Fig. 2. Co-immunoprecipitation of dopamine D₂ receptor and S100B.

A, co-immunoprecipitation from HEK293 cells. Upper panel: Representative co-IP of myc-D₂ and FLAG-S100B from myc-D₂/FLAG-S100B-HEK293 cells is shown. FLAG immunoreactivity was present in the eluates when the immunoprecipitation was with anti-myc (lanes 1–3), but not when using an irrelevant antibody to a hemaglutinin epitope (anti-HA, lane 4). Additionally, FLAG-S100B immunoreactivity was similar in eluates from cells treated with vehicle (lane 1) or with the D₂ receptor agonist quinpirole (1 μM) for 5 min or 2 hr (lanes 2&3). Middle panel: immunoblot analysis of the input material with anti-FLAG suggests that all immunoprecipitation samples had similar amounts of FLAG-S100B. Lower panel: the results shown are the mean ± SE from three independent experiments. There was no significant difference between samples prepared from vehicle- or quinpirole- (quin) treated cells ( p > 0.05). B, co-immunoprecipitation from rat striatal homogenate. Upper panel: S100B immunoreactivity was present in the eluates when anti-D₂ was used to precipitate the D₂ receptor (lane 1), with little present when normal rabbit IgG was used (lane 2). Lower panel: The results shown are the mean ± SE from three independent experiments, demonstrating a constitutive interaction between the endogenous dopamine D₂ receptor and S100B in rat neostriatum. *p < 0.05 compared to anti-myc + vehicle, Bonferroni post hoc comparison