Proteolytic Regulation of Troponin T & Cardiac Function

肌钙蛋白 T 的蛋白水解调节

• 批准号: 8291272
• 负责人: Jian-Ping Jin
• 金额: $ 51.92万
• 依托单位: WAYNE STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2014-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8291272
• 关键词: ATP phosphohydrolase; Actomyosin Adenosinetriphosphatase; Acute; Affect; Alternative Splicing; Animals; Binding; Binding Sites; Biochemical; Biochemistry; C-terminal; Calcium; Calmodulin; Calpain; Cardiac; Cardiac Muscle Contraction; Cardiac Myocytes; Cessation of life; Chronic; Complex; Congestive Heart Failure; Development; Dose; Excision; Exercise; Family; Financial compensation; Foundations; Functional disorder; Future; Genes; Health; Heart; Heart failure; Immunoglobulin Variable Region; Infarction; Injury; Ischemia; Knowledge; Lead; Life; Link; Mechanics; Microfilaments; Modeling; Modification; Molecular Conformation; Motor; Mus; Muscle; Muscle Cells; Myocardial; Myocardial Contraction; Myocardial Ischemia; Myocardial dysfunction; Myocardium; Myofibrils; Myosin ATPase; Myosin Light Chains; N-terminal; Nature; Phase; Phenotype; Physiologic intraventricular pressure; Physiological; Plant Roots; Post-Translational Protein Processing; Post-Translational Regulation; Preparation; Prevention approach; Production; Protein Binding; Protein Subunits; Proteolysis; Pump; Rattus; Regulation; Regulation of Proteolysis; Reperfusion Injury; Reperfusion Therapy; Reporting; Research Project Grants; Role; Skin; Stress; Stretching; Striated Muscles; Structure; Structure-Activity Relationship; System; Testing; Thin Filament; Time; Transgenic Mice; Transgenic Organisms; Translating; Tropomyosin; Troponin; Troponin C; Troponin I; Troponin T; Variant; Ventricular; Work; base; cardiogenesis; clinical application; connectin; coping; functional loss; genetic regulatory protein; heart function; improved; in vivo; novel; postnatal; pressure; protein complex; receptor; reconstitution; research study; response; therapeutic development

DESCRIPTION (provided by applicant): Cardiac muscle contraction is regulated by Ca2+ through the troponin complex that consists of three protein subunits: troponin C, troponin I, and troponin T (TnT). This research project investigates the role of a novel posttranslational modification of cardiac TnT (cTnT) in myocardial adaptation to energetic crisis. We recently reported a restricted N-terminal proteolysis of cTnT in myocardial ischemia-reperfusion (Zhang et al., Biochemistry 45:11681-94, 2006) and pressure overload (Feng et al., J. Physiol. 586:3537-50, 2008). This modification selectively removes the N-terminal variable region of cTnT but keeps the conserved middle and C-terminal regions intact. Initial studies in transgenic mouse hearts showed that the N-terminal truncated cTnT (cTnT-ND) remains functional in the myofilaments and alters myocardial contractility. This finding has lead to a hypothesis that the proteolytic removal of the N-terminal variable region of cTnT produces a functional state in cardiac muscle thin filaments as acute adaptation to energetic crisis. To test this hypothesis and understand the physiological and pathophysiological significance of cTnT- ND, three Specific Aims are proposed in this research project: Aim I will characterize the effects of the selective deletion of the N-terminal variable region on the function of cTnT. We will examine the interactions of cTnT-ND with other thin filament regulatory proteins and its functional impacts on the Ca2+ activation of myofibril ATPase and the contractility of cardiac muscle. Aim II will study the role of N-terminal truncated cTnT in compensating cardiac function and providing myocardial protection against ischemia-reperfusion injury. The acute and chronic effects of cTnT-ND on heart function and its role in overcoming energetic crisis will be investigated in ex vivo working hearts and in vivo. Aim III will investigate the role of mechanical stretch of the cardiac muscle in inducing the restricted proteolytic cleavage of cTnT N-terminal segment in order to understand the mechanisms that regulates this posttranslational regulation. Using integrated experimental systems, this study will gain new knowledge for the structure-function relationships of TnT and lay a foundation for future development of new treatment of ischemic heart disease and heart failure. PUBLIC HEALTH RELEVANCE: Myocardial contraction is essential for heart function. The contraction of cardiac muscle is regulated by calcium via the function of troponin, a protein complex in muscle cells. Cardiac troponin T (cTnT) is a subunit of the troponin complex in cardiac muscle. In a recent study, we found a restricted cleavage of cTnT in stress conditions such as acute myocardial ischemia. This modification of cTnT selectively removes the N-terminal variable region and keeps the remaining conserved structure in the myofibrils with functional consequences. Initial studies of transgenic mouse hearts showed that the N-terminal truncated cTnT (cTnT- ND) has a beneficial effect on the pumping efficiency of the heart. This observation lead us to propose a novel hypothesis that the removal of the N-terminal segment of cTnT is a rapid posttranslational mechanism to produce a transient functional state in the cardiac muscle for coping with energetic crisis. In the present study, we will characterize the physiological and pathophysiological functions of cTnT-ND. We shall examine the effects of restricted N-terminal truncation on the biochemical function of cTnT, the calcium activation of myofibril motors and the contractility of cardiac muscle. The potential role of cTnT-ND in reducing myocardial dysfunction and protecting the cardiac muscle during ischemia will be studied in isolated working hearts and in living animals. The mechanisms for mechanical stretch to induce the production of cTnT-ND will also be investigated. These experiments will provide new information for understanding the role of cTnT-ND in myocardial adaptation to energetic crisis. Using integrated physiological systems, this experimental research will also contribute key information for the structure-function relationship of TnT and lay a foundation for future development of new treatment of ischemic heart diseases and heart failure.

描述（由申请人提供）： 心肌收缩由 Ca2+ 通过肌钙蛋白复合物调节，该复合物由三个蛋白质亚基组成：肌钙蛋白 C、肌钙蛋白 I 和肌钙蛋白 T (TnT)。该研究项目研究了心脏 TnT (cTnT) 的新型翻译后修饰在心肌适应能量危机中的作用。我们最近报道了心肌缺血再灌注中 cTnT 的 N 端受限蛋白水解（Zhang 等人，Biochemistry 45：11681-94，2006）和压力超负荷（Feng 等人，J. Physiol. 586：3537-50， 2008）。这种修饰选择性地去除了 cTnT 的 N 端可变区，但保留了保守的中间和 C 端区域完整。对转基因小鼠心脏的初步研究表明，N 端截短的 cTnT (cTnT-ND) 在肌丝中仍然具有功能并改变心肌收缩力。这一发现引发了一个假设：cTnT N 末端可变区的蛋白水解去除会在心肌细丝中产生功能状态，作为对能量危机的急性适应。为了检验这一假设并了解 cTnT-ND 的生理和病理生理学意义，本研究项目提出了三个具体目标： 目标 I 将表征选择性删除 N 端可变区对 cTnT 功能的影响。我们将研究 cTnT-ND 与其他细丝调节蛋白的相互作用及其对肌原纤维 ATP 酶 Ca2+ 激活和心肌收缩力的功能影响。 Aim II 将研究 N 端截短的 cTnT 在代偿心脏功能和提供心肌保护以防止缺血再灌注损伤中的作用。 cTnT-ND 对心脏功能的急性和慢性影响及其在克服能量危机中的作用将在离体工作心脏和体内进行研究。目标 III 将研究心肌机械拉伸在诱导 cTnT N 末端片段的限制性蛋白水解裂解中的作用，以了解调节这种翻译后调节的机制。 利用集成的实验系统，本研究将获得关于TnT结构与功能关系的新知识，并为未来开发缺血性心脏病和心力衰竭的新疗法奠定基础。 公共卫生相关性： 心肌收缩对于心脏功能至关重要。心肌的收缩由钙通过肌钙蛋白（肌肉细胞中的一种蛋白质复合物）的功能来调节。心肌肌钙蛋白 T (cTnT) 是心肌肌钙蛋白复合物的一个亚基。在最近的一项研究中，我们发现在急性心肌缺血等应激条件下，cTnT 的裂解受到限制。 cTnT 的这种修饰选择性地去除 N 末端可变区，并保留肌原纤维中剩余的保守结构，从而产生功能后果。对转基因小鼠心脏的初步研究表明，N 端截短的 cTnT (cTnT-ND) 对心脏的泵血效率具有有益的影响。这一观察结果使我们提出了一个新的假设，即 cTnT N 末端片段的去除是一种快速翻译后机制，可以在心肌中产生短暂的功能状态，以应对能量危机。在本研究中，我们将描述 cTnT-ND 的生理和病理生理功能。我们将研究限制性 N 末端截断对 cTnT 的生化功能、肌原纤维运动的钙激活和心肌收缩力的影响。 cTnT-ND 在减少心肌功能障碍和保护缺血期间心肌方面的潜在作用将在离体工作心脏和活体动物中进行研究。还将研究机械拉伸诱导 cTnT-ND 产生的机制。这些实验将为理解 cTnT-ND 在心肌适应能量危机中的作用提供新的信息。利用整合的生理系统，这项实验研究还将为TnT的结构与功能关系提供关键信息，并为未来开发缺血性心脏病和心力衰竭的新疗法奠定基础。