Molecular mechanisms of bundled actin structure assembly by formins

项目摘要 本研究的目的是了解formins如何塑造肌动蛋白的结构和动力学 细胞骨架形成蛋白是一个独特的多功能肌动蛋白调节蛋白家族， 成核和伸长。由formins组装的肌动蛋白丝被整合到一组不同的高级- 有序结构支持基本的细胞功能，包括迁移，分裂和运输。哺乳动物 表达15种肌动蛋白亚型，每种亚型都具有独特的肌动蛋白组装特性， 细胞中的作用。与这种特化相一致的是，单个p53基因的突变与广泛的 一系列疾病和病理，包括神经系统疾病，肾脏疾病，小头畸形， 心肌病和几种癌症然而，尽管它们作为肌动蛋白调节器的基础作用， 在组装过程中，不知道如何定制每种β-同种型的聚合活性以组装β-淀粉样蛋白。 特殊的肌动蛋白结构。为了弥合这一理解上的差距，我们的目标是建立如何广泛的 肌动蛋白活动影响肌动蛋白网络的生理和动力学。我们的中心假设是， 高级肌动蛋白结构的组装和特化，通过产生用于捆绑的结合位点， 以同种型特异性速率切割蛋白质。我们将结合生物物理学和细胞生物学 通过追求三个具体目标来检验这一假设的方法：（1）阐明 支持formin的适应性聚合活性，（2）研究formin介导的 肌动蛋白丝成束的伸长，和（3）评估丝成核的相互依赖的贡献， 延伸和周转到肌动蛋白结构动力学。我们的工作将在分子水平上建立 动态调节细胞骨架结构的构建、特化和功能， 对细胞活力和人类发育的影响。鉴于β异构体的多样性，我们的结果将产生 对大量细胞过程的分子和时间调节的基本见解。这 将告知和指导我们对各种人类疾病的分子病理学的理解， 与基因突变有关的疾病。

PROJECT SUMMARY The goal of this research is to understand how formins shape the architecture and dynamics of the actin cytoskeleton. Formins are a uniquely versatile family of actin regulatory proteins that stimulate both filament nucleation and elongation. Actin filaments assembled by formins are incorporated into a diverse set of higher- order structures that support essential cellular functions, including migration, division, and transport. Mammals express 15 formin isoforms, each of which possesses unique actin assembly properties and plays a specific role in cells. Consistent with this specialization, mutations in individual formin genes are linked to a broad range of diseases and pathologies, including neurological disorders, kidney disease, microcephaly, cardiomyopathy, and several cancers. However, despite their foundational roles as regulators of actin assembly, it is unknown how the polymerization activity of each formin isoform is tailored for the assembly of a specific actin structure. To bridge this gap in understanding, our goal is to establish how the broad range of formin activities influences actin network physiology and dynamics. Our central hypothesis is that formins direct the assembly and specialization of higher-order actin structures by generating binding sites for bundling and severing proteins at isoform-specific rates. We will use a combination of biophysical and cell biological approaches to test this hypothesis by pursuing three specific aims: (1) to elucidate the mechanism that underpins the adaptable polymerization activities of formins, (2) to investigate the effects of formin-mediated elongation on actin filament bundling, and (3) to assess the interdependent contributions of filament nucleation, elongation, and turnover to actin structure dynamics. Our work will establish at a molecular level how formins dynamically regulate the construction, specialization, and function of cytoskeletal structures that are essential for cellular viability and human development. In light of the diversity of formin isoforms, our results will generate fundamental insights into the molecular and temporal regulation of a large number of cellular processes. This will inform and guide our understanding of the molecular pathologies underlying a diverse set of human diseases linked to mutations in formin genes.