alanine and C1 domains of cMyBP-C outside the M-domain contribute the function of cMyBP-C in vivo using new and existing transgenic mice; and 3) define structural interactions of cMyBP-C with thin and thick filaments. Results from the proposed experiments will provide new insights into the function of MyBP-C and regulatory mechanisms of myocardial contraction in health and disease. PUBLIC HEALTH RELEVANCE: The proposed experiments will investigate the basic molecular mechanisms by which cardiac myosin binding protein-C (cMyBP-C) regulates the strength and speed of heart muscle contraction. Mutations in cMyBP-C are a significant cause hypertrophic cardiomyopathy (HCM), a clinical condition with an incidence of 1 in 500 people. Because HCM is a common cause of sudden cardiac death in adolescents and of heart failure in older populations, improving our understanding of the mechanisms by which cMyBP-C affects cardiac function in both healthy and diseased hearts is expected to ultimately contribute to advancements in disease diagnosis, prognosis, and treatment. Proposed experiments will investigate the ability of cMyBP-C to regulate cardiac contraction by investigating functional effects that result from cMyBP-C binding to thin and thick filaments of muscle sarcomeres.