Protein Arginine Deiminase 2 (PAD2) and Protein Citrullination in ALS

项目摘要 肌萎缩侧索硬化症（Amyotrophic lateral sclerosis，ALS）是一种进行性神经退行性疾病， 退化、肌肉无力、瘫痪和死亡。运动神经元变性的机制是 目前还不完全了解，并且目前没有治疗可以阻止或逆转疾病进展。到 了解疾病并开辟新的治疗途径，探索疾病的新机制是 needed.为此，徐和汤普森实验室联手调查蛋白质的作用 在ALS中，瓜氨酸酶由蛋白质精氨酸脱亚胺酶（PAD）催化。瓜氨酸去除阳性 来自蛋白质的电荷因此，这种修饰可以改变蛋白质的功能及其与其他蛋白质的相互作用。 蛋白质、膜和核酸。哺乳动物有五个PAD：PAD 1-4和PAD 6。PAD 2是 在中枢神经系统（CNS）中占主导地位。先前的研究表明，PAD 2和蛋白质 瓜氨酸在神经退行性疾病如阿尔茨海默病和朊病毒病中增加。 然而，没有研究将PAD和蛋白质瓜氨酸与ALS联系起来。此外，没有任何研究 研究了PAD 2和瓜氨酸蛋白在神经变性中的功能作用。为了填补这些知识 Xu和Thompson实验室将他们在ALS和蛋白质瓜氨酸方面的综合专业知识， 发起了这次调查我们的初步研究表明，明确的证据表明，PAD 2表达（但不表达）， PAD 3，4）和瓜氨酸蛋白在两种ALS小鼠模型中发生了空间和时间上的改变， 表达突变体SOD 1G 93 A和另一个表达突变体PFN 1C 71 G。当PAD 2表达增加时， 在星形胶质细胞中，其表达在疾病进展期间在神经元中减少。通过蛋白质组学， 在脊髓中发现了几百种瓜氨酸化蛋白。在ALS小鼠中，早期疾病阶段是 主要是瓜氨酸蛋白减少。相反，疾病晚期显示瓜氨酸增加， 一半的蛋白质减少，另一半的瓜氨酸减少。有趣的是，高瓜氨酸 蛋白质在后期富集在不溶性部分中。我们建议进一步调查 回答以下七个问题：（1）蛋白质瓜氨酸在ALS中是如何改变的？(2)有哪些 脊髓中的瓜氨酸化蛋白质，以及在ALS中瓜氨酸在这些蛋白质中是如何改变的？(3)是什么 瓜氨酸在ALS相关蛋白上的位置(4)PAD 2是导致蛋白质改变的原因吗？ 瓜氨酸肌萎缩侧索硬化症？(5)瓜氨酸蛋白如何影响蛋白质聚集？(6)如何 ALS相关靶点的瓜氨酸会影响其蛋白质功能吗？(7)蛋白质瓜氨酸是如何改变的 人类ALS？通过回答这些问题，我们将进入和调查一个迄今为止尚未探索的研究领域 在ALS，从而打开了一个新的层面，了解神经退行性病变的机制在ALS。 由于PAD抑制剂已经在汤普森实验室开发，这一新的维度可能会导致 靶向PAD 2活性的新治疗途径。由于蛋白质瓜氨酸的显著变化， 这项研究还可能鉴定出早期ALS的新生物标志物。 1

Project Summary Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that causes motor neuron degeneration, muscle weakness, paralysis, and death. The mechanism of motor neuron degeneration is incompletely understood, and currently, no therapy can arrest or reverse the disease progression. To understand the disease and open new avenues for therapy, exploring new mechanisms of the disease is needed. To this end, the Xu and Thompson labs have joined forces to investigate the role of protein citrullination, which is catalyzed by Protein Arginine Deiminases (PADs), in ALS. Citrullination removes positive charges from proteins. Therefore, this modification can alter the protein function and its interaction with other proteins, membranes, and nucleic acids. Mammals have five PADs: PADs 1–4 and PAD6. PAD2 is the dominant form in the central nervous system (CNS). Previous studies have shown that PAD2 and protein citrullination are increased in neurodegenerative diseases such as Alzheimer's disease and Prion disease. However, no studies have linked PADs and protein citrullination with ALS. Furthermore, no studies have investigated the functional role of PAD2 and protein citrullination in neurodegeneration. To fill these knowledge gaps, the Xu and Thompson labs have applied their combined expertise in ALS and protein citrullination and initiated this investigation. Our preliminary studies show unequivocal evidence that PAD2 expression (but not PAD3, 4) and protein citrullination are spatially and temporally altered in two ALS mouse models, one expressing mutant SOD1G93A and the other expressing mutant PFN1C71G. While PAD2 expression is increased in astrocytes, its expression is decreased in neurons during the disease progression. By proteomics, we identified several hundred citrullinated proteins in the spinal cord. In ALS mice, the early disease stage is dominated by decreased protein citrullination. In contrast, the late disease stage shows increased citrullination in one-half of the proteins and decreased citrullination in the other half. Intriguingly, the highly citrullinated proteins are enriched in the insoluble fractions in the late stage. We propose to further our investigation by answering the following seven questions: (1) How is protein citrullination altered in ALS? (2) What are the citrullinated proteins in the spinal cord, and how is citrullination altered in these proteins in ALS? (3) What are the sites of citrullination on ALS-associated proteins? (4) Is PAD2 responsible for the altered protein citrullination in ALS? (5) How does protein citrullination impact protein aggregation? (6) How does the citrullination of ALS-associated targets impact their protein function? (7) How is protein citrullination altered in human ALS? By answering these questions, we will enter and investigate a hitherto unexplored research area in ALS, thereby opening a new dimension in understanding the mechanism of neurodegeneration in ALS. Because PAD inhibitors have already been developed in the Thompson lab, this new dimension may lead to new therapeutic avenues targeting PAD2 activity. Because of the significant changes in protein citrullination, this research may also identify novel biomarkers of early-stage ALS. 1