Transcriptional Regulation in Murine Regulatory T Cells and Suppressed CD4+ T Cells: Identification and Functional Analyses

外周耐受性的维持主要基于CD4+FoxP3+胸腺源性调节性T细胞（Tregs）。Tregs一方面可以预防自身免疫性和过敏性疾病的发展，另一方面也有助于癌症的发病和进展。因此，体内调节treg衍生的抑制机制是一项有价值但具有挑战性的任务。这可以通过直接靶向treg的抑制特性或通过使应答细胞（例如CD4+ T细胞）抵抗treg介导的抑制来实现。然而，抑制的分子原理仍然相对模糊。我们的分析清楚地揭示了cAMP在treg介导的抑制中的重要作用。在体内和体外实验中，我们观察到转录因子Inducible cAMP Early Repressor （ICER）在被抑制的CD4+ T细胞中具有强烈的诱导作用和核定位。来自icer缺陷小鼠的CD4+ T细胞对treg介导的体外抑制的易感性明显降低。此外，这些小鼠在B16F10黑色素瘤模型中不太敏感，这表明icer缺陷T细胞对treg介导的抑制的敏感性降低。由于激酶强烈影响转录调节，我们进行了比较常规CD4+ T细胞和Tregs的激酶组分析。酪蛋白激酶2 （Casein kinase 2, CK2）在活化的Tregs中活性最高。体外药物抑制和基因消融CK2亚基特异性在Tregs中证明了该激酶对Tregs抑制特性的重要贡献。因此，本项目重点关注1。CD4+ T细胞受抑的分子机制分析，2。CK2在treg中引发的下游信号事件有助于其抑制特性；CK2与camp介导的ICER诱导的相互关系。

The maintenance of peripheral tolerance is largely based on CD4+FoxP3+ Thymus-derived regulatory T cells (Tregs). While on the one hand preventing the development of autoimmune and allergic diseases, Tregs contribute to cancer pathogenesis and progression. Therefore, the in vivo modulation of Treg-derived suppressive mechanisms is a worthwhile but challenging task. This can be achieved by either targeting the suppressive properties of Tregs directly or by rendering the responder cells, e.g. CD4+ T cells resistant to Treg-mediated suppression. However, the molecular principles of suppression still remain relatively obscure. Our analyses clearly revealed an important role of cAMP in Treg-mediated suppression. Coherently, we observed a strong induction and nuclear localization of the transcription factor Inducible cAMP Early Repressor (ICER) in suppressed CD4+ T cells in vitro as well as in vivo. CD4+ T cells from Icer-deficient mice revealed a strongly reduced susceptibility to Treg-mediated suppression in vitro. In addition, such mice are less susceptible in a B16F10 melanoma model indicating a reduced sensitivity of Icer-deficient T cells to Treg-mediated suppression.Since kinases strongly influence transcriptional regulation, we performed kinome analysis comparing conventional CD4+ T cells and Tregs. Casein kinase 2 (CK2) showed the highest activity in activated Tregs. Pharmacologic inhibition in vitro as well as genetic ablation of the beta subunit of CK2 specifically in Tregs demonstrated a crucial contribution of this kinase to the suppressive properties of Tregs. Hence, this project focuses on 1. the analysis of the molecular mechanisms steered by ICER in suppressed CD4+ T cells, 2. the downstream signaling events evoked by CK2 in Tregs contributing to their suppressive properties as well as 3. the interrelation of CK2 and cAMP-mediated induction of ICER.