Sema3A down-regulates surface Npn-1 and promotes Npn-1 internalization. (A) Surface Npn-1 detected on endothelial cells incubated (25°C, 1 hour) with Sema3A (0-4 μg/mL). Shaded graphs reflect control staining. (B) Npn-1 detected by confocal microscopy in endothelial cells stimulated with Sema3A (2 μg/mL) at 37°C for 0, 5, 30, or 60 minutes. Scale bar, 20 μm. Images were acquired and processed as described for Figure 5F.