THYROID HORMONE CONTROL OF CARDIAC SODIUM/POTASSIUM ATPASE EXPRESSION

Na+，K+-ATPase是一种普遍存在的质膜结合酶，其 连续函数对正则函数是至关重要的 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 受到甲状腺激素(T3)作用的显著刺激。在 目前，我们探讨了生理学的分子基础。 T3对心肌Na~+，K~+-ATPase表达的调控作用 实现以下三大目标： 1.验证心肌Na~+，K~+-ATPase的诱导 T3亚基的mRNAs是在转录水平上调节的。 A.确定心肌Na+，K+-ATPase转录增强的作用 促进α-1、α-2和β-1基因的表达 T3。 1)如果响应是转录的，则使用最近的 描述了将表达质粒直接注射到 收缩心肌，鉴定5‘-DNA序列 字母1的侧翼区域。字母2。和β1基因，这些基因介导了 在体心肌组织中对T3的转录反应。 2)如果T_3诱导Na~+，K~+-ATPase亚基增加的机制 MRNAs是转录后的，然后检验序列 包含在α1、α2和β1 RNA的3‘-非翻译区 转录本介导T3诱导的细胞内mRNAs的稳定 活体心肌。 2.验证Na+，K+-ATPase基因表达受调控的假说 在异位同种异体心脏中被T3所取代，因此不依赖于 收缩功。 A.检测Na+，K+-ATPase亚单位mRNA蛋白和α1、α2 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， K+-ATPase在异位心脏中的表达 3.检验各种mRNAbeta1物种存在差异的假设 在心肌中受T3调节，它们表现出不同的 翻译效率。 A.确定不同的mRNAbeta1物种在 低、高、甲亢大鼠心肌组织，并测定其相对分子质量。 每种mRNAbeta1的翻译效率。 对Na~+，K~+-ATPase表达和功能调控的认识 与几种人类疾病的发病机制有关，包括 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.