THYROID HORMONE CONTROL OF CARDIAC SODIUM/POTASSIUM ATPASE EXPRESSION

Na+，K+ -ATP酶是一种普遍存在的质膜结合酶， 连续函数对于正规函数是至关重要的， 几乎所有的动物细胞。 在心肌中，这种酶代表 洋地黄苷的细胞受体及其活性， 甲状腺激素（T3）的作用显着刺激。 在 本申请我们探索了生理学的分子基础 通过T3控制心肌Na+，K+-ATP酶表达，并计划 实现以下三大目标： 1. 验证心肌Na+，K+ -ATP酶的诱导 T3对亚基mRNA的作用是在转录水平上介导的。 a. 确定心肌Na+，K+-ATP酶转录增强的作用 基因在增强α 1，α 2和β 1 mRNA表达中的作用， T3 1)如果反应是转录的，那么使用最近的 所述的将表达质粒直接注射到 收缩的心室肌，确定DNA序列中的5 '- alpha 1的侧翼区域。α 2。和β 1基因， 在体内心肌组织中对T3的转录应答。 2)如果T3诱导Na+，K+ -ATP酶亚基增加的机制 mRNA是转录后的，然后测试序列 包含在α 1、α 2和β 1 RNA的3 '-非翻译区中 转录物介导T3诱导的mRNA稳定， 体内心肌。 2. 检验Na+，K+ -ATP酶基因表达受调控的假设 T3在异位同种移植心脏中的作用，因此与 收缩功 a. 检测Na+，K+ -ATP酶亚单位mRNA蛋白及α 1和α 2 异位心脏中的酶活性 B. 测定甲状腺激素缺乏和过量对Na+的影响， 异位心脏K ~+ -ATP酶的表达 3. 检验不同的mRNAbeta 1种类是不同的假设。 在心肌中由T3调节，并且它们表现出不同的 翻译效率。 a. 确定在细胞中表达的不同mRNAbeta 1种类， 心肌的低，欧盟，和甲状腺功能亢进症大鼠，并确定相对 每个mRNA β 1种类的翻译效率。 对Na+，K+ -ATP酶表达和功能调节的认识 与几种人类疾病的发病机制有关， 充血性心力衰竭、高血压、肥胖和甲状腺状态改变。

Na+, K+ -ATPase is a ubiquitous plasma membrane-bound enzyme whose continuous function is of critical importance tot he normal function of virtually all animal cells. In the myocardium the enzyme represents the cellular receptor for digitalis glycosides and its activity is significantly stimulated by the action of thyroid hormone (T3). In the present application we explore the molecular basis for the physiological control of myocardial Na+, K+-ATPase expression by T3, and plan to accomplish the following three major goals: 1. Test the hypothesis that the induction of myocardial Na+, K+ -ATPase subunit mRNAs by T3 is mediated at the transcriptional level. a. Determine the role of enhanced transcription of cardiac Na+, K+-ATPase genes in the enhancement of alpha1, alpha2, and beta1 mRNA expression by T3. 1) If the response is transcriptional, then employing the recently described method of direct injection of expression plasmids into the contracting ventricular myocardium, identify DNA sequences in the 5'- flanking regions of the alpha1. alpha2. and beta1 genes that mediate the transcriptional response to T3 in myocardial tissue in vivo. 2) If the mechanism of the T3-induced increase of Na+, K+ -ATPase subunit mRNAs is post-transcriptional then test the hypothesis that sequences contained in the 3'-untranslated region of alpha1, alpha2, and beta1 RNA transcripts mediate the T3-induced stabilization of the mRNAs in the myocardium in vivo. 2. Test the hypothesis that Na+, K+ -ATPase gene expression is regulated by T3 in the heterotopic isografted heart and is hence independent of contractile work. a. Examine Na+, K+ -ATPase subunit mRNA protein and alpha1 and alpha2 enzyme activity in the heterotopic heart. b. Determine the effect of thyroid hormone deficiency and excess on Na+, K+ -ATPase expression in the heterotopic heart. 3. Test the hypothesis that various mRNAbeta1 species are differentially regulated by T3 in the myocardium and that they exhibit distinct translational efficiencies. a. Identify the different mRNAbeta1 species that are expressed in the myocardium of hypo-, eu-, and hyperthyroid rats, and determine the relative translational efficiency of each mRNAbeta1 species. Understanding of the regulation of Na+, K+ -ATPase expression and function is of relevance to the pathogenesis of several human diseases including congestive heart failure, hypertension, obesity, and altered thyroid state.