Fig. 1. Expression of sG_i2 reduces the dopamine D₂ receptor density at the plasma membrane. (A) Infection of BHK cells with 30 µl pseudovirions of D_2L (long isoform of D₂ receptor) and 0-15 µl of sG_i2 () or G_i2 (G_i2, ) protein showed a gradual decrease in the number of plasma-membrane-bound D₂ receptors as the expression of sG_i2 protein was increased. G_i2 had no effect. (B) Immunoblots of cells from A show that, as the addition of sG_i2 pseudovirion was increased, higher expression of this protein. D_2L expression remained the same. Non-transfected cells are shown in lane 4. (C) In JEG-3 cells that lack endogenous G_i2 protein, co-expression of sG_i2 with either D_2L or D_2S (short isoform of D₂ receptor) receptors also yielded a 32-35% reduction in cell surface D₂ receptors, similar to that as seen in BHK cells in A. ^*P<0.05, significant change from control. Values are representative of six to eight different experiments.