FIGURE 5.
Clathrin-mediated and fluid phase endocytosis is decreased in the absence of CIP4. A, transferrin endocytosis in SV40-transformed Cip4−/− and Cip4+/+ MEF was measured following stimulation with a saturating concentration of 125I-transferrin for the indicated times ± S.E. (n = 3, p < 0.05). Asterisks indicate means that differ significantly from the scrambled/vector control. B, Cip4 wild-type (WT) or knock-out (KO) MEF were treated for 30 min with 0.25 mg/ml of FITC-dextran and the amount internalized determined by flow cytometry ± S.E. (n = 5, p < 0.05). C, fluid phase uptake in Cip4+/+ and Cip4−/− MEF was assessed by serum starvation and treatment with 4 mg/ml of HRP for 7 min. Cells were collected, nonspecifically bound HRP removed, and internalized HRP determined via enzymatic assay ± S.E. (n = 4, p < 0.05).