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

描述（由申请方提供）：拟定实验的长期目标是了解心肌肌球蛋白结合蛋白-C（cMyBP-C）在心肌收缩调节中的功能。cMyBP-C的突变导致全世界数百万人的肥厚性心肌病和心力衰竭，在正常情况下，cMyBP-C在心跳的基础上调节收缩。然而，无论是cMyBP-C突变引起疾病的机制，还是cMyBP-C影响收缩的机制都没有完全理解。到目前为止，流行的假设是MyBP-C通过与肌球蛋白结合并限制肌球蛋白头从粗肌丝延伸并与细肌丝上的肌动蛋白进行相互作用的能力来可逆地限制收缩速度。然而，我们实验室在该资助的第一阶段所做的发现挑战了这一想法，并表明cMyBP-C本身可以与肌动蛋白或其他配体结合以影响收缩。本文的目的是通过探测cMyBP-C的调节M结构域中的新型分子识别特征（MoRF）的功能意义来测试cMyBP-C介导的配体结合相互作用的作用，所述新型分子识别特征赋予cMyBP-C N末端与肌动蛋白的特异性结合或介导N末端的其他体外功能效应。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内。具体目的将1）使用新的转基因小鼠在体外和体内对M-结构域MoRF中介导肌动蛋白结合和M-结构域的其他功能效应的残基进行作图; 2）使用新的和现有的转基因小鼠确定M-结构域之外的cMyBP-C的脯氨酸-丙氨酸和C1结构域是否有助于cMyBP-C的体内功能;和3）定义cMyBP-C与薄和厚细丝的结构相互作用。从拟议的实验结果将提供新的见解MyBP-C的功能和心肌收缩的调节机制在健康和疾病。 公共卫生相关性：本实验旨在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，HCM是一种发病率为1/500的临床疾病。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，因此提高我们对cMyBP-C影响健康和患病心脏心功能的机制的理解，预计最终将有助于疾病诊断，预后和治疗的进步。拟议的实验将通过研究cMyBP-C与肌肉肌节的薄丝和粗丝结合产生的功能效应来研究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.