Ezrin Mediates Neuritogenesis via Down-Regulation of RhoA Activity in Cultured Cortical Neurons

Neuronal morphogenesis is implicated in neuronal function and development with rearrangement of cytoskeletal organization. Ezrin, a member of Ezrin/Radixin/Moesin (ERM) proteins links between membrane proteins and actin cytoskeleton, and contributes to maintenance of cellular function and morphology. In cultured hippocampal neurons, suppression of both radixin and moesin showed deficits in growth cone morphology and neurite extensions. Down-regulation of ezrin using siRNA caused impairment of netrin-1-induced axon outgrowth in cultured cortical neurons. However, roles of ezrin in the neuronal morphogenesis of the cultured neurons have been poorly understood. In this report, we performed detailed studies on the roles of ezrin in the cultured cortical neurons prepared from the ezrin knockdown (Vil2(kd/kd)) mice embryo that showed a very small amount of ezrin expression compared with the wild-type (Vil2(+/+)) neurons. Ezrin was mainly expressed in cell body in the cultured cortical neurons. We demonstrated that the cultured cortical neurons prepared from the Vil2(kd/kd) mice embryo exhibited impairment of neuritogenesis. Moreover, we observed increased RhoA activity and phosphorylation of myosin light chain 2 (MLC2), as a downstream effector of RhoA in the Vil2(kd/kd) neurons. In addition, inhibition of Rho kinase and myosin II rescued the impairment of neuritogenesis in the Vil2(kd/kd) neurons. These data altogether suggest a novel role of ezrin in the neuritogenesis of the cultured cortical neurons through down-regulation of RhoA activity.