BETA-AMYLOID PRECURSOR PROTEIN (BETA-APP) AS A MARKER FOR AXONAL INJURY AFTER HEAD-INJURY

It has been demonstrated recently that beta-amyloid protein (betaAP), generally associated with the plaques of Alzheimer's disease, can also be found in the brains of survivors of head injury. In this study the distribution of the betaAP precursor protein (betaAPP) was examined immunohistochemically to determine if it is colocalized with betaAP in such cases. BetaAPP immunoreactivity was observed in neuronal perikarya in the neocortex and in dystrophic neurites surrounding betaAP immunoreactive plaques i.e. in a distribution similar to that seen in Alzheimer's disease. In addition, betaAPP immunoreactivity was noted within white matter tracts where it marked damaged axons. However, no colocalisation of betaAPP with betaAP was observed in any white matter region. These results indicate that processing of betaAPP to produce betaAP occurs in the synaptic terminal field of axons and illustrate the utility of betaAPP immunoreactivity as a general marker for axonal injury.