PDGF-BB stimulates integrin β3 macropinocytosis at CDRs and recycling back to the ventral cell surface to form new focal adhesions. (A and B) Primary mouse fibroblasts were stimulated with PDGF-BB in TMR-dextran (red)–containing medium for 5 (top) or 10 min (bottom). Cells were then washed, fixed, and IF stained. Insets of structures in the dashed boxes are shown enlarged in the bottom right corners. (C) Primary mouse fibroblasts were stimulated with or without PDGF-BB. Cells were then detached and live stained by the anti–integrin β3 antibody (1–55-4) or isotype control antibody for 1 h at RT. Cells were fixed and subjected to flow cytometry analysis. A total cell surface integrin β3 fluorescence intensity histogram is plotted. (D) Primary mouse fibroblasts were live stained by a nonblocking anti–integrin β3 antibody and subjected to the endocytosis and recycling assay. Arrowheads denote internalized integrin β3 at macropinosomes. Arrows denote recycled integrin β3 at focal adhesions. Bars: (A and B) 20 µm; (A and B, insets) 5 µm; (D) 100 µm.