Functional studies of PGRMC1 in cholesterol homeostasis

描述（由申请人提供）：胆固醇是细胞膜的基本成分，在调节其结构特性方面起着至关重要的作用。此外，胆固醇是胆汁酸、类固醇和氧固醇等重要化合物的前体。虽然是必需的，但血清胆固醇升高与心脏病和动脉粥样硬化有关。值得注意的是，超过3800万美国成年人的血液总胆固醇e 240 mg/dL，这被认为是心血管疾病的高风险。出于这些原因，了解如何保持低但足够的血清胆固醇水平对人类健康至关重要。胆固醇的供应受多种因素控制：膳食摄入、合成、储存、代谢和排泄。细胞色素P450单加氧酶通过其在胆固醇、氧化固醇、胆汁酸和类固醇合成中的功能在调节胆固醇稳态中起关键作用。最近，我们确定了血红素结合蛋白PGRMC 1作为结合伴侣和细胞色素P450 Cyp 51 A1在胆固醇合成的正调节剂。使用转染的培养细胞，我们发现PGRMC 1与一组不同的P450酶紧密结合，包括Cyp 3A 4，Cyp 21 A2和Cyp 7A 1，它们分别在药物代谢，类固醇和胆汁酸合成中起作用。基于这些发现，我们假设PGRMC 1是动物胆固醇稳态的重要调节因子。作为第一步，我们提出了以下目的，以测试是否需要PGRMC 1的胆固醇稳态在小鼠肝脏通过Cyp 51 A1和其他P450酶的调节。AIM 1.研究PGRMC 1在肝脏胆固醇合成中的作用。AIM 2.从小鼠肝脏中鉴定PGRMC 1相互作用蛋白。这些实验是我们了解PGRMC 1在系统胆固醇稳态中功能的长期目标的第一步。细胞色素P450酶在调节血清胆固醇中发挥的核心作用表明，对PGRMC 1功能的清楚理解将导致降低血清胆固醇和预防心脏病的治疗策略的改进。公共卫生相关性：超过3800万美国成年人的血液总胆固醇为240 mg/dL，这被认为是心血管疾病的高风险。在这个项目中，我们将确定新的细胞色素P450调节剂PGRMC 1在系统胆固醇稳态中的功能。细胞色素P450酶在调节血清胆固醇中发挥的核心作用表明，对PGRMC 1功能的清楚理解将导致降低血清胆固醇和预防心脏病的治疗策略的改进。

DESCRIPTION (provided by applicant): Cholesterol is a fundamental component of cellular membranes and plays a crucial role in regulating their structural properties. In addition, cholesterol serves as a precursor for important compounds, such as bile acids, steroids, and oxysterols. Although essential, elevated serum cholesterol is associated with heart disease and atherosclerosis. Notably, more than 38 million American adults have a total blood cholesterol e 240 mg/dL, which is considered high risk for cardiovascular disease. For these reasons, understanding how to maintain low, but sufficient, serum cholesterol levels is critical for human health. Cholesterol supply is controlled by multiple factors: dietary intake, synthesis, storage, catabolism and excretion. Cytochrome P450 monoxygenases play a key role in regulating cholesterol homeostasis through their functions in cholesterol, oxysterol, bile acid and steroid synthesis. Recently, we identified the heme-binding protein PGRMC1 as a binding partner and positive regulator of the cytochrome P450 Cyp51A1 in cholesterol synthesis. Using transfected cultured cells, we found that PGRMC1 binds tightly to a diverse set of P450 enzymes, including Cyp3A4, Cyp21A2 and Cyp7A1 that function in drug metabolism, steroid and bile acid synthesis, respectively. Based on these findings, we hypothesize that PGRMC1 is an important regulator of cholesterol homeostasis in animals. As a first step, we propose the following aims to test whether PGRMC1 is required for cholesterol homeostasis in mouse liver through regulation of Cyp51A1 and other P450 enzymes. AIM 1. To determine the function of PGRMC1 in liver cholesterol synthesis. AIM 2. To identify PGRMC1-interacting proteins from mouse liver. These experiments are a first step toward our long-term goal of understanding the function of PGRMC1 in systemic cholesterol homeostasis. The central role that cytochrome P450 enzymes play in regulation of serum cholesterol suggests that a clear understanding of PGRMC1 function will lead to improved therapeutic strategies for lowering serum cholesterol and preventing heart disease. PUBLIC HEALTH RELEVANCE: More than 38 million American adults have a total blood cholesterol e 240 mg/dL, which is considered high risk for cardiovascular disease. In this project, we will determine the function of the novel cytochrome P450 regulator PGRMC1 in systemic cholesterol homeostasis. The central role that cytochrome P450 enzymes play in regulation of serum cholesterol suggests that a clear understanding of PGRMC1 function will lead to improved therapeutic strategies for lowering serum cholesterol and preventing heart disease.