Basaran Rahman, Ning Xinyu, Budhadev Darshita, Hondow Nicole, Guo Yuan, Zhou Dejian
School of Chemistry, Astbury Centre for Structural Molecular Biology, University of Leeds Leeds LS2 9JT UK
School of Chemical and Process Engineering, University of Leeds Leeds LS2 9JT UK.
Nanoscale Adv. 2024 Mar 11;6(8):2198-2208. doi: 10.1039/d3na01013a. eCollection 2024 Apr 16.
The dendritic cell tetrameric lectin, DC-SIGN, and its closely related endothelial cell lectin, DC-SIGNR (collectively abbreviated as DC-SIGN/R) play a key role in the binding and transmission of deadly viruses, including Ebola, HIV, HCV, and SARS-CoV-2. Their virus binding/release processes involve a gradually acidifying environment following the natural intracellular trafficking pathways. Therefore, understanding DC-SIGN/R's pH-dependent binding properties with glycan ligands is of great importance. We have recently developed densely glycosylated gold nanoparticles (glycan-GNPs) as a powerful new tool for probing DC-SIGN/R multivalent lectin-glycan interaction (MLGI) mechanisms. They can provide not only quantitative MLGI affinities but also important structural information, such as binding site orientation and binding modes. Herein, we further employ the glycan-GNP probes to investigate the pH dependency of DC-SIGN/R MLGI properties. We find that DC-SIGN/R MLGIs exhibit distinct pH dependence over the normal physiological (7.4) to lysosomal (∼4.6) pH range. DC-SIGN binds glycan-GNPs strongly and stably from pH 7.4 to ∼5.8, but the binding is weakened significantly as pH decreases to ≤5.4 and may be fully dissociated at pH 4.6. This behaviour is fully consistent with DC-SIGN's role as an endocytic recycling receptor. In contrast, DC-SIGNR's affinity with glycan-GNPs is enhanced with the decreasing pH from 7.4 to 5.4, peaking at pH 5.4, and then reduced as pH is further lowered. Interestingly, both DC-SIGN/R binding with glycan-GNPs are found to be partially reversible in a pH-dependent manner.
树突状细胞四聚体凝集素DC-SIGN及其密切相关的内皮细胞凝集素DC-SIGNR（统称为DC-SIGN/R）在包括埃博拉病毒、艾滋病毒、丙型肝炎病毒和严重急性呼吸综合征冠状病毒2（SARS-CoV-2）在内的致命病毒的结合和传播中起关键作用。它们的病毒结合/释放过程涉及遵循自然细胞内运输途径逐渐酸化的环境。因此，了解DC-SIGN/R与聚糖配体的pH依赖性结合特性非常重要。我们最近开发了密集糖基化金纳米颗粒（聚糖-GNP），作为探测DC-SIGN/R多价凝集素-聚糖相互作用（MLGI）机制的强大新工具。它们不仅可以提供MLGI的定量亲和力，还可以提供重要的结构信息，如结合位点方向和结合模式。在此，我们进一步使用聚糖-GNP探针来研究DC-SIGN/R MLGI特性的pH依赖性。我们发现，在正常生理pH（7.4）至溶酶体pH（约4.6）范围内，DC-SIGN/R MLGI表现出明显的pH依赖性。DC-SIGN在pH 7.4至约5.8范围内与聚糖-GNP强烈且稳定地结合，但当pH降至≤5.4时，结合显著减弱，在pH 4.6时可能完全解离。这种行为与DC-SIGN作为内吞再循环受体的作用完全一致。相比之下，DC-SIGNR与聚糖-GNP的亲和力随着pH从7.4降至5.4而增强，在pH 5.4时达到峰值，然后随着pH进一步降低而降低。有趣的是，发现DC-SIGN/R与聚糖-GNP的结合均以pH依赖性方式部分可逆。
