Assembly of the N-cadherin complex during synapse formation involves uncoupling of p120-catenin and association with presenilin 1.

N-cadherin is an adhesion receptor that participates in both interaction between immature pre- and postsynaptic neurons and in the stabilization and function of matured neuron-neuron synapses. To better understand how the N-cadherin complex contributes to synapse formation, we examined its distribution and composition during synapse formation in the chick ciliary neurons. It was found that at early phases of synaptogenesis, N-cadherin is distributed in small clusters on the cell surface and primarily associates with p120-catenin and 3-catenin. In contrast, as synaptic contacts matured, larger N-cadherin clusters were found localized adjacent to the active zone and associated with PSI and y-catenin, while p120- and 3-catenin were dispersed among other cell regions, including axons. As it is known that PSI binds y-catenin and that uncoupled p120-catenin can alter the cytoskeleton via its effect on Rho GTPases, these changes in the molecular composition of the N-cadherin complex (represented by the uncoupling of p120-catenin and association with PS1) may correspond to distinct functional states of the complex involved in synaptic maturation.