Deficiency of the HDL receptor, SR-BI, in humans

人类 HDL 受体 SR-BI 缺乏

• 批准号: 7050146
• 负责人: Annabelle Rodriguez
• 金额: $ 39.91万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-04-01 至 2008-03-01
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7050146
• 关键词: cell surface receptors; cholesterol esters; clinical research; family genetics; genetic polymorphism; high density lipoproteins; human subject; hyperlipoproteinemia; low density lipoprotein; macrophage; nuclear magnetic resonance spectroscopy; protein structure function; receptor expression; scavenger receptor; transfection; western blottings

DESCRIPTION (provided by applicant): Most epidemiological studies have shown that high density lipoprotein cholesterol (HDL) levels are inversely correlated to cardiovascular disease (CVD). Nonetheless, a subset of patients with elevated HDL (hyperalphalipoproteinemia, HA) and elevated LDL cholesterol (hyperbetalipoproteinemia, HB) levels are at increased risk for CVD. This phenotype (HA/HB) with increased risk for CVD is similar to that described in the HDL receptor, scavenger receptor, class B, type I (SR-BI) knockout mouse. In humans, polymorphisms of the SR-BI gene have been associated with HDL and LDL cholesterol levels and body mass index, but to date, no functional defects in the receptor have been reported. We have identified the first case of an adult female heterozygote for SR-BI deficiency; this was based on finding markedly lower SR-BI RNA and protein and decreased SR-BI function in the proband's macrophages, and a novel splice variant within the region of the gene that encodes the functional extracellular loop. We also found decreased SR-BI RNA expression in macrophages cultured from the proband's mother, sister, and an unrelated adult female with HA/HB. We hypothesize that mutations/polymorphisms in the SR-BI gene strongly correlate with decreased SR-BI function and are associated with HA/HB and increased risk for atherosclerosis. The aims of this proposal are 1) to thoroughly characterize the lipoproteins and the fractional clearance of HDL-cholesteryl ester in a cohort of 40 adult subjects with HA/HB; 2) to assess SR-BI expression and function in monocyte-derived macrophages isolated from HA/HB and control subjects. The human macrophage model for SR-BI expression and function is expected to act as a surrogate for hepatic SR-BI, given the limitations in obtaining liver tissue from these donors. SR-BI knockout mice will be used to correlate changes in macrophage SR-BI expression and function with hepatic SR-BI function and to corroborate our findings in human SR-BI deficient macrophages; and 3) to identify polymorphisms and/or mutations of the SR-BI gene in HA/HB and control subjects. Transient transfection experiments with COS-7 cells will also verify the significance of SR-BI variants. This work will provide new insights into the role of SR-BI in human dyslipidemia and atherosclerosis and challenge the concept that desirable HDL cholesterol levels are always cardioprotective.

描述（申请人提供）：大多数流行病学研究表明，高密度脂蛋白胆固醇（HDL）水平与心血管疾病（CVD）呈负相关。尽管如此，一部分HDL（高β脂蛋白血症，HA）和LDL胆固醇（高β脂蛋白血症，HB）水平升高的患者发生CVD的风险增加。这种CVD风险增加的表型（HA/HB）与HDL受体、清道夫受体、B类、I型（SR-BI）敲除小鼠中描述的表型相似。在人类中，SR-BI基因的多态性与HDL和LDL胆固醇水平和体重指数相关，但迄今为止，尚未报道该受体的功能缺陷。我们已经确定了第一例成年女性SR-BI缺陷杂合子;这是基于发现先证者巨噬细胞中SR-BI RNA和蛋白质显著降低，SR-BI功能降低，以及编码功能性细胞外环的基因区域内的新型剪接变体。我们还发现先证者的母亲、姐妹和一名无血缘关系的HA/HB成年女性培养的巨噬细胞中SR-BI RNA表达降低。我们假设SR-BI基因的突变/多态性与SR-BI功能下降密切相关，并与HA/HB和动脉粥样硬化风险增加相关。本提案的目的是：1）全面表征40例HA/HB成人受试者队列中的脂蛋白和HDL-胆固醇酯的清除率; 2）评估从HA/HB和对照受试者中分离的单核细胞源性巨噬细胞中的SR-BI表达和功能。考虑到从这些供体获得肝组织的局限性，预期SR-BI表达和功能的人巨噬细胞模型可作为肝SR-BI的替代物。SR-BI敲除小鼠将用于将巨噬细胞SR-BI表达和功能的变化与肝SR-BI功能相关联，并证实我们在人SR-BI缺陷巨噬细胞中的发现;和3）鉴定HA/HB和对照受试者中SR-BI基因的多态性和/或突变。COS-7细胞的瞬时转染实验也将验证SR-BI变体的意义。这项工作将为SR-BI在人类血脂异常和动脉粥样硬化中的作用提供新的见解，并挑战理想的HDL胆固醇水平始终具有心脏保护作用的概念。