DS04 - Vie, santé et bien-être

Innovative biosensors for G protein-coupled receptor ligand screening. Application to the ghrelin receptor – GHScReen2

Submission summary

Almost every physiological system is controlled by G protein-coupled receptors (GPCRs). As such, these receptors are considered as a most popular class of drug targets with potential applications in many different pathological processes such as neurological and metabolic disorders, inflammation, cancer, or viral infection. So far, all GPCR drug-discovery has relied on cell-based assays that consist in screening chemical compounds on heterologous cells overexpressing target GPCRs, with ligand binding, effector coupling or second messenger generation as the primary readout. Although these assays have delivered compounds that made it to patients, they nevertheless have major limitations. In particular, issues of allosteric modulation, receptor dimerization, and ligand functional selectivity still create challenges in selecting suitable assay formats. Moreover, screening of low-affinity fragments is out of the scope of cell-based systems. For these reasons, development of assays that would detect "universal" signaling pathways, take into account receptor dimerization and would be adapted for screening large fragment libraries is absolutely necessary to lead discovery and optimization. In this context, we propose to develop original biosensors for cell-free assays that rely on the immobilization of purified GPCRs monomers and dimers onto surfaces through functionalized non-ionic polymers. These biosensors recapitulate the important attributes for an assay amenable to screening large libraries of ligands, i.e. receptor pharmacology not affected by the immobilization process, low cost for assay development and reagents, amenability to automation and miniaturization, no radioactivity involved, sensitivity and robustness. In the present proposal, the biosensors will be validated in two different screening assays that will bring complementary information on the pharmacological character of the compounds. The first one, based on Surface Plasmon Resonance technology, will report on the binding features (affinity and kinetic constants) of the drug to the immobilized receptor. The second one, based on the measurement of a fluorescence transfer signal between probes bound to the immobilized receptor, will report on pathway-selective activation events. The proof-of-concept for such biosensors will be brought with the ghrelin receptor GHSR as a model for rhodopsin-like GPCRs. Besides being a prototypical receptor, GHSR is also an invaluable target in biomedicine with potential applications in the treatment of obesity, diabetes or addiction to drugs and alcohol. Our program, which builds upon the experience, reagents and methods accumulated during the past years by the different member of the consortium, will therefore provide innovative and versatile biosensors for screening compound collections directed towards a most important class of pharmacological target. As such, it will likely pave the way to the identification of new, original drugs with applications in a variety of clinical spheres. Besides, development of such a cell-free screening assay in the case of GHSR should allow us to identify compounds with the desired efficacy and selectivity with regard to major pathological conditions where ghrelin is directly involved.

Project coordination

Fehrentz Jean-Alain (Institut des Biomolécules Max Mousseron)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

IBMM Institut des Biomolécules Max Mousseron
IBMM Institut des Biomolécules Max Mousseron
IBMM/CBSA IBMM - Equipe Chimie Bioorganique et Systèmes Amphiphiles

Help of the ANR 477,391 euros
Beginning and duration of the scientific project: - 36 Months

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