Department of Chemistry & Stanford ChEM-H, Stanford University, Stanford, CA 94305.
Max Planck Institute for the Science of Light, 91058 Erlangen, Germany.
Proc Natl Acad Sci U S A. 2021 Feb 2;118(5). doi: 10.1073/pnas.2015024118.
, molecules that inhibit immune cell activity following binding to glycosylated cell-surface antigens, are emerging as attractive targets for cancer immunotherapy. Defining biologically relevant ligands that bind and activate such receptors, however, has historically been a significant challenge. Here, we present a CRISPRi genomic screening strategy that allowed unbiased identification of the key genes required for cell-surface presentation of glycan ligands on leukemia cells that bind the glyco-immune checkpoint receptors Siglec-7 and Siglec-9. This approach revealed a selective interaction between Siglec-7 and the mucin-type glycoprotein CD43. Further work identified a specific N-terminal glycopeptide region of CD43 containing clusters of disialylated O-glycan tetrasaccharides that form specific Siglec-7 binding motifs. Knockout or blockade of CD43 in leukemia cells relieves Siglec-7-mediated inhibition of immune killing activity. This work identifies a potential target for immune checkpoint blockade therapy and represents a generalizable approach to dissection of glycan-receptor interactions in living cells.
，与糖基化细胞表面抗原结合后抑制免疫细胞活性的分子，正成为癌症免疫治疗的有吸引力的靶点。然而，定义与这些受体结合并激活它们的具有生物学相关性的配体在历史上一直是一个重大挑战。在这里，我们提出了一种 CRISPRi 基因组筛选策略，该策略允许在白血病细胞表面展示与糖基免疫检查点受体 Siglec-7 和 Siglec-9 结合的糖配体的关键基因进行无偏鉴定。这种方法揭示了 Siglec-7 与粘蛋白型糖蛋白 CD43 之间的选择性相互作用。进一步的工作确定了 CD43 中含有二唾液酸化 O-聚糖四糖簇的特定 N 端糖肽区域，这些簇形成特定的 Siglec-7 结合基序。在白血病细胞中敲除或阻断 CD43 可解除 Siglec-7 介导的免疫杀伤活性抑制。这项工作确定了免疫检查点阻断治疗的潜在靶点，代表了一种可推广的方法来解析活细胞中糖受体相互作用。
