Le Beau J M, Tedeschi B, Walter G
Department of Pathology, University of California, San Diego, La Jolla.
J Neurosci Res. 1991 Feb;28(2):299-309. doi: 10.1002/jnr.490280217.
Since little is known about the intracellular changes that take place in response to Schwann cell-neuron interactions that occur during neurite outgrowth and myelination, we investigated the expression of a protein-tyrosine kinase, pp60c-src, during peripheral nerve regeneration through a silicone tube. Segments of regenerated nerve, extracted at various times following nerve-transection, showed an induction of in vitro c-src kinase activity as measured by autophosphorylation of immunoprecipitated pp60c-src. This activity occurred at 7 days following nerve transection coincident with the onset of neurite outgrowth in vivo. This kinase activity, which peaked out between 21 and 35 days and decreased thereafter, appeared to be associated with axonal growth and myelination, but not mitogenesis in the tube. Analysis of c-src proteins levels by Western blot showed a similar expression profile as that of the kinase activity. Qualitatively, the expression of an immunoreactive c-src band, migrating slightly slower than pp60, was detected in extracts of regenerating nerve segments as well as in the corresponding L4 and L5 dorsal root ganglia. This protein may be the CNS neuronal-specific form (pp60+) of the c-src protein. In situ hybridization revealed that Schwann cells and sensory and motor neurons associated with the regenerated sciatic nerve were positive for c-src mRNA during regeneration possibly accounting for the increased src protein expression during regeneration. Since the increased expression of pp60c-src in regenerated nerve segments coincides with both axonal sprouting and myelination, our findings suggest that the c-src protein may play a role in Schwann cell-neuron interactions which facilitate the occurrence of these events during regeneration. In addition, although pp60+ is generally not detectable in the mature PNS, our findings show that this protein may be induced during conditions of PNS differentiation which promote neurite outgrowth.
由于对于在神经突生长和髓鞘形成过程中发生的雪旺细胞 - 神经元相互作用所引起的细胞内变化了解甚少，我们研究了一种蛋白酪氨酸激酶pp60c-src在周围神经通过硅胶管再生过程中的表达。在神经横断后的不同时间提取的再生神经节段，通过免疫沉淀的pp60c-src的自磷酸化测定显示体外c-src激酶活性的诱导。这种活性在神经横断后7天出现，与体内神经突生长的开始一致。这种激酶活性在21至35天达到峰值，此后下降，似乎与轴突生长和髓鞘形成有关，但与管内的有丝分裂无关。通过蛋白质印迹分析c-src蛋白水平显示出与激酶活性相似的表达谱。定性地，在再生神经节段提取物以及相应的L4和L5背根神经节中检测到一条免疫反应性c-src条带的表达，其迁移速度略慢于pp60。这种蛋白质可能是c-src蛋白的中枢神经系统神经元特异性形式（pp60+）。原位杂交显示，与再生坐骨神经相关的雪旺细胞以及感觉和运动神经元在再生过程中c-src mRNA呈阳性，这可能是再生过程中src蛋白表达增加的原因。由于再生神经节段中pp60c-src表达的增加与轴突发芽和髓鞘形成同时发生，我们的研究结果表明c-src蛋白可能在雪旺细胞 - 神经元相互作用中发挥作用，促进再生过程中这些事件的发生。此外，虽然在成熟的周围神经系统中通常检测不到pp60+，但我们的研究结果表明，这种蛋白质可能在促进神经突生长的周围神经系统分化条件下被诱导。
