Regulation and Maintenance of Cardiac Muscle Sarcomere Integrity

心肌肌节完整性的调节和维持

基本信息

批准号：
7988075
负责人：
CHEE CHEW LIM
金额：
$ 36.27万
依托单位：
VANDERBILT UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2010
资助国家：
美国
起止时间：
2010-07-05 至 2015-06-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/7988075
关键词：
3&apos Untranslated Regions Actins Affect Amines Antioxidants Attention Calpain Cardiac Cardiac Myocytes Cardiomyopathies Cell Nucleus Complex Data Disease Equilibrium Event Excision Fluorescent in Situ Hybridization Genes Genetic Transcription Goals Half-Life Health Heart Heart Hypertrophy Heart failure Heterogeneity In Vitro Individual Kinetics Lead Macromolecular Complexes Maintenance Mediating Messenger RNA Methods Microfilaments Modeling Molecular Molecular Biology Molecular Weight Mus Muscle Cells Myocardium Myosin ATPase Oxidative Stress Oxis Pathway interactions Physiological Process Protease Inhibitor Protein Biosynthesis Proteins Reactive Oxygen Species Recycling Regulation Regulatory Element Reporter Role Sarcomeres Signaling Protein Structure System Testing Transgenic Organisms Translations Ubiquitin Untranslated Regions Work base calpastatin connectin cost design genetic regulatory protein in vivo insight multicatalytic endopeptidase complex novel therapeutic intervention oxidative damage promoter protein degradation public health relevance titin 1 titin 2

项目摘要

DESCRIPTION (provided by applicant): The cardiac sarcomere is a complex and highly ordered ensemble of contractile and regulatory proteins designed to generate force. To maintain functional sarcomeres, precise turnover of proteins is required that balances new protein synthesis and incorporation into the sarcomere with removal and degradation of worn out or damaged proteins. Given the heterogeneity in protein turnover rates, the mechanisms by which independent turnover of the individual sarcomere components occurs while maintaining the functional integrity of the sarcomere structure, is not well understood. Several studies have shown that a number of myofilament proteins, including actin and myosin, are in kinetic equilibrium with a cytoplasmic precursor pool, suggesting continual replacement of worn out myofilament proteins for their precursors into an otherwise intact sarcomere. As the size of the protein increases, however, several problems arise that make simple sarcomere protein exchange improbable. For one, the maintenance of a precursor pool of high molecular weight proteins comes at an increasing energetic cost to the myocyte. Another problem is that unlike smaller myofilament proteins that are continually recycled in the existing sarcomere, turnover of myofibrillar macromolecular complexes likely requires either partial or complete disassembly of the sarcomere. These considerations have focused our attention on the molecular events regulating the turnover of the giant myofilament protein titin. Titin is an integral part of the sarcomere complex, serving as (1) a molecular template around which the myosins and other structural and signaling proteins assemble, and (2) a molecular spring to impart myofibrillar stiffness to the heart. We therefore postulate that the degradation of titin will trigger local disassembly of the sarcomere. Based on preliminary data, we propose that oxidative damage to titin triggers sequential degradation by the calpains and ubiquitin-proteasome system. We propose that sarcomere mechanosensors are activated during the process of titin degradation, and translocate to the nucleus to activate titin gene transcription. We propose that titin mRNA is targeted to the sarcomere and that localized titin synthesis occurs with concurrent reassembly of the sarcomere. We finally propose that cardiac hypertrophy modulates titin transcription and translation pathways leading to net sarcomere addition. The proposed experimental aims will allow us to evaluate and refine this model, and advance our understanding of the complex physiological and temporal aspects of myofilament sarcomere turnover. PUBLIC HEALTH RELEVANCE: The cardiac sarcomere is the basic contractile unit of the heart and is composed of an ensemble of myofilament and regulatory proteins designed to generate force. It is generally assumed that maintenance of functioning sarcomeres requires precise control of synthesis, assembly, and degradation of myofilament proteins, however, the mechanisms that mediate turnover of large integrated myofilament proteins, such as titin, have not been looked at. Understanding the molecular mechanisms of titin protein turnover will provide insight into the regulatory processes of sarcomere maintenance, and may ultimately lead to novel therapeutic approaches for heart failure cardiomyopathies.

描述（由申请人提供）：心脏肌节是一个复杂且高度有序的收缩蛋白和调节蛋白的集合，旨在产生力。为了维持功能性肌节，需要精确的蛋白质周转，以平衡新蛋白质的合成和并入肌节，以及去除和降解磨损或受损的蛋白质。鉴于蛋白质周转率的异质性，在保持肌节结构的功能完整性的同时发生各个肌节成分的独立周转的机制尚不清楚。多项研究表明，包括肌动蛋白和肌球蛋白在内的许多肌丝蛋白与细胞质前体库处于动力学平衡，这表明磨损的肌丝蛋白不断将其前体替换为完整的肌节。然而，随着蛋白质大小的增加，出现了一些问题，使得简单的肌节蛋白质交换变得不可能。其一，维持高分子量蛋白质的前体池会增加肌细胞的能量消耗。另一个问题是，与在现有肌节中不断循环的较小肌丝蛋白不同，肌原纤维大分子复合物的周转可能需要肌节的部分或完全分解。这些考虑使我们的注意力集中在调节巨型肌丝蛋白肌联蛋白周转的分子事件上。肌联蛋白是肌节复合体的一个组成部分，充当（1）肌球蛋白和其他结构蛋白和信号蛋白围绕其组装的分子模板，以及（2）赋予心脏肌原纤维硬度的分子弹簧。因此，我们假设肌动蛋白的降解将引发肌节的局部分解。根据初步数据，我们提出肌联蛋白的氧化损伤会引发钙蛋白酶和泛素-蛋白酶体系统的连续降解。我们提出肌节机械传感器在肌联蛋白降解过程中被激活，并转移到细胞核以激活肌联蛋白基因转录。我们提出肌联蛋白 mRNA 靶向肌节，并且局部肌联蛋白合成与肌节同时重新组装发生。我们最终提出，心脏肥大调节肌动蛋白转录和翻译途径，导致净肌节添加。拟议的实验目标将使我们能够评估和完善该模型，并增进我们对肌丝肌节周转的复杂生理和时间方面的理解。公众健康相关性：心脏肌节是心脏的基本收缩单位，由一组肌丝和旨在产生力的调节蛋白组成。人们普遍认为，维持功能性肌节需要精确控制肌丝蛋白的合成、组装和降解，然而，介导大型整合肌丝蛋白（例如肌联蛋白）周转的机制尚未被研究。了解肌联蛋白周转的分子机制将有助于深入了解肌节维持的调节过程，并可能最终导致心力衰竭心肌病的新治疗方法。