Metabolic Regulation of Myofibroblast Differentiation

特发性肺纤维化（IPF）是一种致死性疾病，中位生存期为3.5年， 在美国大约有89，000人。IPF没有已知的遗传原因，因此 确定疾病发病机理所需的新机制对于 开发新的治疗策略。IPF的定义特征是肺成纤维细胞分化为 肌成纤维细胞，其分泌过量的细胞外基质（胶原），并且是主要细胞 导致IPF特征性的结构重塑和肺功能损害。我们有 最近发现，肌成纤维细胞依赖于代谢重编程，其特征在于 糖酵解和代谢物通量通过从头丝氨酸，甘氨酸，一碳（SGOC）途径，以促进 用于胶原蛋白合成的甘氨酸生产。甘氨酸占胶原蛋白中所有氨基酸的三分之一 蛋白质和从葡萄糖从头合成甘氨酸是支持胶原蛋白合成所必需的， 肌成纤维细胞然而，这种代谢重编程的信号传导和转录调节因子， 成纤维细胞未知。这项建议的中心目标是确定代谢调节因子， 在肌成纤维细胞中重编程，并确定它们在肺纤维化中的作用。这一目标的前提是 阐明肌成纤维细胞的代谢调节机制将揭示新的策略， IPF严重未满足的治疗需求。我们的初步结果表明，TGF-β（转化生长因子） β因子，纤维化中的关键细胞因子），通过mTOR途径促进信号传导， ATF4（Activating Transcription Factor 4）ATF4是SGOC通路表达所必需的 肌成纤维细胞中的酶。我们进一步表明，SGOC通路激活不仅促进胶原蛋白， 生产的肌成纤维细胞，但改变了这些细胞的表观基因组，可能提供额外的方式， 用于治疗目的靶向肌成纤维细胞生物学。在目前的建议中，我们的目标是确定 调节肌成纤维细胞代谢，并确定改变代谢的机制， 有助于肌纤维母细胞表型。在具体目标1中，我们将确定转录因子 ATF4在体外和体内调节肺成纤维细胞中的SGOC和其他代谢途径。具体目标 2，我们将确定mTOR信号通路如何调节ATF4和其他转录调节因子。 体外和体内肺成纤维细胞的细胞代谢。在具体目标3中，我们将确定SGOC如何 途径激活有助于体外和体内肺成纤维细胞的表观遗传变化。我们提出的 实验将确定和充分表征纤维化所需的多个靶向途径。

Idiopathic Pulmonary Fibrosis (IPF) is a fatal disease which has a median survival of 3.5 years and affects approximately 89,000 people in the United States. There is no known genetic cause of IPF, and thus identification of new mechanisms required for disease pathogenesis is of critical importance for the development of novel treatment strategies. A defining feature of IPF is the differentiation of lung fibroblasts into myofibroblasts, which secrete excessive amounts of extracellular matrix (collagen) and are the primary cell responsible for the structural remodeling and impairment of lung function characteristic of IPF. We have recently discovered that myofibroblasts depend on metabolic reprogramming characterized by increased levels of glycolysis and metabolite flux through the de novo serine, glycine, one-carbon (SGOC) pathway to promote glycine production for collagen protein synthesis. Glycine constitutes one third of all amino acids in collagen protein and de novo synthesis of glycine from glucose is required to support collagen protein synthesis by myofibroblasts. However, the signaling and transcriptional regulators of this metabolic reprogramming in fibroblasts are unknown. The central goal of this proposal is to identify the regulators of metabolic reprogramming in myofibroblasts and to determine their role in lung fibrosis. The premise underlying this goal is that elucidating the mechanisms of metabolic regulation in myofibroblasts will unveil new strategies to fulfill the sorely unmet therapeutic need in IPF. Our preliminary results show that TGF-β (Transforming Growth Factor-β, the key cytokine involved in fibrosis), promotes signaling through the mTOR pathway, which activates ATF4 (activating transcription factor 4). ATF4 is required for the expression of SGOC pathway enzymes in myofibroblasts. We further show that SGOC pathway activation not only promotes collagen protein production by myofibroblasts, but alters the epigenome of these cells, possibly providing additional ways to target myofibroblast biology for therapeutic purposes. In the current proposal, we aim to determine the regulators of myofibroblast metabolism and determine the mechanisms by which altered metabolism contributes to the myofibroblastic phenotype. In Specific Aim 1 we will determine how the transcription factor ATF4 regulates the SGOC and other metabolic pathways in lung fibroblasts in vitro and in vivo. In Specific Aim 2, we will determine how the mTOR signaling pathway regulates ATF4 and other transcriptional regulators of cellular metabolism in lung fibroblasts in vitro and in vivo. In Specific Aim 3, we will determine how SGOC pathway activation contributes to epigenetic changes in lung fibroblasts in vitro and in vivo. Our proposed experiments will identify and fully characterize multiple targetable pathways required for fibrogenesis.