Abstract
LASSBio-579, an N-phenylpiperazine antipsychotic lead compound, has been previously reported as a D2 receptor (D2R) ligand with antipsychotic-like activities in rodent models of schizophrenia. In order to better understand the molecular mechanism of action of LASSBio-579 and of its main metabolite, LQFM 037, we decided to address the hypothesis of functional selectivity at the D2R. HEK-293T cells transiently coexpressing the human long isoform of D2 receptor (D2LR) and bioluminescence resonance energy transfer (BRET)-based biosensors were used. The antagonist activity was evaluated using different concentrations of the compounds in the presence of a submaximal concentration of dopamine (DA), after 5 and 20 min. For both signaling pathways, haloperidol, clozapine, and our compounds act as DA antagonists in a concentration-dependent manner, with haloperidol being by far the most potent, consistent with its nanomolar D2R affinity measured in binding assays. In our experimental conditions, only haloperidol presented a robust functional selectivity, being four- to fivefold more efficient for inhibiting translocation of β-arrestin-2 (β-arr2) than for antagonizing Gi activation. Present data are the first report on the effects of LASSBio-579 and LQFM 037 on the β-arr2 signaling pathway and further illustrate that the functional activity could vary depending on the assay conditions and approaches used.
Highlights
G protein-coupled receptors (GPCRs), known as 7TM receptors, are the targets for the majority of drugs used therapeutically (Hauser et al, 2017), albeit a shift toward kinases and cytokines is occurring in drug discovery programs (Shih et al, 2018).During the last 10 years, increasing evidences indicate that ligands for the 7TM receptors can be functionally selective, bearing differences in potency and/or intrinsic activity at different signaling pathways mediated by the same receptor (Urban et al, 2007)
The present study aimed to better understand the molecular mechanism of action of LASSBio-579, our lead compound rationally designed through hybridization of clozapine and L-741
1.11 0.76 (Menegatti et al, 2003), that was previously reported as a new atypical antipsychotic candidate
Summary
G protein-coupled receptors (GPCRs), known as 7TM receptors (since they have seven hydrophobic transmembrane domains and do not always signal through G proteins), are the targets for the majority of drugs used therapeutically (Hauser et al, 2017), albeit a shift toward kinases and cytokines is occurring in drug discovery programs (Shih et al, 2018).During the last 10 years, increasing evidences indicate that ligands for the 7TM receptors can be functionally selective, bearing differences in potency and/or intrinsic activity at different signaling pathways mediated by the same receptor (Urban et al, 2007). The capability to detect this property ( called biased agonism) could vary depending on the tools used, e.g., the subtype of receptor; the complement of intracellular signaling molecules such as G proteins, second messengers, β-arrestins, and G-protein-coupled receptor kinase (GRK); the approach for labeling the proteins; the assay conditions (concentration and nature of the agonist); the ligand-binding kinetics; and the kinetics intrinsic to different intracellular signaling events (CostaNeto et al, 2016; Klein Herenbrink et al, 2016; Urs et al, 2017) Such a 7TM receptor, the dopamine D2 receptor (D2R), is central for the treatment of schizophrenia since all antipsychotics in clinical use are able to block this receptor at therapeutical concentrations, albeit differences exist between first- and secondgeneration drugs. Some N-phenylpiperazines have been reported as functionally selective for D2R-mediated pathways (Chen et al, 2016; Möller et al, 2017)
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