Methionine Adenosyltransferase as a Therapeutic Target for Liver Fibrosis

肝纤维化是许多慢性肝病的结果，如饮酒、胆道 梗阻和肝炎。长期肝损伤会触发肝星状细胞(HSC)的激活，并导致 关键转录调控因子的调节。蛋氨酸腺苷转移酶(MAT)催化形成 的主要生物甲基供体，S-腺苷蛋氨酸(同)。有两个基因，MAT2A和MAT2B 已知与肝细胞增殖和恶性变性密切相关。在K99阶段， 我们发现Mat2a和MAT2B基因在体外和体内的HSC激活过程中都被诱导了，这 与垫子活动的减少和相同的水平有关。基因沉默研究表明，这些 基因对肝星状细胞的激活很重要。MAT2A基因在正常人群中转录调控， 过氧化物酶体增殖物激活受体(PPAR-γ)与MAT2a结合诱导HSCs分化 推动者。在HSC激活过程中，PPAR-γ及其受体的活性和表达均降低。 对MAT2A的监管被取消，导致MAT2A的表达增加。我们还表明， HSC激活与PPAR-β与MAT2A启动子结合增加和沉默相关 PPAR-β阻断活化的HSC中MAT2A的诱导。在这个奖项的Roo阶段，我们将使用 生物化学和分子生物学技术解决四个具体目标：1)评估MAT是否 肝纤维化大鼠体内HSC激活所需基因及其相互作用研究 肝纤维化HSC中的分子信号，2)检测已知的促纤维化因子，瘦素和 血小板衍生生长因子对大鼠肝星状细胞MAT基因表达的影响 MTA可以阻断这种反应，3)评价MAT基因在人HSC细胞系中的表达 在对促纤维化信号的激活过程中，瘦素和血小板衍生生长因子(PDGF)和 进一步了解从人肝分离的HSCs的这些机制，以及4)建立分子 人肝星状细胞MAT2A和MAT2B表达的调控机制我的长期计划是 在人类肝纤维化和肝硬变领域确立自己作为独立研究者的地位。

Hepatic fibrosis is an outcome of many chronic liver diseases such as alcohol consumption, biliary obstruction and hepatitis. Prolonged liver injury triggers activation of hepatic stellate cells (HSC) and leads to modulation of key transcriptional regulators. Methionine adenosyl transferases (MAT) catalyze the formation of the principle biological methyl donor, S-adenosylmethionine (SAMe). Two genes, MAT2A and MAT2B, are known to be strongly associated with liver cell proliferation and malignant degeneration. In the K99 phase, we showed that MAT2A and MAT2B genes are induced during HSC activation both in vitro and in vivo, This is associated with a decrease in MAT activity and SAMe levels. Gene silencing studies showed that these genes are important for HSC activation. The MAT2A gene is transcriptionally regulated in normal, differentiated HSCs by binding of peroxisome proliferator activated receptor (PPAR-gamma) to the MAT2A promoter. During HSC activation, there is decreased activity and expression of PPAR-gamma and its regulatory control over MAT2A is abolished, leading to increased expression of MAT2A. We also show that HSC activation is associated with increased binding of PPAR-beta to the MAT2A promoter and silencing PPAR-beta blocks MAT2A induction in activated HSCs. In the ROO phase ofthis award, we will use biochemical and molecular biology techniques to address four specific aims: 1) To evaluate whether MAT genes are required for in vivo HSC activation in rat models of liver fibrosis and study their interplay with molecular signals in HSCs from fibrotic liver, 2) to examine whether known pro-fibrogenic factors, leptin and platelet-derived growrth factor (PDGF) can influence MAT gene expression in rat HSCs and whether SAMe and MTA can block this response, 3) to evaluate the expression of MAT genes in human HSC cell lines during activation in response to pro-fibrogenic signals, leptin and platelet-derived growth factor (PDGF) and further'understand these mechanisms in HSCs isolated from human liver, and 4) to establish'molecular mechanisms for regulatory control of MAT2A and MAT2B expression in human HSCs. My long term plan is to establish myself as an independent Investigator in the field of human liver fibrosis and cirrhosis.