Allosteric modulation of dopamine D2L receptor in complex with Gi1 and Gi2 proteins: the effect of subtle structural and stereochemical ligand modifications

Abstract

Background Allosteric modulation of G protein-coupled receptors (GPCRs) is nowadays one of the hot topics in drug discovery. In particular, allosteric modulators of D2 receptor have been proposed as potential modern therapeutics to treat schizophrenia and Parkinson’s disease. Methods To address some subtle structural and stereochemical aspects of allosteric modulation of D2 receptor, we performed extensive in silico studies of both enantiomers of two compounds (compound 1 and compound 2), and one of them (compound 2) was synthesized as a racemate in-house and studied in vitro. Results Our molecular dynamics simulations confirmed literature reports that the R enantiomer of compound 1 is a positive allosteric modulator of the D2L receptor, while its S enantiomer is a negative allosteric modulator. Moreover, based on the principal component analysis (PCA), we hypothesized that both enantiomers of compound 2 behave as silent allosteric modulators, in line with our in vitro studies. PCA calculations suggest that the most pronounced modulator-induced receptor rearrangements occur at the transmembrane helix 7 (TM7). In particular, TM7 bending at the conserved P7.50 and G7.42 was observed. The latter resides next to the Y7.43, which is a significant part of the orthosteric binding site. Moreover, the W7.40 conformation seems to be affected by the presence of the positive allosteric modulator. Conclusions Our work reveals that allosteric modulation of the D2L receptor can be affected by subtle ligand modifications. A change in configuration of a chiral carbon and/or minor structural modulator modifications are solely responsible for the functional outcome of the allosteric modulator. Graphical abstract

The Role of Lipids in Allosteric Modulation of Dopamine D2 Receptor—In Silico Study

“…Furthermore, in the case of S1, the spatial organization of TM5, TM6 and TM7 differs significantly. Regarding all analyses with compound 2, conformations of complexes assume intermediate conformations, in between extremes explored by R1 and S1, which, together with in vitro results [18], supports the conclusion that compound 2 does not affect the conformational states of the protein after binding and plays a role of a neutral allosteric ligand. signalling molecules but also from the observation that some receptors must be transferred to the lipid rafts after ligand binding to initiate a cellular response [13].…”

“…Furthermore, in the case of S1, the spatial organization of TM5, TM6 and TM7 differs significantly. Regarding all analyses with compound 2, conformations of complexes assume intermediate conformations, in between extremes explored by R1 and S1, which, together with in vitro results [18], supports the conclusion that compound 2 does not affect the conformational states of the protein after binding and plays a role of a neutral allosteric ligand. In the present study, we focus on the changes in membrane properties and provide a detailed description of how compounds R1, S1, R2 and S2 bound to D2L dopamine receptor in complex with Giα1 or Giα2 proteins (R1G1, R1G2, S1G1, S1G2, R2G1, R2G2, S2G1 and S2G2) affect the surrounding membrane.…”

“…In our previous work [18] we used molecular docking methods to identify the part of the dopamine D 2L receptor (belonging to GPCRs) that is most probably involved in the binding of allosteric ligands 1 [19] and 2 [18], see Figure 1. Both enantiomers of compound 1 (R1 and S1) and compound 2 (R2 and S2) were studied.…”

“…Both enantiomers of compound 1 (R1 and S1) and compound 2 (R2 and S2) were studied. R1 is a positive allosteric modulator of the D 2L receptor, while S1 is its negative allosteric modulator [18,19]. R2 and S2 were proposed to be silent allosteric ligands [18].…”

“…R1 is a positive allosteric modulator of the D 2L receptor, while S1 is its negative allosteric modulator [18,19]. R2 and S2 were proposed to be silent allosteric ligands [18]. The position of the allosteric pocket was dependent on the type of model used.…”