C Control or LAPTM4B knockdown MDA‐MB‐231 cells were starved overnight, cell surface EGFR was labeled with immuno‐gold on ice. Cells were then stimulated with EGF for 1 h at 37°C and fixed for the EM study. Scale bar, 200 nm. See Materials and Methods for details.D Relative amounts of immuno‐gold‐labeled EGFR in the MVE lumen versus MVE limiting membrane were quantified. Over 80 endosomes for each siRNA treatment from three independent experiments were used for quantification (mean + SD; ***P 0.001, one‐tailed t‐test). 