cMyBPC and Regulation of Myocardial Contraction

cMyBPC 和心肌收缩的调节

• 批准号: 7114287
• 负责人: Samantha P Harris
• 金额: $ 33.94万
• 依托单位: UNIVERSITY OF WASHINGTON
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-01 至 2010-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7114287
• 关键词: actins; asymmetric septal hypertrophy; beta adrenergic receptor; binding proteins; binding sites; biomechanics; calcium flux; disease /disorder model; enzyme activity; gene expression; gene mutation; genetic disorder; genetically modified animals; heart contraction; hypertrophic myocardiopathy; laboratory mouse; laboratory rabbit; microfilaments; muscle cells; myosins; phosphorylation; protein C; protein kinase A; protein structure function; site directed mutagenesis; troponin

DESCRIPTION (provided by applicant): The long range goal of the proposed experiments is to understand the function of myosin binding protein-C in the regulation of cardiac contraction. Mutations in cardiac myosin binding protein-C (cMyBPC) account for nearly half of all instances of inherited hypertrophic cardiomyopathy and cMyBP-C is phosphorylated in response to inotropic stimuli, but neither the mechanisms by which mutations in cMyBP-C cause disease nor the role of cMyBP-C in mediating cardiac contractile responses are well understood. Until now the central difficulty in addressing the function of MyBP-C has been the inability to systematically alter cMyBP-C content or to selectively affect cMyBP-C phosphorylation state without simultaneously affecting other myofilament proteins. However, both these technical limitations will be overcome in the proposed experiments by using cMyBP-C knockout mice that lack cMyBP-C in heart. The cMyBP-C knockout mice therefore provide a "null" background on which to test specific mechanistic hypotheses of cMyBP-C function in health and disease. Based on our initial studies characterizing the cMyBP-C knockout mice, the working hypothesis guiding these experiments is that cMyBP-C normally acts to limit cross-bridge kinetics and power output and that phosphorylation of cMyBP-C relieves this inhibition. We further propose that the contractile effects of cMyBP-C are mediated by binding to myosin at two distinct sites and effects elicited by cMyBP-C binding differ depending on whether one or both sites are occupied. As a corollary to this idea, we propose that unregulated binding of the cMyBP-C N-terminus to myosin S2, as might occur in some familial hypertrophic cardiomyopathies, is sufficient to cause cardiomyopathy. These hypotheses will be tested in four Specific Aims designed to determine 1) contractile effects of cMyBP-C binding to distinct myosin binding sites, alone and in combination; 2) steps in the cross-bridge cycle affected by cMyBP-C binding to myosin S2; 3) the role of cMyBP-C phosphorylation in mediating contractile responses to padrenergic stimuli; and 4) whether expression of cMyBP-C N-terminal regulatory sequences is sufficient to induce cardiac hypertrophy in a dominant negative fashion. Results from the proposed experiments will provide new and relevant information regarding the function of MyBP-C, mechanisms of myosin regulation, and mechanisms by which mutations in the cMyBP-C cause human disease.

描述（由申请人提供）：提出的实验的远距离目标是了解肌球蛋白结合蛋白-C在心脏收缩调节中的功能。 Mutations in cardiac myosin binding protein-C (cMyBPC) account for nearly half of all instances of inherited hypertrophic cardiomyopathy and cMyBP-C is phosphorylated in response to inotropic stimuli, but neither the mechanisms by which mutations in cMyBP-C cause disease nor the role of cMyBP-C in mediating cardiac contractile responses are well understood.到目前为止，解决MYBP-C功能的主要困难是无法系统地改变CMYBP-C含量或选择性地影响CMYBP-C磷酸化状态而不会同时影响其他肌丝蛋白。但是，通过使用缺乏心脏中CMYBP-C的CMYBP-C基因敲除小鼠，将在拟议的实验中克服这两种技术局限性。因此，CMYBP-C敲除小鼠提供了“无效”背景，以测试健康和疾病中CMYBP-C功能的特定机械假设。基于我们表征CMYBP-C基因敲除小鼠的最初研究，指导这些实验的工作假设是，CMYBP-C通常会起作用以限制跨桥动力学和功率输出，以及CMYBP-C-C的磷酸化可以缓解这种抑制作用。我们进一步提出，CMYBP-C的收缩效应是通过在两个不同位点与肌球蛋白结合的结合而介导的，而CMYBP-C结合引起的效果则取决于一个或两个位点的占据。作为这一想法的必然性，我们建议CMYBP-C N末端与肌球蛋白S2的不受管制的结合，就像某些家族性肥厚性心肌病中可能发生的那样，足以引起心肌病。这些假设将在四个旨在确定的特定目的中进行测试1）单独和组合CMYBP-C结合与不同的肌球蛋白结合位点的收缩效应； 2）由CMYBP-C与肌球蛋白S2结合影响的跨桥循环的步骤； 3）CMYBP-C磷酸化在介导收缩反应对pad子刺激的反应中的作用； 4）CMYBP-C N末端调节序列的表达是否足以以主要的负面方式诱导心脏肥大。提出的实验的结果将提供有关MYBP-C功能，肌球蛋白调节机制以及CMYBP-C中突变引起人类疾病的机制的新的相关信息。