cMyBPC and Regulation of Myocardial Contraction

cMyBPC 和心肌收缩的调节

基本信息

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
项目类别：
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

项目摘要

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）：所提出的实验的长期目标是了解肌球蛋白结合蛋白-C 在调节心脏收缩中的功能。心肌肌球蛋白结合蛋白-C (cMyBPC) 突变占遗传性肥厚型心肌病所有病例的近一半，并且 cMyBP-C 响应正性肌力刺激而磷酸化，但 cMyBP-C 突变引起疾病的机制和作用均未阐明。 cMyBP-C 在介导心脏收缩反应中的作用已广为人知。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 含量或选择性影响 cMyBP-C 磷酸化状态而不同时影响其他肌丝蛋白。然而，在所提出的实验中，通过使用心脏中缺乏 cMyBP-C 的 cMyBP-C 敲除小鼠，这两个技术限制都将得到克服。因此，cMyBP-C 敲除小鼠提供了“无效”背景，可用于测试 cMyBP-C 在健康和疾病中功能的特定机制假设。根据我们对 cMyBP-C 敲除小鼠的初步研究，指导这些实验的工作假设是 cMyBP-C 通常起到限制跨桥动力学和功率输出的作用，而 cMyBP-C 的磷酸化可以缓解这种抑制。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来介导的，并且 cMyBP-C 结合引起的效应根据一个位点还是两个位点被占据而不同。作为这一想法的推论，我们提出，cMyBP-C N 末端与肌球蛋白 S2 的不受调节的结合（如某些家族性肥厚性心肌病中可能发生的情况）足以引起心肌病。这些假设将在四个具体目标中进行测试，旨在确定 1) cMyBP-C 与不同肌球蛋白结合位点单独或组合结合的收缩效应； 2) 跨桥循环中受 cMyBP-C 与肌球蛋白 S2 结合影响的步骤； 3) cMyBP-C磷酸化在介导对padrenergic刺激的收缩反应中的作用； 4) cMyBP-C N-末端调节序列的表达是否足以以显性失活方式诱导心脏肥大。拟议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 突变导致人类疾病的机制的新的相关信息。