Dopamine D2, D3, and D4 selective phenylpiperazines as molecular probes to explore the origins of subtype specific receptor binding.
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 beta2-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.
Ehrlich
Katharina
K
Department of Chemistry and Pharmacy, Emil Fischer Center, Friedrich Alexander University, Schuhstrasse 19, 91052 Erlangen, Germany.
Götz
Angela
A
Bollinger
Stefan
S
Tschammer
Nuska
N
Bettinetti
Laura
L
Härterich
Steffen
S
Hübner
Harald
H
Lanig
Harald
H
Gmeiner
Peter
P
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D010879:Piperazines / Q000138:chemical synthesis* / Q000378:metabolism; D011869:Radioligand Assay; D017447:Receptors, Dopamine D1 / Q000737:chemistry / Q000378:metabolism*; D017448:Receptors, Dopamine D2 / Q000737:chemistry / Q000378:metabolism*; D050638:Receptors, Dopamine D4 / Q000737:chemistry / Q000378:metabolism*; D013134:Spiperone / Q000378:metabolism; D013329:Structure-Activity Relationship
D008024:Ligands; D010879:Piperazines; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D050638:Receptors, Dopamine D4; D013134:Spiperone; C031503:phenylpiperazine