REGULATION OF CARDIAC CROSS-BRIDGES BY TROPONIN T

肌钙蛋白 T 对心脏桥的调节

• 批准号: 6734647
• 负责人: SCOTT H BUCK
• 金额: $ 25.46万
• 依托单位: UNIV OF NORTH CAROLINA CHAPEL HILL
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-05-05 至 2006-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6734647
• 关键词: actins; binding sites; biomechanics; calcium flux; flash photolysis; heart contraction; laboratory mouse; laboratory rat; microfilaments; muscle strength; muscle tension; myocardium; myosins; protein isoforms; troponin

Cardiac muscle contraction results from cyclic interaction of actin with myosin cross-bridges under the influence of thick and thin filament regulatory proteins. Of the thin filament regulatory proteins, troponin T (TnT), tropomyosin, and troponin I undergo normal developmental isoform switching in heart. Additionally, TnT isoform expression is altered in cardiac disease states including mutations associated with hypertrophic cardiomyopathy (HCM) and altered TnT isoform distribution in heart failure. While effects of TnT isoform expression upon steady-state Ca2+-sensitivity of tension are recognized, the role of TnT isoforms in regulating actin-myosin cross-bridge kinetics and in regulating cooperative activation of the thin filament by strongly-bound cross-bridges are largely unknown. Experiments proposed in this application will address the mechanisms by which TnT isoform expression influences kinetics of myocardial force generation. Rates of Ca2+-activated tension development (kCa), relaxation (kr), and tension redevelopment (ktr) of permeabilized multicellular ventricular preparations will be measured to determine the effects TnT isoform expression upon transition of cross-bridges to the strongly-bound force-generating state, and upon rates of cross-bridge detachment. Velocity of loaded shortening of permeabilized myocytes at maximal and submaximal Ca2+ will be measured in order to determine TnT isoform-mediated effects upon force-velocity and power-load curves and upon optimum force for mechanical output. The tension-pCa relationship, kCa, kr, and ktr of permeabilized multicellular ventricular preparations treated with the non-force generating strong-binding myosin derivative, N-ethylmaleimide myosin S1 (NEM-S1) will be measured to determine the influence TnT isoform expression upon cooperative activation of thin filament by bound cross-bridges. Overall, the results of the proposed experiments will provide new information regarding the role of TnT in influencing myocardial contractility and will provide insight as well into thin filament regulatory protein modification to improve function of diseased hearts.

在粗丝和细丝调节蛋白的影响下，肌动蛋白与肌球蛋白跨桥的循环相互作用导致心肌收缩。 在细丝调节蛋白中，肌钙蛋白 T (TnT)、原肌球蛋白和肌钙蛋白 I 在心脏中经历正常的发育亚型转换。此外，TnT 同工型表达在心脏病状态下发生改变，包括与肥厚性心肌病 (HCM) 相关的突变和心力衰竭中 TnT 同工型分布的改变。 虽然 TnT 同工型表达对稳态 Ca2+ 张力敏感性的影响已被认识，但 TnT 同工型在调节肌动蛋白-肌球蛋白跨桥动力学和通过强结合跨桥调节细丝协同激活中的作用在很大程度上是未知的。 本申请中提出的实验将解决 TnT 同工型表达影响心肌力产生动力学的机制。 将测量透化的多细胞心室制剂的 Ca2+ 激活的张力发展 (kCa)、松弛 (kr) 和张力再发展 (ktr) 的速率，以确定 TnT 同工型表达对横桥转变为强束缚力生成状态以及对横桥脱离速率的影响。 将测量最大和次最大 Ca2+ 下透化肌细胞的负载缩短速度，以确定 TnT 同工型介导的对力-速度和功率-负载曲线以及对机械输出的最佳力的影响。 将测量用非力产生强结合肌球蛋白衍生物 N-乙基马来酰亚胺肌球蛋白 S1 (NEM-S1) 处理的透化多细胞心室制剂的张力 -pCa 关系、kCa、kr 和 ktr，以确定通过结合的横桥协同激活细丝的 TnT 同工型表达的影响。 总体而言，拟议实验的结果将提供有关 TnT 在影响心肌收缩力中的作用的新信息，并将提供对细丝调节蛋白修饰以改善患病心脏功能的见解。