PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical & Medicinal Chemistry, University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany.
Molecular Modeling Section (MMS), Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via Marzolo 5, Padua, Italy.
Biochem Pharmacol. 2020 Feb;172:113718. doi: 10.1016/j.bcp.2019.113718. Epub 2019 Nov 18.
A and A adenosine receptors (ARs) are closely related G protein-coupled receptor subtypes, which represent important (potential) drug targets. Despite their almost identical binding sites for adenosine, AARs are activated by low (nanomolar) adenosine concentrations, while AARs require micromolar concentrations. In the present study, we exchanged the extracellular loop 2 (ECL2) of the human AAR for that of the AAR. The resulting chimeric A(ECL2-A)AR was investigated in radioligand binding and cAMP accumulation assays in comparison to the wildtype AAR. While the ribose-modified adenosine analog N-ethylcarboxamidoadenosine (NECA) and its 2-substituted derivative CGS-21680 did not exhibit significant changes, adenosine showed dramatically reduced potency and affinity for the A(ECL2-A)AR mutant displaying similarly low potency as for the wt AAR. Supervised molecular dynamics simulation studies predicted a meta-binding site with high affinity for adenosine, but not for NECA, which may contribute to the observed effects.
A 和 A 腺苷受体 (ARs) 是密切相关的 G 蛋白偶联受体亚型，它们代表着重要的（潜在）药物靶点。尽管它们与腺苷的结合位点几乎相同，但 AARs 被低浓度（纳摩尔）的腺苷激活，而 AARs 需要微摩尔浓度。在本研究中，我们将人 AAR 的细胞外环 2（ECL2）交换为 AAR 的 ECL2。与野生型 AAR 相比，研究了所得嵌合 A（ECL2-A）AR 在放射性配体结合和 cAMP 积累测定中的情况。虽然核糖修饰的腺苷类似物 N-乙基羧酰胺腺苷（NECA）及其 2-取代衍生物 CGS-21680 没有显示出显著变化，但对于 A（ECL2-A）AR 突变体，腺苷的效力和亲和力显著降低，其效力与野生型 AAR 相似低。受监督的分子动力学模拟研究预测了一个具有高亲和力的元结合位点，可与腺苷结合，但不能与 NECA 结合，这可能有助于解释观察到的效果。
