Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive & Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA.
Purinergic Signal. 2009 Mar;5(1):39-50. doi: 10.1007/s11302-008-9113-3. Epub 2008 Jul 4.
As a continued effort to develop multivalent ligands to enhance the pharmacological effects of monomeric drugs, DITC-APEC, a chemically reactive nucleoside A(2A) adenosine receptor (AR) agonist, was employed to derivatize the surface of third-generation (G3) polyamidoamine (PAMAM) dendrimers. The resulting conjugates carried multiple copies of the agonist attached through a thiourea linkage and differed in the number of attachments and in the presence of a fluorophore or additional surface modification. Computer modeling studies suggested that these DITC-APEC-loaded dendrimers extended the overall diameter of the previously reported PAMAM-CGS21680 dendrimer derivatives (Kim et al., Bioconjugate Chem 2008 19:406-411) by ca. 20 A, potentially increasing the conformational flexibility of the appended ligands to achieve optimal geometry for efficient binding at A(2A) ARs. Increased affinity and selectivity in binding in comparison to the CGS21680 conjugate were envisioned, due to the presence of an extended linker, i.e., a dithioureylenephenyl functionality. In vitro radioligand competition experiments showed effective binding of these PAMAM-DITC-APEC dendrimer conjugates at the human A(2A) and A(3) ARs with submicromolar K (i) values and selectivity in comparison to the human A(1) AR. Furthermore, these nucleoside-loaded dendrimers exhibited an A(2A) AR-mediated inhibitory effect on ADP-induced aggregation of human platelets. The present study demonstrates the potential of applying the functionalized congener concept to engineer dendrimer-based multivalent ligands for G protein-coupled receptors.
作为开发多价配体以增强单体药物药理作用的持续努力，DITC-APEC，一种化学活性核苷 A2A 腺苷受体（AR）激动剂，被用于修饰第三代（G3）聚酰胺胺（PAMAM）树枝状大分子的表面。所得缀合物通过硫脲键连接携带多个激动剂拷贝，其连接数和存在荧光团或额外的表面修饰不同。计算机建模研究表明，这些负载 DITC-APEC 的树枝状大分子将先前报道的 PAMAM-CGS21680 树枝状大分子衍生物（Kim 等人，Bioconjugate Chem 2008 19:406-411）的整体直径延长了约 20Å，可能增加了附着配体的构象灵活性，以实现与 A2A AR 高效结合的最佳几何形状。由于存在扩展的连接子，即二硫代脲基苯官能团，预计与 CGS21680 缀合物相比，在结合方面具有更高的亲和力和选择性。体外放射性配体竞争实验表明，这些 PAMAM-DITC-APEC 树枝状大分子缀合物与人 A2A 和 A3 AR 有效结合，具有亚微摩尔 K(i)值和与人类 A1 AR 相比的选择性。此外，这些负载核苷的树枝状大分子表现出 A2A AR 介导的对 ADP 诱导的人血小板聚集的抑制作用。本研究证明了应用功能化同系物概念来设计用于 G 蛋白偶联受体的基于树枝状大分子的多价配体的潜力。
