Sacchetti P, Mitchell T R, Granneman J G, Bannon M J
Department of Psychiatry, Wayne State University School of Medicine, Detroit, USA.
J Neurochem. 2001 Mar;76(5):1565-72. doi: 10.1046/j.1471-4159.2001.00181.x.
The importance of the nuclear receptor nurr1 for the appropriate development of mesencephalic dopamine-synthesizing neurons has been clearly demonstrated through the targeted disruption of the nurr1 gene. The persistence of nurr1 expression in adult tissue suggests a possible role for this transcription factor in the maintenance, as well as development, of the dopaminergic phenotype. To address this issue, we analyzed the effects of nurr1 on the transcriptional expression of the human dopamine transporter gene (hDAT), one of the most specific phenotypic markers for dopaminergic neurons. Nurr1 enhanced the transcriptional activity of hDAT gene constructs transiently transfected into a newly described cell line (SN4741) that expresses a dopaminergic phenotype, whereas other members of the NGFI-B subfamily of nuclear receptors had lesser or no effects. Nurr1 activation of hDAT was not dependent upon heterodimerization with the retinoid X receptor. Unexpectedly, functional analysis of a series of gene constructs revealed that a region of the hDAT 5'-flanking sequence devoid of NGFI-B response element (NBRE)-like sites mediated nurr1 activation. Additional experiments using a nurr1 mutant construct suggest that nurr1 activates hDAT transcription via a novel NBRE-independent mechanism.
通过对nurr1基因的靶向破坏，已清楚地证明了核受体nurr1对于中脑多巴胺合成神经元正常发育的重要性。nurr1在成年组织中的持续表达表明，这种转录因子在多巴胺能表型的维持以及发育中可能发挥作用。为了解决这个问题，我们分析了nurr1对人多巴胺转运体基因（hDAT）转录表达的影响，hDAT是多巴胺能神经元最特异的表型标志物之一。Nurr1增强了瞬时转染到一种新描述的表达多巴胺能表型的细胞系（SN4741）中的hDAT基因构建体的转录活性，而核受体NGFI-B亚家族的其他成员作用较小或无作用。Nurr1对hDAT的激活不依赖于与视黄酸X受体的异二聚化。出乎意料的是，一系列基因构建体的功能分析表明，hDAT 5'侧翼序列中一个没有NGFI-B反应元件（NBRE）样位点的区域介导了nurr1的激活。使用nurr1突变体构建体的进一步实验表明，nurr1通过一种新的不依赖于NBRE的机制激活hDAT转录。
