Fig. 2. (A-D) Co-accumulation of D₂ receptor and sG_i2 protein complex in cytoplasmic space. (A) D_2S receptors were expressed alone in BHK cells and immunodetected by antibodies to D_2S receptor. In these cells, most of the D_2S proteins were localized at the cell surface (arrowheads). However, when D_2S receptors were co-expressed with sG_i2 proteins (B and C) in these cells, cell surface localization of receptors was reduced markedly (arrowheads indicate protein immunolabeling). They co-accumulated in cytoplasm space with sG_i2 protein (arrowheads in D). To detect the co-labeling of both proteins, specific antibodies against D_2S (B) and sG_i2 (C) were used in double labeling immunofluorescence experiment. Bar, 12 µm.