Orchestration of PI3K-dependent transcriptional programmes by the transcription factor BACH2

CD8+ T细胞强有力地协调免疫反应，对抗细胞内感染和癌症。在免疫应答过程中，CD8+ T细胞增殖并分化为效应细胞，促进靶细胞的消除。效应细胞是短命的，这使得在感染解决后恢复正常的免疫功能。然而，一小部分细胞逃脱了这种命运，并持续形成长寿的记忆细胞。记忆细胞提供了一种持久的自我更新的目标特异性细胞来源，可以在感染后持续数十年，在再次感染时产生更有效的二次反应。在慢性感染和癌症的反应中，CD8+ T细胞也会发生终末分化或衰竭，这损害了它们的功能。我们之前的工作已经确定了一个关键的分子途径，称为磷酸肌苷3-激酶（PI3K）途径，有力地调节CD8+ T细胞分化。PI3K通路的激活驱动基因表达的广泛变化，促进效应细胞分化，阻止记忆细胞的形成。PI3K通路引起基因表达改变的机制尚不完全清楚。在这项研究中，我们将研究PI3K途径如何控制一类称为转录因子（tf）的蛋白质的功能。tf结合DNA内的调控区域，调节基因表达，控制细胞分化。我们最近发现，PI3K通路通过磷酸化过程控制转录因子BACH2的功能。我们将研究这个新的分子轴，确定PI3K途径如何调节BACH2的功能来控制CD8+ T细胞反应。我们的实验方法分为三个部分：1)我们将确定BACH2在调节CD8+ T细胞对感染的反应中的功能。为此，我们将使用CD8+ T细胞特异性缺失BACH2的小鼠模型，研究实验病原体感染后的免疫反应。2)我们将利用BACH2不能磷酸化的新小鼠模型来确定PI3K途径如何控制BACH2调节感染免疫应答的功能。我们还将确定BACH2磷酸化如何在分子水平上调节BACH2的功能。3)我们将测试BACH2在CD8+ T细胞中对pi3k介导的转录程序的贡献。为了实现这一目标，我们将利用小鼠遗传学来特异性地操纵PI3K通路，并调节CD8+ T细胞中的转录因子，测量这些实验操作对全球基因表达的影响，并将这些数据与整个基因组中转录因子结合的分析相对应。这项工作将扩展我们对PI3K途径如何对CD8+ T细胞分化施加如此普遍控制的理解，并为外部线索如何控制基因表达以塑造免疫反应的结果提供见解。这将为开发针对慢性感染和癌症的新疫苗方法和基于免疫的疗法提供目标。

CD8+ T cells powerfully coordinate immune responses against intracellular infections and cancer. During immune responses, CD8+ T cells proliferate and differentiate into effector cells that promote elimination of target cells. Effector cells are short-lived and this enables restoration of normal immune function upon resolution of infection. However, a fraction of cells escape this fate and persist to form long-lived memory cells. Memory cells provide a durable self-renewing source of target-specific cells and can persist for decades following infection to generate more efficient secondary responses upon reinfection. CD8+ T cells also become terminally differentiated or exhausted in response to chronic infections and cancer and this impairs their function. Our previous work has identified a key molecular pathway, termed the phosphoinositide 3-kinase (PI3K) pathway, that powerfully regulates CD8+ T cell differentiation. Activation of the PI3K pathway drives widespread changes in gene expression to promote effector differentiation and prevent the formation of memory cells. Mechanisms by which the PI3K pathway causes changes in gene expression are not fully understood. In this study, we will investigate how the PI3K pathway controls the function of a class of proteins called transcription factors (TFs). TFs bind to regulatory regions within DNA and modulate gene expression to control cellular differentiation. We have recently found that the PI3K pathway controls the function of a transcription factor, BACH2, through a process called phosphorylation. We will investigate this new molecular axis, determining how the PI3K pathway regulates the function of BACH2 to control CD8+ T cell responses. Our experimental approach is divided into three components: 1) We will determine the function of BACH2 in regulating CD8+ T cell responses to infection. To do this, we will use a mouse model in which BACH2 is specifically deleted in CD8+ T cells and study immune responses following infection with experimental pathogens. 2) We will determine how the PI3K pathway controls the function of BACH2 to regulate immune responses to infection using a new mouse model in which BACH2 cannot be phosphorylated. We will also determine how BACH2 phosphorylation regulates BACH2 function at a molecular level. 3) We will test the contribution of BACH2 to PI3K-mediated transcriptional programmes in CD8+ T cells. To achieve this, we will utilise mouse genetics to specifically manipulate the PI3K pathway, and regulated transcription factors in CD8+ T cells, measuring consequences of these experimental manipulations on global gene expression and corresponding this data with analyses of transcription factor binding throughout the genome. This work will extend our understanding of how the PI3K pathway exerts such pervasive control over CD8+ T cell differentiation and provide insights into how external cues control gene expression to shape the outcome of immune responses. This will provide targets for development of new vaccine approaches and immune-based therapies for chronic infections and cancer.