共价型唾液酸结合免疫球蛋白样凝集素的构建与应用

糖基化是一种重要的翻译后修饰，参与调控多种生命过程。研究表明，糖及糖结合蛋白与肿瘤等疾病息息相关，肿瘤细胞上唾液酸化的糖通过与免疫抑制性受体唾液酸结合免疫球蛋白样凝集素（Siglecs）结合，抑制肿瘤微环境中的免疫监视，促进肿瘤生存，因此，研究肿瘤细胞中的Siglec配体将为肿瘤免疫治疗提供新思路。目前Siglecs与配体的研究依赖于重组Siglecs和人工合成糖链，缺少直接在细胞中鉴定Siglecs配体的工具和方法。我们提出，利用临近标记和靶向共价型药物的思想，将能与糖中的羟基反应的Benzoboroxoles修饰到Siglecs上，使Siglecs与配体结合时形成共价键，提高其结合能力。我们利用这种共价结合型Siglecs来表征并富集肿瘤细胞中的Siglecs配体，并结合质谱分析技术，鉴定肿瘤细胞中的Siglec配体，为肿瘤免疫治疗提供新靶点。

Glycosylation is an important post-translational modification and is involved in the regulation of various biological process. It has been reported that glycans and glycan-binding proteins are tightly related to diseases such as cancer. Sialyl glycans on the surface of tumor cells could inhibit immune surveillance in tumor microenvironment through binding to the immune inhibitory Sialic acid–binding immunoglobulin-like lectins (Siglecs), enabling tumor survival. Thus, identifying Siglec ligands on tumor cells will provide a new direction to tumor immunotherapy. However, current research on Siglecs and ligands highly relies on recombinant Siglecs and synthetic glycans, due to the lack of tools and methods to directly identify Siglec ligands on cells. Inspired by the strategy of proximity labeling and targeted covalent drugs, we propose to construct the covalent Siglecs, which bind covalently to glycan ligands, through chemical modification of Siglecs with hydroxy group reacting Benzoboroxoles to increase its binding affinity to glycan. The covalent Siglecs could be used to probing and enriching the Siglec ligands. Combining the covalent Siglecs with mass spectrometer, we could identify Siglec ligands in tumor cells, which may serve as new targets for tumor immunotherapy.