Myocyte specific regulation of metabolism and the response to biomechanical force

描述（由申请人提供）： 研究及相关其他项目信息6.心脏肥大是心力衰竭最常见的先兆，是心脏对各种外部刺激的反应，包括高血压、心脏瓣膜病和心肌梗死。在此过程中，脂肪酸氧化的平行损伤和葡萄糖利用的增加发生，主要由过氧化物酶体增殖物激活受体（PPAR）家族的转录因子调节。在心肌肥大的发展过程中，调节这种PPAR转录因子活性降低的机制目前尚不清楚。在本提案中，我们将首先确定心脏特异性肌肉环指-1（MuRF 1）泛素化PPAR复合物的机制，靶向其蛋白酶体依赖性降解。然后，将使用我们建立的MuRF 1-/-和MuRF 1心脏转基因小鼠系在体内证实这些发现。MuRF 1表达对PPAR调节的脂肪酸和葡萄糖氧化的作用将通过检测用放射性标记的脂肪酸和葡萄糖灌注的分离的工作心脏制备物的氧化代谢物来确定。在本研究的第二个目的中，我们将确定在心脏肥大期间调节心脏MuRF 1增加的信号通路，重点是NF-B，FOXO和FAK/MAPK信号通路。然后，我们将确定压力超负荷如何影响MuRF 1和过氧化物酶体增殖物激活受体-活性和心肌肥厚的定位，以阐明MuRF 1相互作用和调节过氧化物酶体增殖物激活受体-或过氧化物酶体增殖物激活受体-复合物的其他组分的机制。最后，我们将阐明特定的机制，压力超负荷诱导脂肪酸和葡萄糖氧化的变化，通过连接心肌细胞的机械拉伸增加MuRF 1。在具体的目标三，我们将展示的机制，通过它的上调MuRF 1转录水平，并通过拉伸诱导的易位MuRF 1从肌节到细胞质和细胞核的拉伸增加MuRF 1的活性。然后，我们将确定MuRF 1如何与核PPAR相互作用-在机械拉伸过程中，通过特定目标#1（MuRF 1对PPAR的泛素化-以及随后的蛋白酶体降解）和特定目标#2（拉伸如何通过NF-κ B和FOXO信号通路调节MuRF 1水平）中确定的机制来调节脂肪酸和葡萄糖氧化。这些研究将首次确定各种心脏病理的机械应力如何通过肌联蛋白相关的泛素连接酶MuRF 1导致脂肪酸和葡萄糖氧化的特征性变化。.

DESCRIPTION (provided by applicant): RESEARCH & RELATED Other Project Information 6. Project Summary/Abstract The development of cardiac hypertrophy, the most common precursor to heart failure, is a response of the heart to a wide range of extrinsic stimuli, including hypertension, valvular heart disease, and myocardial infarction. Parallel impairment in fatty acid oxidation and an increase in glucose utilization occur during this process, regulated primarily by the peroxisome proliferator-activated receptor (PPAR) family of transcription factors. The mechanism(s) that regulates this decrease in PPAR transcription factor activity during the development of cardiac hypertrophy is presently unknown. In this proposal, we will first identify the mechanism(s) by which the cardiac specific Muscle Ring Finger-1 (MuRF1) ubiquitinates the PPAR- complex, targeting its proteasome-dependent degradation. These findings will then be confirmed in vivo using our established MuRF1 -/- and MuRF1 cardiac transgenic mouse lines. The role of MuRF1 expression on PPAR-regulated fatty acid and glucose oxidation will then be determined by detecting oxidation metabolites from isolated working heart preparations perfused with radio-labeled fatty acid and glucose. In the second aim of this study, we will determine the signaling pathways which regulate increases in cardiac MuRF1 during cardiac hypertrophy, focusing on NF-B, FOXO, and FAK/MAPK signaling pathways. We will then determine how pressure overload affects MuRF1 and PPAR- activity and localization in cardiac hypertrophy, to elucidate the mechanisms by which MuRF1 interacts and regulates PPAR-, or other components of the PPAR- complex. Lastly, we will elucidate specific mechanisms by which pressure overload induces changes in fatty acid and glucose oxidation by linking the mechanical stretch of cardiomyocytes to increases in MuRF1. In specific aim three, we will demonstrate the mechanisms by which stretch increases MuRF1 activity by its up-regulation of MuRF1 levels transcriptionally and through the stretch-induced translocation of MuRF1 from the sarcomere into the cytoplasm and nucleus. We will then determine how MuRF1 interacts with nuclear PPAR- during mechanical stretch to regulate fatty acid and glucose oxidation through the mechanisms identified in specific aim #1 (MuRF1 ubiquitination of PPAR- and subsequent degradation by the proteasome) and specific aim #2 (how stretch regulates MuRF1 levels through NF- kB and FOXO signaling pathway). These studies will identify for the first time how mechanical stress from a variety of cardiac pathologies leads to characteristic changes in fatty acid and glucose oxidation through the titin-associated ubiquitin ligase MuRF1. .