Fig. 5
Involvement of transactivation of EGFR in the D2-like receptor desensitization. Cells expressing D2-like receptors and related mutants (1.7–2.1 pmol/mg protein) were pretreated with vehicle or 10 ng/mL EGF for 20 min, and the quinpirole-induced inhibition of the cAMP production was determined. A HEK-293 cells expressing D3R or D2R were used. The Veh/D3R group differed significantly from other groups of the cells expressing D3R or D2R at 10–10 to 10−8 M quinpirole (p < 0.001, n = 3). B HEK-293 cells expressing D3R or D4R were used. The EGF/D3R group showed a significant difference from other groups of the cells expressing either D3R or D4R at 10−10 M quinpirole (p < 0.01, n = 3) and 10−9 to 10−8 M quinpirole (p < 0.001, n = 3). C HEK-293 cells expressing WT-D3R or C147K-D3R were used. ***p < 0.001 compared with other groups in WT-D3R- and C147K-D3R-expressing cells; ###p < 0.001 compared with Veh-treated groups of the cells expressing WT-D3R or C147K-D3R (n = 3). D HEK-293 cells expressing WT-D2R or K149C-D3R were used. The EGF/K149C group differed significantly from other groups of WT-D2R- or K149C-D2R-expressing cells at 10−10–10−8 M quinpirole (p < 0.001, n = 3)