U83A blocks clathrin-mediated endocytosis of CCR5 but not transferrin. U373-MAGI-CCR5E cells were grown on coverslips for 24 hours, then exposed to FITC anti-CCR5 (green; bottom) and Alexa Fluor 594-transferrin (red; bottom) for 20 minutes followed by treatment with buffer only, CCR5 ligands 50 nM CCL3 or 100 nM U83A for 10 minutes and mounted with Vectashield mounting solution (DAPI coloration, showing nucleus under incident light in upper panel). Images were taken by a Zeiss 510 laser scanning microscope at × 630 magnification. Fluorochromes were excited at 488 nm for FITC and 543 nm for Alexa Fluor. Serial 0.39-μm confocal slices were captured, and a slice at 3.9 μm is shown from the Z-stack.