Regulation of BileAcid Synthesis by a alpha1-AT Peptide

描述（由申请人提供）：胆汁酸合成在维持胆固醇稳态中起着至关重要的作用，因为它负责从体内排出的超过50%的胆固醇的催化。高血浆胆固醇通常导致动脉粥样硬化，这是一种慢性炎症。在炎症反应中，α 1-抗胰蛋白酶（α 1-AT）的合成速率增加。α 1-抗胰蛋白酶是一种血清蛋白酶抑制剂，在肝脏中合成，其合成速率响应于炎症而增加。这种α 1-AT合成的增加引起肽的增加，如其羧基末端C-36肽，这是由蛋白酶切割α 1-AT引起的。由于血浆胆固醇水平、炎症和α 1-AT合成率之间的这种相关性，我们研究了C-36丝氨酸蛋白酶抑制剂肽对肝胆汁酸生物合成的影响，并表明C-36通过抑制胆固醇7 α-羟化酶/CYP 7A 1，是胆汁酸合成的一种强有力的特异性转录下调剂（7 α-羟化酶）和甾醇12 α-羟化酶/CYP 8B 1（12 α-羟化酶）启动子。这种抑制作用似乎是通过与甲胎蛋白转录因子（FTF）特异性相互作用介导的，FTF是胆汁酸生物合成中的一种正性转录因子。我们假设C-36肽特异性地与FTF相互作用，并且这种相互作用抑制7 α-和12 α-羟化酶启动子活性。提出实验来验证这一假设，并研究这两个分子之间的相互作用，FTF蛋白和α 1-AT衍生的C-36肽的分子机制。该提案的具体目标是：1.确定α 1-AT衍生的C-36肽对动物中胆汁酸生物合成的影响。2.确定α 1-AT衍生的C-36肽在培养细胞和动物中的亚细胞靶向。 3.α 1-AT衍生C-36肽调节7 α-和12 α-羟化酶基因转录的作用机制表征。 4.α 1-AT启动子的表征及其通过C-36肽的自我调节。 该项目的成功完成可能提供胆固醇稳态和炎症之间的重要联系。

DESCRIPTION (provided by applicant): Bile acid synthesis plays a crucial role in maintaining cholesterol homeostasis since it is responsible for the catabolism of more than 50% of the cholesterol excreted from the body. High plasma cholesterol often results in atherosclerosis, which is a form of chronic inflammation. In response to inflammation, the rate of synthesis of alpha1-antitrypsin (alpha1 -AT) increases. Alpha1-antitrypsin is a serum protease inhibitor that is synthesized in the liver and its rate of synthesis increases in response to inflammation. This increase in alpha1-AT synthesis gives rise to an increase in peptides, like its carboxy-terminal C-36 peptide, resulting from alpha1-AT cleavage by proteases. Because of this correlation between plasma cholesterol levels, inflammation and alpha1-AT rate of synthesis, we investigated the effect of the C-36 serpin peptide on hepatic bile acid biosynthesis and showed that C-36 is a powerful and specific transcriptional down-regulator of bile acid synthesis through inhibition of the cholesterol 7alpha-hydroxylase/CYP7A1 (7alpha-hydroxylase) and sterol12alpha-hydroxylase/CYP8B1 (12alpha-hydroxylase) promoters. This inhibition appears to be mediated by specifically interacting with alpha1-fetoprotein transcriptional factor (FTF), a positive transcriptional factor key in bile acid biosynthesis. We hypothesize that the C-36 peptide specifically interacts with FTF, and this interaction suppresses 7alpha- and 12alpha-hydroxylase promoter activities. Experiments are proposed to validate this hypothesis and to study the molecular mechanisms involved in the interaction between these two molecules, the FTF protein and the alpha1-AT-derived C-36 peptide. The specific aims of this proposal are: 1. Determine the effect of the a1-AT derived C-36 peptide on bile acid biosynthesis in animals. 2. Determine the subcellular targeting of the alpha1-AT derived C-36 peptide in both culture cells and animals. 3. Characterization of the mechanism of action involved in the regulation of 7alpha- and 12alpha-hydroxylase gene transcription by the alpha1-AT derived C-36 peptide. 4. Characterization of the alpha1-AT promoter and its self-regulation by the C-36 peptide. The successful completion of this project may provide an important link between cholesterol homeostasis and inflammation.