Expression of neuropsin in oligodendrocytes after injury to the CNS.

Proteases are involved in a variety of processes including demyelination after injury to the central nervous system. Neuropsin is a serine protease, which is constitutively expressed in the neurons of the limbic system. In the present study, intrahippocampal kainate injection and enucleation were performed on adult mice. Neuropsin mRNA and protein expression was detected by in situ hybridization and immunohistochemistry. Double in situ hybridization confirmed that the mRNA expression was induced in oligodendrocytes. One day after kainate injection to the hippocampus, neuropsin mRNA was expressed, peaking 4-8 days postoperatively and disappearing at 14 days. Immunohistochemistry and immunoelectron microscopy revealed that neuropsin was expressed in the cell body of oligodendrocytes and myelin. To see if neuropsin degrades myelin protein, purified myelin was incubated with recombinant neuropsin. A decrease in the intensity of the bands of myelin basic protein was observed. These results indicate that neuropsin is involved in demyelination.