Fig. 6.

From CURL to tubular sorting endosome. Left panel reproduction of the first electron micrograph using double-immunogold labeling, showing the uncoupling of a ligand (asialoglycoprotein (ASGP), indicated by 5 nm gold particles) from its receptor (indicated by 15 nm gold particles) in early endosomes, at that time called CURL (compartment for uncoupling receptor and ligand). The ASGP receptor is found in tubules implicated in its recycling, whereas ASGP en route to lysosomes remains in the vacuole. Originally published by Geuze et al. (1983). Right panel, reproduction from Peden et al. (2004), showing by triple labeling that the adaptor protein AP-3 (15 nm gold particles), the lysosomal membrane protein LAMP-1 (10 nm gold particles) and the recycling ASGP receptor (5 nm gold particles) co-localize in the tubules emanating from endosomal vacuoles. This work gave rise to the concept of the tubular sorting endosome