ToBeLi-for-GPR3-6-12 · Towards high-affinity ligands for orphan receptors GPR3, GPR6 & GPR12

Towards high-affinity ligands for orphan receptors GPR3, GPR6 & GPR12

Members of the protein superfamily of G protein-coupled receptors (GPCRs) are targeted by more than 30% of FDA-approved drugs. However, more than two-thirds of all non-olfactory GPCRs remain untapped for disease therapy, including many orphan GPCRs – receptors with yet unknown endogenous ligands. One of the class A orphan GPCRs, GPR3, has only recently been deorphanized but lacks drug-like ligands. GPR3, together with GPR6 and GPR12, is part of a cluster of orphan GPCRs that is phylogenetically related to receptors that bind sphingosine-1-phosphate (S1P), lysophosphatidic acid (LPA), cannabinoids and proopiomelanocortin-derived peptides. GPR3 activity is involved in both, benign and malig-nant physiological processes. In the central nervous system (CNS), GPR3 mediates neurite outgrowth and neuronal cell survival but has also been implicated in Alzheimer’s disease. In the periphery, GPR3 regulates oocyte maturation and drives thermogenic programs in adipocytes. These examples demonstrate that both, agonists and inverse agonists of GPR3 may be of therapeutic value for various pathologies. However, although researchers have been trying to discover molecules that target GPR3 for more than two decades, only a limited set of ligands, that were validated in independent laboratories, is currently available. The overall goal of ToBeLi-for-GPR3-6-12 was to identify new molecules targeting these orphan class A GPCRs and we used GPR3 is the primary target in our study. The limited number of currently availabe ligands illustrates that today’s GPR3-targeted drug discovery is still hampered by a poor understanding of the role of this receptor in cellular signaling and by a limited panel of assays that reveal GPR3 activity in living cells. Hence, we reasoned that an innovative sensing approach is needed to facilitate tailored GPR3 ligand screening with higher success rates and developed a conformational biosensor that detects compound-induced GPR3 dynamics in a pathway-independent manner and in a medium- to high-throughput screening (HTS) assay format. This biosensor presents the first conformational biosensor for an orphan GPCR with HTS-compatible sensitivity and robustness and we successfully combined this optical tool computer-aided virtual compound screening to identify new GPR3 ligands. A subsequent classic medicinal chemistry approach revealed our most potent GPR3 ligand, which is a receptor inverse agonist inducing conformational changes in GPR3 with low micromolar potency and reducing basal Gs activity downstream of GPR3 with nanomolar potency. The scientific impact of our new GPR3 ligand needs to be tested in further preclinical studies, including toxicology studies and animal models, before its suitability for potential Phase I clinical trials can be assessed. Regardless of their direct use in humans, the ligands discovered through our work are likely to be promising lead structures for further chemical and computational studies aimed at developing even better GPR3 ligands. These future molecules can have a significant economic and societal impact, as GPR3/6/12-targeting therapeutics would represent very promising agents for the treatment of major diseases such as metabolic syndrome and Alzheimer's disease. Our discoveries were made possible by our unprecedented research approach, which combines computational virtual screening with a pathway-independent readout of receptor activity. Our study thus provides a blueprint for other researchers attempting to identify ligands for challenging GPCRs.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз