Fig. 6.

Mechanism of TfR loss in response to Rabenosyn-5 depletion. (A) Western blotting of TfR in cells transfected with TfR-GFP and treated with scrambled (Sc) or Rabenosyn-5 (Si) siRNA for 72 h after transfection. GAPDH is used as a loading control. (B) Cells were transfected with scrambled (Sc) or Rabenosyn-5–directed (Si) oligonucleotides and 48 h were left untreated or were treated with 100 nM Bafilomycin A1 (Baf). After 24 h lysates were harvested and analyzed by Western blotting and immunofluorescence for the TfR. (C) In this model, TfR is internalized into endosomes marked by Rabenosyn-5, which are juxtaposed to clathrin-coated plasma membrane regions; from these endosomes TfR is recycled rapidly to the plasma membrane. A small fraction of TfR may be directed into EEA1-enriched endosomes, which are destined for lysosomal degradation. In the absence of Rabenosyn-5, clathrin-coated structures accumulate, and their cargo enters lysosome-directed pathways, resulting in low recycling rates.