Department of Biology, University of Utah, Salt Lake City, UT 84112-0840.
Department of Physics and Astronomy, University of California, Irvine, CA 92697.
Proc Natl Acad Sci U S A. 2018 Jan 16;115(3):537-542. doi: 10.1073/pnas.1707936115. Epub 2018 Jan 2.
The eukaryotic cell's microtubule cytoskeleton is a complex 3D filament network. Microtubules cross at a wide variety of separation distances and angles. Prior studies in vivo and in vitro suggest that cargo transport is affected by intersection geometry. However, geometric complexity is not yet widely appreciated as a regulatory factor in its own right, and mechanisms that underlie this mode of regulation are not well understood. We have used our recently reported 3D microtubule manipulation system to build filament crossings de novo in a purified in vitro environment and used them to assay kinesin-1-driven model cargo navigation. We found that 3D microtubule network geometry indeed significantly influences cargo routing, and in particular that it is possible to bias a cargo to pass or switch just by changing either filament spacing or angle. Furthermore, we captured our experimental results in a model which accounts for full 3D geometry, stochastic motion of the cargo and associated motors, as well as motor force production and force-dependent behavior. We used a combination of experimental and theoretical analysis to establish the detailed mechanisms underlying cargo navigation at microtubule crossings.
真核细胞的微管细胞骨架是一个复杂的三维丝状网络。微管以各种不同的分离距离和角度交叉。体内和体外的先前研究表明，货物运输受到交叉几何形状的影响。然而，几何复杂性尚未被广泛认为是一种独立的调节因子，并且其背后的机制也尚未得到很好的理解。我们使用最近报道的 3D 微管操纵系统在纯化的体外环境中从头构建丝状交叉，并使用它们来测定驱动的模型货物导航。我们发现，3D 微管网络几何形状确实显著影响货物路径选择，特别是通过改变丝状间隔或角度，可以使货物偏向通过或切换。此外，我们将实验结果纳入了一个模型中，该模型考虑了货物和相关马达的全 3D 几何形状、随机运动以及马达力的产生和力依赖性行为。我们使用实验和理论分析的组合，确定了货物在微管交叉处导航的详细机制。
