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，是美国死亡的主要原因。是 以心脏不能充分泵送血液以满足身体的代谢需求为特征。 心脏的病理性重塑是HF的标志，心脏结构的这些大体变化 进一步延续疾病。心脏成纤维细胞是负责维持心脏功能的关键细胞类型。 心脏结构的完整性应激条件，如心肌梗死，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 初始愈合反应，持续的肌成纤维细胞活化导致细胞外基质的过度分泌 促进纤维化的蛋白质。此外，β-平滑肌肌动蛋白的从头表达使得这些细胞能够在细胞内表达。 细胞收缩，破坏协调的心肌细胞收缩力。这些结构和机械变化 会损害心脏功能G蛋白偶联受体（GPCR）激酶（GRKs）是重要的 通过抑制GPCR信号传导调节心血管稳态。最近，非典型 这些GRKs的活性已经阐明。GRK 5已经被证明在细胞核中转位。 心肌细胞，通过激活活化的T细胞核因子促进肥大基因转录， 细胞（NFAT）和核因子B（NF κ B B）。有趣的是，这些转录因子也参与了 成纤维细胞活化和转分化。我们的初步数据有力地表明GRK 5在以下方面的关键作用： 成纤维细胞的活化和转分化。长期的研究目标是阐明新的见解 HF的复杂性和相关的心脏重塑以及GRK 5在这一过程中的作用。的 具体目的如下：（1）评估GRK 5在成纤维细胞活化和转分化中的作用， （2）评估成纤维细胞GRK 5在心肌梗死后心脏纤维化和HF进展中的作用。 体内梗死。具体目标1将使用GRK 5的过表达和敲除模型在小鼠中进行。 心脏成纤维细胞这些成纤维细胞将用血管紧张素II（AngII）和转化生长因子（TGF）处理。 诱导分化。具体目标2将利用成纤维细胞特异性GRK 5敲除小鼠， 心肌梗死手术模拟临床相关疾病。实现这些具体目标将 为成纤维细胞生理学和GRK 5在成纤维细胞中的作用提供了新的认识 活化/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 用于治疗HF和心脏纤维化的转化方法。

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.