Molecular mechanisms underlying T cell resistance to PD-1 signaling

摘要 T细胞激活启动分化程序，产生不同记忆T细胞状态的连续体 具有不同的功能和分子特征。活化的T细胞上调抑制性受体编程 细胞死亡蛋白1（PD-1），以防止过度的T细胞炎症，自身反应性和组织损伤。后 PD-1与其配体结合，干扰调节质量和数量的磷酸化级联反应 T细胞信号传导。癌症通过接合PD-1并因此阻断PD-1来逃避T细胞识别 抗体恢复抗肿瘤T细胞应答并提高患有各种恶性肿瘤的患者的存活率。 不幸的是，大多数癌症患者对PD-1阻断没有反应，高达30%的患者发生PD-1阻断。 炎症毒性突出了PD-1在维持免疫耐受中的关键作用。研究 基础PD-1生物学，以及用PD-1阻断抗体治疗的癌症患者的临床表现， 集中强调PD-1参与复杂的信号传导网络以支持T细胞稳态， 分化和免疫反应。因此，阐明信号级联和分子途径 由PD-1触发的免疫应答对基础T细胞生物学至关重要，并将为推进免疫应答奠定基础。 PD-1靶向治疗的发展。尽管如此，我们的知识，因为它涉及到分子程序 在功能多样的人T细胞群体中支持PD-1抑制的研究是有限的。此外，PD-1具有 两种配体具有不同的组织表达模式和结合亲和力，但功能性后果， 这些差异是未知的。我们的初步数据强调，PD-1参与独特的信号级联， 配体特异性方式跨越幼稚到记忆分化的轨迹，并且分子程序 潜在的功能、表型和发育T细胞异质性也指导了对 PD-1抑制。在这里，我们将利用：（1）定量磷酸蛋白质组学来揭示PD-1配体特异性 在功能上不同的T细胞群中触发的磷酸化级联反应;（2）功能性免疫测定， 与scRNA-seq和细胞条形码的组合以鉴定PD-1响应性的转录调节因子 通过记忆和效应T细胞生成的幼稚轨迹;和（3）功能基因组学， 鉴定对PD-1抑制抵抗的细胞和分子介质。成功完成本提案 将揭示功能性T细胞多样性如何塑造和引导PD-1触发的细胞和分子途径， 其相关的PD-1配体特异性依赖性。总的来说，了解细胞和分子 与PD-1反应性相关的病因和驱动T细胞对PD-1抑制的抗性的机制将 进一步了解这种重要的抑制性受体在免疫学中的基本功能， 耐受性和推进靶向PD-1的新治疗方向，涉及癌症、感染和 自身免疫

ABSTRACT T cell activation initiates a program of differentiation that generates a continuum of different memory T cell states with diverse functional and molecular profiles. Activated T cells upregulate the inhibitory receptor programmed cell death protein 1 (PD-1) to prevent excessive T cell inflammation, autoreactivity and tissue damage. Upon binding to its ligands, PD-1 interferes with the phosphorylation cascade that modulates the quality and quantity of T cell signaling. Cancers evade T cell recognition by engaging PD-1 and consequently PD-1 blocking antibodies restore anti-tumor T cell responses and improve the survival of patients with various malignancies. Unfortunately, the majority of cancer patients do not respond to PD-1 blockade and up to 30% develop inflammatory toxicities highlighting the critical role of PD-1 in the maintenance of immune tolerance. Research into basic PD-1 biology, together with the clinical picture of cancer patients treated with PD-1 blocking antibodies, converge to emphasize that PD-1 engages complex signaling networks to support T cell homeostasis, differentiation and immune responses. Therefore, elucidating the signaling cascades and molecular pathways triggered by PD-1 are paramount to fundamental T cells biology and will lay the foundation for advancing the development of PD-1 targeting therapies. Nevertheless, our knowledge as it pertains to the molecular programs that support PD-1 inhibition in functionally diverse human T cell populations is limited. Furthermore, PD-1 has two ligands with distinct tissues expression patterns and binding affinity, yet the functional consequences of these differences are unknown. Our preliminary data highlight that PD-1 engages unique signaling cascades in ligand specific-manner across the trajectory of naïve to memory differentiation, and that the molecular programs underlying functional, phenotypic and developmental T cell heterogeneity also guide pathways of resistance to PD-1 inhibition. Here we will leverage: (1) quantitative phosphoproteomics to reveal PD-1 ligand specific phosphorylation cascades triggered in functionally distinct T cell populations; (2) functional immuno-assays in combination with scRNA-seq and cellular barcoding to identify transcriptional regulators of PD-1 responsivity across the trajectory of naïve through memory and effector T cell generation; and (3) functional genomics to identify cellular and molecular mediators of resistance to PD-1 inhibition. Successful completion of this proposal will reveal how functional T cell diversity shapes and guides PD-1 triggered cellular and molecular pathways and their associated PD-1 ligand specific dependencies. Collectively, understanding the cellular and molecular etiologies associated with PD-1 responsivity and the mechanisms driving T cell resistance to PD-1 inhibition will further our understanding of the fundamental functions of this critical inhibitory receptor in immunological tolerance and advance novel therapeutic directions targeting PD-1 with implications in cancer, infection and autoimmunity.