Protein Kinase C θ Regulates the Phenotype of Murine CD4+ Th17 Cells

Protein kinase C θ (PKCθ) is involved in signaling downstream of the T cell antigen receptor (TCR) and is important for shaping effector T cell functions and inflammatory disease development. Acquisition of Th1-like effector features by Th17 cells has been linked to increased pathogenic potential. However, the molecular mechanisms underlying Th17/Th1 phenotypic instability remain largely unknown. In the current study, we address the role of PKCθ in differentiation and function of Th17 cells by using genetic knock-out mice. Implementing in vitro (polarizing T cell cultures) and in vivo (experimental autoimmune encephalomyelitis model, EAE) techniques, we demonstrated that PKCθ-deficient CD4+ T cells show normal Th17 marker gene expression (interleukin 17A/F, RORγt), accompanied by enhanced production of the Th1-typical markers such as interferon gamma (IFN-γ) and transcription factor T-bet. Mechanistically, this phenotype was linked to aberrantly elevated Stat4 mRNA levels in PKCθ−/− CD4+ T cells during the priming phase of Th17 differentiation. In contrast, transcription of the Stat4 gene was suppressed in Th17-primed wild-type cells. This change in cellular effector phenotype was reflected in vivo by prolonged neurological impairment of PKCθ-deficient mice during the course of EAE. Taken together, our data provide genetic evidence that PKCθ is critical for stabilizing Th17 cell phenotype by selective suppression of the STAT4/IFN-γ/T-bet axis at the onset of differentiation.蛋白激酶Cθ (Protein kinase C θ, PKCθ) 参与T细胞抗原受体 (T cell antigen receptor, TCR) 下游的信号转导，对于塑造效应T细胞功能以及炎症性疾病的发生发展具有重要作用。Th17细胞获得Th1样效应特性，与其致病潜力升高密切相关。然而，Th17/Th1表型不稳定的分子机制目前仍不明确。本研究借助基因敲除小鼠 (genetic knock-out mice)，探究了PKCθ在Th17细胞分化与功能中的调控作用。我们通过体外 (T细胞极化培养体系) 与体内 (实验性自身免疫性脑脊髓炎模型, experimental autoimmune encephalomyelitis, EAE) 实验手段，证实PKCθ缺陷的CD4+T细胞的Th17标志性基因表达 (白细胞介素17A/F、视黄酸相关孤儿受体γt, RORγt) 并无异常，但Th1典型标志物如干扰素γ (interferon gamma, IFN-γ) 与转录因子T-bet的产生水平显著升高。机制层面，该表型与Th17分化致敏阶段，PKCθ敲除 (PKCθ−/−) 的CD4+T细胞中异常升高的Stat4 mRNA水平密切相关。与之相反，经Th17极化诱导的野生型细胞中，Stat4基因的转录受到显著抑制。这种细胞效应表型的改变在体内实验中得到了验证：PKCθ缺陷小鼠在EAE病程中表现出更持久的神经功能损伤。综上，本研究的遗传学证据表明，PKCθ可通过在分化起始阶段选择性抑制STAT4/IFN-γ/T-bet信号轴，从而稳定Th17细胞表型。