Glutamate-induced delta-catenin redistribution and dissociation from postsynaptic receptor complexes.

Delta-catenin (or neural plakophilin-related arm-repeat protein/neurojungin) is primarily a brain specific member of the p120(ctn) subfamily of armadillo/beta-catenin proteins that play important roles in neuronal development. Our previous studies have shown that the ectopic expression of delta-catenin induces the formation of dendrite-like extensions and that the overexpression of delta-catenin promotes dendritic branching and increases spine density. Here we demonstrate that delta-catenin displays a dendritic distribution pattern in the adult mouse brain and is co-enriched with postsynaptic density-95 (PSD-95) in the detergent insoluble postsynaptic scaffolds. Delta-catenin forms stable complexes with excitatory neurotransmitter receptors including ionotropic N-methyl-D-aspartic acid receptor 2A (NR2A), metabotropic glutamate receptor 1alpha (mGluR1alpha), as well as PSD-95 in vivo. In cultured primary embryonic neurons, delta-catenin clusters co-distribute with filamentous actin and resist detergent extraction. In dissociated hippocampal neurons overexpressing delta-catenin, glutamate stimulation leads to a rapid redistribution of delta-catenin that can be attenuated by 6-cyano-7-nitroquinoxaline-2,3-dione and dizocilpine, selective inhibitors of ionotropic glutamate receptors. Upon glutamate receptor activation, delta-catenin becomes down-regulated and its association with NR2A and mGluR1alpha in cultured neurons is diminished. These findings support a possible functional connection between delta-catenin and the glutamatergic excitatory synaptic signaling pathway during neuronal development.