FIGURE 1. Transient Rab5 activation during phagocytosis monitored by Raichu-Rab5.

a, Schematic representation of Raichu-Rab5 bound to GDP or GTP. b–d, _v3 integrin-expressing Swiss3T3 cells were transfected with pRaichu-Rab5 (b) or pRaichu-Rab5/PM (c, d) and cultured together with apoptotic thymocytes in the presence of MFG-E8. Thereafter, images were obtained every 1 min. Top panels show phase-contrast (PC) and FRET/CFP ratio images at the indicated time points (min). In the intensity-modulated display mode shown here, eight colours from red to blue are used to represent the FRET/CFP ratio, with the intensity of each colour indicating the mean intensity of FRET and CFP. The upper and lower limits of the ratio range are shown at the bottom, and the divisions are evenly spaced. Time sequences in the bottom panels show the PC, FRET/CFP ratio and CFP images of the engulfed sites marked by white squares in the top panels. Scale bars, 20 m.