Culture of Cos7 cells was performed as previously described (6 (link),8 (link)). Cells were cultured in Dulbecco’s Modified Eagle Medium (DMEM) supplemented with 8% heat inactivated FBS and kept in a 37°C humidified 5% CO2 incubator. Cells were seeded into 96-well plates at a density of 15,000–20,000 cells per well (determined using a Countess Counter, Invitrogen) one day prior to transfection. Cells were transiently transfected using polyethylenimine as described previously (6 (link),8 (link)). Hemagglutinin-tagged human CLR, hemagglutinin-tagged human CTR (CT(a) subtype) and myc-tagged human RAMP1 in pcDNA3 or 3.1 plasmid vectors were under the control of the human cytomegalovirus promotor and used as previously described (6 (link),7 (link)).