Phosphorylation of serine 774 of the neural cell adhesion molecule is necessary for cyclic adenosine monophosphate response element binding protein activation and neurite outgrowth.

The neural cell adhesion molecule (NCAM) plays a fundamental role during development and regeneration. NCAM is expressed in three major isoforms, two of them with intracellular domains of different length and one without any intracellular domain. The cytoplasmic domain of NCAM contains, depending on the isoform, up to 49 phosphorylation sites, and it has been demonstrated previously by phosphoproteomic analysis that NCAM is phosphorylated on serine 774. However, the impact of NCAM phosphorylation is unclear. Here we have analyzed the phosphorylation of serine 774 in more detail and found that phosphorylation of this site is crucial for NCAM-mediated signal transduction. A serine-to-alanine exchange at position 774 (NCAM140-S774A) resulted in decreased activation of the cAMP response element binding protein (CREB) after NCAM stimulation and, as a consequence, in decreased neurite outgrowth of NCAM140-S774A-transfected B35 neuroblastoma cells.