PathHunter® β-Arrestin Assays as a Universal Tool For Orphan GPCR Analysis

PathHunter® β-Arrestin Assays as a Universal Tool For Orphan GPCR Analysis

File Name/Number:
SBS 2009


Orphan GPCRs continue to represent a target class with immense potential for the discovery of novel therapeutic compounds. In spite of the proven track record of GPCRs as druggable targets, over 100 non-odorant GPCRs remain to have their cognate ligands identified. Here we present the PathHunter® Arrestin assay as a facile screening approach to orphan GPCR drug discovery. In this system, a small peptide is fused to the GPCR target, and the complementing fragment is fused to β-Arrestin2. Upon activation, the GPCR binds to arrestin forcing complementation of the enzyme fragments. The activity is detected with a single addition, HTS friendly, chemiluminescent reagent and is analyzed without waiting for reporter gene activity, or without knowing the second messenger signaling of the target receptor. The PathHunter® assay is also unique in that only activation of the tagged GPCR will yield signal, providing a system that will not be affected by endogenous receptors. This eliminates many of the common false positives associated with other assays and makes it an ideal format for primary HTS screening. DiscoveRx has created an industry leading portfolio of orphan GPCR stable cell lines that are available for surrogate ligand discovery, de-orphanization, and profiling. This presentation will focus on the validation of the PathHunter® system for orphan GPCR research and screening, the development of a cell line pane for profiling, and proof data from a focused library that receptors can in fact be de-orphanized with our system. Furthermore, we will present exciting examples where orphan GPCRs appear to regulate the function of characterized GPCR, highlighting the potential for orphans to heterodimerize with other GPCR partners and modulate their activities.