REGULATION OF AXON GUIDANCE MOLECULE GENES: RELEVANCE TO BRAIN ADAPTATION

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。轴突引导分子（AGMs）包括信号素、ephrin、netrins及其受体，是神经系统发育和神经适应的重要贡献者。我们之前证明了agm在成年灵长类动物大脑中的存在。本研究探讨了cAMP的变化可能促进AGMs基因表达变化的假设，从而将药物诱导的神经适应与受体介导的事件联系起来。结果：采用real - time PCR技术，我们检测了SK-N-MC人神经上皮瘤细胞系中几种AGMs和可卡因间接靶点D1多巴胺受体的内源性表达。用10uM forskolin （N=5）处理SK-N-MC细胞以增加细胞内cAMP，可增加14个基因EphA5、EphB2和Neuropilin1的表达。这3个基因调控的幅度和方向与Bahi和Dreyer（2005）在可卡因后大鼠海马中的发现相似。相比之下，多巴胺受体激动剂二氢氧定（10uM； N=5）使SK-N-MC细胞中EphrinA1表达上调，EphrinA5、EphB1、DCC和Sema3C表达下调。讨论：可以想象，可卡因通过阻断单胺转运体来改变AGM的表达，从而间接激活单胺受体并改变cAMP的产生。AGM基因的表达可能部分受到cAMP和其他信号转导途径的调节，这可能将受体激活与AGM转录调控联系起来。这些初步数据提供了一种新的机制，药物可以通过改变AGM表达来促进成人大脑中药物诱导的神经适应，这可能与成瘾和药物开发有关。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Axon guidance molecules (AGMs) including semaphorins, ephrins, netrins and their receptors are important contributors to nervous system development and neuroadaptation. We previously demonstrated the presence of AGMs in adult primate brain. The current study investigated the hypothesis that changes in cAMP may promote changes in gene expression of AGMs, thereby linking drug-induced neuroadaptation with receptor-mediated events. Results: Using real time PCR, we detected endogenous expression of several AGMs and the D1 dopamine receptor, an indirect target of cocaine, in the SK-N-MC human neuroepithelioma cell line. Treatment of SK-N-MC cells with 10uM forskolin (N=5) to increase intracellular cAMP resulted in increased expression of EphA5, EphB2 and Neuropilin1, of 14 genes tested. The magnitude and direction of regulation for these 3 genes paralleled the findings of Bahi and Dreyer (2005) in the rat hippocampus after cocaine. In contrast, exposure of SK-N-MC cells to the dopamine receptor agonist dihydrexidine (10uM; N=5) resulted in up-regulation of EphrinA1 and down-regulation of EphrinA5, EphB1, DCC and Sema3C. Discussion: Conceivably, cocaine modifies AGM expression by blocking monoamine transporters, thereby indirectly activating monoamine receptors and altering cAMP production. AGM gene expression may be regulated, in part, by changes in cAMP and other signal transduction pathways, potentially linking receptor activation to AGM transcriptional regulation. These preliminary data offer a novel mechanism by which drugs may modify AGM expression to promote drug-induced neuroadaptation in adult brain which may be of potential relevance to addiction and the development of medications.