High-throughput screening assay of GPCR drug candidates using second harmonic generation for direct detection of structural changes

Abstract Despite extensive drug discovery efforts targeting G protein coupled receptorsGPCRsthese important targets for drug discovery remain challenging proteins for directon target drug discovery campaignsTo answer the challenge posed by GPCRsBiodesy will use its Biodesy Delta devicea platform based on Second Harmonic GenerationSHGthat allows one to measure changes in biomolecule conformation upon ligand addition in real timeto develop a commercial screening assay for identifying compounds that directly modulate the structure and function of GPCRsSHG is a non linear optical process that is highly sensitive to orientational changes of a SH activeDa dye probecovalently attached to a protein of interest at either lysine or cysteine residuesThe technology requirespmol target protein per well and is operated in aorwell microtiter plate format allowing for the collection of tens of thousands of data points per dayUnlike other optical screening methodsthat have been tried and require fusion proteinsthe SHG dye can be added without altering cellular expressionactivity of the targeted receptorand affinity for receptor ligandUsing SHGBiodesy has measured a range of molecular interactions between target proteins and small moleculesfragmentspeptides and antibodiesTo enable screening of GPCRswe have successfully developed a prototype non lipid surface that allows tethering of GPCRs and is resistant to detergents used to solubilize and stabilize membrane protein samples in solutionThe new plate surface demonstrated minimal non specific binding of the purified labeled NTRprototypical GPCRWe have also demonstrated that SHG dye labeled NTRtethered to the surface remains functional by examining the binding of two control ligands to the tethered proteinAdditional changes to the current components of our Biodesy Delta device and screening plates can create a commercial kit that detects and analyzes SHG signals from dyes attached to a GPCR of choiceIn this SBIR phase I projectwe will identify and optimize the surface coating conditions of multi well plates that will enable SHG assays with tethered GPCRsThenwe will explore different labeling positions within a GPCRNTRreceptorfor determination of the optimal labeling location for discriminating small molecule GPCR agonists from antagonistsThe final step will be to integrate the new GPCR compatible multiwell plates and the optimally labeled proteins into a ligand screening procedureTo test the ability of the assay to differentiate between different types of ligandsit be tested against an expanded set of known agonists and antagonists as well as compounds with unknown mechanisms of actionThis test will validate and demonstrate the robustness of the assay and its ability to predict Mechanism of action of GPCR ligands Narrative Despite extensive drug discovery efforts targeting G protein coupled receptorsGPCRsthese important targets for drug discovery remain challenging proteins for directon target drug discovery campaignsThe goal of the proposed project is to solve this problem by developing a high throughputSecond Harmonic GenerationSHGbasedcommercial screening platform for identifying compounds that directly modulate the structure and function of GPCRs