NEUREXIN-IV, CASPR AND PARANODIN - NOVEL MEMBERS OF THE NEUREXIN FAMILY - ENCOUNTERS OF AXONS AND GLIA

Axonal insulation is of key importance for the proper propagation of a ction potentials. In Drosophila and other invertebrates, it has recent ly been demonstrated that septate junctions play an essential role in axonal insulation or blood-brain-barrier formation. Neurexin IV, a mol ecular component of Drosophila septate junctions, has been shown to be essential for axonal insulation in the PNS in embryos and larvae. Int erestingly, a vertebrate homolog of Neurexin IV, caspr - also named pa ranodin - has been shown to localize to septate-like junctional struct ures. These vertebrate junctions are localized to the paranodal region of the nodes of Ranvier, between axons and Schwann cells. Caspr/paran odin might play an important role in barrier formation, and link neuro nal membrane components with the axonal cytoskeletal network.