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取决于甲状腺激素，特别是三碘甲醇（T3），对肌细胞特异性基因转录的作用，该基因转录介导Byt3结合到一个或多个核甲状腺激素受体（TR） 。单个TRS（TR Alpha I，TR Beta 1）及其转录后修饰在确定特定心肌细胞基因的转录方面的确切作用，包括共肌球蛋白重链（Alpha-MHC），仍然未知。病理和生理肥大条件下的心肌表现出许多T3反应性基因的表达改变，可以通过T3处理将其部分归一化。本应用将检验以下假设：肥大心脏中T3反应性受损是TRE同工型表达和磷酸化改变的结果，TRE同工型会影响核受体功能的所有方面活动。在前两个具体目标中，我们建议检验以下假设：肥厚性心脏表型是核的变化，TR同工型的含量变化的结果，并且单个tr alpha I和beta 1同工型是通过通过核隔离而差异化磷酸化的。纯化的成年大鼠心室肌细胞的蛋白质。我们的初步数据表明，非T3结合同工型TR Alpha 2具有抑制心脏α-MHC和SERCA2基因T3诱导转录的独特能力。重组腺病毒策略将用于特定的目标3中，以过表达培养的心肌细胞中的过表达TR Alpha 2蛋白，并且将通过新的测定法测量内源性α-MHC基因转录的结果变化，以量化alpha-MHC MHC杂核RNA。特定目标4将检验将假设在肥厚性心肌中激活的蛋白激酶C信号传导途径导致特异性TR同工型的磷酸化，这反过来介导了与甲状腺功能减退症的心脏表型的变化。我们将研究腺病毒介导的单个PKC Delta，Epsilon和Zeta同工酶对特定TR同工型磷酸化和α-MHC基因转录的影响。这些研究的完成将提供有关TR在介导肥厚表型中作用的新机械信息，并为T3在充血性心力衰竭的情况下提供了潜在的T3治疗效用的基本原理。