Uncovering multiple axonal targeting pathways in hippocampal neurons

J Cell Biol. 2003 Sep 29;162(7):1317-28. doi: 10.1083/jcb.200307069.

Abstract

Neuronal polarity is, at least in part, mediated by the differential sorting of membrane proteins to distinct domains, such as axons and somata/dendrites. We investigated the pathways underlying the subcellular targeting of NgCAM, a cell adhesion molecule residing on the axonal plasma membrane. Following transport of NgCAM kinetically, surprisingly we observed a transient appearance of NgCAM on the somatodendritic plasma membrane. Down-regulation of endocytosis resulted in loss of axonal accumulation of NgCAM, indicating that the axonal localization of NgCAM was dependent on endocytosis. Our data suggest the existence of a dendrite-to-axon transcytotic pathway to achieve axonal accumulation. NgCAM mutants with a point mutation in a crucial cytoplasmic tail motif (YRSL) are unable to access the transcytotic route. Instead, they were found to travel to the axon on a direct route. Therefore, our results suggest that multiple distinct pathways operate in hippocampal neurons to achieve axonal accumulation of membrane proteins.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Axons / physiology*
  • Cell Adhesion Molecules / genetics
  • Cell Adhesion Molecules / metabolism*
  • Cell Membrane / physiology
  • Cell Polarity / physiology
  • Cells, Cultured
  • Dendrites / physiology
  • Endocytosis / physiology
  • Endosomes / metabolism
  • Hippocampus / cytology
  • Kinetics
  • Neurons / physiology*
  • Neurons / ultrastructure
  • Protein Sorting Signals / physiology
  • Protein Transport / physiology*
  • Rats

Substances

  • Cell Adhesion Molecules
  • Protein Sorting Signals