Ohta M, Kawasaki T
Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Kyoto University, Japan.
Glycoconj J. 1994 Aug;11(4):304-8. doi: 10.1007/BF00731203.
Serum mannan-binding protein (S-MBP), a lectin specific for mannose and N-acetylglucosamine, activates complement through the classical pathway. With the help of complement, S-MBP lyses red blood cells which have been coated with yeast mannan and kills bacteria which have N-acetylglucosamine and/or L-glycero-D-manno-heptose on their core oligosaccharide. In this study, we examined whether mammalian cells, on which S-MBP could bound, are killed by a complement-dependent mechanism. When baby hamster kidney (BHK) cells were treated with an alpha-mannosidase inhibitor, 1-deoxymannojirimycin (dMM), most of the cellular oligosaccharides were transformed from the complex-type to the high mannose-type. S-MBP bound to the dMM-treated BHK cells in the presence of Ca2+, and this binding was eliminated by mannose. When dMM-treated cells, labelled with 51Cr, were incubated with complement, radioactivity was released in a dose-dependent manner by S-MBP and complement. This release was not observed with heat-inactivated complement. These observations suggest that S-MBP is able, with the help of complement, to kill not only exogenous microorganisms but also mammalian cells which have high mannose-type oligosaccharides exposed on their surfaces.
血清甘露聚糖结合蛋白（S-MBP）是一种对甘露糖和N-乙酰葡糖胺具有特异性的凝集素，可通过经典途径激活补体。在补体的帮助下，S-MBP可裂解已被酵母甘露聚糖包被的红细胞，并杀死其核心寡糖上含有N-乙酰葡糖胺和/或L-甘油-D-甘露庚糖的细菌。在本研究中，我们检测了S-MBP能够结合的哺乳动物细胞是否会通过补体依赖机制被杀死。当用α-甘露糖苷酶抑制剂1-脱氧甘露基野尻霉素（dMM）处理幼仓鼠肾（BHK）细胞时，大多数细胞寡糖从复合型转变为高甘露糖型。在Ca2+存在的情况下，S-MBP与经dMM处理的BHK细胞结合，且这种结合可被甘露糖消除。当用51Cr标记的经dMM处理的细胞与补体一起孵育时，S-MBP和补体可呈剂量依赖性地释放放射性。热灭活的补体则未观察到这种释放。这些观察结果表明，S-MBP在补体的帮助下，不仅能够杀死外源微生物，还能够杀死其表面暴露有高甘露糖型寡糖的哺乳动物细胞。
