Delineating the role of Matrin-3 in driving aberrant liquid-liquid phase separation that underpins ALS/FTD

摘要 蛋白质错误折叠是几种神经退行性疾病的基础，包括额颞叶痴呆（FTD）。在 FTD：几种不同的RNA结合蛋白（RBP）与朊病毒样结构域的错误折叠，包括TDP-43 和FUS有牵连朊病毒样结构域本质上是无序的，使得这些蛋白质高度 聚集倾向。还已知RBP会经历液-液相分离（LIPS）。LLP是一个 生理反应，允许隔离和保护必要的细胞成分，并为RBP， RNA是这一过程的关键调节剂。然而，蛋白质的局部浓度可以相当高， LLPS，进一步增加聚集倾向。事实上，TDP-43的病理性包涵体在超过100例患者中发现。 FTD患者的一半。此外，已知许多其他蛋白质与TDP-43共聚集，并且协同作用。 蛋白质稳态的破坏可能支持FTD。最近，Matrin-3（MATR 3）聚集被牵连 在FTD中，与TDP-43和FUS相比，MATR 3具有几个关键的相似性和差异性。然而，在这方面， MATR 3仍然知之甚少，在不同的研究中报告了相互矛盾的结果。因此我们 旨在利用我们独特的技能来描述MATR 3在LLPS，RNA结合和 与其他FTD相关蛋白的相互作用。了解这些机制将提供基本的 为新的治疗开发提供信息的知识，特别是对于可能恢复的新RNA疗法， 生理LLPS。我们假设MATR 3与RNA和其他FTD连接蛋白的结合受损， 协同作用，驱动FTD发病机制。在本建议中，我们将研究具体的机制， MATR 3经历LLP以及其LLP在FTD中如何受到干扰。此外，我们将调查具体的 LLPS导致细胞质量控制故障的机制。我们还将研究如何相互作用 MATR 3与RNA和其他FTD相关蛋白在FTD中协同作用。为了验证这些想法，我的实验室 开发了一种遗传上易处理的酵母系统来探测MATR 3毒性和异常LLPS的驱动因素。我们 他们还率先纯化了全长MATR 3，这将使我们能够重建其假定的相互作用 RNA和其他与FTD相关的RBP。关键发现将在哺乳动物细胞中得到验证。总之，我们将 满足以下目的：1）确定Matrin-3液-液相分离的分子决定因素， ALS/FTD中液-液相分离是如何扰动的; 2）阐明Matrin-3与 RNA和其他ALS/FTD相关蛋白。该项目的成功完成将为我们提供新的 调制MATR 3 LLPS的因素的基本知识，MATR 3 LLPS如何在FTD中损坏，以及 LLPS如何在治疗上被调节。

Abstract Protein misfolding underpins several neurodegenerative disorders including frontotemporal dementia (FTD). In FTD the misfolding of several different RNA-binding proteins (RBPs) with prion-like domains, including TDP-43 and FUS, are implicated. Prion-like domains are intrinsically disordered, making these proteins highly aggregation-prone. RBPs are also known to undergo liquid-liquid phase separation (LLPS). LLPS is a physiological response that allows sequestration and protection of essential cellular components, and for RBPs, RNA is a key modulator of this process. However, the localized concentration of proteins can be quite high upon LLPS, further increasing aggregation propensity. Indeed, pathological inclusions of TDP-43 are found in over half of FTD patients. Further, many other proteins are known to co-aggregate with TDP-43, and synergistic corruption of protein homeostasis may underpin FTD. Recently Matrin-3 (MATR3) aggregation was implicated in FTD, and MATR3 has several key similarities and differences as compared to TDP-43 and FUS. However, MATR3 remains poorly understood, and conflicting results have been reported in different studies. We therefore aim to leverage our unique skillset to delineate the properties of MATR3 with respect to LLPS, RNA binding, and interactions with other FTD-linked proteins. Understanding these mechanisms will provide fundamental knowledge to inform new therapeutic development, particularly for new RNA therapeutics that might restore physiological LLPS. We hypothesize that corrupted binding of MATR3 to RNA and other FTD-linked proteins can synergize, driving FTD pathogenesis. In this proposal, we will investigate the specific mechanisms by which MATR3 undergoes LLPS and how its LLPS is perturbed in FTD. Further, we will investigate the specific mechanism by which LLPS leads to quality control malfunction in cells. We will also investigate how interactions of MATR3 with RNA and other FTD-associated proteins synergize in FTD. To test these ideas, my lab has developed a genetically tractable yeast system to probe the drivers of MATR3 toxicity and aberrant LLPS. We have also pioneered purification of full-length MATR3, which will allow us to reconstitute its putative interactions with RNA and other FTD-associated RBPs. Key findings will be validated in mammalian cells. In sum, we will meet the following aims: 1) Define the molecular determinants of Matrin-3 liquid-liquid phase separation, and how liquid-liquid phase separation is perturbed in ALS/FTD and 2) Elucidate the interactions of Matrin-3 with RNA and other ALS/FTD-associated proteins. Successful completion of this project will provide us with new fundamental knowledge of the factors modulating MATR3 LLPS, how MATR3 LLPS is corrupted in FTD, and how LLPS might be therapeutically modulated.