Faloon Patrick W., Dockendorff Chris, Youngsaye Willmen, Yu Miao, Nag Partha Pratim, Lewis Timothy A., Bennion Melissa, Paterson Conor, Lam Garrett, Dandapani Sivaraman, Munoz Benito, Perez Jose, Palmer Michelle, Nieland Thomas J.F., Krieger Monty, Schreiber Stuart L.
Chemical Biology Platform, Broad Institute
Biology Department, Massachusetts Institute of Technology
Scavenger receptor class B, type I (SR-BI) mediates selective uptake of cholesterol from high-density lipoprotein (HDL) particles, a poorly understood process that is distinct from endocytic uptake of lipoproteins, such as low-density lipoprotein (LDL). We set out to find small molecules that inhibit SR-BI function and could be used to characterize the mechanisms involved in HDL uptake. Using a cell-based DiI-HDL uptake assay, we performed a high-throughput screen (HTS) of the National Institutes of Health Molecular Libraries Probe Production Centers Network (NIH MLPCN) compound library. Of 319,533 compounds, 3,046 compounds (0.96%) were classified as inhibitors of DiI-HDL uptake. MLS001217863 (SID 49678600, CID 24761960) was identified in the primary HTS as an inhibitor. It had potent activity in the primary assay, a low hit rate in other MLPCN screens, and possessed structural properties suitable for analog synthesis. Structure activity relationship (SAR) studies were performed to improve potency and to minimize deleterious properties. These efforts generated a probe (CID 53377439/ML278), a low nanomolar inhibitor with improved potency and decreased toxicity liabilities. ML278 was tested for lipid efflux inhibition, modulation of HDL binding to SR-, and inhibition of endocytosis. ML278 functions by inhibiting both SR-BI-mediated lipid uptake and efflux of free cholesterol to HDL particles. As a tool compound, ML278 is superior to existing small-molecule inhibitors of SR-BI (e.g., BLT-1 and ITX-5061) and will be useful in elucidating how SR-BI mediates lipid transport. In addition, it could clarify the role of SR-BI in a number of biological processes where it plays a crucial role.
I型清道夫受体B类（SR-BI）介导从高密度脂蛋白（HDL）颗粒中选择性摄取胆固醇，这一过程尚不清楚，且不同于诸如低密度脂蛋白（LDL）等脂蛋白的内吞摄取。我们着手寻找抑制SR-BI功能且可用于表征HDL摄取所涉及机制的小分子。利用基于细胞的DiI-HDL摄取试验，我们对美国国立卫生研究院分子文库探针生产中心网络（NIH MLPCN）化合物文库进行了高通量筛选（HTS）。在319,533种化合物中，有3046种化合物（0.96%）被归类为DiI-HDL摄取抑制剂。MLS001217863（SID 49678600，CID 24761960）在初次HTS中被鉴定为抑制剂。它在初次试验中具有强效活性，在其他MLPCN筛选中的命中率较低，并且具有适合类似物合成的结构特性。进行了构效关系（SAR）研究以提高效力并使有害特性最小化。这些努力产生了一种探针（CID 53377439/ML278），一种低纳摩尔抑制剂，其效力得到提高且毒性负担降低。对ML278进行了脂质流出抑制、HDL与SR结合的调节以及内吞作用抑制的测试。ML278通过抑制SR-BI介导的脂质摄取以及游离胆固醇向HDL颗粒的流出发挥作用。作为一种工具化合物，ML278优于现有的SR-BI小分子抑制剂（例如BLT-1和ITX-5061），将有助于阐明SR-BI如何介导脂质转运。此外，它可以阐明SR-BI在许多发挥关键作用的生物学过程中的作用。
