Figure 1.

Localization of rab11 in the pericentriolar recycling compartment and the inhibitory effect of the S25N mutant on the accumulation of FITC–transferrin in that compartment. TRVb-1 cells that express the human transferrin receptor were transfected for transient expression with plasmids encoding: (A and B) the wild type (wt); (C and D) constitutively active (Q70L); (E and F) dominant negative (S25N); or (G and H) C-terminally deleted (ΔC) forms of rab11, as indicated on the left side of each pair of panels. Cells on coverslips were incubated with FITC–transferrin (FITC-Tf) for 1 h at 37°C and processed for indirect immunofluorescence with anti-rab11 antibody (rab11 Ab) and Texas Red-conjugated second antibody. Each pair of photographs (A-H) shows, for the same cells, the distribution of FITC–transferrin (left panels) and Texas Red (right panels) fluorescence. All cells express the transferrin receptor, so they all display intense green fluorescence of FITC–transferrin. The long arrows indicate the pericentriolar recycling compartment in the transfected cells, which in the right panels are identified by their intense Texas Red fluorescence. The short arrows point to the pericentriolar compartment in untransfected cells within the same cultures, and the arrowheads point to cytoplasmic vesicles containing both markers. Note that in cultures transfected with the S25N dominant negative rab11 mutant (E and F), the labeling of the pericentriolar compartment is diminished markedly in transfected cells but not in untransfected cells. Cells expressing the ΔC mutant of rab11 show a diffuse distribution of this protein.