Motor-mediated bidirectional transport along an antipolar microtubule bundle: a mathematical model.
Motor-mediated bidirectional transport along an antipolar microtubule bundle: a mathematical model.
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DOI：
10.1103/physreve.87.052709
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发表时间：
2013-05
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影响因子：
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通讯作者：
Congping Lin;P. Ashwin;G. Steinberg
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文献类型：
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作者：
Congping Lin;P. Ashwin;G. Steinberg
细胞器的长距离双向运输依赖于细胞骨架上各种马达蛋白的协调运动。最近的定量活细胞成像在细长的菌丝细胞的玉米黑粉菌已经证明，长距离运动的电机和他们的内体货物发生在单极微管（MT）附近的极端的细胞。这些MT在细胞的中心部分被捆绑成反极束。动力蛋白和驱动蛋白-3马达协调它们的活性以双向方式移动早期内体（EE），其中动力蛋白驱动运动朝向MT负末端，驱动蛋白驱动运动朝向MT正末端。虽然这意味着可以很容易地在单极部分中分配双向运动的驱动器，但束中的双极方向意味着任何一个电机都可以在任何一个方向上驱动运动。在本文中，我们使用一个多车道的不对称简单的排斥过程建模方法来模拟和调查阶段的双向运动的反极MT束的最小模型。在我们的模型中，EE货物（粒子）在每个MT上以转向率Ω改变方向，并且在负端的束中MT之间存在切换。在这些端部，颗粒可以在MT之间跳跃，从单极到双极部分的速率为q（1）（障碍物诱导的切换速率），或者在另一个方向上通过时的速率为q（2）（端部诱导的切换速率）。通过数值模拟和平均场近似的结合，我们研究了这些参数和Θ的不同值下，粒子沿着MT的分布，θ是这个封闭系统中粒子的总密度。我们发现，即使Θ是低的，系统可以表现出各种相位的冲击，在密度分布的正负端附近的粒子排队造成的。我们讨论了如何影响的参数类型的粒子，占主导地位的积极运输的束。
Long-distance bidirectional transport of organelles depends on the coordinated motion of various motor proteins on the cytoskeleton. Recent quantitative live cell imaging in the elongated hyphal cells of Ustilago maydis has demonstrated that long-range motility of motors and their endosomal cargo occurs on unipolar microtubules (MTs) near the extremities of the cell. These MTs are bundled into antipolar bundles within the central part of the cell. Dynein and kinesin-3 motors coordinate their activity to move early endosomes (EEs) in a bidirectional fashion where dynein drives motility towards MT minus ends and kinesin towards MT plus ends. Although this means that one can easily assign the drivers of bidirectional motion in the unipolar section, the bipolar orientations in the bundle mean that it is possible for either motor to drive motion in either direction. In this paper we use a multilane asymmetric simple exclusion process modeling approach to simulate and investigate phases of bidirectional motility in a minimal model of an antipolar MT bundle. In our model, EE cargos (particles) change direction on each MT with a turning rate Ω and there is switching between MTs in the bundle at the minus ends. At these ends, particles can hop between MTs with rate q(1) on passing from a unipolar to a bipolar section (the obstacle-induced switching rate) or q(2) on passing in the other direction (the end-induced switching rate). By a combination of numerical simulations and mean-field approximations, we investigate the distribution of particles along the MTs for different values of these parameters and of Θ, the overall density of particles within this closed system. We find that even if Θ is low, the system can exhibit a variety of phases with shocks in the density profiles near plus and minus ends caused by queuing of particles. We discuss how the parameters influence the type of particle that dominates active transport in the bundle.