Role of sugar chain in the induction of Fc receptor-mediated phagocytosis by macrophages

吞噬作用可分为两个步骤，即异物附着在细胞膜上和吞噬异物。小鼠巨噬细胞样细胞系P388Dl表达的受体可识别与抗原结合的IgG的Fc部分，但不能吸收抗原-抗体复合物。然而，在培养基中添加二甲亚砜（DMSO）， 2天后，90%以上的细胞有摄取能力。众所周知，巨噬细胞的分化伴随着结构变化。因此，本项目比较DMSO诱导P388DL细胞前后的糖链结构，研究结构变化与Fc受体介导的吞噬作用诱导之间的关系。最后，得到如下结果：(1)通过SDS-PAGE分析细胞的NP-40提取物，可以明显看出DMSO诱导后总蛋白格局没有改变。诱导后糖蛋白的染色增加，分子大小大于30kda的蛋白较多。(2) DMSO诱导后，高甘露糖型糖链增加，三、四天线络合型糖链减少。因此，这些数据表明，抑制asn连接糖链的加工参与了DMSO诱导引起的结构变化。(3)当细胞在积累高甘露糖型糖链的加工抑制剂（苦马豆素和castanospermine）存在下培养时，Fc受体介导的吞噬作用取决于抑制剂的剂量和培养时间。这些结果表明糖链的结构变化不仅伴随着诱导，而且会引起Fc受体介导的吞噬作用的诱导。高甘露糖型糖链在某些特定糖蛋白中的表达可能是诱导的关键，提示在不久的将来从分子基础上分析诱导机制是重要的。少

Phagocytosis can be separated into two steps, attachment of the foreign material to the cell membrane and ingestion of the material. A mouse macrophage-like cell line, P388Dl, expresses receptors which recognize Fc portion of IgG bound to antigen, but can not take up the antigen-antibody conplex. However, addition of dimethyl sulfoxide (DMSO) toe the culture medium induces the ability of ingestion in more than 90% of the cells after 2 days. It is known that structural changes are accompanied with macrophage differentiation. Therefore, sugar chain structures were compared before and after DMSO induction of P388DL cells, and the relationship between structural changes and induction of Fc receptor-mediated phagocytosis was studied in this project. Finally, the following results were obtained. (1) From the analysis of NP-40 extracts of the cells by SDS-PAGE, it was obvious that the total protein pattern does not change after DMSO induction. But, increased staining by Concanavalin A of glyc … More oproteins with molecular sizes of more than 30 KDa was observed after induction. (2) After DMSO induction, high mannose-type sugar chains increased with the decrease of tri- and tetraantennary complex-type sugar chains. Thus, the data suggestd that inhibition of the processing of ASN-linked sugar chains is involved in the structural change caused by DMSO induction. (3) When the cells were cultured in the presence of processing inhibitors (swainsonine and castanospermine), which accumulate high mannose-type sugar chains, Fc receptor-mediated phagocytosis was induced depending on the dose of inhibitors and the culture time.These results indicate that structural change of sugar chains is not merely accompanied with the induction, but causes the induction of Fc receptor-mediated phagocytosis. Expression of high mannose-type sguar chains in some specific glycoproteins might be a key for the induction, suggesting that it is important to analyze the mechanism of induction on the molecular basis in the near future. Less