Structure-inspired design of β-arrestin-biased ligands for aminergic GPCRs

Abstract

Development of biased ligands targeting G protein-coupled receptors (GPCRs) is a promising approach for current drug discovery. Although structure-based drug design of biased agonists remains challenging even with an abundance of GPCR crystal structures, we present an approach for translating GPCR structural data into β-arrestin-biased ligands for aminergic GPCRs. We identified specific amino acid-ligand contacts at transmembrane helix 5 (TM5) and extracellular loop 2 (EL2) responsible for Gi/o and β-arrestin signaling, respectively, and targeted those residues to develop biased ligands. For these ligands, we found that bias is conserved at other aminergic GPCRs that retain similar residues at TM5 and EL2. Our approach provides a template for generating arrestin-biased ligands by modifying predicted ligand interactions that block TM5 interactions and promote EL2 interactions. This strategy could facilitate the structure-guided design of arrestin-biased ligands at other GPCRs, including polypharmacological biased ligands.

Catalytic activation of β-arrestin by GPCRs

“…This was not the case because GPCR-activated β-arrestin-2 accumulation in CCSs did not depend on selectivity for G protein coupling and trafficking activated by the Gi-coupled D2 dopamine receptor was unaffected by pertussis toxin (DRD2, Extended Data Figure 3f–h), consistent with another recent report 26 . Further, receptor-independent activation of adenylyl cyclase using forskolin did not promote (or block) β-arrestin-2 trafficking (Extended Data Figure 3i–k).…”

Structural determinants of 5-HT2B receptor activation and biased agonism

“…2a, Supplementary Fig. 2a) at the A225G 5.46 mutant, which we hypothesized to introduce more bulk tolerance for methysergide’s N (1)-methyl—a notion consistent with TM5 engagement appearing to be important for G protein-dependent agonism 25 .…”

“…Additional insights into the mechanisms of biased agonism have recently emerged revealing a key ligand interaction between LSD and Leu209 in extracellular loop 2 (EL2), which increases ligand residence time at the receptor contributing to enhanced time-dependent β-arrestin2 recruitment 13 . Additionally, both TM5 and the EL2 regions have recently been exploited for biased ligand design at aminergic GPCRs 25 , it is unclear how biased activation occurs via contact with these regions of the receptor.…”

Structure of the D2 dopamine receptor bound to the atypical antipsychotic drug risperidone

“…Given the importance of DRD2-targeted drugs, and recent successes in leveraging GPCR structures for the structure-guided discovery of new probes and drug-leads 18,19 , the structure of a DRD2 complexed with non-benzamides ligands will not only clarify the specificity determinants of the family, but will also expand our understanding of how different scaffolds interact with dopamine receptors. We anticipate that the ligand discovery enabled by DRD2 structures would thus inform both basic and translational neuroscience 20 .…”

“…2). This residue has been implicated in the on- and off-rate kinetics and in β-arrestin biased signaling for some ligands at DRD2 and other receptors 19,20,21 . However, because of the rearrangement of EL 2 and its formation of a small helical turn (residues 182–185) in the DRD2/risperidone structure (Fig.…”