NR-CAM - A CELL-ADHESION MOLECULE WITH LIGAND AND RECEPTOR FUNCTIONS

Nr-CAM Ng-CAM-related cell adhesion molecule) is expressed only in the nervous system on a subset of neurons and non-neuronal cells, includi ng floor-plate cells in the spinal cord and Schwann cells. It is a mem ber of the immunoglobulin (Ig) superfamily and can bind by a hemophili c mechanism but its heterophilic interactions may be of greater biolog ical significance. Nr-CAM functions as a neuronal receptor for neurite -growth-promoting stimuli provided by contactin/F11, neurofascin, and RPTP beta. In addition, by binding to neuronal receptors such as axoni n-1, it can modulate axonal guidance. Nr-CAM can also interact lateral ly with contactin/F11 within the plasma membrane in the form of a comp lex that may transmit signals to regulate axonal growth. This review s ummarizes the structure and expression of Nr-CAM and discusses its pot ential functions as a ligand and as a receptor during neural developme nt.