INVESTIGATING CRMP4 FUNCTION IN NERVE REGENERATION

Abstract

Background: The failure of CNS neurons to spontaneously regenerate following injury can be partially attributed to the expression of neurite outgrowth inhibitory myelin associated inhibitors (MAIs). MAIs signal through a tripartite receptor complex to activate the cytosolic protein RhoA and influence cytoskeletal dynamics. RhoA antagonists promote neuronal survival and regeneration in animal models of nerve injury. However, RhoA's potential as a therapeutic target may be limited by its widespread roles in multiple cellular processes and cell types. In an attempt to discover more specific therapeutic targets to promote nerve regeneration, our lab identified the cytosolic phosphoprotein CRMP4b (Collapsin Response Mediator Protein 4b) as a protein that functionally interacts with RhoA to mediate neurite outgrowth inhibition. Blockade of the RhoA-CRMP4b interaction with a competitive peptide (C4RIP) attenuates myelin-dependent neurite outgrowth inhibition. Methods: We are currently investigating the in vivo roles of CRMP4in regeneration in an optic nerve injury model by developing a readily deliverable version of C4RIP. Results: Preliminary results suggest that overexpression of C4RIP in retinal ganglion cells by adeno-associated virus does not promote regeneration. However, studies investigating the ability of C4RIP to promote nerve regeneration into the optic nerve following stimulation of neurons into anactive growth state are currently in progress. Conclusion: Elucidating the role of CRMP4 in nerve regeneration may provide insight into the molecular mechanisms following nervous system injury and lead to the development of more specific therapeutic interventions. Reference: Alabed YZ, Pool M, Ong Tone S, Fournier AE.Identification of CRMP4 as a convergent regulator of axon outgrowth inhibition. J Neurosci 2007;27:1702-11.