Tetrahydrobiopterin Biosynthesis by Dopamine Neurons

多巴胺神经元的四氢生物蝶呤生物合成

基本信息

批准号：
6781268
负责人：
GREGORY KAPATOS
金额：
$ 32.37万
依托单位：
WAYNE STATE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
1987
资助国家：
美国
起止时间：
1987-08-01 至 2009-03-31
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): GTP cyclohydrolase I (GCH1) catalyzes the first and rate-limiting step in the synthesis of tetrahydrobiopterin, the essential cofactor for tyrosine hydroxylase and the production of dopamine (DA) within nigrostriatal DA (NSDA) neurons. A complete analysis of the cis-acting elements in the GCH1 proximal promoter necessary for basal and cAMP-dependent transcription is near and the goal of Aim 1 is to identify cognate binding proteins for the GC-box and determine their role in basal and cAMP-dependent GCH1 transcription. The trans-acting factors recruited by these c/selements are also important and the goal of Aim 2 is to forge a link between phosphorylation of C/EBPbeta and NF-Y and cAMP-dependent GCH1 transcription. Little is known about how NSDA neurons regulate GCH1 gene expression. The goal of Aim 3 is to understand the temporal changes in protein-promoter DNA interactions that take place during cAMP-dependent GCH1 transcription in NSDA neurons and to test the hypothesis that GCH1 transcription is negatively coupled to somatodendritic D2 autoreceptor tone. Heterozygous mutations in GCH1 can cause DOPA-responsive dystonia (DRD), an autosomal dominant disorder with partial penetrance that selectively decreases DA synthesis within NSDA neurons and presents in childhood as a dystonia and in adulthood as Parkinson's disease (PD). Half of DRD patients have no mutation in the GCH1 open reading frame and presumably have mutations in GCH1 gene regulatory regions. The conserved genomic cis-elements we have already described are therefore likely sites for mutations associated with GCH1 deficiency. Unaffected first-degree relatives of DRD patients are also known to have a 23-fold higher incidence of parkinsonism than do normal controls, suggesting a link between DRD, GCH1 and PD. With the hypothesis that background genetic variability in GCH1 may promote susceptibility to familial parkinsonism and idiopathic PD, we propose in Aim 4 to sequence and functionally characterize mutations in GCH1 proximal promoter and coding regions in familial parkinsonism. Because association mapping is potentially a more powerful strategy for identifying genetic variability additional studies in Aim 4 will assess genetic variability within the GCH1 gene in PD cases versus controls. The goal of Aim 5 is to determine whether genetic variability in the human GCH1 gene influences GCH1 transcription or GCH1 enzyme activity. We expect that this multidisciplinary approach will yield important new information on the role of GCH1 in NSDA neuron function and will lead to a new understanding of DRD and familial and idiopathic PD.

描述（由申请人提供）：GTP 环水解酶 I (GCH1) 催化四氢生物蝶呤合成的第一步和限速步骤，四氢生物蝶呤是酪氨酸羟化酶的重要辅助因子，以及黑质纹状体 DA (NSDA) 神经元内多巴胺 (DA) 的产生。对基础和 cAMP 依赖性转录所需的 GCH1 近端启动子中的顺式作用元件的完整分析即将完成，目标 1 的目标是鉴定 GC-box 的同源结合蛋白并确定它们在基础和 cAMP 中的作用依赖GCH1转录。这些 c/s 元件招募的反式作用因子也很重要，Aim 2 的目标是在 C/EBPbeta 和 NF-Y 的磷酸化与 cAMP 依赖性 GCH1 转录之间建立联系。人们对 NSDA 神经元如何调节 GCH1 基因表达知之甚少。目标 3 的目标是了解 NSDA 神经元中 cAMP 依赖性 GCH1 转录期间蛋白质 - 启动子 DNA 相互作用发生的时间变化，并检验 GCH1 转录与体细胞树突 D2 自受体音调负耦合的假设。 GCH1 杂合突变可导致多巴反应性肌张力障碍 (DRD)，这是一种具有部分外显率的常染色体显性遗传疾病，选择性减少 NSDA 神经元内的 DA 合成，在儿童期表现为肌张力障碍，在成年期表现为帕金森病 (PD)。一半的 DRD 患者 GCH1 开放阅读框没有突变，可能 GCH1 基因调控区有突变。因此，我们已经描述过的保守基因组顺式元件可能是与 GCH1 缺陷相关的突变位点。据了解，DRD 患者未受影响的一级亲属的帕金森病发病率比正常对照组高 23 倍，这表明 DRD、GCH1 和 PD 之间存在联系。假设 GCH1 的背景遗传变异可能会增加对家族性帕金森症和特发性 PD 的易感性，我们在目标 4 中建议对家族性帕金森症中 GCH1 近端启动子和编码区的突变进行测序和功能表征。由于关联图谱可能是识别遗传变异性的更强大策略，因此目标 4 中的其他研究将评估 PD 病例与对照中 GCH1 基因内的遗传变异性。目标 5 的目标是确定人类 GCH1 基因的遗传变异是否影响 GCH1 转录或 GCH1 酶活性。我们期望这种多学科方法将产生关于 GCH1 在 NSDA 神经元功能中的作用的重要新信息，并将导致对 DRD 以及家族性和特发性 PD 的新理解。