Caspr1: ProductsContactin-associated protein 1 (Caspr1), also known as Neurexin-4, Paranodin, and NCP1, is an approximately 190 kDa transmembrane protein that is concentrated at paranodal junctions of axons during myelination. It is required for junction formation and ion channel localization and plays an important role in the propagation of saltatory nerve conduction. Caspr1 interacts with Contactins and Nogo-A at the paranodal junction and inhibits the binding of Contactin to glial cell Neurofascin. Caspr1 is proteolytically cleaved by Reelin, and this action is inhibited by the cellular prion protein (PrP). The ECD contains one Factor 5/8-like domain, four Laminin-G-like domains, two EGF-like domains, and one Fibrinogen-like domain.