CONSTITUTIVE EXPRESSION OF HEAT-SHOCK PROTEIN-90 (HSP90) IN NEURONS OF THE RAT-BRAIN

Immunoblot analysis, immunocytochemistry and immune-electron microscopy were employed to study the expression of HSP90 protein in the adult rat brain, using a specific polyclonal antiserum. Immunoblot analysis demonstrated equal levels of HSP90 in microdissected extracts from hippocampus, cortex, striatum and cerebellum. Immunocytochemistry and immune-electron microscopy provided evidence that HSP90 is markedly expressed thoughout all neuronal subpopulations of the CNS but not in non-neuronal cells except ependyma and choroid plexus. At the ultrastructural level, HSP90 immunoreactivity was predominantly found in perikarya but to a lesser extent also in dendrites and nuclei. The constitutive expression of HSP90 in widespread neuronal cell populations suggests a functional role in the physiological molecular program of CNS neurons.