A growing number of orphan G-protein-coupled receptors (GPCRs) have been reported to
be activated by lipid ligands, such as lysophosphatidic acid, sphingosine 1-phosphate
(S1P), and cannabinoids, for which there are already well established receptors. These new
ligand claims are controversial due to either lack of independent confirmations or conflicting
reports. We used the β-arrestin PathHunter™ assay system, a newly developed, generic
GPCR assay format that measures β-arrestin binding to GPCRs, to evaluate lipid receptor …