Signal functions of NCAM

The neuronal protein of cell adhesion belongs to the immunoglobulin superfamily of cell adhesion proteins. It consists of an extracellular domain providing homo-and heterophilic interactions with surrounding molecules that are located on the cell surface or are components of the extracellular matrix, a transmembrane part, and intracellular domains (NCAM140 and NCAM180). In addition to its role in cell adhesion, NCAMs act as a signal receptor molecule. Adhesion and initiation of signal cascades induced by binding to the NCAM extracellular domains occur interdependently but influence each other. The homo-and heterophilic binding of NCAM can activate a number of intracellular signal cascades resulting in neurite growth, axone guidance, axone myelinization, and formation of nerve fibers. It has been established that the intracellular signal is initiated by the interactions between NCAMs and fibroblast growth factor receptors (FGFR), non-receptor tyrosine kinases (Fyn and FAK), glia-derived neurotrophic factor (GDNF), ATP, prion proteins, and several other molecules. The review discusses possible mechanisms of functioning of these signal cascades.