Willison H J, Ilyas A I, O'Shannessy D J, Pulley M, Trapp B D, Quarles R H
Development and Metabolic Neurology Branch, NINCDS, Bethesda, MD 20892.
J Neurochem. 1987 Dec;49(6):1853-62. doi: 10.1111/j.1471-4159.1987.tb02447.x.
The expression and accumulation of the myelin-associated glycoprotein (MAG) and other glycoconjugates have been studied during myelination in the developing cat peripheral nervous system. The glycoconjugates studied have in common a similar carbohydrate determinant which is bound by many antibodies, including the mouse monoclonal antibody HNK-1, and human IgM paraproteins from patients with neuropathy. In addition to MAG, the reactive glycoconjugates include a 60-kilodalton (kD) glycoprotein and a group of 20-26 kD glycoproteins, as well as a group of recently identified acidic glycolipids, the major one of which is sulfate-3-glucuronyl paragloboside (SGPG). The accumulation of these glycoproteins and glycolipids is compared with the established myelin proteins P0, P1, and P2 and with morphometric indices of myelin volume and axonal perimeter. The study demonstrates that MAG appears and accumulates very early during myelination, being present at 15% of the maximum level prior to the appearance of P0, and at 80% of the maximum level when P0 is at 30% of its maximum level. In the adult, the level of MAG falls to 60% maximum. The 60 kD and 20-26 kD glycoproteins accumulate at the same time as or later than P0, suggesting that they are either compact myelin proteins or in membranes closely associated with compact myelin. SGPG accumulates with P0 early in myelination, but falls to 60% of maximum in the adult. By comparing biochemical and morphometric data, we demonstrate that P0 and other compact myelin proteins accumulate synchronously with the increase in myelin area. MAG accumulation, however, is closely related to changes in axonal perimeter, consistent with a predominant localization of MAG to the periaxonal membranes in the peripheral nervous system.
在发育中的猫外周神经系统髓鞘形成过程中，对髓鞘相关糖蛋白（MAG）和其他糖缀合物的表达及积累进行了研究。所研究的糖缀合物具有一个相似的碳水化合物决定簇，许多抗体可与之结合，包括小鼠单克隆抗体HNK - 1以及来自神经病患者的人IgM副蛋白。除MAG外，反应性糖缀合物还包括一种60千道尔顿（kD）的糖蛋白、一组20 - 26 kD的糖蛋白，以及一组最近鉴定出的酸性糖脂，其中主要的是硫酸 - 3 - 葡糖醛酸副球蛋白（SGPG）。将这些糖蛋白和糖脂的积累情况与已确定的髓鞘蛋白P0、P1和P2以及髓鞘体积和轴突周长的形态学指标进行了比较。研究表明，MAG在髓鞘形成过程中很早就出现并积累，在P0出现之前达到最大水平的15%，当P0达到其最大水平的30%时，MAG达到最大水平的80%。在成年动物中，MAG的水平降至最大水平的60%。60 kD和20 - 26 kD的糖蛋白与P0同时或在P0之后积累，这表明它们要么是紧密髓鞘蛋白，要么存在于与紧密髓鞘紧密相关的膜中。SGPG在髓鞘形成早期与P0一起积累，但在成年动物中降至最大水平的60%。通过比较生化和形态学数据，我们证明P0和其他紧密髓鞘蛋白随着髓鞘面积的增加而同步积累。然而，MAG的积累与轴突周长的变化密切相关，这与MAG主要定位于外周神经系统的轴突周围膜一致。
