The Y₈F mutation inhibits lysosome targeting of c-Mpl. (A) Cells expressing wild-type or c-Mpl Y₈F were pretreated with cycloheximide for 30 minutes with or without lysosome or proteasome inhibitors for an additional 30 minutes before Tpo stimulation for 60 minutes. Receptor expression was determined by Western blot and degradation was quantified by comparing the density of cells with or without Tpo. The data represent 3 independent experiments. (B) Flow cytometry for surface c-Mpl expression of wild-type and c-Mpl Y₈F–expressing cell lines after Tpo stimulation, followed by Tpo removal. The data represent mean of 3 independent experiments. Error bars represent SD.