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

细胞内不同种类的蛋白质最近被观察到自组装成液体状的液滴。虽然它们最初是在细胞内部或细胞质中发现的，但越来越清楚的是，蛋白质液滴经常与其他细胞结构偶联，包括生物膜和细胞骨架。受这些发现的启发，在这个项目中，研究人员正在寻求理解蛋白质滴、膜和细胞骨架细丝之间的生物物理偶联。该项目分为两部分执行。在第一部分中，该项目研究了蛋白质液滴如何对生物膜施加力，从而导致膜曲率。该项目的第二部分研究了蛋白质液滴如何对细胞骨架细丝施加力，导致细丝组织成束和网格。该项目的研究结果通过提高对病原体入侵细胞的机制，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认识，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结合起来，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凝聚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形成。了解这些功能的传统努力集中在结构蛋白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，如何提供以前未知的力产生机制。这幅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。该项目的方法是基于这样一个假设：通过与二维膜或一维细丝连接，降低3D蛋白滴的空间维度，产生的力将改变降维复合材料的形态。这一假设是通过开发实验约束，液体蛋白滴，细胞骨架聚合物和膜之间的界面耦合的数学模型来验证的。模型预测通过直接观察液滴、细丝和膜之间耦合的实验系统进行测试，从而能够测量验证和改进模型所需的关键几何和物理参数。结合理论，计算和实验的工具被用来设计研究，揭示蛋白质凝聚体的独特的机械功能。该项目增强了对已知的通过液-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压力的理解。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门共同资助。该奖项反映了美国国家科学基金会的法定使命，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.