Protein O-GlcNAcylation and the regulation of cardiac function

描述（由申请人提供）：已明确糖尿病导致心力衰竭发生的风险显著增加，与其他风险因素无关;然而，对于所涉及的机制或最适当的治疗策略尚未达成共识。β-N-乙酰基-葡糖胺（O-GlcNAc）与丝氨酸和苏氨酸残基的O-连接连接是核和胞质蛋白质的高度动态翻译后修饰。这种新型的代谢调节信号通路正在成为关键生物过程的关键调节剂，并且O-GlcNAc酰化的持续增加与糖尿病相关的心血管并发症有关。相反，最近的研究表明，O-GlcNAc水平的急性激活可防止缺氧和缺血性应激。然而，尽管我们越来越认识到O-GlcNAc酰化在介导心肌细胞对急性和慢性应激的反应中的重要性，但关于O-GlcNAc酰化在调节正常心肌细胞功能中的基本作用知之甚少。因此，基于我们的初步研究，本提案的目标是测试以下假设：1）在正常心脏中，蛋白质O-GlcNAc化有助于调节心肌细胞基因表达、代谢和自噬，以及2）O-GlcNAc合成和降解的失调有助于糖尿病对心脏的不利影响，包括改变的基因表达、代谢功能障碍和受损的自噬反应。1）心肌细胞基因表达的调节以及这种调节如何响应2型糖尿病而改变，并鉴定对O-GlcNAc水平的急性和慢性变化敏感的O-GlcNAc修饰的心肌细胞蛋白; 2）心脏代谢的急性和慢性调节，并鉴定参与调节正常和2型糖尿病小鼠心脏中O-GlcNAc周转的代谢因子; 3）调节正常和2型糖尿病心肌细胞自噬和凋亡之间的平衡。本提案中概述的研究的成功完成将显著增强我们对这种新型代谢介导的信号通路在正常条件下对心肌细胞功能的影响以及蛋白质O-GlcNAc酰化的失调如何导致糖尿病对心脏的不良影响的理解。因此，本申请的结果将是关于蛋白质O-GlcNAc酰化对心肌生理学和病理生理学的影响的新机制见解，可能识别新的治疗靶点。 公共卫生相关性：尽管在心血管疾病的治疗方面已经取得了巨大的进步，但与非糖尿病患者相比，糖尿病患者发生心力衰竭和死于心脏病的风险仍然显著增加。该项目的总体目标是研究一种新发现的蛋白质修饰的变化如何影响心脏细胞（也称为心肌细胞）的功能，这种蛋白质修饰在很大程度上受到葡萄糖代谢的调节。该项目的结果将为糖尿病对心脏的有害影响提供新的见解，可能会发现治疗糖尿病心脏病患者的新方法。

DESCRIPTION (provided by applicant): It is well established that diabetes leads to a marked increased risk for the development of heart failure independent of other risk factors; however, there is no consensus as to the mechanisms involved or the most appropriate treatment strategies. The O-linked attachment of ss-N-acetyl- glucosamine (O-GlcNAc) to serine and threonine residues is a highly dynamic post-translational modification of nuclear and cytoplasmic proteins. This novel, metabolically regulated signaling pathway is emerging as a key regulator of critical biological processes and sustained increases in O-GlcNAcylation have been linked to the cardiovascular complications associated with diabetes. Conversely, recent studies have shown that acute activation of O-GlcNAc levels protects against hypoxic and ischemic stress. However, despite our increasing appreciation for the significance of O-GlcNAcylation in mediating the response of cardiomyocytes to acute and chronic stress, little is known regarding the fundamental role of O-GlcNAcylation in regulating normal cardiomyocyte function. Therefore, based on our preliminary studies the goal of this proposal is to test the following hypotheses: 1) In the normal heart protein O-GlcNAcylation contributes to regulation of cardiomyocyte gene expression, metabolism and autophagy and 2) Dysregulation in O-GlcNAc synthesis and degradation contribute to the adverse effects of diabetes on the heart including altered gene expression, metabolic dysfunction and impaired autophagic response. Thus the aims of this proposal are to determine the role of O-GlcNAcylation in: 1) The regulation of cardiomyocyte gene expression and e how this is altered in response to type-2 diabetes and identify O-GlcNAc modified cardiomyocyte proteins that are susceptible to acute and chronic changes in O-GlcNAc levels; 2) Acute and chronic regulation of cardiac metabolism and identify the metabolic factors involved in regulating O- GlcNAc turnover in hearts from normal and type-2 diabetic mice; 3) Mediating the balance between cardiomyocyte autophagy and apoptosis in normal and type-2 diabetic cardiomyocytes. The successful completion of the studies outlined in this proposal will significantly enhance our understanding of the impact of this novel metabolically mediated signaling pathway on the cardiomyocyte function under normal conditions as well as how dysregulation in protein O- GlcNAcylation contributes to adverse effects of diabetes on the heart. Consequently, the outcome of this application will be novel mechanistic insights regarding the influence of protein O-GlcNAcylation on myocardial physiology and pathophysiology, potentially identifying novel therapeutic targets. PUBLIC HEALTH RELEVANCE: Although the there have been tremendous advances in treatment of cardiovascular disease; diabetic patients remain at substantially increased risk in for developing heart failure and dying from cardiac disease than non-diabetic patients. The overall goal of this project is to examine how changes in a newly identified modification of proteins, which is regulated in large part by glucose metabolism, affects the function of heart cells also known as cardiomyocytes. The outcome of this project will provide new insights into the detrimental effects of diabetes on the heart, potentially identifying of new approaches for treating diabetic patients with heart disease.