GTPγS Binding Assay: Test method: wetting membranes by saponin solution, and preparing [35S]-GTPγS in binding solution (4×). The test compound was prepared as 4× of the final concentration which was then performed serial 3× dilution in 100% DMSO. Membranes with high-expressed S1P1 were collected in 5 ml binding buffer, and 50 μL was added to 96-well (containing 5 μg membrane protein with high-expressed S1P1). 25 μL, test compound was added in each well. The compound was incubated with the membranes for 30 min at room temperature, then 25 μL [35S]-GTPγS was added, and the experiment was initiated. The 96-well detection plate was incubated for 1 hour at room temperature, filtered by filtermat B, and washed with washing solution for three times. After the plate was dried for 1 h at 50° C., 8 ml scintillator solution was added and counted using scintillation counter.
β-Arrestin Assay: Assay procedures: OCC culture solution was preheated in water tank at 37° C. Cells were taken out from liquor nitrogen tank, left on the dry-ice, and dissolved in water tank at 37° C. 0.5 ml OCC culture solution was added and blended slowly. The cells were diluted in 11.5 mL OCC culture solution, and 100 μL cell suspension (containing 8333 cells) was added to each well of the 96-well plate. The 96-well plate was incubated for 8 hours under 5% CO2 at 37° C., and 10 μL test compound dissolved in DMSO was added in; 10 μL DMSO was used as negative control. After the plate was incubated for 90 min at 37° C., 55 μL detection solution was added to each well. Then the results were read out by EnVision after the cell plate was incubated for 90 min at room temperature.