PHYSIOLOGY OF THYROID HORMONE DEPENDENT GENE EXPRESSION

描述：(摘自申请者的摘要)我们实验室已经专注于 25岁以上三碘甲状腺原氨酸(T_3)稳态调节机制的研究 好几年了。对这一过程至关重要的是碘甲状腺原氨酸的作用 脱碘酶协同调节甲状腺激素(T4)的激活和 T_4、T_3失活。这项提案延续了这一主题。在第一个 我们将继续我们对一种特定细胞类型的研究 人甲状腺激素启动子区的阴性甲状腺激素反应元件(NTRE) 1型脱碘酶(DL)基因。该甲状腺受体(TR)结合序列还 与新型JEG细胞转录因子(JTF)高亲和力结合 专一性。JTF促进含有该序列的基因的表达，并 APO-TRs增强了这一效应。T3消除了这种影响。使用DNA 亲和力矩阵技术我们将分离和鉴定这个新发现的 蛋白质，并确定TR如何与其合作作为特定的 甲状腺激素负调控基因表达的机制。 不受控制的甲状腺激素迅速失活会导致甲状腺功能减退 我们最近在患有大血管瘤的婴儿中发现了这种综合征。 婴儿血管瘤表达3型碘甲状腺原氨酸脱碘酶(D3)，主要 生理灭活剂13和14，水平高达8倍于 胎盘。大肿瘤可以比婴儿更快地使T4和T3脱碘 甲状腺可以分泌它们。《特定目标2》将阐明 D3在这些肿瘤中的异位表达。我们将比较血管瘤来源的 和正常的人类毛细血管内皮细胞，以发现可以 激活类似于胎盘的D3表达。具体目标三是 明确正常甲状腺心脏对心肌的反应机制 甲亢状态，如甲亢患者出现的甲亢状态。我们有 建立一种诱导小鼠慢性心肌甲状腺功能亢进的新方法 通过使用其中驱动2型碘甲状腺原氨酸脱碘酶(D2)的转基因 由α-MHC启动子启动。我们将首先定义两个方面的机制 这些药物增加心肌细胞膜对Forskolin的cAMP反应 转基因小鼠。我们还将记录基因表达的差异 青年与老年人甲状腺功能正常心肌与甲亢心肌的比较 老鼠。目前只发现了几个能增加其表达的基因。 甲状腺功能正常和甲状腺功能亢进状态之间的显著差异。确定这样的 心肌中的基因将对理解 甲状腺功能亢进症患者T3过量对心脏的影响。这些研究将 提供与基础和临床甲状腺生理学相关的新信息。

DESCRIPTION: (Scanned from the applicant's abstract) Our laboratory has focused on the mechanisms regulating triiodothyronine (T3) homeostasis for over 25 years. Critical to this process are the actions of the iodothyronine deiodinases which function in concert to regulate thyroxine (T4) activation and the inactivation of T4 and T3. This proposal continues this theme. In the first Specific Aim we will continue our investigations of a cell type specific negative thyroid hormone response element (nTRE) in the promoter of the human Type 1 deiodinase (Dl) gene. This thyroid receptor (TR) binding sequence also binds a novel JEG cell transcription factor (JTF) with high affinity and specificity. JTF increases expression of genes containing this sequence and this effect is enhanced by APO-TRs. T3 eliminates this effect. Using DNA affinity matrix techniques we will isolate and identify this newly discovered protein and determine how TR cooperates with it as an example of a specific mechanism for negative regulation of gene expression by thyroid hormone. Uncontrolled, rapid inactivation of thyroid hormone causes hypothyroidism in a syndrome which we recently identified in infants with large hemangiomas. Infantile hemangiomas express Type 3 iodothyronine deiodinase (D3), the major physiological inactivator of 13 and 14, at levels up to 8-fold that in placenta. Large tumors can deiodinate T4 and T3 more rapidly than the infant's thyroid can secrete them. Specific Aim 2 will elucidate the mechanism for ectopic expression of D3 in these tumors. We will compare hemangioma-derived and normal human capillary endothelial cells to discover pathways which could activate D3 expression analogous to those in placenta. Specific Aim III is to define the mechanism for the myocardial response of the euthyroid heart to the thyrotoxic state such as occurs in patients with hyperthyroidism. We have developed a novel method for inducing chronic myocardial thyrotoxicosis in mice by use of a transgene in which Type 2 iodothyronine deiodinase (D2) is driven by the alpha-MHC promoter. We will first define the mechanism for the two-fold increase in the cAMP response to forskolin in myocardial membranes from these transgenic mice. We will also document the differences n gene expression profiles between euthyroid and thyrotoxic myocardium from both young and old mice. Only a few genes have been identified which increase their expression significantly between the euthyroid and hyperthyroid state. Identifying such genes in the myocardium will be especially critical to the understanding of the effects of T3 excess on the heart in human hyperthyroidism. These studies will provide new information relevant to both basic and clinical thyroid physiology.