Regulation of actin dynamics during myofibril assembly

项目摘要 横纹肌中的肌节是收缩器官的基本单位。装配和维护 有组织的肌节结构对于肌肉的适当收缩和放松是必不可少的。肌动蛋白是 肌节细丝的主要成分，以及细丝的长度和取向 在横纹肌中调节。然而，肌节肌动蛋白的组装和维持机制 细丝是复杂的，人们对它知之甚少。已经确定了许多肌动蛋白动态的调节因子 骨骼肌，其中一些与遗传性肌肉疾病有关。线状肌病涉及 肌动蛋白在骨骼肌中形成异常的富含肌动蛋白的聚集体或杆，由肌动蛋白或肌动蛋白突变引起 肌动蛋白动力学的调节者。因此，肌动蛋白动力学的调节对于构建 骨骼肌中的功能性收缩装置，这一系统的故障会导致肌肉功能紊乱。 为了研究横纹肌中肌动蛋白动力学的调节机制，我们使用线虫 秀丽隐杆线虫作为模式系统。线虫的体壁肌肉为横纹肌，大部分 肌节蛋白在线虫和人类之间是保守的。在线虫中，我们已经鉴定出 ADF/cofilin(UNC-60B)、AIP1(UNC-78和AIPL-1)和环化酶相关蛋白(CAS-1)促进周转 肌动蛋白细丝，对肌节肌动蛋白细丝的有组织组装是必不可少的。此外，我们还确定了 Sup-13作为一种新的肌肉肌动蛋白调节因子。此外，我们还获得了证据表明， 在线虫肌肉中，肌节肌动蛋白细丝与以前未被识别的Z线样结构对齐。 这个项目的中心假设是，肌动蛋白细丝动力学的适当位点特异性调节是 肌节肌动蛋白细丝的组装和维护所必需的。我们提出三个目标：(目标1) 确定ADF/cofilin、AIP1和SUP-13如何调节肌瘤肌动蛋白组装(Aim 2)以确定 肌动蛋白细丝动力学如何由环化酶相关蛋白调节，以及(目标3)确定如何 肌节肌动蛋白细丝锚定在其带刺的末端附近。我们预计，这项研究的结果将 为横纹肌中肌动蛋白动力学的调节提供新的见解。大多数肌动蛋白的调控 该项目中研究的蛋白质也在哺乳动物骨骼肌中表达，其中一些是 与人类的遗传性肌肉疾病有关。我们希望我们在模型生物体中的研究将有助于 了解肌原纤维在正常和病理状态下组装和维持的保守机制 条件。

Project Summary Sarcomere in striated muscle is the basic unit of contractile apparatuses. Assembly and maintenance of organized sarcomeric structures are essential for proper contraction and relaxation in muscle. 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. A number of regulators of actin dynamics have been identified in skeletal muscle, and some of them are linked to genetic muscle disorders. 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. 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 use 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. In C. elegans, we have identified that ADF/cofilin (UNC-60B), AIP1 (UNC-78 and AIPL-1), and cyclase-associated protein (CAS-1) enhance turnover of actin filaments and essential for organized assembly of sarcomeric actin filaments. In addition, we identified SUP-13 as a new regulator of muscle actin. Furthermore, we obtained evidence that the barbed ends of sarcomeric actin filaments are aligned to previously unrecognized Z-line-like structures in C. elegans muscle. The central hypothesis of this project is that proper site-specific regulation of actin filament dynamics is required for assembly and maintenance of sarcomeric actin filaments. We propose three aims: (Aim 1) to determine how sarcomeric actin assembly is regulated by ADF/cofilin, AIP1, and SUP-13, (Aim 2) to determine how actin filament dynamics are regulated by cyclase-associated protein, and (Aim 3) to determine how sarcomeric actin filaments are anchored near their barbed ends. We expect that results of this research will provide new insight into the regulation of actin dynamics in striated muscle. Most of the actin-regulatory proteins studied in this project are also expressed in mammalian skeletal muscle, and some of them are involved in genetic muscle disorders in humans. We hope that our research in a model organism will help to understand the conserved mechanism of myofibril assembly and maintenance under normal and pathological conditions.