Fig. 4. Endocytic transferrin is transported through RIN3-positive vesicles to early endosomes in HeLa cells. HeLa cells expressing RFP-RIN3 were pulse-chased with Alexa-488/transferrin at 4°C, shifted to 25°C to allow its internalization and further incubated for the indicated times. The fluorescence of RFP-RIN3 (left) and transferrin (middle) was visualized by confocal microscopy, and merged images of the two signals are displayed in yellow (right). Arrowheads indicate the co-localization of RIN3 and transferrin. Scale bars, 10 µm.