Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602.
Department of Medicine, Division of Allergy and Clinical Immunology, The Johns Hopkins University School of Medicine, 5501 Hopkins Bayview Circle, Baltimore, MD 21224.
Glycobiology. 2018 Jun 1;28(6):406-417. doi: 10.1093/glycob/cwy025.
Siglec-F is a pro-apoptotic receptor on mouse eosinophils that recognizes 6'-sulfated sialyl Lewis X and 6'-sulfated sialyl N-acetyl-lactosamine as well as multivalent sialyl N-acetyl-lactosamine structures on glycan arrays. We hypothesized that attenuation of the carbohydrate sulfotransferase 1 (CHST1) gene encoding keratan sulfate galactose 6-O-sulfotransferase, an enzyme likely required for 6'-sulfation of some of these putative Siglec-F glycan ligands, would result in decreased Siglec-F lung ligand levels and enhanced allergic eosinophilic airway inflammation. Tissue analysis detected CHST1 expression predominantly not only in parenchymal cells but not in airway epithelium, the latter being a location where Siglec-F ligands are located. Western blotting of lung extracts with Siglec-F-Fc fusion proteins detected ≈500 kDa and ≈200 kDa candidate Siglec-F ligands that were not appreciably altered in CHST1-/- lungs compared with normal mouse lungs. Characterization of the O-linked glycans of lung tissue and bronchoalveolar lavage fluid detected altered sialylation but minimal change in sulfation. Eosinophilic airway inflammation was induced in wild-type (WT) and CHST1-/- mice via sensitization to ovalbumin (OVA) and repeated airway challenge. After OVA sensitization and challenge, Siglec-F ligands on airway cells, and numbers of eosinophils and neutrophils accumulating in the airways, both increased to a similar degree in WT and CHST1-/- mouse lungs, while macrophages and lymphocytes increased significantly more in CHST1-/- mouse airway compared with normal mouse lungs. Therefore, keratan sulfate galactose 6-O-sulfotransferase does not contribute to the synthesis of glycan ligands for Siglec-F in the airways, although its absence results in exaggerated accumulation of airway macrophages and lymphocytes.
Siglec-F 是一种在小鼠嗜酸性粒细胞上的促凋亡受体，它识别糖基阵列上的 6'-硫酸化唾液酸 Lewis X 和 6'-硫酸化唾液酸 N-乙酰乳糖胺以及多价唾液酸 N-乙酰乳糖胺结构。我们假设，减弱编码半乳糖 6-O-硫酸转移酶的碳水化合物硫酸转移酶 1（CHST1）基因的表达，该酶可能是某些假定的 Siglec-F 聚糖配体 6'-硫酸化所必需的，会导致 Siglec-F 肺配体水平降低，并增强过敏性嗜酸性气道炎症。组织分析检测到 CHST1 表达主要不仅在实质细胞中，而且不在气道上皮细胞中，后者是 Siglec-F 配体所在的位置。用 Siglec-F-Fc 融合蛋白对肺提取物进行 Western 印迹检测到 ≈500 kDa 和 ≈200 kDa 的候选 Siglec-F 配体，与正常小鼠肺相比，CHST1-/-肺中这些配体没有明显改变。对肺组织和支气管肺泡灌洗液的 O-连接糖的表征检测到唾液酸化改变，但硫酸化变化最小。通过卵清蛋白（OVA）致敏和反复气道挑战在野生型（WT）和 CHST1-/-小鼠中诱导嗜酸性气道炎症。OVA 致敏和挑战后，气道细胞上的 Siglec-F 配体以及在气道中积累的嗜酸性粒细胞和中性粒细胞的数量，在 WT 和 CHST1-/- 小鼠肺中增加到相似程度，而巨噬细胞和淋巴细胞在 CHST1-/- 小鼠气道中比在正常小鼠肺中显著增加。因此，半乳糖 6-O-硫酸转移酶不参与气道中 Siglec-F 聚糖配体的合成，尽管其缺失会导致气道巨噬细胞和淋巴细胞的积累增加。
