Control of cargo distributions by microtubule motor physical interactions with cargo, cytoplasm and MAPs

项目总结 微管马达研究的主要悬而未决的问题是如何确定货物比例 运动行为受到(分子水平)的调节，以协调对细胞的控制 空间组织(在10-100微米的尺度上)，同时用于所有电机- 驱动小区内流量。这涉及到微管相关蛋白Tau，即 这是脊椎病的特征。挑战的出现是因为组合 Tau变种的复杂性和问题的多尺度性质--两个挑战 对于这些问题，计算模型特别适合于对抗。在目标1中，我们将 开发一个模型来模拟机动地图的动力学，以及这些如何导致货物运输。 我们假设，一个装饰着MAP和其他分子的微管可以 根据货物的大小和机械选择性地影响货物的定位 变形性。这种选择性可以根据地图的大小、机械 属性和丰富性，它们共同提供了一种交通编码系统，该系统缺少 受疾病控制的。我们将开发一个计算模型并模拟电机 通过MT-货物间距探索货物尺度上的运输的专一性和多重性 控制力。缺少的一个关键参数是马达的附着率，一直以来 在技术上太具挑战性，无法直接测量，因此需要一种新的 实验-理论分析。然后我们将模拟一维空间中的汽车运输 用于识别灵敏地导致细胞尺度的货物尺度参数的微管阵列 定位，使用已知的空间异质性，例如，跨轴突的Tau。在目标2中，我们 将探讨电机调制器的基于间隔的方面。我们假设有很多人 运输调节分子的部分作用是通过调节间隔(均值和方差 微管和货物之间的距离)。基于间距的监管赋予了 具有其他调节模式所不具备的控制特性的系统。我们将发展 一种基于光钳的分析方法，用于量化运输参数的调制 调整MT-货物间距，以及基于模拟的推断测量间距的方法 用于任意地图。我们将具体工作，了解监管机制 高度结构的分子，如动力蛋白和RABS，以及高度无序的 Tau和Map2等分子。在目标3中，我们将探索货物 和细胞的局部流变性。我们假设，表面的内部动力学- 货物上的结合分子和细胞的局部流变性影响运输 属性。这为系统提供了一种自然的货物分拣机制。使用我们的 模拟，我们将量化货物的内部粘度的影响(对于 水泡状货物，脂滴的中级，高密度的刚性货物，如RNA)和 这与细胞质的粘弹性如何相互作用。

PROJECT SUMMARY The major open question in microtubule motor research is to determine how cargo-scale motor behavior is regulated (at the molecular scale) to orchestrate control of a cell's spatial organization (on the scale of 10-100 microns), simultaneously for all of motor- driven intracellular traffic. This involves the microtubule associated protein Tau, the hallmark of Tauopathy diseases. Challenges arise because of the combinatorial complexity of Tau variants and the multi-scale nature of the question – two challenges for which computational modeling is particularly well suited to confront. In Aim 1, we will develop a model to simulate motor-MAP kinetics and how these lead to cargo transport. We hypothesize that a microtubule adorned with MAPs and other molecules can selectively influence cargo localization depending on the cargo's size and mechanical deformability. This selectivity can be understood in terms of the MAP's size, mechanical properties and abundance, which together provide a traffic coding system that is mis- regulated in disease. We will develop a computational model and simulate motor transport at the cargo-scale to explore specificity and multiplexing by MT-cargo spacing control. A key missing parameter is the motor's attachment rates, which have been so far too technically challenging to measure directly and will therefore require a novel experimental-theoretical assay. We will then simulate motor transport in a 1-dimensional array of microtubules to identify cargo-scale parameters that sensitively lead to cell-scale localization, using known spatial heterogeneity of, e.g., Tau across axons. In Aim 2, we will explore the spacing-based aspect of motor modulators. We hypothesize that many transport-regulating molecules operate in part by tuning the spacing (mean and variance of distance) between the microtubule and cargo. Spacing-based regulation endows the system with control properties not present in other modes of regulation. We will develop an optical tweezer-based assay to quantify the modulation of transport parameters by tuning MT-cargo spacing, and a simulation-based inference method to measure spacing for arbitrary MAPs. We will specifically work to understand the regulatory mechanism of highly-structured molecules such as Dynactin and Rabs, and highly-disordered molecules such as Tau and MAP2. In Aim 3, we will explore the effects of the cargo's and cell's local rheology. We hypothesize that both the internal dynamics of surface- bound molecules on the cargo, and the cell's local rheology influence transport properties. This provides the system with a natural cargo sorting mechanism. Using our simulation, we will quantify the influence of the cargo's internal viscosity (low for vesicular cargo, intermediate for lipid droplets, and high for rigid cargo like RNA) and how this interacts with the viscoelasticity of the cytoplasm.