Savedia S, Kiernan J A
Department of Anatomy, University of Western Ontario, London, Canada.
Neuropathol Appl Neurobiol. 1994 Dec;20(6):577-86. doi: 10.1111/j.1365-2990.1994.tb01012.x.
Ubiquitin targets proteins for attack by certain proteolytic enzymes, but the ubiquitinated cytoplasmic inclusions seen in some chronic neurodegenerative diseases may indicate the occurrence of reparative rather than destructive metabolic events. We have examined the production of ubiquitin in motor neurons of the rat's left hypoglossal nucleus after transection of their axons in circumstances that favour or prevent axonal regeneration. One week after axotomy, in situ hybridization with a radiolabelled cRNA probe revealed a twofold increase in the ubiquitin mRNA content of neurons with regenerating axons (nerve crushed) but not significant change when axonal regeneration had been prevented (nerve transected and ligated). After 2 weeks, ubiquitin mRNA was elevated to about 1.5 times the contralateral control level, regardless of the type of nerve injury, and by 4 weeks there were no longer any differences between the left and right sides. Despite the increased transcription, axotomy was not followed by any change in the quantity of ubiquitin-immunoreactive material in the nuclei or perikarya of hypoglossal neurons as measured by video image analysis of immunohistochemically stained sections. We suggest that ubiquitin is synthesized in neuronal cell bodies and transported into their axons, and that ubiquitin-mediated proteolysis is a metabolic process involved in the elongation of regenerating axons.
泛素将蛋白质作为某些蛋白水解酶的攻击目标，但在一些慢性神经退行性疾病中看到的泛素化胞质内含物可能表明发生的是修复性而非破坏性的代谢事件。我们研究了在有利于或阻止轴突再生的情况下，大鼠左舌下神经核运动神经元轴突横断后泛素的产生情况。轴突切断术后一周，用放射性标记的cRNA探针进行原位杂交显示，轴突再生的神经元（神经挤压）中泛素mRNA含量增加了两倍，但在轴突再生被阻止的情况下（神经切断并结扎）没有显著变化。两周后，无论神经损伤类型如何，泛素mRNA都升高到对侧对照水平的约1.5倍，到四周时左右两侧不再有任何差异。尽管转录增加，但通过对免疫组织化学染色切片进行视频图像分析测量，轴突切断后舌下神经元细胞核或胞体中泛素免疫反应性物质的数量没有任何变化。我们认为泛素在神经元细胞体中合成并运输到它们的轴突中，并且泛素介导的蛋白水解是参与再生轴突伸长的一个代谢过程。
