RHOGAP2 functional and molecular characterization in adult mouse brain

RhoGAP2, a member of the RhoGTPase-activating protein family, is involved in many processes in eukaryotic cells including organization of actin cytoskeleton, regulation of cell polarity, gene transcription and vesicular trafficking. RhoGAP2 is expressed in neurons, preferentially in the post-synaptic compartment of excitatory synapses, where it is thought to regulate cytoskeleton remodeling and dendritic spines morphology. The aim of this work is to define molecular and functional mechanisms underlying biological properties of RhoGAP2 in the central nervous system using an animal model knock out for RhoGAP2. First, we evaluated the behavioral phenotype in RhoGAP2 knock out (KO) adult animals compared to wild type (WT). KO animals exhibit a significant reduction of anxiety-like behavior tested in both elevated plus maze and marble burying tests. Animals were tested also for episodic and spatial memory and we found that KO mice had a significant impairment compared to WT mice. These data suggest that KO mice have a marked deficit in different hippocampal functions. To identify molecular mechanisms associated with behavioral impairments, we analyzed the expression profile of several synaptic markers in hippocampus lysates. We found statistically significant reduction of glutamate receptors and post-synaptic scaffold proteins suggesting possible alterations in spine formation and function. Furthermore, using yeast two hybrid and co-immunoprecipitation experiments, we demonstrated that RhoGAP2 is able to interact with KIF5A, a motor protein that mediates anterograde vesicular transport in neurons. All together these results suggest that RhoGAP2 could be involved in the regulation of both synaptic proteins transport along dendrites and spines formation.