Furman Cheryse A, Roof Rebecca A, Moritz Amy E, Miller Brittney N, Doyle Trevor B, Free R Benjamin, Banala Ashwini K, Paul Noel M, Kumar Vivek, Sibley Christopher D, Newman Amy Hauck, Sibley David R
Molecular Neuropharmacology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA.
Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA.
Eur Neuropsychopharmacol. 2015 Sep;25(9):1448-61. doi: 10.1016/j.euroneuro.2014.11.013. Epub 2014 Nov 29.
The D3 dopamine receptor represents an important target in drug addiction in that reducing receptor activity may attenuate the self-administration of drugs and/or disrupt drug or cue-induced relapse. Medicinal chemistry efforts have led to the development of D3 preferring antagonists and partial agonists that are >100-fold selective vs. the closely related D2 receptor, as best exemplified by extended-length 4-phenylpiperazine derivatives. Based on the D3 receptor crystal structure, these molecules are known to dock to two sites on the receptor where the 4-phenylpiperazine moiety binds to the orthosteric site and an extended aryl amide moiety docks to a secondary binding pocket. The bivalent nature of the receptor binding of these compounds is believed to contribute to their D3 selectivity. In this study, we examined if such compounds might also be "bitopic" such that their aryl amide moieties act as allosteric modulators to further enhance the affinities of the full-length molecules for the receptor. First, we deconstructed several extended-length D3-selective ligands into fragments, termed "synthons", representing either orthosteric or secondary aryl amide pharmacophores and investigated their effects on D3 receptor binding and function. The orthosteric synthons were found to inhibit radioligand binding and to antagonize dopamine activation of the D3 receptor, albeit with lower affinities than the full-length compounds. Notably, the aryl amide-based synthons had no effect on the affinities or potencies of the orthosteric synthons, nor did they have any effect on receptor activation by dopamine. Additionally, pharmacological investigation of the full-length D3-selective antagonists revealed that these compounds interacted with the D3 receptor in a purely competitive manner. Our data further support that the 4-phenylpiperazine D3-selective antagonists are bivalent and that their enhanced affinity for the D3 receptor is due to binding at both the orthosteric site as well as a secondary binding pocket. Importantly, however, their interactions at the secondary site do not allosterically modulate their binding to the orthosteric site.
D3多巴胺受体是药物成瘾中的一个重要靶点，因为降低受体活性可能会减弱药物的自我给药行为和/或破坏药物或线索诱导的复吸。药物化学研究已开发出对D3有偏好的拮抗剂和部分激动剂，它们对密切相关的D2受体的选择性大于100倍，以延长长度的4-苯基哌嗪衍生物最为典型。基于D3受体晶体结构，已知这些分子与受体上的两个位点对接，其中4-苯基哌嗪部分与正构位点结合，延长的芳基酰胺部分对接至一个二级结合口袋。这些化合物与受体结合的二价性质被认为有助于它们对D3的选择性。在本研究中，我们研究了此类化合物是否也具有“双位点”特性，即它们的芳基酰胺部分作为变构调节剂，进一步增强全长分子对受体的亲和力。首先，我们将几种延长长度的D3选择性配体解构为片段，称为“合成子”，分别代表正构或二级芳基酰胺药效团，并研究它们对D3受体结合和功能的影响。发现正构合成子可抑制放射性配体结合并拮抗多巴胺对D3受体的激活，尽管其亲和力低于全长化合物。值得注意的是，基于芳基酰胺的合成子对正构合成子的亲和力或效力没有影响，对多巴胺激活受体也没有任何影响。此外，对全长D3选择性拮抗剂的药理学研究表明，这些化合物以纯竞争性方式与D3受体相互作用。我们的数据进一步支持4-苯基哌嗪D3选择性拮抗剂是二价的，它们对D3受体增强的亲和力是由于在正构位点以及二级结合口袋处均有结合。然而，重要的是，它们在二级位点的相互作用并不会变构调节它们与正构位点的结合。
