Regulation of Purine Metabolism by Protein Methyltransferase Smyd1

项目摘要 对慢性心力衰竭的病理生理学认识已从单纯的血流动力学紊乱转变为 一种更为复杂的综合征，包括神经激素、免疫、转录 和代谢功能。在代谢异常中，慢性心力衰竭与 尿酸水平升高（高尿酸血症），嘌呤代谢的最终产物。具体来说，研究表明， 显示血清尿酸水平与心血管疾病发病率和死亡率之间有很强的相关性， 高心血管风险人群，包括高血压、糖尿病和充血性心脏病患者 失败嘌呤代谢异常也是已知的，其通过黄嘌呤促进ROS的产生 氧化酶，在这一途径中的最后一种酶，这是越来越多的赞赏作为一个重要的贡献者， 慢性心力衰竭的症状以及疾病的进展。事实上， 心力衰竭患者中黄嘌呤氧化酶活性的增加（通过别嘌呤醇）已被证明可以抵消 在外周血流量中观察到嘌呤代谢的适应不良慢性上调与特定益处 和减少自由氧自由基的产生，这表明在治疗上靶向这一途径， 对心力衰竭患者有益。然而，驱动嘌呤这些变化的潜在机制 心肌细胞中的代谢以及最终在心力衰竭患者中的ROS和尿酸积累仍然存在。 大部分未知。 我们最近发现，甲基转移酶Smyd1b，它显示在细胞质和细胞外基质中的独特作用， 与代谢酶Adss（腺苷琥珀酸合成酶）相互作用，Adss是嘌呤的关键成分 心脏的新陈代谢。我们已经证实，Smyd1b和Adss之间的这种新型相互作用在 苯肾上腺素诱导的心肌细胞肥大性生长，并与甲基化增加有关 的Adss。此外，我们已经表明Smyd1增强了Adss的酶活性，因为它将IMP转化为 体外cAMP。尽管有这些有趣的结果，Smyd1如何调节Adss活性及其对嘌呤的影响， 代谢和尿酸产生是完全未知的。我的奖学金申请将利用一种独特的基因 动物模型和最先进的蛋白质组学技术，从概念上推进我们对心肌细胞的理解 生物学和生理学。具体来说，这项工作将确定Smyd1在调节Adss活性中的作用， 成人心脏，表征其影响ROS产生和尿酸积累的能力，并确定 Smyd1的过度表达是否可以抑制这些有害过程。我的实验将建立 基于我们先前的结果，并允许我阐明Smyd1b 调节心脏中的嘌呤代谢，以及在正常和肥大状态下如何调节这一过程 条件

PROJECT ABSTRACT The pathophysiological understanding of chronic heart failure has shifted from a mere hemodynamic disorder to a much more complex syndrome including changes and imbalances in neurohormonal, immune, transcriptional and metabolic functions. Among the metabolic abnormalities, chronic heart failure has been associated with increased levels of uric acid (hyperuricemia), the end product of purine metabolism. Specifically, studies have shown a strong association between serum uric acid levels and cardiovascular morbidity and mortality, especially among individuals with high cardiovascular risk, including those with hypertension, diabetes and congestive heart failure. Abnormal purine metabolism is also known for its contribution to ROS production through xanthine oxidase, the final enzyme in this pathway, which is increasingly appreciated as an important contributor to both symptoms of chronic heart failure as well as progression of the disease. Indeed, therapeutic inhibition of increased xanthine oxidase activity (via allopurinol) in heart failure patients has been shown to counteract maladaptive chronic upregulation of purine metabolism with specific benefits observed in peripheral blood flow and decreased free oxygen radical generation, suggesting that targeting this pathway therapeutically can be beneficial for heart failure patients. However, the underlying mechanisms which drive these changes in purine metabolism in the cardiomyocyte and ultimately ROS and uric acid accumulation in heart failure patients remain largely unknown. We recently discovered that the methyltransferase Smyd1b, which displays unique roles in both the cytosol and nucleus, interacts with the metabolic enzyme Adss (Adenylossuccinate Synthatase), a key component of purine metabolism in the heart. We have confirmed this novel interaction between Smyd1b and Adss is enhanced during phenylephrine-induced hypertrophic growth in the cardiomyocyte and is associated with increased methylation of Adss. In addition, we have shown that Smyd1 enhances the enzymatic activity of Adss as it converts IMP to sAMP in vitro. Despite these intriguing results, how Smyd1 regulates Adss activity and its effect on purine metabolism and uric acid production is completely unknown. My fellowship application will utilize a unique genetic animal model and state-of-the-art proteomic technologies to conceptually advance our understanding of myocyte biology and physiology. Specifically, this work will determine the role of Smyd1 in regulating Adss activity in the adult heart, characterize its ability to influence ROS production and uric acid accumulation, and determine whether overexpression of Smyd1 can inhibit these deleterious processes. Together, my experiments will build upon our previous results and allow me to elucidate the specific molecular mechanism by which Smyd1b regulates purine metabolism in the heart and how this process is regulated under normal and hypertrophic conditions.