RICS, a novel GTPase-activating protein for Cdc42 and Rac1, is involved in the β-catenin-N-cadherin and N-methyl-D-aspartate receptor signaling

Cadherin adhesion molecules are believed to be important for synaptic plasticity. beta-Catenin, which links cadherins and the actin cytoskeleton, is a modulator of cadherin adhesion and regulates synaptic structure and function. Here we show that)beta-catenin interacts with a novel GTPase-activating protein, named RICS, that acts on Cdc42 and Rac1. The RICS-betacatenin complex was found to be associated with N-cadherin, N-methyl-D-aspartate receptors, and postsynaptic density-95, and localized to the postsynaptic density. Furthermore, the GTPase-activating protein activity of RICS was inhibited by phosphorylation by Ca2+ /calmodulin-dependent protein kinase H. These results suggest that RICS is involved in the synaptic adhesion- and N-methyl-D-aspartate-mediated organization of cytoskeletal networks and signal transduction. Thus, RICS may regulate dendritic spine morphology and strength by modulating Rho GTPases.