Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, CLS 11087 - 3 Blackfan Circle, Boston, MA, 02115, USA.
Department of Molecular Cell Biology and Immunology, Amsterdam UMC (VU Medical Center), Amsterdam, The Netherlands.
Cell Mol Life Sci. 2021 Jul;78(14):5569-5585. doi: 10.1007/s00018-021-03863-1. Epub 2021 Jun 5.
The macrophage mannose receptor (CD206, MR) is an endocytic lectin receptor which plays an important role in homeostasis and innate immunity, however, the endogenous glycan and glycoprotein ligands recognized by its C-type lectin domains (CTLD) have not been well studied. Here we used the murine MR CTLD4-7 coupled to the Fc-portion of human IgG (MR-Fc) to investigate the MR glycan and glycoprotein recognition. We probed 16 different cancer and control tissues using the MR-Fc, and observed cell- and tissue-specific binding with varying intensity. All cancer tissues and several control tissues exhibited MR-Fc ligands, intracellular and/or surface-located. We further confirmed the presence of ligands on the surface of cancer cells by flow cytometry. To characterize the fine specificity of the MR for glycans, we screened a panel of glycan microarrays. Remarkably, the results indicate that the CTLD4-7 of the MR is highly selective for specific types of pauci- and oligomannose N-glycans among hundreds of glycans tested. As lung cancer tissue and the lung cancer cell line A549 showed intense MR-Fc binding, we further investigated the MR glycoprotein ligands in those cells by immunoprecipitation and glycoproteomic analysis. All enriched glycoproteins, of which 42 were identified, contained pauci- or oligomannose N-glycans, confirming the microarray results. Our study demonstrates that the MR CTLD4-7 is highly selective for pauci- and oligomannosidic N-glycans, structures that are often elevated in tumor cells, and suggest a potential role for the MR in tumor biology.
巨噬细胞甘露糖受体（CD206，MR）是一种内吞凝集素受体，在体内平衡和先天免疫中发挥重要作用，然而，其 C 型凝集素结构域（CTLD）识别的内源性糖和糖蛋白配体尚未得到很好的研究。在这里，我们使用与人类 IgG 的 Fc 部分偶联的小鼠 MR CTLD4-7（MR-Fc）来研究 MR 的糖和糖蛋白识别。我们使用 MR-Fc 探测了 16 种不同的癌症和对照组织，并观察到细胞和组织特异性结合，强度不同。所有癌症组织和几种对照组织都表现出 MR-Fc 配体，存在于细胞内和/或细胞表面。我们进一步通过流式细胞术证实了癌细胞表面配体的存在。为了表征 MR 对聚糖的精细特异性，我们筛选了一组聚糖微阵列。值得注意的是，结果表明，MR 的 CTLD4-7 对数百种测试的糖中特定类型的寡甘露糖和低甘露糖 N-聚糖具有高度选择性。由于肺癌组织和肺癌细胞系 A549 显示出强烈的 MR-Fc 结合，我们进一步通过免疫沉淀和糖蛋白质组学分析研究了这些细胞中的 MR 糖蛋白配体。所有富集的糖蛋白，其中 42 种被鉴定，都含有寡甘露糖或低甘露糖 N-聚糖，证实了微阵列的结果。我们的研究表明，MR CTLD4-7 对低甘露糖和寡甘露糖 N-聚糖具有高度选择性，这些结构在肿瘤细胞中经常升高，并提示 MR 在肿瘤生物学中可能具有潜在作用。
