Highly Potent 5-Aminotetrahydropyrazolopyridines: Enantioselective Dopamine D₃ Receptor Binding, Functional Selectivity, and Analysis of Receptor−Ligand Interactions

Abstract

Heterocyclic dopamine surrogates of types 5 and 7 were synthesized and investigated for their dopaminergic properties. The enantiomerically pure biphenylcarboxamide (S)-5a displayed an outstanding K(i) of 27 pM at the agonist-labeled D(3) receptor and significant selectivity over the D(2) subtype. Measurement of [(35)S]GTPγS incorporation in the presence of a coexpressed PTX-insensitive G(α0-1) subunit indicated highly efficient G-protein coupling. Comparison of ligand efficacy data from cAMP accumulation and [(3)H]thymidine incorporation experiments revealed that ligand biased signaling is exerted by the test compound (S)-5a. Starting from the D(3) crystal structure, a combination of homology modeling and site directed mutagenesis gave valuable insights into the binding mode and the intermolecular origins of stereospecific receptor recognition. According to these data, the superior affinity of the eutomer 5a is caused by the favorable binding energy that results from interaction between the ligand's central ammonium unit and the aspartate residue in position 3.32 of the receptor.

Pharmacological Profile of 2-Bromoterguride at Human Dopamine D2, Porcine Serotonin 5-Hydroxytryptamine 2A, and α2C-Adrenergic Receptors, and Its Antipsychotic-Like Effects in Rats

“…The experiment was terminated by rapid filtration through GF/B filters using an automated cell harvester; the filters were washed five times with ice-cold washing buffer (140 mM NaCl, 10 mM KCl, 1.5 mM KH 2 PO 4 , 8 mM Na 2 HPO 4 , pH 7.4), dried at 60°C for 3 hours, and the trapped radioactivity was counted in a microplate scintillation counter. (Tschammer et al, 2011). Receptor expression determined in saturation experiments was 1640-1850 fmol/mg protein.…”

Advances in G Protein-Coupled Receptor Allostery: From Function to Structure

“…An advantage of the operational model as applied to SAR is that it can almost always be fitted to experimentally derived data to provide estimates of some, or all, of its parameters with regards both to allosteric modulators (Aurelio et al, 2009;Gregory et al, 2012;Valant et al, 2012a;Huynh et al, 2013;Mistry et al, 2013) and biased agonists (Tschammer et al, 2011b;Shonberg et al, 2013;Szabo et al, 2014). Table 1 illustrates an example of allosteric modulator SAR determined through analysis of the effects of various thienopyridine modulators on acetylcholine-mediated ERK1/2 phosphorylation at the M 4 mAChR.…”

1,4-Disubstituted aromatic piperazines with high 5-HT2A/D2 selectivity: Quantitative structure-selectivity investigations, docking, synthesis and biological evaluation

“…Bound radioactivity was measured as described previously. 86 Four to six experiments per compound were performed with each concentration in triplicate. Dose response curves were analyzed using the algorithms for non-linear regression in Prism 6.0.…”