Microtubule Mechanics at the Nanoscale

描述（由申请人提供）：微管（MTs）是刚性聚合物，在细胞结构中起着关键作用，作为结构支撑和运动蛋白的轨道。在这种能力中，mt是细胞过程的中心，从有丝分裂染色体分离到细胞形态和囊泡运输的变化。mt也是诸如长春花生物碱和紫杉醇等抗癌药物的重要靶点。mt本身是动态的，它们的聚合是由细胞调节的，以实现细胞骨架的快速重组。MT聚合动力学的分子机制尚不清楚，这使人们难以严格理解MT是如何被细胞结构和调节的，以及化疗药物的作用机制。这一提议表征了微管聚合过程中的分子事件。通过将光学镊子与光刻产生的新型屏障系统相结合，动态MT尖端的事件以纳米精度跟踪。这揭示了聚合的关键细节，由于光分辨率的限制，以前没有观察到。该分析将用于表征介导微管生长、缩短和稳定性的分子事件。进一步的研究将研究紫杉醇和微管相关蛋白tau对微管动力学调节的分子动力学。为了建立对微管动力学的机制理解，这些结果将在描述微管尖端结构演变与亚基添加和损失动力学之间相互作用的物理模型的背景下进行解释。相关性：这项工作将提供对生命维持基础的细胞力学的理解。通过描述MT动力学的基本机制，这项工作将增加我们对涉及MT的疾病过程的理解，例如有丝分裂失败（例如在衰老和唐氏综合症等遗传疾病中）和神经退行性疾病。特别讨论的是重要的化疗药物紫杉醇的机制，以及MT结合蛋白tau在各种神经退行性疾病中起核心作用。

DESCRIPTION (provided by applicant): Microtubules (MTs) are rigid polymers that serve a critical role in cellular architecture as structural buttresses and tracks for motor proteins. In this capacity MTs are central to cellular processes ranging from mitotic chromosome segregation to changes in cellular morphology and vesicle transport. MTs are also important targets for anticancer drugs such as the vinca alkaloids and taxol. MTs are inherently dynamic, and their polymerization is regulated by cells to achieve rapid restructuring of the cytoskeleton. The molecular mechanisms of MT polymerization dynamics are not well understood, and this confounds rigorous understanding how MTs are structured and regulated by cells, as well as the mechanism of action of chemotherapy agents. This proposal characterizes the molecular events during microtubule polymerization. By combining optical tweezers with a novel system of photolithographically produced barriers, the events at the tip of a dynamic MT are tracked with nanometer precision. This reveals critical details of polymerization that have not been previously observed due to the light resolution limit. This assay will be applied to characterize molecular events that mediate microtubule growth, shortening, and stability. Additional studies will examine the molecular kinetics underlying modulation of microtubule dynamics by taxol and the microtubule associated protein tau. To build a mechanistic understanding of microtubule dynamics/these results will be interpreted in the context of physical models that describe the interplay between the evolving structure at a microtubule tip and the kinetics of subunit addition and loss. Relevance: This work will provide an understanding of cellular mechanics fundamental to the sustenance of life. By describing the fundamental mechanics of MT dynamics this work will increase our understanding of disease processes that involve MTs, such as mitotic failures (e.g. in aging and genetic diseases such as Down's syndrome), and neurodegenerative disease. Specifically addressed are the mechanisms of the important chemotherapy agent taxol, and the MT binding protein tau which plays a central role in a variety of neurodegenerative diseases.