AbstractThe interactions of glycosaminoglycans (GAG) with proteins of the extracellular matrix govern and regulate complex physiological functions including cellular growth, immune response, and inflammation. Repetitive presentation of GAG binding motifs, as found in native proteoglycans, might enhance GAG‐protein binding through multivalent interactions. Here, we report the chemical synthesis of dendritic GAG oligomers constructed of nonasulfated hyaluronan tetrasaccharides for investigating the binding of the protein chemokine interleukin 8 (IL‐8) to artificial, well‐defined proteoglycan architectures. Binding of mutant monomeric and native dimerizable IL‐8 was investigated by NMR spectroscopy and isothermal titration calorimetry. Dendritic oligomerization of GAG increased the binding affinity of both monomeric and dimeric IL‐8. Monomeric IL‐8 bound to monomeric and dimeric GAG with KD values of 7.3 and 0.108 μM, respectively. The effect was less pronounced for dimerizable wild‐type IL‐8, for which GAG dimerization improved the affinity from 34 to 5 nM. Binding of dimeric IL‐8 to oligomeric GAG was limited by steric crowding effects, strongly reducing the affinity of subsequent binding events. In conclusion, the strongest effect of GAG oligomerization was the amplified binding of IL‐8 monomers, which might concentrate monomeric protein in the extracellular matrix and thus promote protein dimerization under physiological conditions.
摘要糖胺聚糖(GAG)与细胞外基质蛋白质之间的相互作用控制和调节着复杂的生理功能,包括细胞生长、免疫反应和炎症反应。在原生蛋白多糖中发现的 GAG 结合基团的重复呈现可能会通过多价相互作用增强 GAG 与蛋白质的结合。在此,我们报告了由非硫酸化透明质酸四糖构建的树枝状 GAG 寡聚体的化学合成,用于研究蛋白质趋化因子白细胞介素 8(IL-8)与人工的、定义明确的蛋白多糖结构的结合。通过核磁共振光谱和等温滴定量热法研究了突变单体和原生二聚体 IL-8 的结合情况。GAG 的树枝状寡聚化增加了单体和二聚 IL-8 的结合亲和力。单体 IL-8 与单体和二聚 GAG 结合的 KD 值分别为 7.3 和 0.108 μM。对可二聚化的野生型 IL-8 而言,这种效应并不明显,GAG 二聚化可将其亲和力从 34 nM 提高到 5 nM。二聚 IL-8 与低聚 GAG 的结合受到立体拥挤效应的限制,大大降低了后续结合事件的亲和力。总之,GAG低聚化的最大作用是扩大了IL-8单体的结合,这可能会使单体蛋白质集中在细胞外基质中,从而促进蛋白质在生理条件下的二聚化。