The neural cell adhesion molecule (NCAM) in development and plasticity of the nervous system

The neural cell adhesion molecule (NCAM) is a member of the immunoglobulin superfamily and is strongly expressed in the nervous system. NCAM is found in three major forms, of which two-NCAM-140 and NCAM 180-are transmembrane proteins, while the third-NCAM-120-is attached to the membrane via a glycos ylphosphatidyl inositol anchor. In addition, soluble NCAM forms exist in br ain, cerebrospinal fluid, and plasma. NCAM mediates cell adhesion through h emophilic as well as through heterophilic interactions. Following NCAM bind ing, transmembrane signalling is believed to be activated, resulting in inc reased intracellular calcium. By mediating cell adhesion to other cells and to the extracellular matrix and by activating intracellular signaling path ways, NCAM influences cell migration, neurite extension, and fasciculation, and possibly formation of synapses in the brain. From studies on NCAM knoc k-out mice, NCAM have been shown to be crucial for the formation of the olf actory bulb and the mossy fiber system in the hippocampus. In addition, NCA M is important for neuronal plasticity in the adult brain associated with l earning and regeneration. (C) 1998 Elsevier Science Inc.