Roles of src tyrosine kinase on neuronal regeneration

为了了解src酪氨酸激酶在腋部切除后神经元再生机制中的作用，我们采用免疫组织化学方法研究了p60c-src、磷酸酪氨酸（pTyr）、血小板衍生生长因子（PDGF）和PDGF受体的变化。我们还研究了成年大鼠迷走神经背侧运动核中p60c- srin的western blotting分析，该核在神经切开术后表现为退变，在神经横断后表现为再生。1. pTyr是酪氨酸激酶的反应产物，是检测酪氨酸激酶活性的敏感标志物，在迷走神经和舌下核的axonized神经元中均观察到免疫反应性增加。这些结果表明酪氨酸激酶与轴突反应有关。断轴后迷走神经核PDGF减少，而与Src蛋白激酶直接相关的PDGF受体未见明显变化。这些结果表明，迷走神经细胞PDGF的减少导致了轴切后神经元中Src蛋白的失活。两核切开术后Src蛋白本身无明显变化，而舌下核切开术后Src SH3区的免疫反应性明显增强，迷走核则略有增强。这些发现表明，与Src激活相关的Src构象改变在轴切后在再生的舌下神经元中强烈发生，而在退行性迷走神经元中仅轻微发生。因此，Src的激活被认为与轴切后的神经元再生有关。2. Western blotting检测Src蛋白显示，经轴突切开术后迷走神经和舌下核均无明显变化。该结果与免疫组化研究一致。

In order to obtain information of the roles of src tyrosine kinase on regenerative mechanisms of neurons after axtomy, we immnuhistochemically investigated changes of p60c-src, phosphtyrosine (pTyr), platelet derived growth factor (PDGF) and PDGF receptor. We also studied western blotting analysis of p60c-srcin the dorsal motor nucleus of vagus, nerve, which shows degeneration after axotomy, and the hypoglossal nucleus, which shows regeneration, after nerve transection in adult rats. 1. Increased immunoreactivity of pTyr, which is the reaction product of tyrosine kinase, is a sensitive marker for detection of the activity of tyrosine kinases, was observed in the axotomized neurons in bothe vagal and hypoglossal nuclei. These results indicate that tyrosine kinases concern with axonal reaction. PDGF decreased in the vagal nucleus after axoltomy, while PDGF receptor, which direct associated with Src protein kinase, showed no remarkable change after axotomy. These findings suggest that decrease of PDGF in vagal neurons result in inactivation of Src protein in neurons after axotomy. Src protein itself ashowed no remarkable changes after axotomy in both nuclei, while immunoreactivity for SH3 region of Src was strongly increased in the hypoglossal nucleus after axotomy, while only slightly in the vagal nucleus. These findings suggest that conformational change of Src, which related with activation Src, occurs after axotomy strongly in reganerative hypoglossal neurons, while only slightly in degenerative vagal neurons. Therefore, the activation of Src is thought to concern with neuronal regeneration after axotomy. 2. Western blotting for Src protein showed no significant changes in both vagal and hypoglossal nuclei after axotomy. This result consistent with the immunohistochemical study.