Brunden K R
Department of Biochemistry, University of Mississippi Medical Center, Jackson.
J Neurochem. 1992 May;58(5):1659-66. doi: 10.1111/j.1471-4159.1992.tb10038.x.
The single oligosaccharide moiety of the major myelin glycoprotein, P0, resides in an immunoglobulin-like domain that appears to participate in homophilic binding. The studies presented here indicate that the structure of the P0 oligosaccharide from rat nerve changes as a function of Schwann cell age. Examination of 5-day-old nerve revealed that P0 contained predominantly endo-beta-N-acetylglucosaminidase H (endo H)-resistant, complex-type oligosaccharide. In contrast, P0 from adult rats had mostly endo H-sensitive carbohydrate, indicating the presence of appreciable high-mannose and/or hybrid-type oligosaccharide on the glycoprotein. The endo H-sensitive and -resistant P0 of adult nerve could be readily phosphorylated by protein kinase C, as could the complex-type P0 from 5-day-old nerve. This suggests that the glycoprotein progresses to the plasma membrane and myelin regardless of the type of oligosaccharide chain. Analysis of 35SO4(2-)-labeled P0 showed that the sulfate group was found on both endo H-sensitive and -resistant oligosaccharide. The endo H-sensitive P0 carbohydrate from adult nerve appears to be primarily of the hybrid type, as evidenced by (a) the elution profile of [3H]mannose-labeled P0 glycopeptides from adult nerve during concanavalin A chromatography and (b) the inability of P0 from adult nerve to interact with Galanthus nivalis agglutinin. The observed age-dependent changes of P0 oligosaccharide may modify the binding properties of this myelin glycoprotein.
主要髓磷脂糖蛋白P0的单一寡糖部分位于一个免疫球蛋白样结构域中，该结构域似乎参与同源性结合。本文所呈现的研究表明，大鼠神经中P0寡糖的结构随雪旺细胞年龄的变化而改变。对5日龄神经的检测显示，P0主要含有对内切β-N-乙酰葡糖胺糖苷酶H（内切H）有抗性的复合型寡糖。相比之下，成年大鼠的P0大多含有对内切H敏感的碳水化合物，这表明该糖蛋白上存在相当数量的高甘露糖型和/或杂合型寡糖。成年神经中对内切H敏感和有抗性的P0都能被蛋白激酶C轻易磷酸化，5日龄神经中的复合型P0也是如此。这表明无论寡糖链的类型如何，该糖蛋白都会进入质膜和髓磷脂。对35SO4(2-)标记的P0的分析表明，硫酸基团存在于对内切H敏感和有抗性的寡糖上。成年神经中对内切H敏感的P0碳水化合物似乎主要是杂合型的，这一点可通过以下两点证明：(a) 伴刀豆球蛋白A层析过程中成年神经中[3H]甘露糖标记的P0糖肽的洗脱图谱；(b) 成年神经中的P0无法与雪花莲凝集素相互作用。观察到的P0寡糖随年龄的变化可能会改变这种髓磷脂糖蛋白的结合特性。
