Mechanobiology of Phagocytosis

巨噬细胞是免疫细胞，是抵御细菌、病毒、癌细胞和其他病原体的第一道防线。巨噬细胞将自己包裹在异物颗粒周围，吞噬并消化它。这一过程称为吞噬作用，涉及化学和物理两种力量。虽然对吞噬过程的生物化学研究已经很好了，但这个项目采取了不同的观点：它将巨噬细胞视为机器，将吞噬过程视为机械事件。这些力量是什么？他们是如何协调的？这台机器是怎么工作的？如果不了解作用力，我们就缺乏对吞噬作用的完整科学描述，更广泛地说，缺乏对免疫反应本身的描述。该项目使用先进的显微技术以及独特的力测量方法来实时研究巨噬细胞的三维结构，同时测量其产生的力。该项目产生的数据将为这一基本生物过程提供一个更全面的模型，该模型集成了生物化学、结构和生物物理力。整个项目的另一个关键组成部分是将研究成果公之于众，帮助人们了解实验室正在发生的最新令人兴奋的科学。更广泛的影响项目包括将在当地一家博物馆开发的基于虚拟现实的展览，以及将在当地一所高中教授的为期一周的生物物理学“迷你学期”。这个项目的首要目标是使用先进的成像和力测量工具来揭示吞噬过程中力的产生和机械感觉的机制。吞噬作用是巨噬细胞、中性粒细胞和其他细胞吞噬大量外来病原体颗粒作为免疫系统第一道防线的过程。为了吞噬目标粒子，一个或多个不同的由肌动蛋白驱动的机械过程将目标吸引、包围和包围。除了生化信号动力学，吞噬作用也是由牵涉力和结构动力学的基本机械过程驱动的。最基本的问题仍未得到解答：巨噬细胞产生什么力量？是什么肌动蛋白动力学和相关的细胞形态动力学导致了它们？外力和机械环境如何影响吞噬过程中的决策？将巨噬细胞-靶向力与肌动蛋白动力学直接联系起来的测量是发展吞噬过程模型的关键缺失部分。在这个项目中，将测试一组假说，这些假说是由为其他细胞系统提出的类似机制指导的，例如间充质运动中的“分子离合器”机制，它提供力产生和机械传感。吞噬过程中巨噬细胞力量产生的测量将伴随着细胞形态和细胞骨架动力学的高质量实时细胞体积成像而进行。这将通过使用软珠作为目标来补充，以测量巨噬细胞施加在目标上的局部压缩和剪切力。还将进行体积肌动蛋白动力学和力测量的定量时空相关分析。这将提供丰富的详细数据，告知局部动态肌动蛋白重塑的位置和时间，从而产生特定的巨噬细胞力事件。如果成功，该项目将产生一个全新的巨噬细胞动态图谱，它映射了动态3D细胞形态和肌动蛋白动力学与局部力量产生和机械传感的关系。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Macrophages are immune cells that act as one of the first lines of defense against bacteria, viruses, cancer cells and other pathogens. Macrophages wrap themselves around a foreign particle, engulfing and digesting it. This process, called phagocytosis, involves both chemistry and physical forces. Though the process of phagocytosis has been well studied biochemically, this project takes a different perspective: it treats the macrophage as a machine and the phagocytic process as a mechanical event. What are the forces? How do they coordinate? How does the machine work? Without understanding forces, we lack a complete scientific description of phagocytosis and, more broadly, the immune response itself. The project employs both advanced microscopic techniques as well as unique force measurement methods to investigate the three-dimensional structure of the macrophage in real time while simultaneously measuring the forces it generates. The data generated from this project will provide a more comprehensive model of this fundamental biological process that integrates the biochemistry, the structure, and the biophysical forces. Another critical component of the overall project is bringing the research to the public to help inform folks on the latest exciting science that is happening in the lab. Broader impact projects include a virtual-reality-based exhibit that will be developed at a local museum, and a week-long biophysics “mini-term” that will be taught at a local high school. The overarching goal of this project is to use advanced imaging and force measurement tools to reveal the mechanisms of force generation and mechanosensing in phagocytosis. Phagocytosis is the process through which macrophages, neutrophils and other cells engulf large foreign pathogen particles as a first line of immune system defense. To engulf a target particle, one or more distinct actin-driven mechanical processes draws in the target, surrounds and encloses it. Along with biochemical signaling dynamics, phagocytosis is also driven by fundamentally mechanical processes involving forces and structural dynamics. The most fundamental questions are unanswered: What forces does a macrophage produce? What actin dynamics and associated cell morphological dynamics give rise to them? How do external forces and mechanical environment affect decision making in phagocytosis? Measurements directly associating macrophage-target forces with actin dynamics are a crucial missing piece to developing models of the engulfment process. Within this project, a set of hypotheses will be tested that are guided by analogous mechanisms that have been proposed for other cell systems such as the “molecular clutch” mechanism in mesenchymal motility which provides force generation as well as mechanosensing. Measurements of macrophage force generation during engulfment will be performed along with accompanying high quality, live cell volumetric imaging of cell morphology and cytoskeletal dynamics. This will be complemented by use of soft beads as targets to measure local compressive and shear forces being imposed by the macrophage on the target. Quantitative spatio-temporal correlation analysis of volumetric actin dynamics and force measurements will also be performed. This will provide rich detailed data informing location and timing of the local dynamic actin remodeling that produce a specific macrophage force event. If successful, the project will produce a completely new dynamical atlas of the macrophage that maps the relationship of dynamic 3D cell morphology and actin dynamics with local force generation and mechanosensing.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.