Brecht S, Gass P, Anton F, Bravo R, Zimmermann M, Herdegen T
II. Institute of Physiology, University of Heidelberg, Germany.
Mol Cell Neurosci. 1994 Oct;5(5):431-41. doi: 10.1006/mcne.1994.1053.
In adult rats, the expression of transcription factor proteins c-Jun and CREB and their colocalization with tyrosine hydroxylase (TH) were investigated in neurons of the substantia nigra compacta (SNC) axotomized by stereotaxic unilateral transection of the medial forebrain bundle (MFB). Axotomized SNC neurons were identified by injection of the retrograde tracer horseradish-peroxidase-coupled-gold (HRP-gold) into the ipsilateral striatum 5 days prior to MFB transection. Nuclear c-Jun immunoreactivity (IR) appeared 36 h after MFB transection in SNC neurons, was maximal after 5 days, and declined after 10 days. c-Jun-IR was visible in HRP-gold-labeled SNC neurons, demonstrating that c-Jun is in fact expressed in axotomized neurons. The constitutively expressed CREB (calcium/cAMP response element-binding protein, syn. CREB-1) was present in apparently all neuronal and glial cells in the brains of untreated rats including those SNC neurons that coexpressed TH. Three days following MFB transection, the nuclear CREB-IR disappeared in the axotomized SNC neurons labeled by TH-IR and was almost completely absent after 20 days in this neuronal population. The TH-IR rapidly declined 5 days after MFB transection, and 10 and 100 days post-axotomy the number of TH-labeled neurons was reduced by 52 and 80%, respectively. During this period, the majority of surviving TH positive neurons coexpressed c-Jun but were immunonegative for CREB. Between 3 and 60 days following MFB transection, the number of CREB-labeled glial cell nuclei increased in the ipsilateral substantia nigra by about 80%. Concomitantly, expression of GFAP, a marker protein for astrocytes, was also enhanced whereas nuclear c-Jun-, JunD-, and c-Fos-IR did not change in glial cells. These findings demonstrate that c-Jun can be expressed in axotomized neurons during the absence of CREB and suggest a role of c-Jun in the transcriptional control of the TH gene.
在成年大鼠中，通过立体定向单侧横断内侧前脑束（MFB）使黑质致密部（SNC）神经元轴突切断，研究转录因子蛋白c-Jun和CREB的表达及其与酪氨酸羟化酶（TH）的共定位。在MFB横断前5天，将逆行示踪剂辣根过氧化物酶偶联金（HRP-金）注入同侧纹状体，以识别轴突切断的SNC神经元。MFB横断后36小时，SNC神经元中出现核c-Jun免疫反应性（IR），5天后达到最大值，10天后下降。c-Jun-IR在HRP-金标记的SNC神经元中可见，表明c-Jun实际上在轴突切断的神经元中表达。组成型表达的CREB（钙/ cAMP反应元件结合蛋白，同义词CREB-1）在未处理大鼠大脑中的所有神经元和神经胶质细胞中均有表达，包括那些共表达TH的SNC神经元。MFB横断后三天，由TH-IR标记的轴突切断的SNC神经元中的核CREB-IR消失，在该神经元群体中20天后几乎完全不存在。MFB横断后5天，TH-IR迅速下降，轴突切断后10天和100天，TH标记的神经元数量分别减少了52％和80％。在此期间，大多数存活的TH阳性神经元共表达c-Jun，但对CREB免疫阴性。MFB横断后3至60天，同侧黑质中CREB标记的神经胶质细胞核数量增加了约80％。同时，星形胶质细胞的标记蛋白GFAP的表达也增强，而神经胶质细胞中的核c-Jun、JunD和c-Fos-IR没有变化。这些发现表明，在缺乏CREB的情况下，c-Jun可以在轴突切断的神经元中表达，并提示c-Jun在TH基因的转录控制中起作用。
