Fig. 4. BRII binds to caveolin-1 and caveolin-1 ß. COS-7 cells were co-transfected with plasmids encoding BRII-HA or BRIa-myc and one of the two caveolin isoforms, caveolin-1 or ß. After 48 hours, cells were lysed and proteins were immunoprecipitated as indicated. The immunoprecipitated proteins were subjected to SDS PAGE and transferred onto nitrocellulose. The nitrocellulose membrane was incubated with an antibody recognizing caveolin-1 and ß, the HA or myc-epitopes, and a secondary HRP conjugeated antibody. The top panel shows that the interactions with the caveolin isoforms is specific for BRII and that there are no direct interactions between BRIa and the caveolin-1. The two bottom panels show that BRIa is present in the transfected cells.