A phorbol ester-sensitive kinase catalyzes the phosphorylation of P0 glycoprotein in myelin.
A phorbol ester-sensitive kinase catalyzes the phosphorylation of P0 glycoprotein in myelin.
复制标题
佛波酯敏感激酶催化髓磷脂中 P0 糖蛋白的磷酸化。
DOI：
10.1111/j.1471-4159.1987.tb02448.x
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发表时间：
1987
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;Poduslo,JF
所提出的周围神经髓鞘结构蛋白P0已被证明具有几个共价修饰。P0除了被糖基化、硫化和酰化外，还被磷酸化，后一种加成的胞内位置还有待商榷。通过使用神经损伤模型，在没有和存在髓鞘组装的情况下显示不同水平的P0生物合成，我们研究了P0磷酸化的细胞位置。结果表明，在正常和挤压损伤的成年大鼠坐骨神经中都有类似的P0磷酸化，尽管这两种髓鞘维持和积极髓鞘形成的神经模型中P0的生物合成水平不同。在横断的成人坐骨神经中，这种糖蛋白似乎不容易被磷酸化，这种制备物中可以观察到P0的生物合成，但缺乏髓鞘膜。这些观察结果表明，这种修饰与内质网或高尔基体中P0的生物合成或成熟无关，而是发生在髓鞘组装之后。即使在环己亚胺治疗抑制翻译的情况下，正常神经中也会发生P0的磷酸化，这进一步支持了这一结论。脉冲追逐分析表明，P0在一个或多个丝氨酸残基上被磷酸化，所有或大部分磷酸基团(S)是不稳定的。加入生物活性佛波酯12-O-十四酰佛波醇-13-乙酸酯或4-β-佛波酯12，13-二丁酸酯，可显著增加[~(32)P]正磷酸盐掺入正常和损伤神经的糖蛋白的程度，但不能增加切断神经的[~(32)P]正磷酸盐掺入程度。生物活性失活的4-α-佛波酯12，13-十二酸对P0的磷酸化没有影响。同样，添加环AMP类似物8-溴-环AMP没有引起P0标记的明显变化。这些发现表明，佛波酯敏感的酶，蛋白激酶C，可能是导致髓鞘膜内P0的磷酸化的原因。
The proposed structural protein of peripheral nerve myelin, P0, has been shown to have several covalent modifications. In addition to being glycosylated, sulfated, and acylated, P0is phosphorylated, with the intracellular site of this latter addition being in question. By employing nerve injury models that exhibit different levels of P0biosynthesis in the absence and presence of myelin assembly, we have examined the cellular location of P0phosphorylation. It is demonstrated that there is comparable P0phosphorylation in both normal and crush‐injured adult rat sciatic nerves, although the level of biosynthesis of P0differs between these myelin maintaining and actively myelinating nerve models, respectively. The glycoprotein does not appear to be phosphorylated readily in the transected adult sciatic nerve, a preparation in which P0biosynthesis is observed but that lacks myelin membrane. These observations suggest that the modification is not associated with the biosynthesis or maturation of P0in the endoplasmic reticulum or Golgi, but that it instead occurs after myelin assembly. That P0phosphorylation occurs in the normal nerve even when translation is inhibited by cycloheximide treatment lends further support to this conclusion. P0is shown to be phosphorylated on one or more serine residues, with all or most of the phosphate group(s) being labile as evidenced by pulse‐chase analysis. Addition of a biologically active phorbol ester, 12‐O‐tetradecanoylphorbol‐13‐acetate or 4β‐phorbol 12, 13‐dibutyrate, substantially increases the extent of [32P]orthophosphate incorporation into the glycoprotein of normal and crushed nerve but not transected nerve. Biologically inactive 4α‐phorbol 12, 13‐didecanoate has no effect on P0phosphorylation. Similarly, the addition of the cyclic AMP analog 8‐bromo‐cyclic AMP causes no appreciable changes in P0labeling. These findings indicate that the phorbol ester‐sensitive enzyme, protein kinase C, may be responsible for the phosphorylation of P0within the myelin membrane.