Fig. 1.

a BRET² saturation experiments in HEK cells. Cotransfection of D_2L^Rluc or D_2SR ^Rluc and Sigma 1R^GFP2 form D_2LR^Rluc-Sigma 1R^GFP2 and D_2SR^Rluc-Sigma 1R^GFP2 heteromers, respectively. The BRET signal obtained gives similar BRETmax and BRET 50 values, for the two heteromers demonstrated. b BRET² competition experiments. D_2LR and D_2SR receptor cDNAs were shown to produce similar competition curves with marked and highly significant reductions of the BRET² signal. Instead Sigma 1R cDNA in increasing concentrations only resulted in a small reduction of the BRET2 signal with a low statistical significance compared with the competition curves obtained with D_2LR and D_2SR cDNAs. The data represent the means ± S.E.M. of three independent experiments performed in triplicate. Statistical analysis was performed by TWO-WAY ANOVA