Lack of NFATc1 SUMOylation protects from inflammatory diseases

Post-translational modification with SUMO is known to regulate the activity of transcription factors, but how SUMOylation of individual proteins might influence immunity is mostly unexplored. NFATc1 is a transcription factor of the family of ‘Nuclear Factors of Activated T-cells’ which plays an essential role in antigen receptor-mediated gene regulation. It is expressed in multiple isoforms of which the longer isoforms can be modified by SUMOylation. SUMO modification of NFATc1 represses IL-2 in vitro, but its role in T cell-mediated immune responses in vivo is not clear. To this end, we generated a novel Nfatc1 transgenic mouse with lysine to arginine mutations, which abolish the SUMO modification within NFATc1’s C-terminal domain. Inhibition of NFATc1 SUMOylation ameliorated experimental autoimmune encephalomyelitis as well as graft-versus-host disease. This was due to elevated IL-2 production that promoted Treg expansion and suppressed autoreactive or alloreactive T cells. Mechanistically, increased IL-2 secretion counteracted IL-17 and IFN-γ expression through STAT5 and Blimp-1 induction. Blimp-1 also repressed IL-2 itself and the as well induced survival factor Bcl2A1. Still, lack of NFATc1 sumoylation fine-tunes T-cell responses towards lasting tolerance implying a novel approach to treat inflammatory diseases. CD4+ CD90.1+ T cells from GvHD-induced mice on d4. CD4+ T cells were either of WT (3 samples) or NFATc1/ΔS (3 samples) genotype

已知小泛素样修饰蛋白（SUMO）介导的翻译后修饰可调控转录因子活性，但单个蛋白质的SUMO化修饰如何影响免疫进程，目前仍鲜有探索。活化T细胞核因子c1（NFATc1）属于活化T细胞核因子（Nuclear Factors of Activated T-cells）家族的转录因子，在抗原受体介导的基因调控中发挥核心作用。该蛋白存在多种剪接异构体，其中较长的异构体可发生SUMO化修饰。体外实验显示，NFATc1的SUMO化修饰会抑制白细胞介素2（IL-2）的表达，但该修饰在T细胞介导的体内免疫应答中的功能尚不明确。为此，我们构建了一款新型Nfatc1转基因小鼠，其携带赖氨酸-精氨酸点突变，可消除NFATc1 C端结构域内的SUMO化修饰位点。抑制NFATc1的SUMO化修饰可缓解实验性自身免疫性脑脊髓炎（EAE）与移植物抗宿主病（GVHD），该保护效应源于IL-2表达水平升高：IL-2可促进调节性T细胞（Treg）增殖，并抑制自身反应性或同种反应性T细胞的活化。从机制上来看，IL-2分泌增加可通过诱导信号转导与转录激活因子5（STAT5）及B淋巴细胞诱导成熟蛋白1（Blimp-1）的表达，拮抗白细胞介素17（IL-17）与干扰素γ（IFN-γ）的生成。此外，Blimp-1还可直接抑制IL-2的表达，并下调其诱导产生的生存因子B细胞淋巴瘤因子2A1（Bcl2A1）。尽管如此，NFATc1的SUMO化缺失可精准调控T细胞应答以诱导持久免疫耐受，这为炎症性疾病的治疗提供了全新策略。实验采集了造模后第4天的移植物抗宿主病（GvHD）小鼠的CD4+ CD90.1+ T细胞，所获取的CD4+ T细胞分为两类：野生型（WT，3份样本）与NFATc1/ΔS基因型（3份样本）。