Expression of a novel serine protease by oligodendrocytes

Using a degenerate oligonucleotide cloning strategy we have identified a novel serine protease termed Myelencephalon-Specific Protease (MSP). MSP rnRNA is predominantly expressed in the nervous system and is most dense in the spinal cord and brain stem. Using in situ hybridization histochemistry, we have shown that MSP mRNA is abundantly expressed throughout all regions of the normal adult rat spinal cord, including the alpha motoneurons of lamina IX, and that it is higher by a factor of three in the white compared to the gray matter. MSP mRNA expression was shown to increase 3-fold in the white matter and 1.5 fold in the gray matter after intraperitoneal injection of the AMPA/kainate glutamate receptor-specific agonist kainic acid (Scarisbrick et al., 1997). These observations indicate that MSP may play a fundamental role in normal homeostasis and in the response of the spinal cord to injury. To explore this idea we have generated a monoclonal antibody to MSP and have used this to further characterize the neuronal and neuroglial specific expression patterns of this novel protease. In the white matter of the normal adult rat spinal cord we have shown that MSP predominates in 2′, 3′-cyclic nucleotide 3′-phosphodiesterase immunoreactive oligodendrocytes These findings suggest a potential role for MSP in myelination of CNS fiber tracts.