Determining the Role of GRK5 in Cardiac Fibroblasts

项目摘要 心力衰竭(HF)是一种临床综合征，在美国是导致死亡的主要原因。它是 以心脏不能泵出足够的血液来满足身体的新陈代谢需求为特征。 心脏的病理重塑是心衰的一个标志，心脏结构的这些大体变化 进一步使疾病永久化。心脏成纤维细胞是负责维持心脏功能的关键细胞类型 心脏的结构完整性。应激状态，如心肌梗塞，激活并诱导 静止的成纤维细胞转分化为合成的和收缩的肌成纤维细胞。虽然需要为 最初的愈合反应，持续的肌成纤维细胞激活导致细胞外基质的过度分泌 促进纤维化的蛋白质。此外，-平滑肌肌动蛋白的从头表达使这些 细胞收缩，扰乱协调的心肌细胞收缩能力。这些结构和机械上的变化 对心脏造成损害，损害心脏功能。G蛋白偶联受体(GPCRK)是非常重要的 通过抑制GPCR信号调节心血管动态平衡的介质。最近，非规范的 这些GRK的活性已被阐明。GRK5已被证明移位到细胞核在 心肌细胞，通过激活活化的T-核因子促进肥大基因转录 细胞(NFAT)和核因子B(NFB)。有趣的是，这些转录因子也参与了 成纤维细胞的激活和转分化。我们的初步数据有力地表明GRK5在 成纤维细胞的激活和转分化。长期的研究目标是阐明新的洞察力 探讨心衰和相关心脏重构的复杂性以及GRK5在这一过程中的作用。这个 具体目的如下：(1)探讨GRK5在成纤维细胞活化和转分化中的作用。 体外和(2)评价成纤维细胞GRK5在心肌梗死后心肌纤维化和心衰进展中的作用 活体内梗塞。具体目标1将使用GRK5的过度表达和敲除模型在 心脏成纤维细胞。这些成纤维细胞将被血管紧张素II(AngII)和转化生长因子处理 诱导分化。特殊目的2将利用成纤维细胞特异性GRK5基因敲除小鼠，将经历 模拟临床相关疾病的心肌梗死手术。实现这些具体目标将 对成纤维细胞生理学及GRK5‘S在成纤维细胞中的作用提供新的认识 激活/转分化。在公共卫生方面，靶向心脏成纤维细胞提供了一种新的 治疗心力衰竭和心脏纤维化的翻译法。

Project Summary Heart Failure (HF) is a clinical syndrome that is the leading cause of mortality in the United States. It is characterized by the heart’s inability to pump blood sufficiently to meet the metabolic demands of the body. Pathological remodeling of the heart is a hallmark of HF and these gross changes in the structure of the heart further perpetuates the disease. Cardiac fibroblasts are the critical cell type that is responsible for maintaining the structural integrity of the heart. Stress conditions, such as a myocardial infarction, activate and induce the transdifferentiation of quiescent fibroblasts into synthetic and contractile myofibroblasts. While required for the initial healing response, sustained myofibroblast activation leads to over-secretion of extracellular matrix proteins which promotes fibrosis. Furthermore, de novo expression of -smooth muscle actin allows these cells to contract, disrupting coordinated cardiomyocyte contractility. These structural and mechanical changes to the heart impair cardiac function. G protein-coupled receptor (GPCR) kinases (GRKs) are important mediators of cardiovascular homeostasis through dampening of GPCR signaling. Recently, non-canonical activities of these GRKs have been elucidated. GRK5 has been demonstrated to translocate to the nucleus in cardiomyocytes, promoting hypertrophic gene transcription through activation of nuclear factor of activated T- cells (NFAT) and nuclear factor B (NFB). Interestingly, these transcription factors are also involved in fibroblast activation and transdifferentiation. Our preliminary data strongly suggests a critical role for GRK5 in the activation and transdifferentiation of fibroblasts. The long-term research goal is to elucidate novel insight into the complexity of HF and associated cardiac remodeling as well as the role of GRK5 in this process. The specific aims are as follows: (1) To assess the role of GRK5 in fibroblast activation and transdifferentiation in vitro and (2) To assess the role of fibroblast GRK5 in cardiac fibrosis and HF progression after myocardial infarction in vivo. Specific aim 1 will be conducted using overexpression and knockout models of GRK5 in cardiac fibroblasts. These fibroblasts will be treated with Angiotensin II (AngII) and Transforming Growth Factor  to induce differentiation. Specific aim 2 will utilize fibroblast specific GRK5 knockout mice which will undergo myocardial infarction surgery to mimic a clinically relevant disease. Accomplishment of these specific aims will provide novel understanding of fibroblast physiology and GRK5’s role in fibroblast activation/transdifferentiation. In terms of public health, targeting of cardiac fibroblasts provides a novel translational approach for the treatment of HF and cardiac fibrosis.