Fig. 2. Caveolin knockdown inhibits the effects of uPAR stimulation on β1-integrin activation. Cells were transfected with caveolin siRNA or control non-targeting siRNA for 72 hours. Cells were treated with 50 µM of the uPAR ligand, P25, or the control peptide, S25, for 1 hour. (A) Cells were fixed and incubated with HUTS-4, a monoclonal antibody against the activated β1 integrin, for an additional 1 hour. Bound antibody was detected by ELISA. (B) Cells were fixed and incubated with P5D2, a monoclonal antibody against total β1, for an additional 1 hour. Bound antibody was detected by ELISA. Bars represent the standard error of triplicate samples. Asterisk (*) indicates siRNA knockdown is statistically different from control cells receiving non-targeting siRNA (t-test, P<0.05).