Inactivation of the ERK pathway inhibited CD71 internalization in orthochromatic erythroblasts. (A) Representative flow cytometry analysis showing the expression of CD71 on DMSO- or U0126-treated erythroblasts. (B) Quantitative analyses of CD71 surface expression from 3 independent experiments. (C) Representative western blot showing CD71 expression in plasma membrane, cytoplasm, and total cells on DMSO- or U0126-treated erythroblasts. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) served as the loading control. (D) Quantitative analyses of CD71 protein levels from 3 independent experiments. (E) Representative immunofluorescence images showing localization of CD71 in DMSO-treated erythroblasts. White arrows indicate internalization of CD71. (F) Representative immunofluorescence images showing localization of CD71 in U0126-treated erythroblasts. White arrowheads indicate CD71 on cell membrane. Scale bar, 10 μm. Data are expressed as mean ± standard deviation. ***P < .001. n.s., not statistically significant.