title: The cellular distribution of fluorescently labeled arrestins provides a robust, sensitive, and universal assay for screening G protein-coupled receptors.
abstract: G protein-coupled receptors (GPCRs) have proven to be a rich source of therapeutic targets; therefore, finding compounds that regulate these receptors is a critical goal in drug discovery. The Transfluor technology utilizes the redistribution of fluorescently labeled arrestins from the cytoplasm to agonist-occupied receptors at the plasma membrane to monitor quantitatively the activation or inactivation of GPCRs. Here, we show that the Transfluor technology can be quantitated on the INCell Analyzer system (INCAS) using the vasopressin V(2) receptor (V(2)R), which binds arrestin with high affinity, and the beta(2)-adrenergic receptor (beta(2)AR), which binds arrestin with low affinity. U2OS cells stably expressing an arrestin-green fluorescent protein conjugate and either the V(2)R or the beta(2)AR were plated in 96-well plastic plates and analyzed by the INCAS at a screening rate of 5 min per plate. Agonist dose-response and antagonist dose-inhibition curves revealed signal-to-background ratios of approximately 25:1 and 8:1 for the V(2)R and beta(2)AR, respectively. EC(50) values agreed closely with K(d) values reported in the literature for the different receptor agonists. In addition, small amounts of arrestin translocation induced by sub-EC(50) doses of agonist were distinguished from the background noise of untreated cells. Furthermore, differences in the magnitude of arrestin translocation distinguished partial agonists from full agonists, and Z' values for these ligands were >0.5. These data show that the Transfluor technology, combined with an automated image analysis system, provides a direct, robust, and universal assay for high throughput screening of known and orphan GPCRs.
authors.affiliation: Norak Biosciences, Inc, Research Triangle Park, NC, USA.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Oakley
authors.forename: Christine C
authors.initials: CC
authors.lastname: Hudson
authors.forename: Rachael D
authors.initials: RD
authors.lastname: Cruickshank
authors.forename: Diane M
authors.initials: DM
authors.lastname: Meyers
authors.forename: Richard E
authors.initials: RE
authors.lastname: Payne
authors.forename: Shay M
authors.initials: SM
authors.lastname: Rhem
authors.forename: Carson R
authors.initials: CR
authors.lastname: Loomis
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D019390:Arrestins / Q000378:metabolism*; D001681:Biological Assay; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004247:DNA / Q000235:genetics; D004353:Drug Evaluation, Preclinical; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008024:Ligands; D008164:Luminescent Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D010957:Plasmids / Q000235:genetics; D011485:Protein Binding; D018343:Receptors, Adrenergic, beta-2 / Q000187:drug effects / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000502:physiology*
chemical_list: D000319:Adrenergic beta-Antagonists; D019390:Arrestins; D005456:Fluorescent Dyes; D008024:Ligands; D008164:Luminescent Proteins; D018343:Receptors, Adrenergic, beta-2; D043562:Receptors, G-Protein-Coupled; D049452:Green Fluorescent Proteins; D004247:DNA