CALCINEURIN (PHOSPHATASE 2B) IS PRESENT IN NEURONS CONTAINING NEUROFIBRILLARY TANGLES AND IN A SUBSET OF SENILE PLAQUES IN ALZHEIMERS-DISEASE

The accumulation of hyperphosphorylated tau species in neurons in Alzh eimer's disease (AD) might result from a relative decrease in their co ntent of protein phosphatases. In this study we have investigated the immunocytochemical distribution of calcineurin (phosphatase 2B) in the hippocampus and temporal cortex of human control subjects and in AD. Calcineurin was strongly expressed in neuronal perikarya and dendrites but only weakly in white matter tracts, both in controls and in AD. T he distribution of calcineurin was preserved in AD. By double-immunola belling with calcineurin antibodies and the AT8 antibody to paired hel ical filament-tau, it was observed that a strong calcineurin immunorea ctivity was still present in many neurons containing neurofibrillary t angles (NFT). Calcineurin was present in dystrophic neurites in some s enile plaques (SP) located in the hippocampal formation but more rarel y in neocortical areas; this calcineurin immunoreactivity did not alwa ys overlap with the tau immunoreactivity in SP. These results suggest that development of NFT in most neurons does not result from a major d ecrease of calcineurin expression.