β-Arrestin assay

β-Arrestin recruitment was measured using the PathHunter™ enzyme fragment complementation assay from DiscoveRx and carried out according to the manufacturer's instructions. In short, 3500 cells per well in Opti-MEM were incubated together with different concentrations of AZD8797 and CX₃CL1 in a 384-well plate. After 90 min of incubation at 37°C, detection reagent was added and incubation continued for 1 h at room temperature, before reading the plate with a Victor² luminescence plate reader (PerkinElmer). As in the [³⁵S]GTPγS binding assay, the final DMSO concentration was held constant at 1%.