T Cell Histone Glcnacylation Participates in the Epigenetics of Lupus

 T细胞组蛋白GlcNAc化参与狼疮的表观遗传学系统性红斑狼疮（SLE）是一种慢性自身免疫性疾病，女性发病率是男性的10倍。改变的T细胞信号传导将遗传和环境因素联系起来，并有助于疾病的发病机制。DNA甲基化、组蛋白修饰和miRNA通过修饰表观基因组来调节基因表达和染色质结构。DNA甲基化抑制基因转录，并且在SLE中，女性失活的X染色体是低甲基化的，这导致使女性易患狼疮的基因过表达。SLE的特征还在于整体T细胞DNA低甲基化，其引起免疫相关基因的过表达和随后的自身免疫。我们最近发现，OGT（O-连锁N-乙酰葡糖胺转移酶），一个X连锁基因，在女性狼疮T细胞中过表达。OGT可逆地将β-N-乙酰基-葡糖胺（O-GlcNAc）添加到与磷酸化竞争的蛋白质的丝氨酸和苏氨酸残基。这使得OGT成为细胞信号传导和转录的调节剂。有趣的是，GlcNAc酰化蛋白水平在女性而非男性T细胞狼疮患者中增加，这与OGT过表达相关。此外，O-GlcNAc被认为是组蛋白密码的一部分，并且OGT调节组蛋白的O-GlcNAc化。组蛋白2B（H2 B）是Ser 112处的GlcNAc，其是促进转录激活所需的H2 BK 120泛素化的修饰。此外，10 - 11易位酶TET 2和TET 3直接与OGT相互作用，并在活性启动子处共定位于染色质上。OGT在信号通路和T细胞染色质结构上的作用尚不清楚，但可能在狼疮的T细胞功能障碍以及一般的自身免疫中起重要作用。我们假设，女性狼疮T细胞中的OGT过表达通过蛋白质靶标和染色质重塑物的O-GlcNAc改变信号传导途径和DNA-组蛋白结合谱。因此，OGT最终可能是狼疮的表观遗传调节剂。为了验证这一假设，我们建议使用蛋白质组学和遗传学方法：1）确定OGT的分子靶点，这是T细胞信号传导中的关键蛋白，可能有助于狼疮的发病机制：2）确定OGT在CD 4 T细胞中的过表达是否导致组蛋白糖基化的改变;和3）检查H2 B修饰对过表达OGT的细胞中基因调节的影响本研究将揭示由OGT引起的SLE中T细胞途径的异常和基因调节的变化，一种在女性狼疮T细胞中异常表达的基因，可能使女性易患此病。通过确定新的生物标志物和目标，该项目将作为未来研究的基础 旨在改善对患有SLE和潜在的其他自身免疫性疾病的患者的治疗。

 DESCRIPTION (provided by applicant): T cell histone GlcNAcylation participates in the epigenetics of lupus ABSTRACT Systemic Lupus Erythematosus (SLE) is a chronic autoimmune disease that affects women ten times more often than men. Altered T cell signaling links genetic and environmental factors and contributes to disease etiopathogenesis. DNA methylation, histone modification, and miRNA regulate gene expression and chromatin structure by modifying the epigenome. DNA methylation suppresses gene transcription and in SLE, the female inactive X-chromosome is hypomethylated, which causes overexpression of genes that predispose females to lupus. SLE is also characterized by global T cell DNA hypomethylation that causes overexpression of immune- related genes and subsequent autoimmunity. We recently found that OGT (O-linked N-acetylglucosamine transferase), an X-linked gene, is overexpressed in female lupus T cells. OGT reversibly adds ß-N-acetyl-glucosamine (O-GlcNAc) to serine and threonine residues of proteins competing with phosphorylation. This makes OGT a regulator of cell signaling and transcription. Interestingly, GlcNAcylated protein levels are increased in female, but not male, T cell lupus patients, which correlate with OGT overexpression. Furthermore, O-GlcNAc is considered part of the histone code, and OGT regulates O-GlcNAcylation of histones. Histone 2B (H2B) is GlcNAc at Ser 112, a modification that facilitates H2BK120 ubiquitination required for transcriptional activation. Additionally, Ten Eleven Translocation enzymes TET2 and TET3 interact directly with OGT and co-localize on chromatin at active promoters. The effects of OGT in signaling pathways and on chromatin structure of T cells are unknown but may play an important role in T cell dysfunction in lupus as well as autoimmunity in general. We hypothesize that OGT overexpression in female lupus T cells modifies signaling pathways and DNA- histone binding profiles by O-GlcNAc of protein targets and chromatin remodelers. Hence, OGT may ultimately be an epigenetic modulator in lupus. To test this hypothesis, we propose to use proteomic and genetic approaches to: 1) Identify molecular targets of OGT, which are key proteins in T cell signaling that may contribute to the pathogenesis of lupus; 2) Determine whether overexpression of OGT in CD4 T cells results in altered glycosylation of histone proteins; and 3) Examine the effects of H2B modifications on gene regulation in cells that overexpress OGT This study will uncover abnormalities in T cell pathways and changes in gene regulation in SLE caused by OGT, a gene aberrantly expressed in female lupus T cells that may predispose females to the disease. By identifying new biomarkers and targets this project will serve as the foundation for future studies aimed at improving therapies for patients suffering from SLE and potentially other autoimmune diseases.