CAREER: PolyQ Proteins Phase Transition Induced by Lipid Vesicles

结构-功能范式认为蛋白质结构决定功能。然而，这一概念受到了最近发现的挑战，即真核细胞中约40%具有重要生物学功能的蛋白质缺乏稳定的三维（3D）结构。这些内在无序蛋白质（IDP）中的许多可以通过称为相变的过程凝聚成无膜的液体状或凝胶状组装体。这些组装体的形成使这些蛋白质在隔离的微环境中富集，从而调节它们的生物活性。目前，相变组装体的超微结构如何支持所包封蛋白质功能的时空调控仍是一个谜。由于其结构的灵活性，国内流离失所者的实验结构研究提出了固有的挑战。通过应用最先进的结构方法，即冷冻电子断层扫描（cryoET）和先进的亚断层扫描分析，该项目将揭示相变组件的结构，并建立这类重要蛋白质的3D结构，动力学和功能之间的联系。总体而言，该项目将有助于基础生物学中更完整的结构-功能范式。与此同时，PI将开发一个研究驱动的教育课程，向本科生介绍跨学科研究，促进互动式研究生教学，并为年轻学者提供有关尖端cryoET生物结构成像的在线培训资源。cryoET教育门户网站的开发具有更广泛的影响。该项目的目标是解析蛋白质相变组装体的结构组织，以更深入地了解这些组装体的生物物理和结构特性如何支持封闭的IDPs的生物活性。具有延伸的多聚谷氨酰胺（polyQ）同源重复的蛋白质代表最简单的IDP之一。使用这个系统，PI将解决，在亚纳米级，在生理相关的实验条件下形成的相变组件的3D结构组织。本计画亦将探讨内点与脂质囊泡的序列特性如何影响相转变集合体的形成、稳定性与聚集倾向。这项工作将推进我们对IDP相变的分子机制的理解。更重要的是，这项工作的结果将促进调控这些亚稳态组装的策略的发展，从而调节细胞中的蛋白质稳态。该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

The structure-function paradigm states that protein structure dictates function. However, this concept has been challenged by recent discoveries that ~40% of proteins in eukaryotic cells with important biological functions lack a stable three-dimensional (3D) structure. Many of these intrinsically disordered proteins (IDPs) can condense into membraneless liquid-like or gel-like assemblies through a process termed phase transition. Formation of these assemblies enriches these proteins within an isolated microenvironment, and thus regulates their biological activities. At present, it remains a mystery how the ultrastructure of phase transition assemblies supports spatiotemporal control of functions of the enclosed proteins. Due to their structural flexibility, IDPs present inherent challenges for experimental structural studies. By applying state-of-the-art structural methods, namely cryo-electron tomography (cryoET) and advanced subtomogram analyses, this project will reveal the architecture of phase transition assemblies, and establish a connection between the 3D structure, dynamics, and function for this important class of proteins. Overall, this project will contribute towards a more complete structure-function paradigm in fundamental biology. In parallel, the PI will develop a research-driven education curriculum that introduces interdisciplinary research to undergraduate students, promotes interactive graduate student teaching, and provides engaging online training resources on cutting-edge cryoET biostructure imaging to young scholars. Development of the cryoET educational portal has broader impacts. It will showcase to the general public the exciting potential of this novel bioimaging technique for unraveling dynamic biological processes in nature.The goal of this project is to resolve the structural organization of protein phase transition assemblies to provide a deeper understanding of how biophysical and structural properties of these assemblies support biological activities of enclosed IDPs. Proteins with extended polyglutamine (polyQ) homo-repeats represent one of the simplest IDPs. Using this system, the PI will resolve, at the subnanometer level, the 3D structural organization of phase transition assemblies formed under physiologically relevant experimental conditions. This project will also investigate how the formation, stability, and aggregation propensity of phase transition assemblies are affected by sequence characteristics of the IDPs and lipid vesicles. This work will advance our understanding of the molecular mechanisms underlying IDP phase transitions. More importantly, results from this work will facilitate development of strategies for regulating these metastable assemblies and thereby modulating protein homeostasis in cells.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.