Department of Immunobiology, University of Lausanne, Epalinges, Switzerland.
Department of Laboratory Medicine and Pathology, Institute of Pathology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland.
Blood Adv. 2024 Jun 11;8(11):2908-2923. doi: 10.1182/bloodadvances.2023011901.
The inhibitory surface receptor programmed cell death protein 1 (PD1) is a major target for antibody-based cancer immunotherapies. Nevertheless, a substantial number of patients fail to respond to the treatment or experience adverse effects. An improved understanding of intracellular pathways targeted by PD1 is thus needed to develop better predictive and prognostic biomarkers. Here, via unbiased phosphoproteome analysis of primary human T cells, we demonstrate that PD1 triggering inhibited the phosphorylation and physical association with protein kinase Cθ (PKCθ) of a variety of cytoskeleton-related proteins. PD1 blocked activation and recruitment of PKCθ to the forming immune synapse (IS) in a Src homology-2 domain-containing phosphatase-1/2 (SHP1/SHP2)-dependent manner. Consequently, PD1 engagement led to impaired synaptic phosphorylation of cytoskeleton-related proteins and formation of smaller IS. T-cell receptor induced phosphorylation of the PKCθ substrate and binding partner vimentin was long-lasting and it could be durably inhibited by PD1 triggering. Vimentin phosphorylation in intratumoral T cells also inversely correlated with the levels of the PD1 ligand, PDL1, in human lung carcinoma. Thus, PKCθ and its substrate vimentin represent important targets of PD1-mediated T-cell inhibition, and low levels of vimentin phosphorylation may serve as a biomarker for the activation of the PD1 pathway.
抑制性表面受体程序性细胞死亡蛋白 1（PD1）是抗体癌症免疫疗法的主要靶点。然而，相当数量的患者对治疗无反应或出现不良反应。因此，需要更好地了解 PD1 靶向的细胞内途径，以开发更好的预测和预后生物标志物。在这里，我们通过对原代人 T 细胞进行无偏磷酸化组分析，证明 PD1 触发抑制了多种细胞骨架相关蛋白的磷酸化和与蛋白激酶 Cθ（PKCθ）的物理结合。PD1 以Src 同源-2 结构域包含的磷酸酶-1/2（SHP1/SHP2）依赖性方式阻止 PKCθ 在形成免疫突触（IS）中的激活和募集。因此，PD1 的结合导致细胞骨架相关蛋白突触磷酸化受损和 IS 形成变小。T 细胞受体诱导 PKCθ 底物和结合伴侣波形蛋白的磷酸化是持久的，并且可以被 PD1 触发持久抑制。肿瘤内 T 细胞中的波形蛋白磷酸化也与人类肺癌中 PD1 配体 PDL1 的水平呈负相关。因此，PKCθ 及其底物波形蛋白是 PD1 介导的 T 细胞抑制的重要靶点，低水平的波形蛋白磷酸化可能作为 PD1 通路激活的生物标志物。
