da Silva R P, Gordon S
Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK.
Biochem J. 1999 Mar 15;338 ( Pt 3)(Pt 3):687-94.
Macrosialin (mouse CD68), a macrophage-specific member of the lysosomal-associated membrane protein family, displays N-linked glycosylation and a heavily sialylated, mucin-like domain. We show that phagocytosis of zymosan by inflammatory peritoneal macrophages potently alters glycan processing of macrosialin in vitro. The phagocytic glycoform is not induced by other forms of endocytosis and depends on particle internalization. Zymosan uptake does not influence macrosialin protein synthesis, but increases the specific incorporation of D-[2-3H]mannose, D-[6-3H]galactose, N-acetyl-D-[1-3H]glucosamine and L-[5,6-3H]fucose by 2-15-fold. The phagocytic glycoform displays increased binding of agglutinins from peanut, Amaranthus caudatus and Galanthus nivalis, whereas binding of the sialic-acid-specific Maakia amurensis agglutinin is slightly reduced. Digestion by N-Glycanase abolishes the incorporation of [3H]mannose label and Galanthus nivalis agglutinin binding activity, but preserves the incorporation of galactose and N-acetylglucosamine and specific lectin binding. We also show that phagocytosis increases the complexity and length of O-linked chains. The data presented highlight the importance of differential glycosylation in the biology of macrosialin, phagosomes and macrophages in general.
巨唾液酸蛋白（小鼠CD68）是溶酶体相关膜蛋白家族的巨噬细胞特异性成员，具有N-连接糖基化以及高度唾液酸化的黏蛋白样结构域。我们发现，炎症性腹膜巨噬细胞对酵母聚糖的吞噬作用在体外能显著改变巨唾液酸蛋白的聚糖加工过程。吞噬性糖型并非由其他形式的内吞作用诱导产生，而是依赖于颗粒的内化。酵母聚糖的摄取并不影响巨唾液酸蛋白的蛋白质合成，但会使D-[2-³H]甘露糖、D-[6-³H]半乳糖、N-乙酰-D-[1-³H]葡糖胺和L-[5,6-³H]岩藻糖的特异性掺入增加2至15倍。吞噬性糖型表现出与来自花生、尾穗苋和雪花莲的凝集素的结合增加，而唾液酸特异性的黑水凝集素的结合略有减少。用N-聚糖酶消化可消除[³H]甘露糖标记的掺入以及雪花莲凝集素的结合活性，但保留半乳糖和N-乙酰葡糖胺的掺入以及特异性凝集素结合。我们还表明，吞噬作用会增加O-连接链的复杂性和长度。所呈现的数据突出了差异糖基化在巨唾液酸蛋白、吞噬体以及一般巨噬细胞生物学中的重要性。
