Kim H S, Hong S J, LeDoux M S, Kim K S
Department of Neurology, University of Tennessee, College of Medicine, Memphis, Tennessee, USA.
J Neurochem. 2001 Jan;76(1):280-94. doi: 10.1046/j.1471-4159.2001.00044.x.
The retinoic acid-inducible and developmentally regulated transcription factor AP-2 plays an important role during development. In adult mammals, AP-2 is expressed in both neural and non-neural tissues. However, the function of AP-2 in different neuronal phenotypes is poorly understood. In this study, transcriptional regulation of tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH) genes by AP-2 was investigated. AP-2 binding sites were identified in the upstream regions of both genes. Electrophoretic mobility shift assays (EMSA) and DNase I footprinting analyses indicate that the AP-2 interaction with these motifs is more prominent in catecholaminergic SK-N-BE(2)C and CATH.a than in non-catecholaminergic HeLa and HepG2 cell lines. Exogenous expression of AP-2 robustly transactivated TH and DBH promoter activities in non-catecholaminergic cell lines. While AP-2 regulates the DBH promoter activity via a single site, transactivation of the TH promoter by AP-2 appears to require multiple sites. In support of this, mutation of multiple AP-2 binding sites but not that of single site diminished the basal promoter activity of the TH gene in cell lines that express TH and abolished transactivation by exogenous AP-2 expression in cell lines that do not express TH. In contrast, mutation of a single AP-2 binding site of the DBH gene completely abolished transactivation by AP-2. Double-label immunohistochemistry showed that AP-2 is coexpressed with TH in noradrenergic and adrenergic neurons in both the central and peripheral nervous systems of adult rodents. Numerous non-catecholaminergic cell groups within the spinal cord, medulla, cerebellum, and pons also express AP-2. The concentration of AP-2 in dorsomedial locations along the neuraxis suggests a regionally specific role for this transcription factor in the regulation of neuronal function. Based on these findings we propose that AP-2 may coregulate TH and DBH gene expression and thus participate in expression/maintenance of neurotransmitter phenotypes in (nor)adrenergic neurons and neuroendocrine cells.
维甲酸诱导且受发育调控的转录因子AP-2在发育过程中发挥重要作用。在成年哺乳动物中，AP-2在神经组织和非神经组织中均有表达。然而，人们对AP-2在不同神经元表型中的功能了解甚少。在本研究中，对AP-2对酪氨酸羟化酶（TH）和多巴胺β-羟化酶（DBH）基因的转录调控进行了研究。在这两个基因的上游区域鉴定出了AP-2结合位点。电泳迁移率变动分析（EMSA）和DNase I足迹分析表明，与非儿茶酚胺能的HeLa和HepG2细胞系相比，AP-2与这些基序的相互作用在儿茶酚胺能的SK-N-BE(2)C和CATH.a细胞系中更为显著。AP-2的外源性表达在非儿茶酚胺能细胞系中强烈激活TH和DBH启动子活性。虽然AP-2通过单个位点调节DBH启动子活性，但AP-2对TH启动子的反式激活似乎需要多个位点。支持这一点的是，多个AP-2结合位点的突变而非单个位点的突变降低了表达TH的细胞系中TH基因的基础启动子活性，并消除了不表达TH的细胞系中外源性AP-2表达的反式激活作用。相比之下，DBH基因单个AP-2结合位点的突变完全消除了AP-2的反式激活作用。双标免疫组化显示，在成年啮齿动物的中枢和外周神经系统中，AP-2与去甲肾上腺素能和肾上腺素能神经元中的TH共表达。脊髓、延髓、小脑和脑桥内的许多非儿茶酚胺能细胞群也表达AP-2。沿神经轴背内侧位置的AP-2浓度表明该转录因子在调节神经元功能中具有区域特异性作用。基于这些发现，我们提出AP-2可能共同调节TH和DBH基因表达，从而参与（去甲）肾上腺素能神经元和神经内分泌细胞中神经递质表型的表达/维持。
