Skene J H, Willard M
J Cell Biol. 1981 Apr;89(1):86-95. doi: 10.1083/jcb.89.1.86.
In an effort to understand the regulation of the transition of a mature neuron to the growth, or regenerating, state we have analyzed the composition of the axonally transported proteins in the retinal ganglion cells of the toad Bufo marinus after inducing axon regeneration by crushing the optic nerve. At increasing intervals after axotomy, we labeled the retinal ganglion cells with [35S]methionine and subsequently analyzed the labeled transported polypeptides in the crushed optic nerve by means of one- and two-dimensional electrophoretic techniques. The most significant conclusion from these experiments is that, while the transition from the mature to the regenerating state does not require a gross qualitative alteration in the composition of axonally transported proteins, the relative labeling of a small subset of rapidly transported proteins is altered dramatically (changes of more than 20-fold) and reproducibly (more than 30 animals) by axotomy. One of these growth-associated proteins (GAPs) was soluble in an aqueous buffer, while three were associated with a crude membrane fraction. The labeling of all three of the membrane-associated GAPs increased during the first 8 d after axotomy, and they continued to be labeled for at least 4 wk. The modulation of these proteins after axotomy is consistent with the possibility that they are involve in growth-specific functions and that the altered expression of a small number of genes is a crucial regulatory event in the transition of a mature neuron to a growth state. In addition to these selective changes in rapidly transported proteins, we observed the following more general metabolic correlates of the regeneration process: The total radioactive label associated with the most rapidly transported proteins (groups I and II) increased three to fourfold during the first 8 d after the nerve was crushed, while the total label associated with more slowly moving proteins (group IV) increased about 10-fold during this same period. Among these more slowly transported polypeptides, five were observed whose labeling increased much more than the average. Three of these five polypeptides resemble actin and alpha- and beta-tubulin in their electrophoretic properties.
为了了解成熟神经元向生长或再生状态转变的调控机制，我们通过挤压蟾蜍（Bufo marinus）的视神经诱导轴突再生，然后分析了视网膜神经节细胞中轴突运输蛋白的组成。在轴突切断后的不同时间间隔，我们用[35S]甲硫氨酸标记视网膜神经节细胞，随后通过一维和二维电泳技术分析挤压视神经中标记的运输多肽。这些实验得出的最重要结论是，虽然从成熟状态向再生状态的转变并不需要轴突运输蛋白组成发生总体性质的改变，但一小部分快速运输蛋白的相对标记量会因轴突切断而发生显著变化（超过20倍）且具有可重复性（超过30只动物）。其中一种生长相关蛋白（GAPs）可溶于水性缓冲液，而另外三种与粗膜部分相关。所有三种膜相关GAPs的标记在轴突切断后的前8天增加，并且至少持续标记4周。轴突切断后这些蛋白的调节与它们参与生长特异性功能的可能性一致，并且少数基因表达的改变是成熟神经元向生长状态转变中的关键调控事件。除了快速运输蛋白的这些选择性变化外，我们还观察到了再生过程中以下更普遍的代谢相关性：与最快运输蛋白（I组和II组）相关的总放射性标记在神经挤压后的前8天增加了三到四倍，而与移动较慢的蛋白（IV组）相关的总标记在同一时期增加了约10倍。在这些移动较慢的多肽中，观察到有五种的标记增加幅度远超过平均水平。这五种多肽中的三种在电泳性质上类似于肌动蛋白、α-和β-微管蛋白。
