Silencing of IRP1 or IRP2 increases CD63 expression. (A) IRP1 and IRP2 expression were silenced by shRNA. Cells were lysed in lysis buffer, and 20 µg of protein per sample was analyzed with anti-IRP1, anti-IRP2, anti-CD63, anti-CD81, anti-FTL, and anti–β-actin antibodies. (B) Quantification of IRP1, IRP2, FTL, CD63, and CD81 from panel A. Results are mean ± SEM (3 experiments). Significance was determined using the Student t test. **P < .01; ***P < .001; ****P < .0001.