Radioligand binding to Drosophila nAChR subunit combinations in cultured cell lines. Cell surface [125I]-α-bungarotoxin binding to cell lines transiently transfected with combinations of Dα5, Dα6 and Dα7 subunits. In all cases, subunit combinations were co-transfected with either CeRIC-3 (filled bars) or DmRIC-3 (open bars). No specific binding was detected for any subunit combination in the absence of RIC-3 (not shown). Data are presented for Drosophila S2 cells (A) and for human tsA201 cells cultured at 25 °C (B). Controls represent mock-transfected cells. Experiments were performed in triplicate and are means ± SEM of 5–8 independent experiments.