Collaborative Research: MODULUS: Protein droplets drive membrane bending and cytoskeletal organization

最近观察到细胞内不同种类的蛋白质自组装成液体状液滴。虽然它们最初是在细胞内部或细胞溶质中发现的，但越来越清楚的是，蛋白质液滴经常与其他细胞结构偶联，包括生物膜和细胞的细胞骨架。受这些发现的启发，在这个项目中，研究人员正在寻求蛋白质液滴，膜和细胞骨架丝之间的生物物理耦合的理解。该项目分两部分执行。在第一部分，该项目，检查蛋白质液滴如何对生物膜施加力，导致膜弯曲。该项目的第二部分研究了蛋白质液滴如何对细胞骨架丝施加力，从而将丝组织成束和网格。该项目的研究结果通过提高对病原体用于入侵细胞的机制，内吞囊泡如何内化细胞外物质以及细胞运动如何建立和调节的知识而使社会受益。该项目还揭示了组织软物质的基本机制，从表面活性剂和燃料到化妆品和食品。该项目将科学工作与多层次教育推广计划的实施相结合，该计划使从K-12教室到本科研究人员的不同学生受益。该项目揭示了蛋白质缩合物在两个关键细胞功能中的作用：细胞骨架细丝的组织和膜表面的成形。理解这些功能的传统努力集中在结构蛋白质之间的特定相互作用上。相比之下，这项工作说明了蛋白质凝聚物，主要由内在无序的蛋白质组成，提供了以前未知的力产生机制。这幅插图提出了一个新的范例，其中软材料之间的界面相互作用可以用来理解细胞结构是如何产生的。该项目的方法是由以下假设指导的，即通过与2D膜或1D细丝连接来降低3D蛋白质液滴的空间维度，产生将改变降维复合材料的形态的力。这一假设是通过开发实验约束，液体蛋白液滴，细胞骨架聚合物和膜之间的界面耦合的数学模型进行测试。模型预测测试与实验系统，直接观察液滴，长丝和膜之间的耦合，使验证和完善模型所需的关键几何和物理参数的测量。理论，计算和实验工具的组合被用来设计研究，揭示蛋白质凝聚物的独特的机械功能。该项目增强了对已知通过液-液相分离组装成3D液滴的蛋白质如何对膜和细胞骨架施加应力的理解。该奖项由分子和细胞生物科学部的系统和合成生物学项目以及数学科学部的数学生物学部共同资助。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Diverse classes of proteins within cells have recently been observed to self-assemble into liquid-like droplets. While they were first discovered in the cellular interior, or cytosol, it is increasingly clear that protein droplets frequently become coupled to other cellular structures, including biological membranes and the cell’s cytoskeleton. Inspired by these findings, in this project the investigators are seeking an understanding of the biophysical coupling between protein droplets, membranes, and cytoskeletal filaments. The project is executed in two parts. In the first part, the project, examines how protein droplets exert forces on biological membranes, resulting in membrane curvature. The second part of the project examines how protein droplets exert forces on cytoskeletal filaments, resulting in the organization of filaments into bundles and meshes. The project findings benefit society by improving knowledge on the mechanisms that pathogens use to invade cells, how endocytic vesicles internalize extracellular material and how cellular motility is established and regulated. The project also reveals fundamental mechanisms that organize soft matter, from surfactants and fuels to cosmetics and foods. The project couples scientific work to the implementation of a multi-level educational outreach program that benefits diverse students from K-12 classrooms to undergraduate researchers. This project sheds light on the role of protein condensates in two critical cellular functions: organization of cytoskeletal filaments and shaping of membrane surfaces. Traditional efforts to understand these functions have focused on specific interactions between structured proteins. In contrast, this work illustrates how protein condensates, composed largely of intrinsically disordered proteins, provide previously unknown mechanisms of force generation. This illustration suggests a new paradigm in which interfacial interactions among soft materials can be used to understand how cellular architectures arise. The project approaches are guided by the hypothesis that reducing the spatial dimensionality of 3D protein droplets, by interfacing either with 2D membranes or with 1D filaments, generates forces that will alter the morphology of the reduced-dimension composite. This hypothesis is tested by developing experimentally constrained, mathematical models of interfacial coupling between liquid protein droplets, cytoskeletal polymers, and membranes. Model predictions are tested with experimental systems that directly observe the coupling between droplets, filaments, and membranes, enabling measurement of the key geometrical and physical parameters required to validate and refine the models. A combination of theoretical, computational, and experimental tools is used to design studies that reveal the unique mechanical functions of protein condensates. The project enhances understanding of how proteins that are known to assemble into 3D liquid droplets, through liquid-liquid phase separation, can exert stresses on the membrane and on the cytoskeleton. This award is co-funded by the Systems and Synthetic Biology program in the Division of Molecular and Cellular Biosciences and the Division of Mathematical Biology in the Division of Mathematical Sciences.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.