Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
INRS-Institut Armand-Frappier, Laval, Québec H7V 1B7, Canada.
Anal Chem. 2020 Oct 20;92(20):14189-14196. doi: 10.1021/acs.analchem.0c03344. Epub 2020 Oct 5.
Interactions between glycan-binding proteins (GBPs) and glycosphingolipids (GSLs) in the membranes of cells are implicated in a wide variety of normal and pathophysiological processes. Despite the critical biological roles these interactions play, the GSL ligands of most GBPs have not yet been identified. The limited availability of purified GSLs represents a significant challenge to the discovery and characterization of biologically relevant GBP-GSL interactions. The present work investigates the use of neoglycolipids (NGLs) as surrogates for GSLs for catch-and-release-electrospray ionization mass spectrometry (CaR-ESI-MS)-based screening, implemented with nanodiscs, for the discovery of GSL ligands. Three pairs of NGLs based on the blood group type A and B trisaccharides, with three different lipid head groups but all with "ring-closed" monosaccharide residue at the reducing end, were synthesized. The incorporation efficiencies (into nanodiscs) of the NGLs and their affinities for a fragment of family 51 carbohydrate-binding module (CBM) identified an amide-linked 1,3-di--hexadecyl-glycerol moiety as the optimal lipid structure. Binding measurements performed on cholera toxin B subunit homopentamer (CTB) and nanodiscs containing an NGL consisting of the optimal lipid moiety and the GM1 ganglioside pentasaccharide yielded affinities similar, within a factor of 2, to those of native GM1. Finally, nanodiscs containing the optimal A and B trisaccharide NGLs, as well as the corresponding NGLs of lactose, A type 2 tetrasaccharide, and the GM1 and GD2 pentasaccharides were screened against the family 51 CBM, human galectin-7, and CTB to illustrate the potential of NGLs to accelerate the discovery of GSL ligands of GBPs.
糖基结合蛋白(GBP)与细胞膜中的糖脂(GSL)之间的相互作用涉及到广泛的正常和病理生理过程。尽管这些相互作用具有关键的生物学作用,但大多数 GBP 的 GSL 配体尚未被确定。纯化的 GSL 的有限可用性对发现和表征具有生物学相关性的 GBP-GSL 相互作用构成了重大挑战。本研究探讨了使用神经糖脂(NGL)作为 GSL 的替代品,用于基于捕获和释放-电喷雾电离质谱(CaR-ESI-MS)的筛选,该筛选使用纳米盘进行,用于发现 GSL 配体。基于 A 型和 B 型三糖的三种 NGL 对,具有三种不同的脂质头部基团,但所有的还原端都具有“闭环”单糖残基,被合成。NGL 的掺入效率(进入纳米盘)及其对家族 51 碳水化合物结合模块(CBM)片段的亲和力,确定酰胺连接的 1,3-二-十六烷基-甘油基部分为最佳脂质结构。在霍乱毒素 B 亚基五聚体(CTB)和包含由最佳脂质部分和 GM1 神经节苷脂五糖组成的 NGL 的纳米盘中进行的结合测量,得到的亲和力与天然 GM1 的亲和力相似(相差 2 倍以内)。最后,用家族 51 CBM、人半乳糖凝集素-7 和 CTB 对含有最佳 A 和 B 三糖 NGL 以及相应乳糖、A 型 2 四糖、GM1 和 GD2 五糖的 NGL 的纳米盘进行筛选,以说明 NGL 加速发现 GBP 的 GSL 配体的潜力。