CoMFA-Based Prediction of Agonist Affinities at Recombinant Wild Type versus Serine to Alanine Point Mutated D2 Dopamine Receptors

Abstract

Agonist affinity changes dramatically as a result of serine to alanine mutations (S193A, S194A, and S197A) within the fifth transmembrane region of D2 dopamine receptors and other receptors for monoamine neurotransmitters. However, agonist 2D-structure does not predict which drugs will be sensitive to which point mutations. Modeling drug-receptor interactions at the 3D level offers considerably more promise in this regard. In particular, a comparison of the same test set of agonists across receptors differing minimally (point mutations) offers promise to enhance the understanding of the structural bases for drug-receptor interactions. We have previously shown that comparative molecular field analysis (CoMFA) can be applied to comparisons of affinity at recombinant D1 and D2 dopamine receptors for the same set of agonists, a differential QSAR. Here, we predicted agonist K(L) for the same set of agonists at wild type D2 vs S193A, S194A, and S197A receptors using CoMFA. Each model used bromocriptine as the template. ln(1/K(L)) values for the low-affinity agonist binding conformation at recombinant wild type and mutant D2 dopamine receptors stably expressed in C6 glioma cells were used as the target property for the CoMFA of the 16 aligned agonist structures. The resulting CoMFA models yielded cross-validated R(2) (q(2)) values ranging from 0.835 to 0.864 and simple R(2) values ranging from 0.999 to 1.000. Predictions of test compound affinities at WT and each mutant receptor were close to measured affinity values. This finding confirmed the predictive ability of the models and their differences from one another. The results strongly support the idea that CoMFA models of the same training set of compounds applied to WT vs mutant receptors can accurately predict differences in drug affinity at each. Furthermore, in a "proof of principle", two different templates were used to derive the CoMFA model for the WT and S193A mutant receptors. Pergolide was chosen as an alternate template because it showed a significant increase in affinity as a result of the S193A mutation. In this instance both the bromocriptine- and pergolide-based CoMFA models were similar to one another but different from those for the WT receptor using bromocriptine- or pergolide- as templates. The pergolide-based S193A model was more strikingly different from that of the WT receptor than was the bromocriptine-based S193A model. This suggests that a "dual-template" approach to differential CoMFA may have special value in elucidating key differences across related receptor types and in determining important elements of the drug-receptor interaction.

Transmembrane Segment Five Serines of the D4 Dopamine Receptor Uniquely Influence the Interactions of Dopamine, Norepinephrine, and Ro10-4548

“…At the D4 receptor, the affinity of dopamine was drastically reduced by S5.42A and S5.46A mutations (Ͼ150-fold) but moderately reduced by S5.43A (Ͻ 8-fold). This loss in dopamine's affinity for the D4-S5.43A mutant is consistent with changes for D2-S5.43A (average 7.5-fold reduction, range 1.2-to 20-fold), D3-S5.43A (2.1-fold reduction), and D1-S5.43A mutants (9.9-fold reduction) (Cox et al, 1992;Pollock et al, 1992;Woodward et al, 1996;Wiens et al, 1998;Sartania and Strange, 1999;Wilcox et al, 2000). Although the reduced affinity of dopamine for the D4-S5.42A mutant was consistent with that observed for other D2-like receptors (average 101-fold reduction for D2-S5.42A across different studies, range 43-to 250-fold, and 62-fold reduction for D3-S5.42A), the large reduction in dopamine affinity for the D4-S5.46A mutant was not (average 1.5-fold reduction for D2-S5.42A, range 0.8-to 8.4-fold, and 1.2-fold increase for D3-S5.46A) (Cox et al, 1992;Woodward et al, 1996;Wiens et al, 1998;Sartania and Strange, 1999;Wilcox et al, 2000) and surprisingly more similar to the D1 subtype (47-fold reduction for D1-S5.46A) (Pollock et al, 1992).…”

Pharmacological Characterization of the D1- and D2-Like Dopamine Receptors from the Brain of the Leopard Frog, <i>Rana pipiens</i>

“…In addition, pharmacological characteristics of each receptor subtype are further typified by differential affinities to agonists and antagonists. Such differences in pharmacological profiles provide useful clues about the nature of the binding reactions that occur when active compounds (transmitters or other agonists) interact with these proteins and change their shape [Brusniak et al, 1996;Wilcox et al, 1998bWilcox et al, , 2000Wilcox et al, , 2001. Thus, an important aspect of the functional characterization of novel receptor subtypes is the determination of the relative potency of key drugs.…”

2,3,9- and 2,3,11-Trisubstituted tetrahydroprotoberberines as D2 dopaminergic ligands

“…Consistent with previous experimental [36] and theoretical [37] data, the simulation indicated the relevance of the negatively charged aspartate 114 (D114) for ligand binding. In this contex, the highly conserved D114 in trans-membrane helix 3 (TM3) is important for both D 2 DR agonists and antagonists binding [36,38], and its terminal carboxyl group may function as an anchoring point for ligands with protonated amino groups [39][40][41]. In the current study, all the compounds simulated were docked into the receptor with the protonated amino group close to D114.…”