PD-L1 Binds to B7-1 Only In Cis on the Same Cell Surface.
PD-L1 Binds to B7-1 Only In Cis on the Same Cell Surface.
复制标题
DOI：
10.1158/2326-6066.cir-17-0316
复制
发表时间：
2018-08
影响因子：
10.1
通讯作者：
Freeman GJ
中科院分区：
文献类型：
--
作者：
Chaudhri A;Xiao Y;Klee AN;Wang X;Zhu B;Freeman GJ
程序性死亡配体1（PD-L1）介导的免疫抑制调节外周耐受性，通常被肿瘤吸收以逃避免疫攻击。PD-L1与PD-1结合，但也与B7-1（CD 80）结合以调节T细胞功能。PD-L1与B7-1的结合相互作用及其功能作用需要进一步研究，以了解PD-1和PD-L1肿瘤免疫治疗之间的差异。我们使用细胞间结合试验、ELISA和流式细胞术检查了PD-L1与B7-1结合的分子方向。如预期，PD-L1转染的细胞与PD-1转染的细胞结合，B7-1细胞与CD 28或CTLA-4转染的细胞结合;然而，PD-L1细胞不与B7-1细胞结合。通过ELISA和流式细胞术检测纯化蛋白，我们发现PD-L1和B7-1只有在PD-L1是柔性的时才有较强的结合作用。可溶性PD-1和B7-1竞争结合PD-L1。用NanoBiT邻近测定证明了天然PD-L1和B7-1在相同细胞表面上的顺式结合。因此，PD-L1-B7-1相互作用可以在同一细胞上顺式发生，但不能在两个细胞之间反式发生，这表明了一种模型，其中PD-L1可以通过其11个氨基酸的柔性茎弯曲以顺式结合B7-1，其方式可以竞争性阻断PD-L1与PD-1或B7-1与CD 28的结合。这种结合方向强调了PD-L1和B7-1在同一细胞上共表达的功能重要性。我们在肿瘤浸润的骨髓细胞上发现了这种共表达。我们的发现可能有助于更好地利用这些途径进行癌症免疫治疗。
Programmed death ligand 1 (PD-L1)–mediated immune suppression regulates peripheral tolerance and is often co-opted by tumors to evade immune attack. PD-L1 binds to PD-1 but also binds to B7–1 (CD80) to regulate T-cell function. The binding interaction of PD-L1 with B7–1 and its functional role need further investigation to understand differences between PD-1 and PD-L1 tumor immunotherapy. We examined the molecular orientation of PD-L1 binding to B7–1 using cell-to-cell binding assays, ELISA, and flow cytometry. As expected, PD-L1 transfected cells bound to PD-1 transfected cells and B7–1 cells bound to CD28 or CTLA-4 transfected cells; however, PD-L1 cells did not bind to B7–1 cells. By ELISA and flow cytometry with purified proteins, we found PD-L1 and B7–1 had a strong binding interaction only when PD-L1 was flexible. Soluble PD-1 and B7–1 competed for binding to PD-L1. Binding of native PD-L1 and B7–1 in cis on the same cell surface was demonstrated with NanoBiT proximity assays. Thus, PD-L1–B7–1 interaction can occur in cis on the same cell but not in trans between two cells, which suggests a model in which PD-L1 can bend via its 11-amino acid, flexible stalk to bind to B7–1 in cis, in a manner that can competitively block the binding of PD-L1 to PD-1 or of B7–1 to CD28. This binding orientation emphasizes the functional importance of coexpression of PD-L1 and B7–1 on the same cell. We found such coexpression on tumor-infiltrating myeloid cells. Our findings may help better utilize these pathways in cancer immunotherapy.