NgCAM takes a scenic route to the axon

To establish and maintain their asymmetrical structure, neurons must sort different proteins to their somatodendritic and axonal membranes. Previous work has supported three different models to explain selective transport to axons: direct transport to the axon; selective fusion of vesicles with the axon; and transport to the somatodendritic membrane followed by transcytosis. A detailed analysis by Wisco et al. (page 1317) now identifies evidence that the adhesion molecule NgCAM can take two of these three paths.

Some recent evidence suggests that vesicles containing NgCAM are blocked from fusing with the somatodendritic membrane in the first place. But in a kinetic analysis, Wisco et al. show that in fact NgCAM does transiently appear on the somatodendritic membrane, but is then endocytosed and sent to the axonal membrane by a transcytotic pathway.

The NgCAM...