Actin networks are highly dynamic cytoskeletal structures that continuously undergo structural remodeling. One prominent way to probe these processes is via Fluorescence Recovery After Photobleaching (FRAP), which can be used to estimate the rate of turnover for filamentous actin monomers. It is thought that head‐to‐tail treadmilling and de novo filament nucleation constitute two primary mechanisms underlying turnover kinetics. More generally, these self‐assembly activities are responsible for many important cellular functions such as force generation, cellular shape dynamics, and cellular motility. In what relative proportions filament treadmilling and de novo filament nucleation contribute to actin network turnover is still not fully understood. We used an advanced stochastic reaction–diffusion model in three dimensions, MEDYAN, to study turnover dynamics of actin networks containing Arp2/3, formin and capping protein at experimentally meaningful length‐ and time‐scales. Our results reveal that, most commonly, treadmilling of older filaments is the main contributor to actin network turnover. On the other hand, although turnover and treadmilling are often used interchangeably, we show clear instances where this assumption would not be justified, for example, finding that rapid turnover is accompanied by slow treadmilling in highly dendritic Arp2/3 networks.

中文翻译：

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肌动蛋白网络装配和重塑中的周转与跑步。

肌动蛋白网络是高度动态的细胞骨架结构，不断进行结构重塑。探测这些过程的一种突出方法是通过光漂白后荧光恢复（FRAP），该方法可用于估计丝状肌动蛋白单体的周转率。人们认为，从头到尾的跑步机和从头开始的长丝成核是潜在的周转动力学的两个主要机理。一般而言，这些自组装活动负责许多重要的细胞功能，例如力的产生，细胞形状动力学和细胞运动。丝线跑步机和从头开始的长丝成核作用在肌动蛋白网络周转中所占的相对比例仍不完全清楚。我们在三个维度（MEDYAN）中使用了先进的随机反应扩散模型 在实验上有意义的长度和时间尺度上研究包含Arp2 / 3，甲酸和封端蛋白的肌动蛋白网络的更新动态。我们的结果表明，最常见的是，对旧丝进行跑步机是肌动蛋白网络更新的主要原因。另一方面，尽管营业额和跑步机经常互换使用，但我们显示出明显的情况，这种假设是不合理的，例如，发现在高树突状Arp2 / 3网络中，快速营业额伴随着缓慢的跑步机。