Fig. 3. Rab22aS19N, a mutant with low affinity for GTP, is mostly cytosolic, whereas Rab22aQ64L, a mutant with low GTPase activity, localizes in large vesicles that are labeled by early and late endosomal markers. Cells expressing GFP-Rab22aS19N presented a diffuse cytosolic fluorescence. The protein was enriched in a perinuclear region that colocalized with a Golgi marker (BODIPY-TR ceramide) (A-C). The distribution of the Rab22aQ64L mutant was completely different. This GTPase-deficient mutant localized to large ring-shaped vacuoles that were labeled by a 5 minute uptake of Rh-HRP (D-F) or Rh-Tf (G-I). The protein also localized to late endosomes labeled by a 5 minute uptake of Rh-HRP followed by a 15 minute chase (J-L) or by immunocytochemistry using an anti CI-M6PR antibody (M-O). In some cells, Rab22aQ64L was also present at the plasma membrane (arrow). The bars represent 7 µm.
