Catabolic regulation of the expression of the major myelin glycoprotein by Schwann cells in culture.
Catabolic regulation of the expression of the major myelin glycoprotein by Schwann cells in culture.
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培养中雪旺细胞对主要髓磷脂糖蛋白表达的分解代谢调节。
DOI：
10.1111/j.1471-4159.1990.tb01894.x
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发表时间：
1990
影响因子：
4.7
通讯作者：
Poduslo,JF
中科院分区：
文献类型：
--
作者：
Brunden,KR;Windebank,AJ;Poduslo,JF
先前的研究表明，缺乏轴突接触的新生儿雪旺细胞培养物不表达髓磷脂膜成分，包括主要的髓磷脂糖蛋白P0。相比之下，来自永久横断的成年神经的雪旺细胞在培养后表现出持续的p0生物合成，这表明表达髓磷脂糖蛋白的能力可能取决于细胞分化的程度。为了进一步检验雪旺细胞培养物表达po0随年龄变化的能力，我们在培养5天后，对4 - 12天大的大鼠坐骨神经内皮外植体进行了前体植入研究。数据显示，当用[3H]甘露糖掺入法测定12日龄动物的外植体时，即使在培养物中没有明显的髓磷脂组装，也能合成可检测水平的这种整体髓磷脂蛋白。12天龄大鼠培养物的脉冲追踪分析表明，[3H]甘糖标记的p0在3小时内基本降解。通过在脉冲追踪培养基中添加马豆素、氯化铵或L -蛋氨酸甲酯，可以在很大程度上阻止这种分解代谢。前者改变寡糖加工，而后两种化合物抑制溶酶体功能。在添加马豆素后的12天外植体培养中合成的p0很容易聚焦，这意味着蛋白质在退出和随后的分解代谢之前至少已经进展到内侧高尔基体。如果对4日龄、6日龄和8日龄动物的培养物进行分析，在马豆素存在的情况下，通过[3H]甘露糖掺入进行p0生物合成，可以观察到可检测的糖蛋白水平。在早期的新生儿培养研究中无法证明po0的存在，部分原因可能是翻译后蛋白质的溶酶体分解代谢迅速。
Previous studies have suggested that neonatal Schwann cell cultures deprived of axonal contact do not express components of the myelin membrane, including the major myelin glycoprotein, P0. In contrast, Schwann cells from permanently transected, adult nerve exhibit continued biosynthesis of P0after culture, suggesting that the ability to express the myelin glycoprotein may depend on the degree of cellular differentiation. To examine further the ability of Schwann cell cultures to express P0as a function of age, we have performed precursor incorporation studies on endoneurial explants from 4‐ to 12‐day‐old rat sciatic nerves after 5 days in culture. The data reveal that explants from 12‐day‐old animals synthesize detectable levels of this integral myelin protein when assayed by [3H]mannose incorporation, even though there is no apparent myelin assembly in the cultures. Pulse–chase analysis of cultures from 12‐day‐old rats demonstrates that [3H]mannose‐labeled P0is substantially degraded within 3 h. This catabolism largely can be prevented by the addition of swainsonine, ammonium chloride, or L‐methionine methyl ester to the pulse‐chase media. The former agent alters oligosaccharide processing whereas the latter two compounds inhibit lysosomal function. The P0synthesized by the 12‐day explant cultures following the addition of swainsonine is readily fucosylated, implying that the protein has progressed at least as far as themedialGolgi before its exit and subsequent catabolism. If cultures from 4‐, 6‐, and 8‐day‐old animals are analyzed for P0biosynthesis by [3H]mannose incorporation in the presence of swainsonine, detectable levels of the glyoprotein are seen. The inability to demonstrate the presence of P0in earlier studies of neonatal cultures was presumably due in part to the rapid lysosomal catabolism of the protein after translation.