Facilitated transport of actin monomer and cytoskeletal remodeling

所有细胞都通过不断拆分和重建内部支架来移动和改变形状，这种支架被称为细胞骨架。关于细胞是如何移除和替换细胞骨架碎片的，人们已经知道了很多。然而，细胞面临的一个根本挑战是如何回收分解的碎片。这个项目的一个目标是了解细胞如何将新分解的部分移动到新的位置，在那里它们需要足够快地响应外部信号而改变形状。这项工作将揭示细胞如何能够将自己拆开，将分解的碎片移动到正确的位置，并在每次移动时将自己重新组装起来。这项工作很重要，因为它将揭示整个细胞内部动态重组的基本原理。了解这些原理对于学习如何协调细胞骨架重塑至关重要，而这一知识对于各种应用来说都是至关重要的。更广泛的影响活动将包括与当地一家科学博物馆的联系，以及帮助在西北部建立一个定量生物学社区。对肌动蛋白细胞骨架的动态控制是运动、分裂和极化等过程的基础。尽管几十年的研究已经确定了控制在细胞前端添加单体和在后面移除单体的机制，但细胞如何将单体从网络的后面运送到网络的前端，从哪里移除，到哪里添加，还不清楚。这一转运过程对细胞内环境的稳定至关重要，由于其快速且难以测量，因此被默认为扩散过程。PI首次直接测量了正向单体传输。从他们的测量可以清楚地看出，前向单体的运输比扩散更快，并且依赖于肌球蛋白II的收缩。本研究的目的是确定使肌动蛋白前向运输比扩散更快的机制，并确定肌球蛋白II收缩在驱动和指导前向运输以重塑细胞骨架中的作用。这些目标将通过结合生物物理分析、分子生物学、光子学、单分子成像和数学/质量传输分析来实现。该项目预计将查明长途运输机制，在这些机制中，由于预期运输目的地的空间和时间变化很快，扩散太慢，不太可能实现直接马达耦合。

All cells move and change shape by continuously taking apart and rebuilding their internal scaffolding, called a cytoskeleton. A great deal is known about how cells remove and replace cytoskeletal pieces. However, a fundamental challenge for the cell is how to recycle the disassembled pieces. A goal of this project is to understand how cells move the newly disassembled parts to new places where they need to be fast enough to change shape in response to external signals. This work will reveal how cells are able to pull themselves apart, move the disassembled pieces to the right place, and put themselves back together every time they move. The work is important because it will reveal basic principals of dynamic reorganization of the entire cell interior. Understanding these principals is essential to learning how to coordinate cytoskeletal remodeling, knowledge that is critical for a variety of applications. Broader Impact activities will include outreach to a local science museum along with helping to build a quantitative biology community in the northwest.Dynamic control of the actin cytoskeleton is fundamental to processes such as motility, division, and polarization. Although decades of research have defined the mechanisms that control the addition of monomers at the front of the cell and removal of monomers at the back, how the cell transports monomer from the back of the network, where it is removed, to the front of the network, where it is added is unknown. This transport process is essential to cell homeostasis, and it is tacitly assumed to be diffusion because it is fast and difficult to measure. The PIs have for the first time directly measured forward monomer transport. From their measurements it is clear that forward monomer transport is faster than diffusion and dependent upon myosin II contraction. The objectives of this study are to identify the mechanism that makes forward transport of actin faster than diffusion and to define the role of myosin II contraction in driving and directing forward transport to remodel the cytoskeleton. These objectives will be achieved by combining biophysical assays, molecular biology, photonics, single molecule imaging, and mathematical/mass transport analysis. This project is expected to identify long-distance transport mechanisms where diffusion is too slow and direct motor coupling is unlikely because of rapid spatial and temporal changes of the intended transport destination.