Fig. 2. Reversal of SARA-mediated endosome enlargement by Rab5S34N overexpression. MDCK cells cotransfected with GFP-SARA (green) with Rab5Q79L (A-C) or Rab5S34N (D-F) were fixed for Rab5 immunostaining (red). Rab5 transfected cells can be easily distinguished from the neighboring untransfected cells based on their higher level of Rab5 immunolabeling. Because the photographic exposure was chosen to highlight the transfected cells, the endogenous Rab5 labeling is negligible in these figures. (A-C) Rab5Q79L labeling is extensively colocalized with SARA on enlarged early endosomal membranes. (D-F) In contrast to the cells singly transfected with GFP-SARA, in which green fluorescence is observed on enlarged endosomal membranes (arrowheads), GFP signals are distributed diffusely in the cytosol and on small puncta in the cells co-transfected with GFA-SARA and Rab5S34N (arrow). Bar, 10 µm.