Role of Transglutaminase 2 in Synucleinopathies

项目总结： α-突触核蛋白是帕金森病和路易痴呆的关键致病蛋白 基于遗传学、神经病理学、细胞生物学和动物模型研究的身体(DLB)。这 本质上无序的蛋白质可以寡聚、错误折叠并形成纤维，然后传播到 神经元分布在大脑中，并聚集在路易小体和路易神经突内。据信， 寡聚形式的α-突触核蛋白代表有毒物质，这些物质可以使单体成核 使疾病进行性的病理过程永久化。因此， 了解触发齐聚的初始步骤的因素对于设计是至关重要的 疾病修正治疗策略。到目前为止还未被研究的一个因素是分子交叉 谷氨酰胺和赖氨酸残基之间的转谷氨酰胺酶2连接α-突触核蛋白 形成分子间的异肽键，高度抵抗蛋白质的降解。几行 有证据表明，Tg2交联型α-突触核蛋白导致其在体外、体外和培养中聚集。 哺乳动物细胞、酵母细胞和转基因小鼠的大脑中。我们发现， α-突触核蛋白转基因小鼠的表型因过度表达Tg2和IS而加剧 通过击倒它来减轻罪责。对α-突触核素病患者的研究也证实了 假设TG2起致病作用。TG2在实质中的表达增加 帕金森病患者黑质和脑脊液中TG2与 帕金森病脑内应激多巴胺能神经元中α-突触核蛋白聚集及Tg2催化 在帕金森病患者的大脑中，交联物与α-突触核蛋白共定位于路易体。尽管 这一证据，目前尚不清楚Tg2是否介导了α-突触核蛋白的交联 促进这些聚集体在大脑中的传播。我们假设是这样的，而且 建议通过两个具体目标来检验这一假设：1)调查TG2是否存在 以及其表达水平影响α-突触核蛋白原纤维的增殖，以及2)检测 转谷氨酰胺酶TG2的活性参与了这一过程。获得的知识 这些研究将解决关于致病机理的一个基本科学问题 Tg2介导的α-突触核蛋白增殖机制及其在靶向疾病中的作用 修改联体核病的治疗方法。

Project Summary: α-Synuclein is a key pathogenic protein in Parkinson’s disease (PD) and Dementia with Lewy Bodies (DLB) based on genetic, neuropathologic, cell biologic and animal model studies. This intrinsically disordered protein can oligomerize, misfold, and form fibrils that propagate across neurons in the brain and accumulate in Lewy bodies and Lewy neurites. It is believed that the oligomeric forms of α-synuclein represent the toxic species, and these can nucleate monomers to perpetuate the pathologic process underlying the progressive nature of the disease. Thus, understanding the factors that trigger the initial steps of oligomerization is critical for designing disease modifying therapeutic strategies. A hitherto under-explored factor is molecular cross- linking of α-synuclein by transglutaminase 2 (TG2) between glutamine and lysine residues creating intermolecular isopeptide bonds that are highly resistant to proteolysis. Several lines of evidence indicate that TG2 cross-links α-synuclein leading to its aggregation in vitro, in cultured mammalian cells, in yeast cells, and in the brains of transgenic mice. We have found that the phenotype of α-synuclein transgenic mice is exacerbated by over-expressing TG2 and is mitigated by knocking it out. Studies in patients with α-synucleinopathy also corroborate the hypothesis that TG2 plays a pathogenetic role. TG2 expression is increased in the substantia nigra and cerebrospinal fluid of PD patients compared with control subjects, TG2 co-localizes with α-synuclein aggregates in stressed dopaminergic neurons in PD brains, and TG2-catalyzed cross-links co-localize with α-synuclein in Lewy bodies in PD and DLB affected brains. Despite this body of evidence, it remains unknown whether TG2-mediated cross-linking of α-synuclein promotes the propagation of these aggregates across the brain. We hypothesize that it does and propose to test this hypothesis through two specific aims: 1) Investigate if the presence of TG2 and its expression level influence the propagation of α-synuclein fibrils, and 2) Examine if the transglutaminase enzymatic activity of TG2 is responsible for this process. Knowledge gained from these studies will address a fundamental scientific question about the pathogenetic mechanism of TG2-mediated α-synuclein propagation and aid in developing targeted disease modifying therapeutic for synucleinopathies.