Characterization of HEK293 cells expressing mouse uPAR variants. (A) muPAR variants are expressed at comparable levels in transfected 293 cells. Cell surface expression profiles of mock (black), muPAR (red), muPAR^W32A (blue), and muPAR^ΔD1 (green) transfected cells were analyzed by flow cytometry using a monoclonal antibody against mouse uPAR. (B) Western blot analysis illustrating the molecular weights of the different mouse uPAR variants. Equal amounts of cell extracts were fractionated by nonreducing SDS-PAGE and probed with the same antibody used in FACS analysis with an anti-GFP antibody as control. (C) W32A substitution or deletion of the entire domain 1 impairs the activity of muPAR in promoting cell adhesion to VN. Cells expressing the different receptor variants were seeded in wells coated with VN(1-66), VN(1-66)^RAD, or FN and allowed to adhere for 30 minutes at 37°C. After washing, adherent cells were fixed and quantified. Specific cell adhesion is shown as percent of cell binding to poly-D-lysine. Data represents the mean ± standard error of the mean of independent experiments (n = 3).