Role of Motor/cargo Attachment Mechanics in Collective Kinesin Transport

细胞的生存依赖于蛋白质和化学物质的有效运输和分类进入不同的功能隔间。纳米级的马达蛋白可以抓住结合在膜上的货物，并将它们沿着聚合物细丝移动，从而实现这种运输。由此产生的货物运动被认为是多个马达蛋白协同作用的结果，但人们对协同作用的程度和使其成为可能的分子机制知之甚少。一种可能的合作机制是多个马达分担移动货物所需的负荷的能力。这样的载荷分割预计将强烈依赖于货物表面的力学性质，但载荷分割、运输效率和货物力学之间的详细关系尚不清楚。这项研究项目的目的是确定膜机械如何影响马达蛋白协同运输货物的能力。为此，将产生界面化学和机械性能可控的仿生货物，并在体外将其偶联到马达蛋白上。货物表面的机械性能将从具有固定马达附着点的纯刚性表面到由脂类制成的可重新排列其位置的纯流体表面。这种液体货物被认为更好地模拟了活细胞中货物的性质，它将使马达结合部位随着马达蛋白的移动而在货物表面轻松移动。这些界面脂类重排对货物运动的影响将使用精密的生物物理工具进行评估。具体地说，马达对抗外力协同移动液体和刚性货物的能力将被确定和定量比较。将开发计算机模拟和分析理论来理解实验数据，并为膜力学对细胞内货物运输的影响产生可检验的预测。如果成功，这项研究将为细胞内运输的基本机制和调控提供重要的新见解，同时在生物学、物理学和工程学的界面上创建扩展和培训活动。特别是，社区学院和本科生将参与实践研究，这项工作将形成一名研究生的论文项目，该研究生将发展实验、计算和分析理论方面的专业知识。该项目的成果将被纳入UCSB和圣巴巴拉数量生物学高级学校的跨学科生物物理学/生物力学课程，并将在出版物和会议上广泛传播。

Cell survival depends on the efficient transport and sorting of protein and chemical species into different functional compartments. Nanoscale motor proteins that grasp membrane-bound cargos and move them along polymer filaments enable this transport. The resultant cargo motion is thought to arise from the cooperative action of multiple motor proteins, but the extent of cooperation and the molecular mechanisms that enable it are poorly understood. One possible mechanism for cooperation lies in the ability of multiple motors to share the load necessary to move the cargo. Such load splitting is expected to depend strongly on the mechanical properties of the cargo surface, but the detailed relationship between load splitting, transport efficiency, and cargo mechanics is unknown. The objective of this research project is to determine how membrane mechanics influences the ability of motor proteins to cooperatively transport cargos. To this end, biomimetic cargos with well-controlled interfacial chemistry and mechanical properties will be generated and coupled to motor proteins in vitro. The mechanical properties of the cargo surfaces will be varied from purely rigid surfaces with immobile motor attachment sites to purely fluid surfaces made of lipids that can rearrange their positions. The fluid cargos, which are thought to better mimic the properties of cargos in living cells, would allow motor binding sites to easily move on the cargo surface as the motor proteins move. The impact of these interfacial lipid rearrangements on cargo motion will be assessed using precision biophysical tools. Specifically, the ability of motors to cooperatively move fluid and rigid cargos against an external force will be determined and quantitatively compared. Computer simulations and analytical theory will be developed to understand the experimental data and generate testable predictions for the effects of membrane mechanics on cargo transport in cells. If successful, this research will provide important new insight into the fundamental mechanisms and regulation of intracellular transport, while creating outreach and training activities at the interface of biology, physics, and engineering. In particular, community college and undergraduate students will participate in hands-on research, and this work will form the thesis project of one graduate student, who will develop expertise in experiments, computation and analytical theory. The outcomes of this project will be incorporated into interdisciplinary biophysics/biomechanics courses at UCSB and the Santa Barbara Advanced School for Quantitative Biology, and will be disseminated broadly in publications and conferences.