Department of Surgery, Division of Surgical Oncology, University of Illinois at Chicago, Chicago, IL 60612.
Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, NY 10065.
Proc Natl Acad Sci U S A. 2020 Apr 7;117(14):7961-7970. doi: 10.1073/pnas.1921325117. Epub 2020 Mar 24.
Mixed lineage kinase 3 (MLK3), also known as MAP3K11, was initially identified in a megakaryocytic cell line and is an emerging therapeutic target in cancer, yet its role in immune cells is not known. Here, we report that loss or pharmacological inhibition of MLK3 promotes activation and cytotoxicity of T cells. MLK3 is abundantly expressed in T cells, and its loss alters serum chemokines, cytokines, and CD28 protein expression on T cells and its subsets. MLK3 loss or pharmacological inhibition induces activation of T cells in in vitro, ex vivo, and in vivo conditions, irrespective of T cell activating agents. Conversely, overexpression of MLK3 decreases T cell activation. Mechanistically, loss or inhibition of MLK3 down-regulates expression of a prolyl-isomerase, Ppia, which is directly phosphorylated by MLK3 to increase its isomerase activity. Moreover, MLK3 also phosphorylates nuclear factor of activated T cells 1 (NFATc1) and regulates its nuclear translocation via interaction with Ppia, and this regulates T cell effector function. In an immune-competent mouse model of breast cancer, MLK3 inhibitor increases Granzyme B-positive CD8 T cells and decreases MLK3 and Ppia gene expression in tumor-infiltrating T cells. Likewise, the MLK3 inhibitor in pan T cells, isolated from breast cancer patients, also increases cytotoxic CD8 T cells. These results collectively demonstrate that MLK3 plays an important role in T cell biology, and targeting MLK3 could serve as a potential therapeutic intervention via increasing T cell cytotoxicity in cancer.
混合谱系激酶 3（MLK3），也称为 MAP3K11，最初在巨核细胞系中被发现，是癌症治疗的新兴靶点，但它在免疫细胞中的作用尚不清楚。在这里，我们报告说，MLK3 的缺失或药理学抑制促进了 T 细胞的激活和细胞毒性。MLK3 在 T 细胞中大量表达，其缺失改变了 T 细胞及其亚群上的血清趋化因子、细胞因子和 CD28 蛋白表达。无论是否存在 T 细胞激活剂，MLK3 的缺失或药理学抑制均可诱导体外、离体和体内 T 细胞的激活。相反，MLK3 的过表达降低了 T 细胞的激活。从机制上讲，MLK3 的缺失或抑制下调了脯氨酰异构酶 Ppia 的表达，而 MLK3 可直接磷酸化 Ppia 以增加其异构酶活性。此外，MLK3 还磷酸化激活 T 细胞核因子 1（NFATc1），并通过与 Ppia 的相互作用调节其核易位，从而调节 T 细胞效应功能。在乳腺癌免疫功能正常的小鼠模型中，MLK3 抑制剂增加了肿瘤浸润性 T 细胞中 Granzymes B 阳性 CD8 T 细胞的数量，并降低了 MLK3 和 Ppia 基因的表达。同样，从乳腺癌患者中分离出的泛 T 细胞中的 MLK3 抑制剂也增加了细胞毒性 CD8 T 细胞。这些结果共同表明，MLK3 在 T 细胞生物学中发挥重要作用，通过增加肿瘤中的 T 细胞细胞毒性，靶向 MLK3 可能成为一种潜在的治疗干预手段。
