A single glycine in extracellular loop 1 is the critical determinant for pharmacological specificity of dopamine D2 and D3 receptors.
Subtype-selective agents for the dopamine D3 receptor (D3R) have been considered as potential medications for drug addiction and other neuropsychiatric disorders. Medicinal chemistry efforts have led to the discovery of 4-phenylpiperazine derivatives that are >100-fold selective for the dopamine D3 receptor over dopamine D2 receptor (D2R), despite high sequence identity (78% in the transmembrane domain). Based on the recent crystal structure of D3R, we demonstrated that the 4-phenylpiperazine moiety in this class of D3R-selective compounds binds to the conserved orthosteric binding site, whereas the extended aryl amide moiety is oriented toward a divergent secondary binding pocket (SBP). In an effort to further characterize molecular determinants of the selectivity of these compounds, we modeled their binding modes in D3R and D2R by comparative ligand docking and molecular dynamics simulations. We found that the aryl amide moiety in the SBP differentially induces conformational changes in transmembrane segment 2 and extracellular loop 1 (EL1), which amplify the divergence of the SBP in D3R and D2R. Receptor chimera and site-directed mutagenesis studies were used to validate these binding modes and to identify a divergent glycine in EL1 as critical to D3R over D2R subtype selectivity. A better understanding of drug-dependent receptor conformations such as these is key to the rational design of compounds targeting a specific receptor among closely related homologs, and may also lead to discovery of novel chemotypes that exploit subtle differences in protein conformations.
Department of Physiology and Biophysics, Institute for Computational Biomedicine, Weill Medical College of Cornell University, New York, New York (M.M., L.S.); Departments of Psychiatry and Pharmacology, Columbia University College of Physicians and Surgeons, New York, New York (P.D., L.D., Y.H., J.A.J.); Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York (P.D., L.D., Y.H., J.A.J.); Schrödinger, Inc., New York, New York (T.B.); Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, Intramural Research Program of the National Institutes of Health National Institute on Drug Abuse, Baltimore, Maryland (A.B., A.H.N.); and Cisbio Bioassays, Codolet, France (T.R., E.T.).
Mayako
M
Michino
Prashant
P
Donthamsetti
Thijs
T
Beuming
Ashwini
A
Banala
Lihua
L
Duan
Thomas
T
Roux
Yang
Y
Han
Eric
E
Trinquet
Amy Hauck
AH
Newman
Jonathan A
JA
Javitch
Lei
L
Shi
D001665:Binding Sites; D001667:Binding, Competitive; D005998:Glycine / Q000737:chemistry*; D057809:HEK293 Cells; D006801:Humans; D008024:Ligands; D062105:Molecular Docking Simulation; D056004:Molecular Dynamics Simulation; D016297:Mutagenesis, Site-Directed; D010879:Piperazines / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D011869:Radioligand Assay; D017448:Receptors, Dopamine D2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D050637:Receptors, Dopamine D3 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry
D008024:Ligands; D010879:Piperazines; D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3; D011993:Recombinant Fusion Proteins; D005998:Glycine