The role of RNA-binding protein Lin28a in hypertrophic cardiomyopathy

摘要 病理性心肌肥厚是心力衰竭和心脏性猝死的主要危险因素， 在美国和世界范围内的死亡原因。尽管我们对分子的理解取得了实质性的进展 而这一有害过程的生理基础，仍有许多有待研究。心脏肥厚反应 对病理性刺激是一个复杂的生物过程，涉及转录、转录后和 心脏基因组的表观遗传调控。核糖核酸结合蛋白(RNAbindingProtein，RBPs)是构成分子的主要分子层 组织转录本的建立所必需的调节。限制性商业惯例在这两个过程中发挥着基础性的作用 通过调节RNA的生物发生、结构、稳定性、运输和细胞定位来调控发育和疾病。 其中，Lin28a被发现控制着许多发育和细胞过程，包括多能性， 肿瘤发生、组织修复和新陈代谢通过其在增加信使核糖核酸的稳定性和/或翻译效率方面的作用。 尽管先前的研究表明转录因子和信号分子与病理性心脏疾病有关 对于肥大，限制性商业惯例在这一过程中的作用鲜有人关注。通过基因表达分析，我们 发现Lin28a在病理性心肌肥厚早期呈现动态表达。心脏 LIN28a特异性缺失钝性压力超负荷诱导的心肌肥厚。同样，在体外模型中 在心肌肥厚中，敲除Lin28a可减弱去甲肾上腺素(NE)诱导的心肌肥厚，而 仅过表达Lin28a就足以增强心肌细胞的糖酵解，并刺激随后的 心肌细胞肥大生长。从机制上讲，我们发现Lin28a直接与Pck 2的mRNA结合， 编码线粒体磷酸烯醇式丙酮酸羧激酶，并对其转录本产生积极影响 水平。此外，对Pck-2表达的调控可影响血管内皮细胞的代谢和肥大表型。 操作Lin28a表达式。基于这些观察结果，我们假设林28a及其下游 介体蛋白Pck 2通过其调节作用成为病理性心肌肥厚的重要调节因子 心肌细胞代谢。这项建议的目的将利用我们一系列独特的工具、试剂和动物 阐明病理性心脏病发生发展所必需的分子和细胞途径的模型 肥大。在这样做的过程中，我们将解决一个中心问题，即代谢是否以及如何转变为 心肌肥厚时糖酵解程度较高的表型可能有助于结构重塑。

Abstract Pathological cardiac hypertrophy is a major risk factor of heart failure and sudden cardiac death, the leading cause of mortality in the US and worldwide. Despite substantial progress in our understanding of the molecular and physiological basis of this detrimental process, much remains to be learned. Cardiac hypertrophic response to pathological stimuli is a complex biological process that involves transcriptional, posttranscriptional and epigenetic regulation of the cardiac genome. RNA-binding protein (RBPs) constitutes a major layer of molecular regulation integral to the establishment of tissue transcriptomes. The RBPs play fundamental roles during both development and disease by regulating RNA biogenesis, structure, stability, transport and cellular localization. Among them, Lin28a was found to control many developmental and cellular processes including pluripotency, oncogenesis, tissue repair and metabolism via its role in increasing mRNA stability and/or translation efficiency. Although previous studies have implicated transcriptional factors and signaling molecules in pathological cardiac hypertrophy, the role of RBPs in this process received little attention. Through gene expression analysis, we found that Lin28a exhibited a dynamic expression during early stage of pathological cardiac hypertrophy. Cardiac specific deletion of Lin28a blunted pressure overload-induced cardiac hypertrophy. Likewise, in an in vitro model of cardiac hypertrophy, knockdown of Lin28a attenuated norepinephrine (NE)-induced hypertrophy, while overexpressing Lin28a alone was sufficient to enhance cardiomyocyte glycolysis and stimulate subsequent cardiomyocyte hypertrophic growth. Mechanistically, we found that Lin28a directly bound to the mRNA of Pck2, which encodes the mitochondrial phosphoenolpyruvate carboxykinase, and positively impacted its transcript level. Additionally, manipulation of Pck2 expression phenocopied the metabolic and hypertrophic phenotypes of manipulating Lin28a expression. Based on these observations, we hypothesize that Lin28a and its downstream mediator Pck2 act as crucial regulators of pathological cardiac hypertrophy via their roles in regulating cardiomyocyte metabolism. The aim of this proposal will leverage our series of unique tools, reagents, and animal models to elucidate the molecular and cellular pathways essential for the development of pathological cardiac hypertrophy. In doing so, we will address a central question concerning whether and how a metabolic switch to a more glycolytic phenotype during cardiac hypertrophy could contribute to the structural remodeling.