Mechanisms of Transglutaminase 2 (TG2)-Mediated Gene Expression in Astrocyte

星形胶质细胞在维持神经元功能的健康环境中发挥着不可或缺的作用，而且在 调节中枢神经系统对损伤的反应。损伤后，星形胶质细胞变得“反应性”，并调节两者 有益和有害的结果取决于它们的基因表达谱。然而，分子机制 调控星形胶质细胞中基因表达的基因，因此它们对损伤的反应还没有完全被描述。一 转谷氨酰胺酶2(TG2)在调节星形胶质细胞对侮辱的反应中起着关键作用。 TG2的缺失或缺失会导致星形胶质细胞呈现出更有帮助的表型，但潜在的 分子机制尚不清楚。TG2是一种多功能蛋白质，它催化钙依赖的 转酰胺化反应，结合和水解GTP，可以作为支架或连接蛋白发挥作用。TG2 在钙和GTP结合的作用下，经历了很大的构象变化，它的构象可以决定 它的功能独立于它的酶活性。这些构象状态是决定 细胞存活/细胞死亡结果。人们越来越意识到TG2可能调节基因表达， 然而，TG2介导的星形胶质细胞基因表达调控机制尚不完全清楚 探索过了。一种可能的机制可能是TG2与蛋白质相互作用，并调节蛋白质的功能 这在调控基因表达方面起着关键作用。在调节染色质中起关键作用的一个因素 可及性和活性特异的转录因子是Zbtb7a。有趣的是，初步数据显示 TG2与Zbtb7a相互作用，这些转录因子的结合部位大多是有利于生存的 在TG2-/-星形胶质细胞中上调的基因。这一提议的基本前提是TG2扮演 在调节星形胶质细胞的基因表达方面的作用，以及它们如何对损伤做出反应。然而，一个关键的 知识缺口是TG2调控基因表达的方式。此应用程序的总体假设 TG2以构象依赖的方式调节染色质的可及性和基因表达 景观，这有助于星形胶质细胞如何对伤害做出反应。这个项目的新奇之处在于我们将 采用综合的“基因组学”方法(ATAC-SEQ、RNA-SEQ、CHIP-SEQ)和体外和体内模型。 TG2/和TG2-/-星形胶质细胞建立TG2在特定构象中调节的机制 基因表达。这一提议的具体目的是检验以下假设：(1)TG2的构象 在决定其调节染色质可及性和基因表达的能力方面发挥重要作用，以及(2) TG2部分通过调节Zbtb7a的功能来调节星形胶质细胞的基因表达。生成的数据 来自这些新颖和探索性的研究将为未来的R01赠款申请提供基础，重点是 TG2调控星形胶质细胞转归的分子机制和途径 中枢神经系统损伤。

Astrocytes play an indispensable role in maintaining a healthy environment for neuronal function, and in mediating the response of the CNS to injury. Following an injury astrocytes become “reactive” and mediate both helpful and harmful outcomes depending on their gene expression profile. However the molecular mechanisms that regulate gene expression in astrocytes and thus their response to injury has not been fully delineated. One protein that plays a key role in regulating the response of astrocytes to insults is transglutaminase 2 (TG2). Deletion or depletion of TG2 results in astrocytes taking on a more “helpful” phenotype, however the underlying molecular mechanisms are unknown. TG2 is a multifunctional protein; it catalyzes a calcium dependent transamidation reaction, binds and hydrolyzes GTP and can function as a scaffold or linker protein. TG2 undergoes large conformational changes mediated by calcium and GTP binding, and its conformation can dictate its function independent of its enzymatic activities. These conformational states are key a factors in determining cell survival/cell death outcomes. There is a growing awareness that TG2 likely regulates gene expression, however the mechanisms of TG2-mediated regulation of gene expression in astrocytes has not been fully explored. One possible mechanism may be by TG2 interacting with, and modulating the function of, a protein that plays a pivotal role in regulating gene expression. One factor that plays a key role in regulating chromatin accessibility and the activity of specific transcription factors is Zbtb7a. Intriguingly, preliminary data indicate that TG2 interacts with Zbtb7a, and binding sites for these transcription factors are in the majority of pro-survival genes that are upregulated in TG2-/- astrocytes. The UNDERLYING PREMISE of this proposal is that TG2 plays a role in regulating gene expression in astrocytes, and thus how they respond to injury. However, a CRITICAL KNOWLEDGE GAP is how TG2 regulates gene expression. The OVERALL HYPOTHESIS of this application is that TG2, in a conformational dependent manner, moderates chromatin accessibility and the gene expression landscape, which contributes to how astrocytes respond to injury. The NOVELTY of this project is that we will be using an integrated “omic” approach (ATAC-seq, RNA-seq, ChIP-seq) and both in vitro and in vivo models of TG2+/+ and TG2-/- astrocytes to establish the mechanisms by which TG2 in a specific conformation regulates gene expression. The specific aims of this proposal are to test the hypothesis that: (1) the conformation of TG2 play an essential role in determining its ability to regulate chromatin accessibility and gene expression, and (2) TG2 mediates gene expression in astrocytes in part by regulating the function of Zbtb7a. The data generated from these novel and exploratory studies will provide the basis for a future R01 grant application focused on delineating the molecular mechanisms and pathways regulated by TG2 in astrocytes to direct outcomes following CNS injury.