Control of actin filament networks by Arp2/3 complex and its regulators

Arp2/3 复合物及其调节剂对肌动蛋白丝网络的控制

• 批准号: 10396979
• 负责人: Bradley J Nolen
• 金额: $ 56.58万
• 依托单位: UNIVERSITY OF OREGON
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-05-01 至 2025-04-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10396979
• 关键词: Actins; Architecture; Bacteria; Bacterial Infections; Binding; Biochemical; Biological; Biological Process; Biophysics; Cancerous; Cell physiology; Cells; Complex; Cytoskeleton; Disease; Endocytosis; Filament; Goals; Human; Mediating; Microfilaments; Molecular; Molecular Conformation; Neoplasm Metastasis; Pathogenicity; Process; Proteins; Regulation; Seeds; Virus; WASP protein; Work; cell motility; density; genetic regulatory protein; improved; monomer; network architecture; polymerization; recruit

Summary To orchestrate complex processes like motility and endocytosis, cells rely on regulatory proteins that control the dynamics and architectures of the actin cytoskeleton. Actin filament nucleators are important actin regulators because they allow cells to control the initiation of new actin networks and dictate the architectures of these networks. Arp2/3 complex is a seven subunit actin filament nucleating machine that specifically generates branched actin filaments. Regulated branching by Arp2/3 complex is important not only for processes required for normal cellular function, such as endocytosis and protrusion of lamellipodia, but also in pathogenic processes like host cell infection by bacteria or metastasis of tumor cells. The majority of studies on Arp2/3 complex regulation have focused on WASP proteins, an activator that mediates propagation of branched actin networks. These studies revealed the basic tenets of WASP mediated activation; that WASP binds to Arp2/3 complex, recruits actin monomers, and stimulates an activating conformational change. However, the molecular aspects of WASP mediated-activation most important for understanding the biological function of the complex are still unknown. For instance, it is unknown why WASP proteins require actin filaments to activate Arp2/3 complex, a requirement that allows Arp2/3 complex to function specifically as a branched actin filament nucleator. Further, it is not known why WASP (but not other activators) must recruit actin monomers to Arp2/3 complex to trigger nucleation, despite the fact that this requirement regulates the density of branched filament ends in Arp2/3-assembled actin networks. In addition to WASP, several other regulatory proteins are now known to activate Arp2/3 complex. We recently discovered that the WISH/DIP/SPIN90 (WDS) proteins are distinct from WASP in that they can activate Arp2/3 complex without preformed filaments to induce it to nucleate linear actin filaments. These linear filaments serve as seeds to kickstart WASP-mediated branching thereby initiating actin network assembly. Despite the fact that initiation is perhaps the most important step in controlling branched network assembly, how WDS proteins activate the complex to create seed filaments is unknown. Furthermore, it is not understood how the activity of WDS proteins is coordinated with other activators like WASP, or how WDS proteins themselves are regulated. Here we propose a combination of biochemical, biophysical, structural, computational, and cell biological approaches to investigate these questions, with a long-term goal of understanding how these regulatory mechanisms allow Arp2/3 complex to control actin dynamics in complex cellular processes.

概括 为了协调运动和内吞作用等复杂过程，细胞依赖于控制蛋白质 肌动蛋白细胞骨架的动力学和结构。肌动蛋白丝成核剂是重要的肌动蛋白调节剂 因为它们允许细胞控制新肌动蛋白网络的启动并决定这些网络的结构 网络。 Arp2/3 复合物是一个七亚基肌动蛋白丝成核机器，专门生成 分支肌动蛋白丝。 Arp2/3 复合体调节的分支不仅对于进程很重要 正常细胞功能所必需的，例如胞吞作用和片状伪足的突出，而且在致病性中也是如此 诸如细菌感染宿主细胞或肿瘤细胞转移等过程。大部分研究都是关于Arp2/3 复杂的调控集中在 WASP 蛋白上，它是一种介导分支肌动蛋白增殖的激活剂 网络。这些研究揭示了 WASP 介导的激活的基本原理； WASP 与 Arp2/3 结合 复合体，招募肌动蛋白单体，并刺激激活的构象变化。然而， WASP 介导的激活的分子方面对于理解 WASP 的生物学功能最重要 复杂程度仍未知。例如，尚不清楚为什么 WASP 蛋白需要肌动蛋白丝来激活 Arp2/3 复合体，这是允许 Arp2/3 复合体专门作为分支肌动蛋白丝发挥作用的要求 成核剂。此外，尚不清楚为什么 WASP（但不是其他激活剂）必须将肌动蛋白单体募集到 Arp2/3 复杂的触发成核，尽管这一要求调节分支丝的密度 以 Arp2/3 组装的肌动蛋白网络结束。除了 WASP 之外，现在还有其他几种调节蛋白 已知可激活 Arp2/3 复合体。我们最近发现 WISH/DIP/SPIN90 (WDS) 蛋白是 与 WASP 不同的是，它们可以激活 Arp2/3 复合体，而无需预先形成细丝来诱导其 有核线性肌动蛋白丝。这些线性细丝充当种子来启动 WASP 介导的分支 从而启动肌动蛋白网络组装。尽管事实上启动可能是最重要的 控制分支网络组装的步骤，WDS 蛋白如何激活复合物以产生种子 细丝未知。此外，尚不清楚 WDS 蛋白的活性如何与 其他激活剂，如 WASP，或 WDS 蛋白本身的调节方式。在这里我们提出了一个组合 生物化学、生物物理、结构、计算和细胞生物学方法来研究这些 问题，长期目标是了解这些调控机制如何允许 Arp2/3 复合物 控制复杂细胞过程中的肌动蛋白动力学。