Thyroid Hormone Receptor Function in Cardiac Hypertrophy

甲状腺激素受体在心脏肥大中的功能

• 批准号: 6879120
• 负责人: Kaie Margareeta OJAMAA
• 金额: $ 36.18万
• 依托单位: FEINSTEIN INSTITUTE FOR MEDICAL RESEARCH
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-04-28 至 2007-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6879120
• 关键词: DNA binding protein; calcium transporting ATPase; cardiac myocytes; congestive heart failure; genetic transcription; heart contraction; hypothyroidism; isozymes; laboratory rat; mitogen activated protein kinase; myosins; nuclear receptors; phosphorylation; posttranslational modifications; protein isoforms; protein kinase C; tissue /cell culture; transfection; triiodothyronine; two dimensional gel electrophoresis; ventricular hypertrophy; western blottings

DESCRIPTION (provided by applicant): Many aspects of cardiac contractile function are determined by the action of thyroid hormones, specifically triiodothyronine (T3), on myocyte-specific gene transcription that is mediated byT3 binding to one or more nuclear thyroid hormone receptors (TR). The precise role of the individual TRs (TR alpha I,TR beta 1) and their post-transcriptional modification in determining transcription of specific cardiomyocyte genes, including co-myosin heavy chain (alpha-MHC), remains unknown. The myocardium in conditions of pathologic and physiologic hypertrophy exhibits altered expression of many T3-responsive genes, which can be partially normalized by T3 treatment. The present application will test the hypothesis that impaired T3 responsiveness in the hypertrophied heart is the result of altered expression and phosphorylation of TR isoforms which affect all aspects of nuclear receptor function including DNA binding, dimerization, interaction with co-regulators, ligand affinity and transcriptional activity. In the first two specific aims, we propose to test the hypothesis that the hypertrophic cardiac phenotype is a result of changes in nuclear, content of TR isoforms and that the individual TR alpha I and beta 1 isoforms are differentially phosphorylated as assessed by isolation of nuclear proteins from purified adult rat ventricular myocytes. Our preliminary data suggest that the non-T3 binding isoform, TR alpha 2,has the unique ability to repress T3-inducible transcription of cardiac alpha-MHC and SERCA2 genes. A recombinant adenovirus strategy will be used in specific aim 3 to overexpress TR alpha 2 protein in cultured cardiomyocytes,and the resulting changes in transcription of the endogenous alpha-MHC gene will be measured by a novel assay to quantify alpha-MHC heteronuclear RNA. Specific aim 4 will test will the hypothesis that protein kinase C signaling pathways that are activated in the hypertrophic myocardium result in phosphorylation of specific TR isoforms, which in turn mediate changes in cardiac phenotype remarkably similar to that of the hypothyroid heart. We will study the effects of adenoviral-mediated overexpression of individual PKC delta, epsilon, and zeta isoenzymes on specific TR isoform phosphorylation and alpha-MHC gene transcription. Completion of these studies will provide novel mechanistic information regarding the role of TRs in mediating the hypertrophic phenotype, and provide the rationale for the potential therapeutic utility of T3 in the setting of congestive heart failure.

描述（由申请人提供）：心脏收缩功能的许多方面是由甲状腺激素，特别是三碘甲状腺原氨酸（T3）对心肌细胞特异性基因转录的作用决定的，而心肌细胞特异性基因转录是由T3与一种或多种核甲状腺激素受体（TR）结合介导的。各个 TR（TR α I、TR β 1）及其转录后修饰在确定特定心肌细胞基因（包括共肌球蛋白重链 (α-MHC)）转录中的确切作用仍不清楚。病理性和生理性肥大的心肌表现出许多 T3 反应基因的表达改变，这些基因可以通过 T3 治疗部分正常化。本申请将检验以下假设：肥大心脏中 T3 反应性受损是 TR 亚型表达和磷酸化改变的结果，TR 亚型影响核受体功能的所有方面，包括 DNA 结合、二聚化、与共调节因子的相互作用、配体亲和力和转录活性。在前两个具体目标中，我们建议检验以下假设：肥厚的心脏表型是核内 TR 异构体含量变化的结果，并且通过从纯化的成年大鼠心室肌细胞中分离核蛋白来评估，各个 TR α I 和 β 1 异构体被差异磷酸化。我们的初步数据表明，非 T3 结合亚型 TR α 2 具有抑制 T3 诱导的心脏 α-MHC 和 SERCA2 基因转录的独特能力。具体目标 3 将使用重组腺病毒策略在培养的心肌细胞中过表达 TR α 2 蛋白，并通过定量 α-MHC 异核 RNA 的新方法来测量内源 α-MHC 基因转录的变化。具体目标 4 将检验以下假设：肥厚心肌中激活的蛋白激酶 C 信号通路会导致特定 TR 亚型的磷酸化，进而介导与甲状腺功能减退心脏非常相似的心脏表型变化。我们将研究腺病毒介导的个体 PKC δ、ε 和 zeta 同工酶的过度表达对特定 TR 亚型磷酸化和 α-MHC 基因转录的影响。这些研究的完成将提供有关 TR 在介导肥厚表型中的作用的新机制信息，并为 T3 在充血性心力衰竭中的潜在治疗效用提供理论依据。