Method for rapid optimization of recombinant GPCR protein expression and stability using virus-like particles.

Recent innovative approaches to stabilize and crystallize GPCRs have resulted in an unprecedented breakthrough in GPCR crystal structures as well as application of the purified receptor protein in biophysical and biochemical ligand binding assays. However, the protein optimization process to enable these technologies is lengthy and requires iterative overexpression, solubilization, purification and functional analysis of tens to hundreds of protein variants. Here, we report a new and versatile method to screen in parallel hundreds of GPCR variants in HEK293 produced virus-like particles (VLPs) for protein yield, stability, functionality and ligand binding. This approach reduces the time and resources during GPCR construct optimization by eliminating lengthy protein solubilization and purification steps and by its adaptability to many binding assay formats (label or label-free detection). We exemplified the robustness of our VLP method by screening 210 GALR3-VLP variants in a radiometric agonist-based binding assay and a subset of 88 variants in a label-free antagonist-based assay. The resulting GALR3 agonist or antagonist stabilizing variants were then further used for recombinant protein expression in transfected insect cells. The final purified protein variants were successfully immobilized on a biosensor chip and used in a surface plasmon resonance binding assay.

Dataset on Galanin Receptor 3 mutants that improve recombinant receptor expression and stability in an agonist and antagonist bound form.

Galanin Receptor 3 (GALR3) is a G-protein-coupled receptor with a widespread distribution in the brain and plays a role in a variety of physiologic processes including cognition/memory, sensory/pain processing, hormone secretion, and feeding behavior. Therefore, GALR3 is considered an attractive CNS drug target (Freimann et al., 2015) [1]. This dataset contains GALR3 point mutants that improve recombinant protein expression and thermal stability of the receptor contained in virus-like particles (VLPs) or obtained by detergent-purification of baculovirus-infected insect cells. The mutations listed can be grouped in those that improve the stability of the agonist-bound and the antagonist-bound form of the receptor. Protein characteristics in terms of protein expression and thermal stability were comparable between GPCR-VLP and GPCR overexpressing Sf9 cultures. The further analysis and detailed results of these mutants as well as their impact on biophysical assay development for drug discovery can be found in "Method for Rapid Optimization of Recombinant GPCR Protein Expression and Stability using Virus-Like Particles" (Ho et al., 2017) [2].