Division of Respiratory and Critical Care Medicine, State Key Laboratory of Biotherapy, West China Hospital of Sichuan University, 610041, Chengdu, China.
Collaborative Innovation Center of Biotherapy, 610041, Chengdu, China.
Commun Biol. 2022 Aug 30;5(1):887. doi: 10.1038/s42003-022-03845-4.
Whether membrane-anchored PD-L1 homodimerizes in living cells is controversial. The biological significance of the homodimer waits to be expeditiously explored. However, characterization of the membrane-anchored full-length PD-L1 homodimer is challenging, and unconventional approaches are needed. By using genetically incorporated crosslinkers, we showed that full length PD-L1 forms homodimers and tetramers in living cells. Importantly, the homodimerized intracellular domains of PD-L1 play critical roles in its complex glycosylation. Further analysis identified three key arginine residues in the intracellular domain of PD-L1 as the regulating unit. In the PD-L1/PD-L1-3RE homodimer, mutations result in a decrease in the membrane abundance and an increase in the Golgi of wild-type PD-L1. Notably, PD-1 binding to abnormally glycosylated PD-L1 on cancer cells was attenuated, and subsequent T-cell induced toxicity increased. Collectively, our study demonstrated that PD-L1 indeed forms homodimers in cells, and the homodimers play important roles in PD-L1 complex glycosylation and T-cell mediated toxicity.
膜锚定 PD-L1 同源二聚体是否在活细胞中形成存在争议。同源二聚体的生物学意义有待迅速探索。然而，膜锚定全长 PD-L1 同源二聚体的表征具有挑战性，需要采用非常规方法。通过使用遗传整合的交联剂，我们表明全长 PD-L1 在活细胞中形成同源二聚体和四聚体。重要的是，PD-L1 同源二聚化的细胞内结构域在其复杂糖基化中发挥关键作用。进一步的分析确定了 PD-L1 细胞内结构域中的三个关键精氨酸残基作为调节单元。在 PD-L1/PD-L1-3RE 同源二聚体中，突变导致膜丰度降低和高尔基体中野生型 PD-L1 增加。值得注意的是，PD-1 与癌细胞上异常糖基化的 PD-L1 的结合被削弱，随后 T 细胞诱导的毒性增加。总之，我们的研究表明 PD-L1 确实在细胞中形成同源二聚体，并且同源二聚体在 PD-L1 复杂糖基化和 T 细胞介导的毒性中发挥重要作用。
