Physics of Centrosome Reorientation during Signaling Activation in Immune Cells

免疫系统是抵御感染和癌症的重要防御机制。T细胞是适应性免疫反应的中心效应器。它们识别细胞表面的分子，并启动导致免疫反应的信号。在这个过程中，一个重要的步骤是T细胞微管组织中心(中心体)的重新定位。中心体的正确定位是通过T细胞受体的正常信号和T辅助细胞中的淋巴因子分子或细胞毒性T细胞中的细胞毒素的定向释放所必需的。虽然T细胞激活和中心体定位之间的信号通路已经得到了很好的研究，但不对称中心体定位背后的物理机制尚不清楚。PI将结合定量成像和生物物理测量与分子动力学模拟来揭示细胞骨架力量在中心体定位中的作用。PI将开发一门关于细胞生物物理学的课程，涵盖从细胞骨架作用力到信号传递的机械力化学等主题。拟议项目的研究成果将用于开发一种新的实验室部件。PI和共同PI将提供一门初级本科课程，重点是向学生介绍批判性思维的概念和研究实践，利用在相关主题上的实践研究经验，如细胞力量生成。PI和共同PI将指导研究生和本科生的研究，并鼓励该地区的少数民族学生和高中生参与研究。PI将组织为期一周的生物物理实验室演示，作为物理系暑期女孩计划的一部分，以鼓励女高中生参与科学。该合作项目将开发用户友好的教学软件模块，教授如何从简单的分子相互作用中产生复杂的细胞骨架动力学。这些研究，使用集成的实验和计算方法，将导致对中心体定位的基本理解，中心体定位在许多细胞类型的许多细胞功能中至关重要。该小组将使用最先进的成像技术来定量分析微管的三维形状和动力学。同时，他们将开发一个由MT动力学和运动活动驱动的中心体运动的计算模型。模型参数将通过与实验观测结果(目标1)的比较来确定。PI将研究Acto-myosin细胞骨架和MT-dynein系统之间的相互作用以及它们在中心体定位中各自的作用。PI还将扩展模型，以包括肌动蛋白和微管细胞骨架以及相关的马达，它们的相互耦合，并系统地模拟在平行实验中进行的扰动(目标2)。这项研究将揭开两个不同但相互作用的生物聚合物细丝系统和相关马达的集体动力学中涉及的新的物理原理。机械力化学模型的发展将适用于细胞生物学中的许多其他现象，从而对该领域做出有价值的贡献。更广泛地说，这项工作将为高度复杂的活性物质系统的自组织原理提供新的见解。该项目由物理学部的生命系统物理学项目和分子和细胞生物科学部的细胞团共同支持。

The immune system is an important defense mechanism against infections and cancer. T cells are central effectors of the adaptive immune response. They recognize molecules on the surface of cells, and initiate signaling that results in the immune response. An essential step during this process is the reorientation of the T cell microtubule-organizing center (centrosome). Proper positioning of the centrosome is required for normal signaling through the T cell receptor and the directed release of lymphokine molecules in T helper cells or cytotoxins in cytotoxic T cells. While the signaling pathways between T cell activation and centrosome positioning have been well studied, the physical mechanisms underlying asymmetric centrosome positioning are not understood. The PI will combine quantitative imaging and biophysical measurements with molecular dynamics simulations to unravel the role of cytoskeletal forces in centrosome positioning. The PI will develop a course on Biophysics of the Cell covering topics ranging from cytoskeletal forces to mechano-chemistry of signaling. Research results from the proposed projects will be used to develop a novel laboratory component. The PI and co-PI will offer a beginning undergraduate course focused on introducing students to concepts of critical thinking and research practice using hands on research experience on relevant themes such as cellular force generation. The PI and co-PI will mentor graduate and undergraduate student research and encourage minority students and high school students from the area to participate in research. The PI will organize a week-long biophysics lab demonstration as part of the Summer Girls Program in the Physics Department to encourage participation of female high school students in science. The co-PI will develop user friendly educational software modules teaching how complex cytoskeletal dynamics emerges from simple molecular interactions.These studies, using an integrated experimental and computational approach, will lead to fundamental understanding of centrosome positioning which is critical in many cellular functions in many cell types. The group will use state-of-the-art imaging techniques to quantitatively analyze the 3-dimensional shape and dynamics of microtubules. In parallel, they will develop a computational model of centrosome movement driven by MT dynamics and motor activity. Model parameters will be set by comparisons with experimental observations (Objective 1). The PI will investigate the interactions between the acto-myosin cytoskeleton and the MT-dynein systems and their respective roles in centrosome positioning. The PI will also extend the model to include both actin and microtubule cytoskeletons and associated motors, their mutual couplings and systematically model perturbations carried out in parallel experiments (Objective 2). This research will unravel novel physical principles involved in the collective dynamics of two distinct but interacting force-generating biopolymer filament systems and associated motors. The development of the mechano-chemical model will be applicable to many other phenomena in cell biology and hence a valuable contribution to the field. More broadly, this work will provide novel insights on the principles of self-organization in highly complex active matter systems. This project is being jointly supported by the Physics of Living Systems program in the Division of Physics and the Cellular Cluster in the Division of Molecular and Cellular Biosciences.