Subunit composition and novel localization of K+ channels in spinal cord.

Axonal K+ channels involved in normal spinal cord function are candidate targets for therapeutics, which improve sensorimotor function in spinal cord injury. To this end, we have investigated the expression, localization, and coassociation of Kv1 alpha and beta subunits in human, rat, and bovine spinal cord. We find that Kv1.1, Kv1.2, and Kvbeta2 form heteromultimeric complexes at juxtaparanodal zones in myelinated fibers. However, these same complexes are also present in paranodal regions of some spinal cord axons, and staining with antibodies against Caspr, a component of the paranodal axoglial junction, overlaps with these paranodal K+ channels. This latter observation suggests a unique role for these channels in normal spinal cord function and may provide an explanation for the sensitivity of spinal cord to K+ channel blockers. Moreover, the conservation of these characteristics between human, rat, and bovine nodes of Ranvier suggests an essential role for this defined channel complex in spinal cord function.