Accumulation of immunoreactivity to ubiquitin carboxyl-terminal hydrolase PGP 9.5 in axons of human cases with spinal cord lesions

The protein gene product PGP 9.5 is one of the major polypeptides in neuron s. It can act as a ubiquitin carboxyl-terminal hydrolase in ubiquitin-media ted degradation of proteins. The present study was performed to find out if human cases with spinal cord trauma present immunohistochemical signs of P GP 9.5 accumulation in injured axons known to accumulate ubiquitin. For com parison, we used six autopsy cases without spinal cord pathology, one case with syringomyelia, one case with ischaemic injury of the cord, and six ALS cases. Controls presented PGP 9.5-immunostained axons of weak to moderate intensity in the longitudinal tracts. Immunoreactivity was not detected in nerve cell bodies, glial cells or axons of the grey matter. All nine trauma cases showed axonal swellings, but their numbers varied. Intensely immunos tained axonal swellings were particularly abundant in cases with a survival period up to I month after trauma. Strongly immunoreactive axons were pres ent also in the cases with infarct and syringomyelia. In conclusion, human cases with spinal cord trauma and other focal injuries present signs of PGP 9.5 accumulation in severed axons possibly resulting from disturbed axonal transport. PGP 9.5 thus seems to be present and may take part in ubiquitin -mediated degradation of proteins in injured axons of the spinal cord.