A Study On The Roles Of Nuclear-localized SrGAPs In Neuronal Differentiation

SrGAPs (Slit-Robo GTPase-activating proteins) are important RhoGAP proteins that are involved in Slit-Robo signaling pathway. In mammals, the srGAP family consists of four members: srGAP1, srGAP2, srGAP3 and ARHGAP4. Recently, srGAP1, srGAP2 and srGAP3 have been implicated in axon guidance, neuronal migration, neurite outgrowth and dendritic morphogenesis. The srGAPs genes highly expressed in SVZ/VZ of neurogenesis indicates that srGAPs may be involved in the early stage of neuronal development. Previously we have found that srGAPs show distinct nucleocytoplasmic localization during different neuronal developmental stages. However, the function of the nuclear-localized srGAPs is largely unknown. In the present study, we are investigating the roles of nuclear-localized srGAPs in neuronal differentiation. Using western blotting, we show that srGAPs are mainly distributed in central nervous system and highly expressed in rat cerebral cortex during P1 to P14 of neuronal development. In cultured cerebral cortical neurons and Neuro2A cells, srGAP3 is found co-localize with Brg1 in the nuclear. Brg1 is the central ATPase of the chromatin remodeling complex (BAF complex). In Neuro2A cells, the endogenous Brg1 could be co-immunoprecipitated with srGAP3. We also demonstrate that srGAP3 negatively regulates VPA-induced neuronal differentiation of Neuro2A cells. The effect of srGAP3 on Neuro2A cells differentiation is related to the Rac1 activity. Further, srGAP3 overexpression in Neuro2A cells dramatically reduces GAP-43 protein level. Together, our data suggest that nuclear-localized srGAPs play critical roles in neuronal differentiation.