Immunology Research Center, National Health Research Institutes, Zhunan, Taiwan.
Department of Pathology & Immunology, Baylor College of Medicine, Houston, Texas, USA.
Theranostics. 2022 Jul 18;12(13):5744-5760. doi: 10.7150/thno.72148. eCollection 2022.
GLK (MAP4K3) activates PKCθ-IKKβ axis in T-cell activation and induces IL-17A-mediated autoimmune diseases. Attenuation of Treg differentiation and function by GLK could also contribute to autoimmune diseases. We analyzed the roles of GLK and IKKβ in Treg differentiation and function using T-cell-specific GLK transgenic mice and IKKβ conditional knockout mice. The mechanism of GLK/IKKβ-mediated attenuation of Treg differentiation/function was studied by chromatin-immunoprecipitation, reporter assays, kinase assays, protein-protein interaction assays, mass spectrometry, confocal microscopy, flow cytometry, and single-cell RNA sequencing (scRNA-seq) analysis. We found that GLK signaling inhibited Foxp3 transcription by blocking the function of the transcription factor FoxO1. Mechanistically, GLK directly phosphorylated and activated IKKβ at Ser733 in a PKCθ-independent manner. The phospho-IKKβ Ser733 induced FoxO1 Ser319 phosphorylation and nuclear export, leading to Foxp3 downregulation. Consistently, scRNA-seq analyses showed that Foxp3 mRNA levels were inversely correlated with FoxO1 mRNA levels in GLK transgenic CD4 T cells. GLK-IKKβ-FoxO1 signaling axis inhibits Foxp3 transcription, leading to reduction of Treg differentiation and suppressive activity, as well as induction of autoimmune disease.
GLK（MAP4K3）在 T 细胞激活中激活 PKCθ-IKKβ 轴，并诱导 IL-17A 介导的自身免疫性疾病。GLK 对 Treg 分化和功能的抑制也可能导致自身免疫性疾病。我们使用 T 细胞特异性 GLK 转基因小鼠和 IKKβ 条件性敲除小鼠分析了 GLK 和 IKKβ 在 Treg 分化和功能中的作用。通过染色质免疫沉淀、报告基因分析、激酶分析、蛋白-蛋白相互作用分析、质谱分析、共聚焦显微镜分析、流式细胞术和单细胞 RNA 测序（scRNA-seq）分析研究了 GLK/IKKβ 介导的 Treg 分化/功能衰减的机制。我们发现 GLK 信号通过阻断转录因子 FoxO1 的功能抑制 Foxp3 转录。在机制上，GLK 以 PKCθ 独立的方式直接磷酸化并激活 IKKβ 的 Ser733。磷酸化的 IKKβ Ser733 诱导 FoxO1 Ser319 磷酸化和核输出，导致 Foxp3 下调。一致地，scRNA-seq 分析表明，GLK 转基因 CD4 T 细胞中 Foxp3 mRNA 水平与 FoxO1 mRNA 水平呈负相关。GLK-IKKβ-FoxO1 信号轴抑制 Foxp3 转录，导致 Treg 分化和抑制活性降低，并诱导自身免疫性疾病。
