Bridging Understanding of Motor-Cargo Transport from Artificial to Cellular Systems

基于微管的运输对细胞功能至关重要。细胞内货物的正确运输涉及 以不同速度和方向运动的马达蛋白和微管之间的相互作用， 其可以以均匀或混合极性束取向，并且也可以通过 翻译后修饰（PTM）和微管相关蛋白（MAP）。主导模式在 描述双向运动的领域是拔河模型，其中反向驱动蛋白和 动力蛋白马达机械地竞争优势并控制短时间的运动。但 在过去15年中，在分离的细胞和模式生物中进行的许多研究发现， 抑制一个运动会减少两个方向的运动，这与拔河模型正好相反 预测.本提案的目的是利用数学建模和体外实验， 研究导致拔河模型的预测在细胞中失败的机制。 规模弥合这一知识差距需要实验和理论的综合发展 模型，以便将分子尺度上的基本机制与观察到的细胞内 运输行为建模将跨越三个级别。纳米级建模将使用已建立的 治疗驱动蛋白和动力蛋白步进动力学和运动微管变化的框架 由于微管蛋白PTM和MAP结合的相互作用。在中尺度上，多个发动机绑定到一个共同的 货物被表示为服从随机微分模型的连续移动者， 从现有的实验数据。最后，在微观尺度上， 具有多个微管的马达-货物复合物和转运对微管的依赖性 组织在细胞水平上进行治疗。 在目标1中，将使用具有限定数量的驱动蛋白和动力蛋白的体外和计算机模拟实验， 挑战双向传输的特定假设模型。在目标2中，这一综合办法将 扩展到了解在细胞模拟微管结构在体外和计算机传输动力学。

Microtubule-based transport is vital for cell function. Proper transport of intracellular cargo involves an interplay between motor proteins that move at different speeds and in different directions, and microtubules, which can be oriented in either uniform or mixed polarity bundles and can also be altered by posttranslational modifications (PTMs) and microtubule associated proteins (MAPs). The dominant model in the field to describe the bidirectional motion is the tug-of-war model in which opposite-directed kinesin and dynein motors mechanically compete for dominance and control movement for short durations. However, a number of studies carried out in isolated cells and model organisms over the last 15 years have found that inhibiting one motor diminishes motility in both directions, just the opposite of the tug-of-war model prediction. The purpose of this proposal is to use mathematical modeling and in vitro experiments to investigate the mechanisms that cause the predictions of the tug-o-war model to fall short at the cellular scale. Closing this knowledge gap requires the integrated development of experiments and theoretical models in order to link fundamental mechanisms at the molecular scale with the observed within-cell transport behavior. The modeling will span three levels. Nanoscale modeling will use established frameworks to treat the kinetics of kinesin and dynein stepping and changes in motor-microtubule interactions due to tubulin PTMs and MAP binding. At the mesoscale, multiple motors bound to a common cargo are represented as continuous movers obeying stochastic differential models with performance characteristics taken from existing experimental data. Finally, at the microscale, the interaction of motor-cargo complexes with multiple microtubules and the dependence of transport on microtubule organization at the cellular level are treated. In Aim 1, in vitro and in silico experiments with defined numbers of kinesins and dyneins will be used to challenge specific hypothetical models of bidirectional transport. In Aim 2, this integrated approach will be extended to understand transport dynamics in cell-mimicking microtubule architectures in vitro and in silico.