PARANODIN, A GLYCOPROTEIN OF NEURONAL PARANODAL MEMBRANES

Ranvier nodes are flanked by paranodal regions, at the level of which oligodendrocytes or Schwann cells interact closely with axons. Paranod es play a critical role in the physiological properties of myelinated nerve fibers. Paranodin, a prominent 180 kDa transmembrane neuronal gl ycoprotein, was purified and cloned from adult rat brain, and found to be highly concentrated in axonal membranes at their junction with mye linating glial cells, in paranodes of central and peripheral nerve fib ers. The large extracellular domain of paranodin is related to neurexi ns, and its short intracellular tail binds protein 4.1, a cytoskeleton -anchoring protein. Paranodin may be a critical component of the macro molecular complex involved in the tight interactions between axons and myelinating glial cells characteristic of the paranodal region.