机械力对PD-1与配体相互作用调控的分子机制研究

T-cells play essential roles in adaptive immunity. The specific recognition of T-cell receptor with antigen peptide-conjugated MHC triggers immune response, which is regulated by the co-signaling molecules such as CD28 and PD-1. The co-inhibitory molecule PD-1 inhibits T-cell activation, and the blocking of PD-1 rescues T-cell functions, making PD-1 an ideal target for anti-cancer drug. On the other hand, recent studies indicated that the functions of TCR and CD28 are regulated by mechanical force, indicating the direct roles of mechanical forces on T-cell activation, suggesting force may also play roles on the function of PD-1. Our preliminary single-molecule force spectroscopy studies on PD-1/PD-L1 interactions show human PD-1/PD-L1 interaction display catch bond (force prolongs bond lifetime), while mouse PD-1/PD-L1 interaction show slip bond only (force shortened bond lifetime). And molecular dynamics simulations suggest the existence of a new conformation of PD-1/PD-L1 interaction which is stabilized by force. These results illustrate the roles of force on PD-1. Based on these preliminary studies, we proposed to perform further systematic investigations to elucidate the molecular mechanism of catch bond and the difference between human and mouse PD-1/PD-L1 interactions, identify the roles of force on PD-1 functions, and providing new information to understand how force may regulate T-cell activation.

T细胞是获得性免疫的核心, TCR与pMHC的特异性识别是触发免疫响应的关键,而这一过程也受到共信号分子如CD28, PD-1等的调控作用。如PD-1会抑制T细胞活性，阻断PD-1则会增强T细胞在抗炎抗肿瘤中的作用,这使PD-1成为理想的抗肿瘤药物靶点。另一方面，最新的研究表明，TCR和CD28的功能都受到机械力的影响，表明机械力可能直接参与T细胞活化过程，显示机械力可能也会影响PD-1的功能。我们前期的单分子力学研究表明人PD-1/PD-L1的相互作用呈逆锁键，但鼠PD-1/PD-L1的相互作用则仅表现出滑移键。分子动力学模拟发现机械力可能会诱发一个新的稳定构象状态。这些结果表明力确实对PD-1存在作用。本项目将在此基础上进一步深入研究，阐明人、鼠PD-1/PD-L1相互作用差异以及逆锁键产生的分子机制，揭示机械力对PD-1功能的调控作用，完善机械力在T细胞活化过程中的协同作用机制。

T细胞是获得性免疫的核心, TCR与pMHC的特异性识别是触发免疫响应的关键,而这一过程也受到共信号分子如CD28, PD-1等的调控作用。如PD-1会抑制T细胞活性，阻断PD-1则会增强T细胞在抗炎抗肿瘤中的作用,这使PD-1成为理想的抗肿瘤药物靶点。另一方面，最新的研究表明，TCR和CD28的功能都受到机械力的影响，表明机械力可能直接参与T细胞活化过程，显示机械力可能也会影响PD-1的功能。本项目集合单分子力学和分子动力学模拟系统研究了PD-1/PD-L1相互作用性质。发现PD-1与PD-L1的相互作用呈现出与TCR/pMHC相互作用相似的力依赖关系，小力时相互作用寿命随外力的增大而增长。而通过分子动力学模拟发现，在外力作用下PD-1与PD-L1存在一个与晶体结构不同的全新的结合状态，而这个新的结合状态具有更长的寿命。这些结果表明PD-1对其配体PD-L1的识别也受到力的调控，而且PD-1很可能也作为力感受分子行使功能。这一结果为发展新的抗病毒、抗肿瘤和自免疫疾病治疗策略提供新信息。

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