Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037.
Department of Biological Sciences, Chemistry, and Bioengineering, Lehigh University, Bethlehem, PA 18015.
Proc Natl Acad Sci U S A. 2020 Aug 4;117(31):18504-18510. doi: 10.1073/pnas.2007699117. Epub 2020 Jul 22.
The human blood protein vitronectin (Vn) is a major component of the abnormal deposits associated with age-related macular degeneration, Alzheimer's disease, and many other age-related disorders. Its accumulation with lipids and hydroxyapatite (HAP) has been demonstrated, but the precise mechanism for deposit formation remains unknown. Using a combination of solution and solid-state NMR experiments, cosedimentation assays, differential scanning fluorimetry (DSF), and binding energy calculations, we demonstrate that Vn is capable of binding both soluble ionic calcium and crystalline HAP, with high affinity and chemical specificity. Calcium ions bind preferentially at an external site, at the top of the hemopexin-like (HX) domain, with a group of four Asp carboxylate groups. The same external site is also implicated in HAP binding. Moreover, Vn acquires thermal stability upon association with either calcium ions or crystalline HAP. The data point to a mechanism whereby Vn plays an active role in orchestrating calcified deposit formation. They provide a platform for understanding the pathogenesis of macular degeneration and other related degenerative disorders, and the normal functions of Vn, especially those related to bone resorption.
人血蛋白 vitronectin（Vn）是与年龄相关的黄斑变性、阿尔茨海默病和许多其他与年龄相关的疾病相关的异常沉积物的主要成分。已经证明其与脂质和羟基磷灰石（HAP）的积累，但沉积物形成的确切机制仍不清楚。使用溶液和固态 NMR 实验、共沉淀测定、差示扫描荧光法（DSF）和结合能计算的组合，我们证明 Vn 能够结合可溶性离子钙和结晶 HAP，具有高亲和力和化学特异性。钙离子优先结合在外部位点，在类血蓝蛋白（HX）结构域的顶部，与一组四个 Asp 羧酸盐结合。同一外部位点也与 HAP 结合有关。此外，Vn 在与钙离子或结晶 HAP 结合时获得热稳定性。这些数据表明了一种机制，即 Vn 在协调钙化沉积物形成中发挥积极作用。它们为理解黄斑变性和其他相关退行性疾病的发病机制以及 Vn 的正常功能，特别是与骨吸收相关的功能提供了一个平台。
