NCAM stimulates the ras‐MAPK pathway and CREB phosphorylation in neuronal cells

The neural cell adhesion molecule NCAM plays an important role in axonal growth, learning, and memory. A signaling pathway has been elucidated in which clustering of the NCAM140 isoform in the neural plasma membrane stimulated the activating phosphorylation of mitogen‐activated protein kinases (MAPKs) and the transcription factor cyclic AMP response‐element binding protein (CREB). NCAM clustering transiently induced dual phosphorylation (activation) of the MAPKs ERK1 and ERK2 (extracellular signal‐regulated kinases) by a pathway regulated by the focal adhesion kinase p125fak, p59fyn, Ras, and MAPK kinase. CREB phosphorylation at serine 133 induced by NCAM was dependent in part on an intact MAPK pathway. c‐Jun N‐terminal kinase, which is associated with apoptosis and cellular stress, was not activated by NCAM. Inhibition of the MAPK pathway in rat cerebellar neuron cultures selectively reduced NCAM‐stimulated neurite outgrowth. These results define an NCAM signal transduction mechanism with the potential for modulating the expression of genes needed for axonal growth, survival, and synaptic plasticity. © 1999 John Wiley & Sons, Inc. J Neurobiol 38: 542–558, 1999