Recent advances in live cell imaging of F-actin structures, combined with pulse-chase imaging and computational modeling have suggested that actin is transported along the axon via biased polymerization of metastable actin fibers (actin trails). This mechanism is distinct from motor driven polymer transport, such as for neurofilaments and can be best described as molecular hitchhiking, where G-actin molecules are intermittently incorporated into actin fibers which grow preferentially in the anterograde direction. In this paper, we discuss how various axonal and actin trail parameters like axon diameter, trail nucleation rates, basal G-actin concentration, and trail length influence the transport rate. These predictions can help guide future experiments to verify this novel protein transport mechanism. We introduce a simplified, analytically solvable model of actin transport which relates these parameters to experimentally measurable quantities. We also discuss why a simple diffusion-based transport mechanism cannot explain bulk actin transport in the axon.

中文翻译：

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基于聚合的轴突肌动蛋白运输的随机模型。

F-肌动蛋白结构的活细胞成像的最新进展，与脉冲追踪成像和计算模型相结合，表明肌动蛋白是通过亚稳态肌动蛋白纤维（肌动蛋白谱）的偏向聚合沿着轴突运输的。这种机制不同于电机驱动的聚合物运输，例如用于神经丝，并且可以最好地描述为分子搭便车，其中G-肌动蛋白分子间歇地结合到肌动蛋白纤维中，后者优先在顺行方向生长。在本文中，我们讨论了各种轴突和肌动蛋白踪迹参数（如轴突直径，踪迹成核速率，基础G-肌动蛋白浓度和踪迹长度）如何影响转运速率。这些预测可以帮助指导未来的实验，以验证这种新颖的蛋白质转运机制。我们介绍一个简化的 肌动蛋白运输的可解析模型，将这些参数与实验可测量量相关联。我们还讨论了为什么简单的基于扩散的运输机制不能解释轴突中的大量肌动蛋白运输。