Abstract
Crystal structures of G protein-coupled receptor (GPCR) ligand complexes allow a rational design of novel molecular probes and drugs. Here we report the structure-guided design, chemical synthesis and biological investigations of bivalent ligands for dopamine D2 receptor/neurotensin NTS1 receptor (D2R/NTS1R) heterodimers. The compounds of types 1–3 consist of three different D2R pharmacophores bound to an affinity-generating lipophilic appendage, a polyethylene glycol-based linker and the NTS1R agonist NT(8-13). The bivalent ligands show binding affinity in the picomolar range for cells coexpressing both GPCRs and unprecedented selectivity (up to three orders of magnitude), compared with cells that only express D2Rs. A functional switch is observed for the bivalent ligands 3b,c inhibiting cAMP formation in cells singly expressing D2Rs but stimulating cAMP accumulation in D2R/NTS1R-coexpressing cells. Moreover, the newly synthesized bivalent ligands show a strong, predominantly NTS1R-mediated β-arrestin-2 recruitment at the D2R/NTS1R-coexpressing cells.
Highlights
Crystal structures of G protein-coupled receptor (GPCR) ligand complexes allow a rational design of novel molecular probes and drugs
Using bivalent ligands containing an agonist D2 receptors (D2Rs) pharmacophore substructure, we demonstrate that Gi/Gopromoted D2R signalling is attenuated in the D2R/NTS1R coexpressing cells, while the compounds behave as full dopamine receptor agonists in cells singly expressing D2R
In an effort to determine a suitable linker length, we generated a D2R/NTS1R heterodimer model (Fig. 2) consisting of a D2R homology model[40] and the NTS1R crystal structure[39] (Supplementary Note 1; Supplementary Tables 1,2; and Supplementary Fig. 1)
Summary
Crystal structures of G protein-coupled receptor (GPCR) ligand complexes allow a rational design of novel molecular probes and drugs. Bivalent ligands bridging the proximate orthosteric-binding sites of a dimer provide valuable insights into the quaternary structure of receptor dimers and the functional relevance of GPCR dimerization Because of their selective recognition properties, bivalent ligands can be used for a tissuespecific targeting of cells expressing an individual GPCR dimer. A carefully designed bivalent ligand bridging two neighboured receptor protomers should exhibit extremely high binding affinity This approach should lead to high tissue selectivity between heterodimer-expressing cells and those that express only one individual receptor[6]. Our work presents heterobivalent D2R/ NTS1R ligands of type 1-3 comprising NT(8-13), the active fragment of the neuropeptide neurotensin, covalently linked to three different D2R-specific pharmacophores These newly synthesized bivalent compounds exhibit high selectivity up to three orders of magnitude and picomolar Ki values in D2R/NTS1R-coexpressing cells compared with cells expressing D2R only. Using bivalent ligands containing an agonist D2R pharmacophore substructure, we demonstrate that Gi/Gopromoted D2R signalling is attenuated in the D2R/NTS1R coexpressing cells, while the compounds behave as full dopamine receptor agonists in cells singly expressing D2R
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