Dopamine D2, D3, and D4 Selective Phenylpiperazines as Molecular Probes To Explore the Origins of Subtype Specific Receptor Binding

• Published in: Journal of medicinal chemistry Vol. 52; no. 15; pp. 4923 - 4935
• Main Authors: Ehrlich, Katharina, Götz, Angela, Bollinger, Stefan, Tschammer, Nuska, Bettinetti, Laura, Härterich, Steffen, Hübner, Harald, Lanig, Harald, Gmeiner, Peter
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 13.08.2009; Amer Chemical Soc
• Subjects: Animals; Biological and medical sciences; Catecholaminergic system; Chemistry, Medicinal; CHO Cells; Cricetinae; Cricetulus; Humans; Life Sciences & Biomedicine; Ligands; Medical sciences; Models, Molecular; Mutagenesis, Site-Directed; Neuropharmacology; Neurotransmitters. Neurotransmission. Receptors; Pharmacology & Pharmacy; Pharmacology. Drug treatments; Piperazines - chemical synthesis; Piperazines - metabolism; Radioligand Assay; Receptors, Dopamine D1 - chemistry; Receptors, Dopamine D1 - metabolism; Receptors, Dopamine D2 - chemistry; Receptors, Dopamine D2 - metabolism; Receptors, Dopamine D4 - chemistry; Receptors, Dopamine D4 - metabolism; Science & Technology; Spiperone - metabolism; Structure-Activity Relationship; SUPER-POTENT; LIGANDS; CRYSTAL-STRUCTURE; PENILE ERECTION; ENVIRONMENT; 2ND; COMFA; SITE-DIRECTED MUTAGENESIS; COMSIA INVESTIGATIONS; NONAROMATIC CATECHOL BIOISOSTERES; D4 Dopamine receptor; D2 Dopamine receptor; Structure activity relation; Ligand; Molecular model; Site directed mutagenesis; Molecular probe; Selectivity; Piperazine derivatives; Modeling; D3 Dopamine receptor
• ISSN: 0022-2623; 1520-4804
• DOI: 10.1021/jm900690y

Assembling phenylpiperazines with 7a-azaindole via different spacer elements, we developed subtype selective dopamine receptor ligands of types 1a,c, 2a, and 3a preferentially interacting with D4, D2, and D3, respectively. To complete this set, the methylthio analogues 2b and 3b exceeding the affinity of 2a and 3a by one order of magnitude and the structural intermediate 1b were synthesized. These chemically similar but biologically divergent target compounds served as molecular probes for radioligand displacement experiments, mutagenesis, and docking studies on homology models based on the recent crystal structure of the β2-adrenergic receptor. Specific interactions with the highly conserved amino acids Asp3.32 and His6.55 and less conserved residues at positions 2.61, 2.64, 3.28, and 3.29 were identified. Inclusion of a carefully modeled extracellular loop 2 displayed two nonconserved residues in EL2 that differently contribute to ligand binding. Obviously, subtype selectivity is caused by nonconserved but frequently mediated by conserved amino acids.