Arf6, Rab11 and transferrin receptor define distinct populations of recycling endosomes.

Recycling endosomes are key platforms for endocytic recycling that return internalized molecules back to the plasma membrane. To determine how recycling endosomes perform their functions, searching for proteins and lipids that specifically localized at recycling endosomes has often been performed by colocalization analyses between candidate molecules and conventional recycling endosome markers. However, it remains unclear whether all the conventional markers have identical localizations. Here we report finding that three well-known recycling endosome markers, i.e., Arf6, Rab11 and transferrin receptor (TfR), have different intracellular localizations in PC12 cells. The results of immunofluorescence analyses showed that the signals of endogenous Arf6, Rab11 and TfR in nerve growth factor-stimulated PC12 cells generally differed, although there was some overlapping. Our findings provide new information about recycling endosome markers, and they highlight the heterogeneity of recycling endosomes.