Supplementary Figure 8: Control studies for co-immunoprecipitation (co-IP) experiments measuring association between Homer proteins and mGluR1 or mGluR5.

(a) After IP of NAc tissue with an mGluR1 or mGluR5 antibody, immunoblotting with the same antibody verified that virtually all of the respective mGluR dimer present in the starting material (Input) is recovered in the Bound material (IP'ed material purified by Protein A/G resin) and not the Unbound material. For the comparison shown in this panel, we loaded half as much Input as Bound or Unbound material. In experiments not shown, we confirmed that the signal observed in the Bound material is not due to non-specific binding because, after IP with IgG (control condition), mGluR protein is detected in the Unbound material rather than the Bound material. (b) To measure changes in the association between Homer proteins and mGluR1 or mGluR5, tissue was IP'ed with mGluR1 or mGluR5 antibodies and the Bound material was probed for Homer1bc or Homer2. As shown in the representative immunoblots, only a portion of Homer protein present in the starting material (Input) is recovered in the Bound material, indicating the existence of a substantial pool of Homer proteins that is not physically associated with group I mGluRs. These findings were replicated over ten times.