RAB11 REGULATES RECYCLING THROUGH THE PERICENTRIOLAR RECYCLING ENDOSOME

Small GTPases of the rab family are crucial elements of the machinery that controls membrane traffic. In the present study, we examined the distribution and function of rab11. Rab11 was shown by confocal immuno fluorescence microscopy and EM to colocalize with internalized transfe rrin in the pericentriolar recycling compartment of CHO and BHK cells. Expression of rab11 mutants that are preferentially in the GTP- or GD P-bound state caused opposite effects on the distribution of transferr in-containing elements; rab11-GTP expression caused accumulation of la beled elements in the perinuclear area of the cell, whereas rab11-GDP caused a dispersion of the transferrin labeling. Functional studies sh owed that the early steps of uptake and recycling for transferrin were not affected by overexpression of rab11 proteins. However, recycling from the later recycling endosome was inhibited in cells overexpressin g the rab11-GDP mutant. Rab5, which regulates early endocytic traffick ing, acted before rab11 in the transferrin-recycling pathway as expres sion of rab5-GTP prevented transport to the rab11-positive. recycling endosome. These results suggest a novel role for rab11 in controlling traffic through the recycling endosome.