Fig. 10. Coexpression of TfR with wt and mutant Rab5a. Confocal images of hippocampal neurons expressing TfR-GFP with or without wt and mutant HA-Rab5a for 72 (A-D) or 24 hours (E-F). Neurons were double immunolabeled for GFP and either HA or endogenous EEA1. (A) A view of a neuron expressing TfR-GFP in somatodendritic endosomes where it colocalizes with endogenous EEA1. High magnification of proximal dendritic puncta (enlarged frame a), however, reveals segregation of TfR-GFP and EEA1 in tubular structures. A view of a distal dendrite (enlarged frame b) reveals puncta that contain TfR-GFP but are devoid of EEA1. (B) TfR-GFP colocalizes with HA-Rab5a(Q79L) in giant endosomal vesicles in the soma (enlarged frame) and in dendrites (arrows) but not in axons (arrowheads). (C) In 72-hour coexpression experiments with Rab5(S34N), TfR traffics to dendritic puncta and its trafficking is similar to conditions without the mutant as shown in D. (E) In 24-hour coexpression experiments, however, with Rab5a(S34N), TfR accumulates in the tips of dendrites (enlarged frames a,b) but not axons (enlarged frame c) and is largely absent from dendritic puncta. (F) For comparison, a view of a neuron coexpressing TfR and wt Rab5a for 24 hours shows trafficking to dendritic puncta. Scale bars, 10 µm.