Table 1_HuR ablation destabilizes Foxp3 mRNA and impairs regulatory T cell function, contributing to an autoimmune phenotype.xlsx

IntroductionThe RNA-binding protein HuR (Elavl1), a key post-transcriptional regulator, plays a critical role in T cell activation and function by stabilizing target mRNAs. To investigate the role of HuR in regulatory T cell (Treg) function, we generated the Foxp3YFP/Cre HuRfl/fl mouse model.
MethodsIn this model, homozygous females and hemizygous males for Foxp3 developed a scurfy-like phenotype displaying autoimmune features, including failure to thrive, splenomegaly, hair loss, tail stippling, and widespread multi-organ immune cell infiltration. Molecular analysis included direct interaction studies between HuR and Foxp3 mRNA to assess mRNA stability, RNA sequencing of YFP⁺ Tregs, Protein-Protein Interaction (PPI) analysis, qPCR, and Treg functional assays.
ResultsTo our knowledge, this is the first study demonstrating that HuR directly binds and stabilizes Foxp3 mRNA in Tregs, using a novel Treg-specific HuR-deficient mouse model, with implications for autoimmune regulation. Foxp3 mRNA stability and expression were significantly reduced in Tregs from these HuR KO mice, despite higher frequencies of YFP⁺ Tregs. RNA sequencing revealed significant dysregulation of several pathways, including the T helper differentiation pathway, in which Foxp3 played a central role. PPI analysis showed a direct link between Foxp3 and Rorc (encoding RORγt), connecting Foxp3 to the T cell differentiation pathway via IL-23R. Our qPCR analysis supported these findings. Functional assays demonstrated a reduction in the suppressive capacity of HuR-deficient Tregs.
ConclusionThese findings together suggest that ablation of HuR in Tregs disrupts Foxp3 expression and Treg function, likely through dysregulation of T cell differentiation pathways involving RORγt. This potentially contributes to a disrupted Treg–Th17 axis and autoimmune dysfunction. These data suggest that HuR-mediated post-transcriptional regulation contributes to maintaining Foxp3 expression and immune homeostasis, although compensatory mechanisms such as increased IL-10 expression may also be involved.

引言：RNA结合蛋白HuR（Elavl1）作为关键的转录后调控因子，可通过稳定靶mRNA在T细胞活化与功能调控中发挥核心作用。为探究HuR在调节性T细胞（regulatory T cell，Treg）功能中的作用，我们构建了Foxp3YFP/Cre HuRfl/fl小鼠模型。
方法：在该模型中，Foxp3纯合雌性与半合子雄性小鼠会出现鳞屑样表型，伴随自身免疫相关特征，包括生长发育迟缓、脾肿大、脱毛、尾斑点状病变及多器官广泛免疫细胞浸润。本研究的分子分析实验包括：HuR与Foxp3 mRNA的直接互作实验（用于评估mRNA稳定性）、YFP阳性Treg的RNA测序、蛋白质相互作用（Protein-Protein Interaction，PPI）分析、实时定量PCR（quantitative real-time PCR，qPCR）以及Treg功能实验。
结果：据我们所知，本研究首次利用新型Treg特异性HuR敲除（knockout，KO）小鼠模型，证实HuR可在Treg中直接结合并稳定Foxp3 mRNA，该发现对自身免疫调控具有潜在指导意义。尽管该模型小鼠的YFP阳性Treg频率更高，但其Treg中Foxp3 mRNA的稳定性与表达水平均显著降低。RNA测序结果显示，包括T辅助细胞分化通路在内的多条通路出现显著失调，而Foxp3在该通路中居于核心调控地位。蛋白质相互作用分析显示，Foxp3与编码RORγt的Rorc基因存在直接关联，通过IL-23R将Foxp3与T细胞分化通路相连。本研究的qPCR实验结果验证了上述发现。功能实验证实，HuR缺陷型Treg的免疫抑制能力显著下降。
结论：综合上述研究结果可见，在Treg中敲除HuR会破坏Foxp3的表达与Treg的功能，这一过程可能通过失调涉及RORγt的T细胞分化通路实现。该现象可能会引发Treg-Th17轴失衡，进而导致自身免疫功能异常。本研究数据表明，HuR介导的转录后调控有助于维持Foxp3的表达与免疫稳态，尽管IL-10表达升高等代偿机制也可能参与其中。