Regulation of actin dynamics during myofibril assembly

肌原纤维组装过程中肌动蛋白动力学的调节

• 批准号: 8900741
• 负责人: Shoichiro Ono
• 金额: $ 35.1万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-05-01 至 2016-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8900741
• 关键词: Actins; Animal Model; Biological Models; Caenorhabditis elegans; Calcium; Cells; Complex; Contractile Proteins; Enhancers; Equilibrium; Family; Filament; Gelsolin; Genetic; Genetic study; Human; In Vitro; Knowledge; Length; Life; Link; Maintenance; Microfilaments; Minus End of the Actin Filament; Muscle; Muscle Cells; Muscle Contraction; Muscle Proteins; Mutation; Myofibrils; Myopathy; Nemaline Myopathies; Nematoda; Pattern; Protein Isoforms; Proteins; Regulation; Research; Role; Sarcomeres; Side; Skeletal Muscle; Striated Muscles; Structure; System; Testing; Thin Filament; Tropomyosin; calponin; cellular imaging; cofilin; genetic regulatory protein; in vitro activity; insight; member; nebulin; novel; pointed protein; retinal rods; tropomodulin

DESCRIPTION (provided by applicant): Sarcomere in striate muscle is the basic unit of contractile apparatuses. Assembly and maintenance of organized sarcomeric structure are essential for producing contractile forces. Actin is one of the major components of sarcomeric thin filaments, and length and orientation of the filaments are precisely regulated in striated muscle. However, the mechanism of assembly and maintenance of sarcomeric actin filaments is complex and poorly understood. What is more puzzling is that actin subunits within thin filaments are dynamically exchanged without compromising overall structure and contractile functions. A number of regulators of actin dynamics have been identified in skeletal muscle, and some of them are linked to genetic muscle disorders. In particular, nemaline myopathy involves formation of abnormal actin-rich aggregates or rods in skeletal muscle and is caused by mutations in actin or regulators of actin dynamics including nebulin, tropomyosin, and cofilin. Therefore, the regulation of actin dynamics is fundamentally important for building functional contractile apparatuses in skeletal muscle, and malfunction in this system leads to muscle disorders. To investigate the regulatory mechanism of actin dynamics in striated muscle, we have been using the nematode Caenorhabditis elegans as a model system. Body wall muscle of C. elegans is striated muscle, and most of sarcomeric proteins are conserved between C. elegans and humans. Powerful genetic studies on these muscle proteins advanced our knowledge on the mechanism of myofibril assembly and function. Using this system, we have identified that ADF/cofilin and AIP1 enhance turnover of actin filaments and essential for organized assembly of sarcomeric actin filaments, and that tropomyosin and calponin-like protein antagonize ADF/cofilin and stabilize sarcomeric actin filaments. These findings led us to hypothesize that a balance between enhancers and suppressors of actin dynamics is crucial for sarcomere assembly and maintenance. Recently, we obtained evidence that additional regulators of actin dynamics are involved in sarcomeric actin regulation. Therefore, we propose to further investigate their roles in myofibril assembly in three specific aims: (Aim 1) We identified a cyclase-associated protein isoform that is enriched in body wall muscle and will determine how cyclase-associated protein cooperate with ADF/cofilin and AIP1 to regulate actin turnover, (Aim 2) We identified a gelsolin-like protein with strong actin-severing activity that is enriched in body wall muscle and will investigate its role in actin organization, and (Aim 3) We demonstrated distinct localization patterns of actin-regulatory proteins near the pointed ends of sarcomeric thin filaments and will investigate how actin dynamics are regulated in this specialized region. We expect that results of this research will provide new insight into the regulation of actin dynamics in striated muscle.

描述（申请人提供）： 横纹肌中的肌节是收缩装置的基本单位。有组织的肌节结构的组装和维护对于产生收缩力至关重要。肌动蛋白是肌节细丝的主要成分之一，细丝的长度和方向在横纹肌中受到精确调节。然而，肌节肌动蛋白丝的组装和维持机制很复杂且知之甚少。更令人费解的是，细丝内的肌动蛋白亚基可以动态交换，而不会影响整体结构和收缩功能。骨骼肌中已发现许多肌动蛋白动力学调节因子，其中一些与遗传性肌肉疾病有关。具体而言，线状肌病涉及骨骼肌中异常富含肌动蛋白的聚集体或杆的形成，并且是由肌动蛋白或肌动蛋白动力学调节剂（包括nebulin、原肌球蛋白和肌丝蛋白丝切蛋白）的突变引起的。因此，肌动蛋白动力学的调节对于在骨骼肌中构建功能性收缩装置至关重要，并且该系统的故障会导致肌肉疾病。为了研究横纹肌肌动蛋白动力学的调节机制，我们一直使用线虫秀丽隐杆线虫作为模型系统。线虫的体壁肌肉是横纹肌，大部分肌节蛋白在线虫和人类之间是保守的。对这些肌肉蛋白的强大遗传学研究增进了我们对肌原纤维组装和功能机制的了解。使用该系统，我们发现 ADF/cofilin 和 AIP1 增强肌动蛋白丝的周转，对于肌节肌动蛋白丝的组织组装至关重要，并且原肌球蛋白和钙调蛋白样蛋白拮抗 ADF/cofilin 并稳定肌节肌动蛋白丝。这些发现使我们假设肌动蛋白动力学的增强子和抑制子之间的平衡对于肌节的组装和维护至关重要。最近，我们获得的证据表明肌动蛋白动力学的其他调节因子参与肌节肌动蛋白调节。因此，我们建议进一步研究它们在肌原纤维组装中的作用，以实现三个具体目标：（目标 1）我们鉴定了一种富含体壁肌肉的环化酶相关蛋白亚型，并将确定环化酶相关蛋白如何与 ADF/cofilin 和 AIP1 合作调节肌动蛋白周转，（目标 2）我们鉴定了一种具有强肌动蛋白切断活性的凝溶胶蛋白样蛋白，即 富含体壁肌肉，并将研究其在肌动蛋白组织中的作用，并且（目标 3）我们展示了肌节细丝尖端附近肌动蛋白调节蛋白的独特定位模式，并将研究肌动蛋白动力学如何在这个特殊区域中受到调节。我们期望这项研究的结果将为横纹肌肌动蛋白动力学的调节提供新的见解。