Regulation of PD-1 gene expression

描述(申请人提供)：程序性细胞死亡-1(PD-1)是一种免疫抑制受体，在免疫激活后瞬时表达在CD4和CD8 T细胞表面，并在长期暴露于抗原的T细胞上高表达。通过PD-1传递信号可能导致T细胞耗尽，在这种状态下，抗原特异性T细胞不再对抗原特异性刺激做出反应。正如在许多持续性病毒感染中观察到的那样，包括艾滋病毒、人类丙型肝炎病毒和小鼠淋巴细胞性脉络膜脑膜炎病毒(LCMV)，PD-1及其配体(PD-L1/L2)之间的抗体阻断导致“耗尽的”抗原特异性T细胞的功能重新激活。结合PD1阻断疗法的临床试验证明了令人印象深刻的成功；突显了该基因表达和调控的重要性。我们的工作表明，PD-1以一种复杂的方式在转录水平上受到调控，涉及9个顺式调控元件；一个由正转录因子(NFATc1和STAT3)和负转录因子(Blimp-1和LSD1)组成的网络；以及一个动态的表观遗传调控程序，包括DNA甲基化。尽管有这些知识，但关于顺式元件、反式因子和表观遗传途径如何整合以提供细胞类型和免疫反应调节的机制细节尚不清楚。这一理解很重要，因为PD-1‘S的表达和活性对于发展对感染和癌症的保护性免疫反应至关重要。为了阐明控制PD-1表达的分子机制，我们提出了三个目标：1)定义感染后抗原特异性细胞中PD-1基因座的顺式调控图谱和相互作用；2)了解NFATc1、Blimp-1和STATS在急性和病毒感染条件下调控PD-1基因的相互作用；以及3)了解表观遗传沉默因子LSD1如何控制PD-1基因的表达和该基因位点的DNA甲基化。为了研究这些目的，我们建立了一系列小鼠系，它们将有条件地删除转录因子顺式元件CR-C BLIMP-1，或激活的CD8T细胞中的表观遗传沉默因子LSD1。我们已经建立了体外分析CD8T细胞的方法，并将利用LCMV在体内纳入急性和慢性病毒感染系统，以探索这些因素控制PD-1的机制。最终，我们的研究将阐明控制PD-1表达的分子遗传学和表观遗传学程序，并将提供新的工具来操纵PD-1基因的表达，这可能有助于感染和癌症的治疗。

DESCRIPTION (provided by applicant): Programmed cell death-1 (PD-1) is an immune inhibitory receptor that is expressed transiently on the surface of CD4 and CD8 T cells following immune activation and is highly expressed on T cells chronically exposed to antigen. Signaling through PD-1 can result in T cell exhaustion, a state in which antigen-specific T cells no longer respond to antigen-specific stimulation. As observed in numerous persistent viral infections, including those from HIV, human hepatitis C virus, and murine lymphocytic choriomeningitis virus (LCMV), antibody blockade between PD-1 and its ligands (PD-L1/L2) results in the functional reactivation of "exhausted" antigen-specific T cells. Clinical trials incorporating a PD1 blockade therapy have demonstrated impressive success; highlighting the importance of the expression and regulation of this gene. Our work has shown that PD-1 is regulated at the level of transcription in a complex manner involving nine cis-regulatory elements; a network of positive (NFATc1 and STAT3) and negative (Blimp-1 and LSD1) transcription factors; and a dynamic epigenetic regulatory program, including DNA methylation. Despite this knowledge, the mechanistic details of how the cis-elements, trans-factors, and epigenetic pathways integrate to provide cell type and immune response regulation is not well understood. This understanding is important as PD-1's expression and activity is critical to the development of protective immune responses to infection and cancer. To elucidate the molecular mechanisms that govern PD-1 expression, we propose three aims designed to 1) define the cis- regulatory map and interactions at the PD-1 locus in antigen-specific cells following infection; 2) understand the interplay between NFATc1, Blimp-1 and STATs in regulating PD-1 during acute and viral infection conditions; and 3) to understand how the epigenetic silencer LSD1 controls PD-1 expression and DNA methylation at this locus. To investigate these aims, we have established a series of mouse lines that will conditionally delete the cis element CR-C, the transcription factor Blimp-1, or the epigenetic silencer LSD1 in activated CD8 T cells. We have established ex vivo methods to analyze the CD8 T cells and will incorporate an in vivo system of acute and chronic viral infection using LCMV to explore the mechanism by which these factors function to control PD-1. Ultimately our studies will elucidate the molecular genetic and epigenetic programs that control PD-1 expression and will provide new tools to manipulate PD-1 gene expression that could aid in the treatment of infection and cancer.