Fig. 5. Transferrin internalized at 20°C reaches Rabip4-positive vesicles. The same experiment was performed using 3T3-L1 adipocytes (a-f) and HeLa cells (g-l). Cells were incubated for 1 hour at 20°C (a-c, g-i) or 4°C (d-f, j-l) with Texas-Red-coupled transferrin (500 µg/ml). Cells were washed in PBS, fixed with paraformaldehyde and permeabilized. Endogenous Rabip4 was detected by using specific antibodies followed by FITC-coupled anti-rabbit antibodies. Arrowheads indicate Rabip4-positive vesicles containing internalized transferrin. The inserts are enlargements of the boxed regions. Bar, 1 µm.