Janowski B A, Grogan M J, Jones S A, Wisely G B, Kliewer S A, Corey E J, Mangelsdorf D J
Howard Hughes Medical Institute and Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75235-9050, USA.
Proc Natl Acad Sci U S A. 1999 Jan 5;96(1):266-71. doi: 10.1073/pnas.96.1.266.
LXRalpha and -beta are nuclear receptors that regulate the metabolism of several important lipids, including cholesterol and bile acids. Previously, we have proposed that LXRs regulate these pathways through their interaction with specific, naturally occurring oxysterols, including 22(R)-hydroxycholesterol, 24(S)-hydroxycholesterol, and 24(S),25-epoxycholesterol. Using a ligand binding assay that incorporates scintillation proximity technology to circumvent many of the problems associated with assaying extremely hydrophobic ligands, we now demonstrate that these oxysterols bind directly to LXRs at concentrations that occur in vivo. To characterize further the structural determinants required for potent LXR ligands, we synthesized and tested a series of related compounds for binding to LXRs and activation of transcription. These studies revealed that position-specific monooxidation of the sterol side chain is requisite for LXR high-affinity binding and activation. Enhanced binding and activation can also be achieved through the use of 24-oxo ligands that act as hydrogen bond acceptors in the side chain. In addition, introduction of an oxygen on the sterol B-ring results in a ligand with LXRalpha-subtype selectivity. These results support the hypothesis that naturally occurring oxysterols are physiological ligands for LXRs and show that a rational, structure-based approach can be used to design potent LXR ligands for pharmacologic use.
肝X受体α（LXRα）和β是核受体，可调节包括胆固醇和胆汁酸在内的几种重要脂质的代谢。此前，我们曾提出肝X受体通过与特定的天然氧甾醇相互作用来调节这些途径，这些氧甾醇包括22（R）-羟基胆固醇、24（S）-羟基胆固醇和24（S），25-环氧胆固醇。我们利用一种结合闪烁邻近技术的配体结合试验，以规避与检测极疏水配体相关的许多问题，现在证明这些氧甾醇在体内出现的浓度下直接与肝X受体结合。为了进一步表征强效肝X受体配体所需的结构决定因素，我们合成并测试了一系列相关化合物与肝X受体的结合及转录激活情况。这些研究表明，甾醇侧链的位置特异性单氧化是肝X受体高亲和力结合和激活所必需的。通过使用在侧链中充当氢键受体的24-氧代配体，也可以实现增强的结合和激活。此外，在甾醇B环上引入一个氧会产生一种具有肝X受体α亚型选择性的配体。这些结果支持了天然氧甾醇是肝X受体的生理配体这一假说，并表明可以采用基于结构的合理方法来设计用于药理学的强效肝X受体配体。
