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: 6557274
• 负责人: Kaie Margareeta OJAMAA
• 金额: $ 35.13万
• 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/6557274
• 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由甲状腺激素，特别是三碘甲状腺原氨酸（T3）对肌细胞特异性基因转录的作用决定，该基因转录由T3与一种或多种甲状腺激素核受体（TR）结合介导。单个TR（TR α I，TR β 1）及其转录后修饰在决定特定心肌细胞基因（包括ω-肌球蛋白重链（α-MHC））转录中的确切作用仍然未知。在病理性和生理性肥大的条件下，心肌表现出许多T3反应基因的表达改变，这可以通过T3治疗部分恢复正常。本申请将检验这样的假设，即在肥大心脏中受损的T3反应性是TR同种型的改变的表达和磷酸化的结果，TR同种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。在前两个具体的目标，我们建议测试的假设，即肥厚的心脏表型是一个结果的变化，核，内容的TR亚型和个人TR α 1和β 1亚型的差异磷酸化的评估，通过分离纯化的成年大鼠心室肌细胞的核蛋白。我们的初步数据表明，非T3结合亚型，TR α 2，具有独特的能力，抑制T3诱导的心脏α-MHC和SERCA 2基因的转录。重组腺病毒策略将用于具体目标3中，以在培养的心肌细胞中过表达TR α 2蛋白，并且将通过定量α-MHC异源RNA的新测定来测量内源性α-MHC基因转录的所得变化。具体目标4将检验以下假设：在肥大心肌中激活的蛋白激酶C信号通路导致特定TR亚型的磷酸化，从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单个PKC delta、epsilon和zeta同工酶的过表达对特定TR亚型磷酸化和alpha-MHC基因转录的影响。这些研究的完成将提供关于TR在介导肥大表型中的作用的新机制信息，并为T3在充血性心力衰竭背景下的潜在治疗效用提供理论基础。