Molecular biophysics of integrin activation by oxysterols and rational discovery of small-molecule modulators

项目总结/摘要 氧固醇是人体内形成的胆固醇的氧化代谢物， 生理和病理过程，如脂质稳态，炎症，先天和适应性 免疫、癌症和脑退化性疾病。具体来说，25-羟基胆固醇（25 HC）现在是 作为免疫系统的重要调节剂，由免疫细胞产生， 病毒感染和模式识别受体的激活。最近，我们发现了一种新的细胞机制， 25 HC介导的促炎反应调节。我们发现25 HC增强了 通过直接结合免疫细胞，增加免疫介质如TNF和IL-6的产生， αvβ3和α5β1整合素并激活整合素-黏着斑激酶途径。我们还发现 25 HC在一个新的结合位点（位点2）与整联蛋白结合，该位点不同于细胞外基质（ECM） 已知含有Arg-Gly-ASP（RGD）基序的配体结合。25 HC在位点2的结合产生显著的 整合素特异性决定环（SDL）的构象变化，靠近RGD结合位点。的 SDL中的这种构象变化对ECM配体结合的影响，以及25 HC- 介导的变构信号传导机制是整联蛋白活化的基础，尚不清楚。我们的假设是 25 HC与整合素在位点2的结合触发SDL的构象变化，导致有效结合 ECM配体产生先天性炎症反应的进一步修饰。我们还假设， 阻断25 HC-整联蛋白相互作用的分子调节剂将作为有效的抗炎治疗剂 防治各种炎症性疾病的战略。因此，本建议的中心目标是 阐明氧化固醇激活整联蛋白的分子机制，并鉴定选择性小分子 用于潜在治疗应用的靶向整合素位点2的调节剂。该项目的目标是 本论文的主要工作包括以下三个方面：1）阐明分子基础和构象动力学 2）检查整合素被非25 HC氧固醇的分子识别;和 3)鉴定和评估靶向整合素25 HC结合位点的小分子调节剂。我们将利用 最先进的计算技术，如分子对接，分子动力学模拟， 基于药效团的虚拟筛选，以描绘所涉及的结构基础和构象动力学 活化整联蛋白和鉴定整联蛋白位点2的高亲和力配体。此外，我们完善的 将采用体外和体内模型来验证我们的计算机研究结果并评价顶级配体。我们 多学科方法是创新的，拟议的研究将通过提供 氧固醇和整合素之间的相互作用的基本见解，最终在放大的 炎症反应。此外，该项目将鉴定一种或多种整合素-25HC的调节剂， 相互作用，从而推进免疫和感染性疾病的潜在抗炎疗法。

PROJECT SUMMARY/ABSTRACT Oxysterols are oxygenated metabolites of cholesterol formed in the human body and are involved in a plethora of physiological and pathological processes such as lipid homeostasis, inflammation, innate and adaptive immunity, cancer, and brain degenerative diseases. Specifically, 25-hydroxycholesterol (25HC) is now established as an important regulator of the immune system, and is produced by immune cells in response to viral infection and activation of pattern recognition receptors. Recently, we uncovered a novel cellular mechanism of 25HC-mediated regulation of the proinflammatory response. We showed that 25HC amplifies the activation of immune cells and increases the production of immune mediators such as TNF and IL-6, by directly binding to αvβ3 and α5β1 integrins and activating the integrin-focal adhesion kinase pathway. We also discovered that 25HC binds to integrins at a novel binding site (site 2), distinct from the site where the extracellular matrix (ECM) ligands containing an Arg-Gly-ASP (RGD) motif are known to bind. Binding of 25HC at site 2 produces significant conformational changes in the specificity-determining loop (SDL) of integrins, near the RGD-binding site. The effect of such conformational changes in the SDL on the binding of ECM ligands, as well as the basis of 25HC- mediated allosteric signaling mechanism underlying integrin activation, are not known. Our hypothesis is that binding of 25HC to integrins at site 2 triggers conformational changes in the SDL that result in efficient binding of ECM ligands producing further modification of innate inflammatory response. We also hypothesize that small molecule modulators blocking 25HC-integrin interaction would serve as an efficient anti-inflammatory therapeutic strategy to combat various inflammatory diseases. Accordingly, the central objective of this proposal is to elucidate the molecular mechanisms of integrin activation by oxysterols and to identify selective small molecule modulators targeting site 2 of integrins for potential therapeutic applications. The objective of this project will be accomplished by the following three specific aims: 1) elucidate the molecular basis and conformational dynamics of integrin activation by 25HC; 2) examine the molecular recognition of integrins by non-25HC oxysterols; and 3) identify and evaluate small-molecule modulators targeting the 25HC binding site of integrins. We will utilize state-of-the-art computational techniques such as molecular docking, molecular dynamics simulations, and pharmacophore-based virtual screening to delineate the structural basis and conformational dynamics involved in activation of integrins and to identify high affinity ligands for site 2 of integrins. In addition, our well-established in vitro and in vivo models will be employed to validate our in silico findings and evaluate top ligands. Our multidisciplinary approach is innovative and together, the proposed studies will have a broad impact by offering fundamental insights to the interplay between oxysterols and integrins that culminates in amplification of the inflammatory response. Furthermore, this project will identify one or more modulators of integrin-25HC interactions, thereby advancing potential anti-inflammatory therapies for immunologic and infectious diseases.