P2P-R interacts with ERα and SRC-1. In the left panel lysates were first immunoprecipitated with the anti-P2P-R, the anti-ERα and the anti-SRC-1 antibodies respectively and the immunoprecipitates were subsequently immunoblotted with the anti-P2P-R antibody. In the right panel immunoprecipitations were performed with the anti-P2P-R and the anti-SRC-1 antibodies respectively and the immunoprecipitates were immunoblotted with the anti-SRC-1 antibody. All immunopreciptiation experiments were carried out using HeLa extracts (1 mg/immunopreciptation), whereas MCF-7 cells were used in experiments with ERα. No immunoprecipitation of P2P-R or SRC-1 was observed when an irrelevant anti-GFP monoclonal antibody was used as control for the immunoprecipitation experiments (data not shown).