c-Mpl internalization is reduced in AP2α2-depleted cells. BaF-Mpl cells were transfected with siRNA specific to the AP2α2 subunit, which is essential for the function of AP2. (A) AP2α2 depletion was analyzed by Western blot and was maximal 48 hours after transfection (approximately 75% depletion). (B) Tpo-stimulated c-Mpl internalization was then determined by flow cytometry in AP2α2-depleted BaF-Mpl cells 48 hours after transfection (**P < .01). Error bars represent SD.