Receptor cavity-based screening reveals potential allosteric modulators of gonadotropin receptors in carp (Cyprinus carpio)

Abstract

The gonadotropins follicle stimulating hormone (FSH) and luteinizing hormone (LH) are key regulators of sexual development and the reproductive cycle in vertebrates. Unlike most G protein-coupled receptors (GPCR), the FSHR and LHR have large extracellular domains containing multiple leucine-rich repeats, which leads to an elaborate mechanism of receptor activation via orthosteric sites that is difficult to manipulate synthetically. To bypass the orthosteric mechanism, in this study using carp as a model organism we identified allosteric sites capable of receptor activation on the transmembrane domain, which are spatially separated from the orthosteric sites. We have further generated pharmacophore hypothesis based on the structural motifs and exposed residues of these cavities. Using available online small compound libraries consisting of >70000 small molecules, we have thereon used receptor cavity-based hypothesis and other screening stages to identify potential modulators of the allosteric binding site on the carp FSHR and LHRin-silico. We then examined byin vitrotransactivation assay the effect of four candidate compounds on FSHR and LHR, as compared to the activity of native ligands. Our results reveal both specific and dual effective allosteric modulators for FSHR and LHR, demonstrating the potential of our approach for efficient pharmacophore-based screening.