Garcia Brandon L, Skaff D Andrew, Chatterjee Arindam, Hanning Anders, Walker John K, Wyckoff Gerald J, Geisbrecht Brian V
Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506.
Division of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, MO 64110.
J Immunol. 2017 May 1;198(9):3705-3718. doi: 10.4049/jimmunol.1601932. Epub 2017 Mar 15.
The complement system is an elegantly regulated biochemical cascade formed by the collective molecular recognition properties and proteolytic activities of more than two dozen membrane-bound or serum proteins. Complement plays diverse roles in human physiology, such as acting as a sentry against invading microorganisms, priming of the adaptive immune response, and removal of immune complexes. However, dysregulation of complement can serve as a trigger for a wide range of human diseases, which include autoimmune, inflammatory, and degenerative conditions. Despite several potential advantages of modulating complement with small-molecule inhibitors, small-molecule drugs are highly underrepresented in the current complement-directed therapeutics pipeline. In this study, we have employed a cheminformatics drug discovery approach based on the extensive structural and functional knowledge available for the central proteolytic fragment of the cascade, C3b. Using parallel in silico screening methodologies, we identified 45 small molecules that putatively bind C3b near ligand-guided functional hot spots. Surface plasmon resonance experiments resulted in the validation of seven dose-dependent C3b-binding compounds. Competition-based biochemical assays demonstrated the ability of several C3b-binding compounds to interfere with binding of the original C3b ligand that guided their discovery. In vitro assays of complement function identified a single complement inhibitory compound, termed cmp-5, and mechanistic studies of the cmp-5 inhibitory mode revealed it acts at the level of C5 activation. This study has led to the identification of a promising new class of C3b-binding small-molecule complement inhibitors and, to our knowledge, provides the first demonstration of cheminformatics-based, complement-directed drug discovery.
补体系统是一种由二十多种膜结合或血清蛋白的集体分子识别特性和蛋白水解活性形成的精妙调节的生化级联反应。补体在人体生理学中发挥着多种作用，例如作为抵御入侵微生物的哨兵、启动适应性免疫反应以及清除免疫复合物。然而，补体失调可引发多种人类疾病，包括自身免疫性、炎症性和退行性疾病。尽管用小分子抑制剂调节补体有几个潜在优势，但小分子药物在当前补体导向治疗药物研发管线中所占比例极低。在本研究中，我们基于对级联反应中心蛋白水解片段C3b的广泛结构和功能知识，采用了一种化学信息学药物发现方法。通过并行的计算机模拟筛选方法，我们鉴定出45种小分子，它们可能在配体引导的功能热点附近与C3b结合。表面等离子体共振实验验证了7种剂量依赖性C3b结合化合物。基于竞争的生化分析表明，几种C3b结合化合物能够干扰引导其发现的原始C3b配体的结合。补体功能的体外分析鉴定出一种单一的补体抑制化合物，称为cmp - 5，对cmp - 5抑制模式的机制研究表明它在C5激活水平起作用。这项研究导致鉴定出一类有前景的新型C3b结合小分子补体抑制剂，据我们所知，首次证明了基于化学信息学的补体导向药物发现。
