Perry G W, Burmeister D W, Grafstein B
Department of Physiology, Cornell University Medical College, New York, New York 10021.
J Neurosci. 1990 Oct;10(10):3439-48. doi: 10.1523/JNEUROSCI.10-10-03439.1990.
How is axonal transport in regenerating neurons affected by contact with their synaptic target? We investigated whether removing the target (homotopic) lobe of the goldfish optic tectum altered the incorporation of 3H-proline into fast axonally transported proteins in the regenerating optic nerve. Regeneration was induced either by an optic tract lesion (to reveal the changes in the original axon segment that remained connected to the cell body) or by an optic nerve lesion (to reveal the changes in the newly formed axon segment). Of 26 proteins analyzed by 2-dimensional gel electrophoresis and fluorography, all but one showed increased labeling as a result of tectal lobe ablation. By 2 d after the lesion, significantly increased labeling of some proteins was seen with a 6-hr labeling interval, but not with a 24-hr labeling interval. This is probably indicative of an increased velocity of transport, which may have been a nonspecific consequence of the surgery. Otherwise, tectal lobe removal had relatively little effect until 3 weeks, when there was a transitory increase in labeling of transported proteins in the new axon segments of the tectum-ablated animals. Beginning at 5 weeks, tectal lobe ablation caused considerably higher labeling of many of the proteins in the original axon segments. Because this was seen with both 6-hr and 24-hr labeling intervals, it is probably indicative of increased protein synthesis. The increased synthesis lasted until at least 12 weeks, though some proteins were beginning to show a diminished effect at this time. In the late stages of regeneration (8-12 weeks), there was also increased labeling of proteins in the new axon segments as a result of the absence of the target tectal lobe. This included a disproportionately large increase in the relative contribution of cytoskeletal proteins and of protein 4, which is the goldfish equivalent of the growth-associated protein GAP-43 (neuromodulin). We conclude that, after the regenerating axons begin to innervate the tectum, the expression of most of the proteins in fast axonal transport is down-regulated by interaction between the axons and their target. However, the changes in expression may be preceded by a modulation of the turnover and/or deposition of proteins in the newly formed axon segment.
再生神经元中的轴突运输如何受到与突触靶标的接触影响？我们研究了切除金鱼视顶盖的靶标（同位）叶是否会改变3H-脯氨酸掺入再生视神经中快速轴突运输蛋白的情况。通过视束损伤（以揭示与细胞体相连的原始轴突段的变化）或视神经损伤（以揭示新形成的轴突段的变化）诱导再生。通过二维凝胶电泳和荧光自显影分析的26种蛋白质中，除一种外，其余所有蛋白质在顶盖叶切除后标记均增加。损伤后2天，在6小时标记间隔时可观察到一些蛋白质的标记显著增加，但在24小时标记间隔时未观察到。这可能表明运输速度增加，这可能是手术的非特异性后果。否则，直到3周时，顶盖叶切除的影响相对较小，此时顶盖切除动物新轴突段中运输蛋白的标记出现短暂增加。从5周开始，顶盖叶切除导致原始轴突段中许多蛋白质的标记显著更高。因为在6小时和24小时标记间隔时均观察到这种情况，这可能表明蛋白质合成增加。合成增加至少持续到12周，尽管此时一些蛋白质开始显示出作用减弱。在再生后期（8 - 12周），由于缺乏靶标顶盖叶，新轴突段中蛋白质的标记也增加。这包括细胞骨架蛋白和蛋白质4的相对贡献不成比例地大幅增加，蛋白质4相当于金鱼中的生长相关蛋白GAP - 43（神经调节蛋白）。我们得出结论，再生轴突开始支配视顶盖后，快速轴突运输中大多数蛋白质的表达通过轴突与其靶标之间的相互作用而下调。然而，表达的变化可能先于新形成轴突段中蛋白质周转和/或沉积的调节。
