Fig. 5. Caveolin-1 interacts with BRIa and BRII in starved A431 cells. A431 cells were serum-starved for 72 hours were then stimulated with BMP-2 or left in medium for 2 hours as indicated. Cells were lysed and BRIa, BRII, the transferrin receptor (TR) and caveolin-1 (cav) were immunoprecipitated with specific antibodies against the proteins. The interaction with caveolin-1 was tested by western-blot. Caveolin-1 interacts with BRII and BRIa in starved A431 cells. After stimulation with BMP-2 these interactions are disrupted.