The structural determinants of the bitopic binding mode of a negative allosteric modulator of the dopamine D 2 receptor

Abstract

SB269652 is a negative allosteric modulator of the dopamine D receptor (DR) yet possesses structural similarity to ligands with a competitive mode of interaction. In this study, we aimed to understand the ligand-receptor interactions that confer its allosteric action. We combined site-directed mutagenesis with molecular dynamics simulations using both SB269652 and derivatives from our previous structure activity studies. We identify residues within the conserved orthosteric binding site (OBS) and a secondary binding pocket (SBP) that determine affinity and cooperativity. Our results indicate that interaction with the SBP is a requirement for allosteric pharmacology, but that both competitive and allosteric derivatives of SB269652 can display sensitivity to the mutation of a glutamate residue (E95) within the SBP. Our findings provide the molecular basis for the differences in affinity between SB269652 derivatives, and reveal how changes to interactions made by the primary pharmacophore of SB269652 in the orthosteric pocket can confer changes in the interactions made by the secondary pharmacophore in the SBP. Our insights provide a structure-activity framework towards rational optimization of bitopic ligands for DR with tailored competitive versus allosteric properties.

Pharmacological Characterization of the Imipridone Anticancer Drug ONC201 Reveals a Negative Allosteric Mechanism of Action at the D2Dopamine Receptor

“…More comprehensive analyses of the D2R mutants by collecting full ONC201 doseresponse curves using Go activation and cAMP inhibition assays showed that mutations of four specific residues, V91 2.61 , E95 2.65 , Y192 5.41 , and I397 6.59 , produced the most severe impact on ONC201's ability to antagonize dopamine-stimulated signaling. Notably, two of these residues, V91 2.61 and E95 2.65 , reside within a SBP formed by the interface between TMs 2 and 7 and have been shown to be involved in allosteric modulation of the D2R by bitopic and negative allosteric modulators (NAMs) (Draper-Joyce et al, 2018;Klein Herenbrink et al, 2019;Verma et al, 2018).…”

Chirality of Novel Bitopic Agonists Determines Unique Pharmacology at the Dopamine D3 Receptor

“…Previous studies reveal that the bitopic ligand strategy can provide improved receptor subtype selectivity, affinity, and functional selectivity [ 37 , 38 , 39 ]. Additionally, bitopic ligands can also confer unique receptor signaling an example of which is the bitopic ligand SB269,652 that behaves as an allosteric antagonist at D 3 Rs and D 2 Rs [ 40 , 41 ]. Indeed, we have successfully utilized a bitopic design strategy to synthesize potent, selective, and G protein biased full agonists at D 2 R [ 42 ].…”

Ligand with Two Modes of Interaction with the Dopamine D2 Receptor–An Induced-Fit Mechanism of Insurmountable Antagonism

“… 16 , 17 In particular, a cluster of residues in transmembrane segment 2, including V91, L94, and E95, has been found to mediate important contacts between the ligand and the secondary binding pocket. 18 − 20 …”