Caspr, also known as contactin-associated protein (CNTNAP), is a transmembrane protein that plays a crucial role in the nervous system. It is particularly important for the formation and maintenance of the myelin sheath in both the central and peripheral nervous systems. Caspr is expressed at high levels in the paranodal regions of myelinated axons, where it contributes to the formation of septate-like junctions between axons and myelinating cells. Caspr is also essential for the proper localization of voltage-gated potassium channels (VGKC) in the nervous system. It helps in the aggregation and development of K channels (Kv1.1 and Kv1.2) in the proximal nodal region, which is crucial for axon formation and stability. Furthermore, Caspr is a component of the paranodal junctions, which are critical for maintaining the integrity of myelinated axons. It helps in the reciprocal signaling between axons and glial cells, ensuring proper axonal function.