PO.TB10.09 · 肿瘤生物学
一个PD-L1乙酰化开关协调染色体黏连与抗肿瘤免疫
A pd-l1 acetylation switch coordinates chromosome cohesion and antitumor immunity
作者与单位 Authors & Affiliations
摘要 Abstract
中文摘要
背景：PD-L1最为人所知的是在细胞表面抑制抗肿瘤免疫，然而新出现的证据提示其存在额外的核内功能。本实验室先前的研究证明，核内PD-L1与黏连蛋白（cohesin）复合体相互作用以维持染色体稳定性。然而，调控这种相互作用的上游调控机制及其免疫学后果仍属未知。
方法与结果：利用乙酰化位点预测、诱变和结构建模，我们鉴定出赖氨酸178（人）/177（小鼠）是调控PD-L1功能的一个保守乙酰化开关。PD-L1的去乙酰化（K178R/K177R）破坏了PD-L1-PDS5B/黏连蛋白结合，而不影响亚细胞定位。这导致姐妹染色单体黏连缺陷、微核形成和胞质DNA积累。RNA-seq、qPCR和免疫印迹证明在PD-L1 K178R细胞中cGAS-STING-IFN-gamma信号轴强劲激活，以及MHC-I抗原呈递机制增强。功能上，K178R细胞增殖更慢，且在共培养实验中对PBMC介导的杀伤高度敏感，在抗PD-L1抗体处理后进一步增强。在异种移植模型（NSG小鼠）中，表达PD-L1 K178R的肿瘤生长显著慢于WT。在免疫功能健全的C57BL/6同基因模型中，PD-L1 K177R肿瘤表现出生长减少以及对PD-L1阻断的响应性增强。结构和生化分析证实，PD-L1在K178/K177处的乙酰化稳定了其与黏连蛋白复合体的相互作用，从而防止染色体不稳定性诱导的免疫激活。
结论：我们鉴定出一个保守的PD-L1乙酰化开关，它将黏连蛋白稳定性与固有免疫激活相偶联。PD-L1去乙酰化促进染色体不稳定性，激活cGAS-STING-IFN-gamma信号，增强抗原呈递，并使肿瘤对PD-L1免疫治疗敏感。这些发现揭示了一个此前未被认识的、将肿瘤基因组完整性与免疫识别相联系的调控轴，为在癌症治疗中靶向PD-L1乙酰化提供了机制基础。
查看英文原文 English abstract
Background: PD-L1 is best known for suppressing antitumor immunity at the cell surface, yet emerging evidence suggests additional nuclear functions. Previous studies from our laboratory demonstrated that nuclear PD-L1 interacts with the cohesin complex to maintain chromosomal stability. However, the upstream regulatory mechanism governing this interaction and its immunological consequences remain unknown.
Methods and Results: Using acetylation-site prediction, mutagenesis, and structural modeling, we identified lysine 178 (human) / 177 (mouse) as a conserved acetylation switch regulating PD-L1 function. Deacetylation of PD-L1 (K178R/K177R) disrupted PD-L1-PDS5B/cohesin binding without affecting subcellular localization. This led to defective sister chromatid cohesion, micronuclei formation, and cytosolic DNA accumulation. RNA-seq, qPCR, and immunoblotting demonstrated robust activation of the cGAS-STING-IFN-gamma signaling axis and enhanced MHC-I antigen-presentation machinery in PD-L1 K178R cells. Functionally, K178R cells proliferated more slowly and were highly susceptible to PBMC-mediated killing in co-culture assays, with further enhancement upon anti-PD-L1 antibody treatment. In xenograft models (NSG mice), tumors expressing PD-L1 K178R grew significantly slower than WT. In immunocompetent C57BL/6 syngeneic models, PD-L1 K177R tumors showed reduced growth and heightened responsiveness to PD-L1 blockade. Structural and biochemical analyses confirmed that PD-L1 acetylation at K178/K177 stabilizes its interaction with the cohesin complex, thereby preventing chromosomal instability-induced immune activation.
Conclusions: We identify a conserved PD-L1 acetylation switch that couples cohesin stability to innate immune activation. PD-L1 deacetylation promotes chromosomal instability, activates cGAS-STING-IFN-gamma signaling, enhances antigen presentation, and sensitizes tumors to PD-L1 immunotherapy. These findings uncover a previously unrecognized regulatory axis linking tumor genomic integrity to immune recognition, providing a mechanistic foundation for targeting PD-L1 acetylation in cancer treatment.
利益披露 Disclosure
M. Wang, None.