帕金森病多巴胺能神经元KATP通道SUR1亚单位选择性上调并导致神经元死亡的机制研究

In Parkinson’s disease (PD), the selective activation of SUR1/Kir6.2 subtype of ATP-sensitive potassium (KATP) channels in substantia nigra (SN) is involved in the degeneration of dopaminergic (DA) neurons. It is found that the mRNA levels of SUR1 subunit of KATP channels in the remaining DA neurons were transcriptionally increased in SN region of PD brains, but the mechanism is not known. In previous work, we found that the upregulation of SUR1 in SN was set on in the early stage of PD. Although FOXA1/2 functions as a transcriptional regulatory factor for SUR1 in pancreatic β cells, the effects of FOXA1/2 on SUR1 in DA neurons were currently not clarified. Because FOXA1/2 plays essential roles in the DA neurons’ development and functions, in this study, we first detect whether FOXA1/2 could regulate the expression of SUR1 subunit in DA cells, and other transcriptional factors will be screened. Furthermore, the causal association between changes in FOXA1/2 as well as SUR1 subunit expressions and the degeneration of DA neurons was studied. This study is expected to find out the specific transcription factor for SUR1, and illustrate the mechanism underlying SUR1/Kir6.2 type of KATP channels induced the selective degeneration of DA neurons in PD.

帕金森病（PD）黑质多巴胺（DA）能神经元死亡与SUR1/Kir6.2型KATP通道激活有关，PD病人残存的DA能神经元上SUR1 mRNA表达升高。我们前期实验发现，PD转基因小鼠在早期也出现黑质SUR1 mRNA水平上调，但机制不明。尽管在胰岛β细胞上发现FOXA1/2是SUR1的转录因子，FOXA1/2在DA能神经元发育及功能维持中非常重要，它是否也是DA能神经元SUR1的转录因子？为阐明SUR1 mRNA上调机制及在DA能神经元损伤中的作用，首先在DA能细胞上，观察FOXA1/2与SUR1启动子的结合及其对SUR1的表达调控，同时寻找其它转录因子。然后利用PD转基因及SUR1-/-小鼠，观察疾病进展中，FOXA1/2和SUR1的变化与DA能神经元功能变化之间的关系。本研究有望发现DA能神经元上SUR1特异性的转录因子，并阐明SUR1/Kir6.2型KATP通道致其损伤的机制。

帕金森病（PD）的发病机制尚不明确，最近的研究表明，黑质区多巴胺（DA）能神经元上ATP敏感性钾通道（KATP通道）的选择性激活可能参与了PD中黑质区DA能神经元的损伤。在PD病人的尸检中发现，脑内残存的单个黑质DA能神经元上虽然SUR1、SUR2和Kir6.2亚单位均有表达，但只有SUR1的mRNA水平增高2倍，其余亚单位mRNA水平没有改变。此外，在1-甲基-4-苯基-1,2,3,6-四氢吡啶（MPTP）制备的PD小鼠模型中发现，黑质区DA能神经元SUR1亚单位的mRNA水平较VTA区升高了2倍。为了探讨黑质DA能神经元SUR1亚单位选择性上调的机制及其在神经元损伤中的作用。本实验采用MES23.5细胞以及携带人A53T突变型α-syn（α-SynA53T）的PD转基因小鼠为主要研究对象，检测α-syn高表达的PD细胞模型与动物模型中KATP通道各亚单位的表达变化，以及转录因子FOXA1和FOXA2的表达变化，并验证FOXA1和FOXA2与SUR1基因启动子的结合情况。应用在体细胞外电生理技术，观察了正常小鼠黑质区KATP通道的开放对DA能神经元自发放电活动的影响；同时，在A53T α-syn转基因小鼠上，观察黑质区DA能神经元自发放电活动随月龄的变化。最后，将携带SUR1干扰序列的慢病毒注射到A53T α-syn转基因动物和MPTP诱导的PD动物模型的黑质区，观察敲低SUR1对两种PD动物模型黑质区DA能神经元功能的影响以及SUR1基因敲低对MPTP所致的小鼠黑质DA能神经元损伤的影响。