Regulation of the actin filament pointed end dynamics in health and disease

参与心脏/骨骼肌收缩的细丝的变化通常会产生 具有致命后果的心肌病/线虫性肌病。我们的长期目标是确定 在正常发育过程中调节肌肉中肌动蛋白结构的组分和分子机制， 疾病在持续赠款支持的提案中，我们的短期目标是确定 肌动蛋白丝尖端结合蛋白leiomodin（Lmod）和 tropomoduin（Tmod）。尖端聚合决定了细丝的长度，并可直接调节 与Lmod的结合。这种结合通过整体的细细丝组分而增强， 原肌球蛋白我们推测，维持细丝长度需要Tmod的拮抗作用 和Lmod;也就是说，Tmod的作用是防止尖端处的伸长，而Lmod允许伸长。 我们还预测Tmod和Lmod在尖端的结合和作用是由不同的 它们的原肌球蛋白和肌动蛋白结合位点的排列。在我们提交的更新提案中，我们将评估 Lmod和Tmod如何影响细丝的形成以及细丝的结构。我们将测试我们最近 提出的Lmod/Tmod依赖性调节薄细胞尖端的分子机制， 细丝。我们还将研究Lmod结合到已经存在的 形成细丝。最后，我们将建立Lmod功能的调节机制。我们的数据将提供 全面鉴定细纤维下的调节机制的关键成分 组装和维护的健康和疾病。拟议的实验将连接Lmod相关的薄 肌丝改变伴家族性肌病。更好地理解细丝功能及其调节 对于更好地了解肌肉疾病的发病机制，改善诊断和潜在的识别至关重要 新的药物靶点

Alterations in the thin filaments involved in cardiac/skeletal muscle contraction often produce cardiomyopathies/nemaline myopathies with fatal consequences. Our long-term goal is to identify the components and molecular mechanisms regulating actin architecture in muscle during normal development and disease. In the proposal supported by the ongoing grant, our short-term goal is to determine the mechanisms of how thin filament lengths are regulated by the actin filament pointed end binding proteins, leiomodin (Lmod) and tropomoduin (Tmod). Polymerization at the pointed end determines thin filament length and is regulated directly by the binding of Tmod and Lmod. This binding is enhanced by the integral thin filament component, tropomyosin. We hypothesize that maintenance of thin filament length requires the antagonistic action of Tmod and Lmod; that is, the role of Tmod is to prevent elongation at the pointed end while Lmod allows elongation. We also predict that Tmod and Lmod binding and action at the pointed end is determined by different arrangements of their tropomyosin- and actin-binding sites. In our submitted renewal proposal, we will evaluate how Lmod and Tmod affect the formation and then the structure of the thin filament. We will test our recently proposed molecular mechanism for the Lmod/Tmod-dependent regulation of the pointed end of the thin filaments. We will also study the structural and functional consequences of Lmod binding to sides of the already formed thin filaments. Finally, we will establish mechanisms of regulation of Lmod functions. Our data will provide a comprehensive identification of critical components of the regulatory mechanisms underlying thin filament assembly and maintenance in health and disease.The proposed experiments will connect Lmod-related thin filament alterations with familial myopathies. A better understanding of thin filament function and of its regulation is critical to better understand muscle disease pathogenesis, to improve diagnostics and to potentially identify novel drug targets.