Ring Substituents on Substituted Benzamide Ligands Indirectly Mediate Interactions with Position 7.39 of Transmembrane Helix 7 of the D4 Dopamine Receptor

Abstract

In an effort to delineate how specific molecular interactions of dopamine receptor ligand classes vary between D2-like dopamine receptor subtypes, a conserved threonine in transmembrane (TM) helix 7 (Thr7.39), implicated as a key ligand interaction site with biogenic amine G protein-coupled receptors, was substituted with alanine in D2 and D4 receptors. Interrogation of different ligand chemotypes for sensitivity to this substitution revealed enhanced affinity in the D4, but not the D2 receptor, specifically for substituted benzamides (SBAs) having polar 4-(para) and/or 5-(meta) benzamide ring substituents. D4-T7.39A was fully functional, and the mutation did not alter the sodium-mediated positive and negative allostery observed with SBAs and agonists, respectively. With the exception of the non-SBA ligand (ϩ)-butaclamol, which, in contrast to certain SBAs, had decreased affinity for the D4-T7.39A mutant, the interactions of numerous other ligands were unaffected by this mutation. SBAs were docked into D4 models in the same mode as observed for eticlopride in the D3 crystal structure. In this mode, interactions with TM5 and TM6 residues constrain the SBA ring position that produces distal steric crowding between pyrrolidinyl/diethylamine moieties and D4-Thr7.39. Ligand-residue interaction energy profiles suggest this crowding is mitigated by substitution with a smaller alanine. The profiles indicate sites that contribute to the SBA binding interaction and site-specific energy changes imparted by the D4-T7.39A mutation. Substantial interaction energy changes are observed at only a few positions, some of which are not conserved among the dopamine receptor subtypes and thus seem to account for this D4 subtype-specific structure-activity relationship.

Activation of the sigma-1 receptor by haloperidol metabolites facilitates brain-derived neurotrophic factor secretion from human astroglia

“…Ligand affinities at the D 2 R were determined by competition binding as described by us previously (Ericksen et al, 2012). Briefly, [ 3 H]methylspiperone (0.5 nM) was the radioligand and (+)-butaclamol (10 μM) was used to define nonspecific binding.…”

A structural chemogenomics analysis of aminergic GPCRs: lessons for histamine receptor ligand design

“…Interestingly, while the D 3 R mimicking N322 7.39 T mutation in β 2 AR diminishes ligand binding (Suryanarayana and Kobilka, ), the beta‐adrenergic receptor mimicking F369 7.39 N mutation in the alpha‐2‐adrenergic receptor promotes stronger binding for aryloxyalkylamine ligands such as S ‐alprenolol ( 58 ), pindolol ( 57 ) and R‐propranolol ( 55 ) (Suryanarayana et al ., ). All these data indicate the important role of this residue in aminergic subtype selectivity (Ericksen et al ., ). Most H 1 R ligands contain linear alkylamines [like doxepin ( 1 ), Figure A] or cyclic amines such as piperazines and piperidines (Simons and Simons, ).…”

A Novel Class of Dopamine D4 Receptor Ligands Bearing an Imidazoline Nucleus

“…27 The availability of the crystal structure of the human D 3 receptor allows development of reliable homology models of other D 2 -like receptors due to the high degree of amino acid sequence conservation, particularly in the transmembrane (TM) segments. 28 Since the D 3 receptor crystal structure was solved in complex with the high-affinity D 2 /D 3 antagonist eticlopride, which binds the D 4 receptor with nanomolar affinity (48 nM), 29 this allows greater potential identification of key receptor-ligand interactions because the ligand-binding cavity is arranged in a ligand-binding state and thus more suitable for docking analysis. The developed D 4 receptor homology model was evaluated using the Protein Geometry Monitor application within MOE, 30 which provides a variety of stereochemical measurements for inspection of the structural quality in a given protein, such as backbone bond lengths, angles and dihedrals, Ramachandran φ-ψ dihedral plots, and sidechain rotamer and non-bonded contact quality.…”