Post-translational modifications of human interleukin-6.
Post-translational modifications of human interleukin-6.
复制标题
人白细胞介素 6 的翻译后修饰。
DOI：
10.1016/0003-9861(89)90427-x
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发表时间：
1989
影响因子：
3.9
通讯作者：
May,LT
中科院分区：
文献类型：
--
作者：
Santhanam,U;Ghrayeb,J;Sehgal,PB;May,LT
我们以前报道过，由IL-1或肿瘤坏死因子（TNF）诱导的人成纤维细胞分泌的白细胞介素(IL)-6由至少6个分子质量为23 - 30 kDa的不同修饰的磷酸糖蛋白组成：一个质量范围为23 - 25 kDa的三联体，另一个质量范围为28 - 30 kDa的三联体。我们现在报道，代谢标记、糖苷酶消化和凝集素色谱实验的结合表明，23至25 kda的物种是o -糖基化的，而28至30 kda的物种是o -和n -糖基化的。脉冲追踪实验表明，新合成的IL-6多肽迅速进入两个独立的蛋白质修饰途径：一个导致过度糖基化，另一个导致n -和o -糖基化；两种途径中的多肽在分泌前都被进一步修饰（磷酸化）。虽然这两种途径似乎在IL-1或tnf诱导的成纤维细胞中同样有效，但通过一种或另一种途径处理的多肽的相对比例可以通过实验进行修改。在tunicamycin存在时，IL-6仅以茶糖基化形式分泌，而在环己亚胺存在时，导致n和o糖基化的途径占主导地位。莫能菌素（1 μm）虽能抑制糖基化，但不能抑制成纤维细胞分泌IL-6。联合免疫沉淀、免疫印迹和免疫亲和层析实验发现，在还原条件下，十二烷基硫酸钠-聚丙烯酰胺凝胶电泳中存在更多分子质量为17-19 kDa和45 kDa的IL-6迁移种，表明该细胞因子发生了进一步的改变。这些观察结果突出了IL-6生物合成的一个方面，似乎代表了研究人类细胞中翻译后蛋白修饰调节机制的一个极好的模型系统，也为调和IL-6结构的相互矛盾的描述提供了基础。
We have previously reported that interleukin (IL)-6 secreted by human fibroblasts induced with either IL-1 or tumor necrosis factor (TNF) consists of at least six differentially modified phosphoglycoproteins of molecular mass 23–30 kDa: a triplet in the mass range from 23 to 25 kDa and another triplet in the range from 28 to 30 kDa. We now report that a combination of metabolic labeling, glycosidase digestion, and lectin chromatography experiments demonstrates that the 23- to 25-kDa species areO-glycosylated and that the 28- to 30-kDa species are bothO- andN-glycosylated. Pulse-chase experiments reveal that newly synthesized IL-6 polypeptides rapidly enter two separate protein modification pathways: one leads toO-glycosylation and the other to bothN- andO-glycosylation; polypeptides in both pathways are further modified (phosphorylation) prior to secretion. Although both pathways appear to be equally utilized in IL-1- or TNF-induced fibroblasts, the relative proportion of polypeptides proceeding through one or the other pathway can be experimentally modified. In the presence of tunicamycin, IL-6 is secreted exclusively in theO-glycosylated form, whereas in the presence of cycloheximide the pathway leading to bothN- andO-glycosylation is dominant. The inclusion of monensin (1 μm) does not inhibit IL-6 secretion from fibroblasts even though it inhibits glycosylation. Combined immunoprecipitation, immunoblotting, and immunoaffinity chromatography experiments reveal additional IL-6 species with mobilities in sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions corresponding to molecular masses 17–19 kDa and 45 kDa, suggesting that this cytokine undergoes further alterations. These observations highlight an aspect of IL-6 biosynthesis that appears to represent an excellent model system for studying the mechanisms regulating post-translational protein modifications in human cells and also suggest a basis for reconciling conflicting descriptions of IL-6 structure.