Caspase-cleaved amyloid precursor protein in Alzheimer's disease

Caspase-3 mediated cleavage of the amyloid precursor protein (APP) has been proposed as a putative mechanism underlying amyloidosis and neuronal cell death in Alzheimer's disease (AD). We utilized an antibody that selectively recognizes the neo epitope generated by caspase-3 mediated cleavage of APP (alphadeltaC(csp)-APP) to determine if this proteolytic event occurs in senile plaques in the inferior frontal gyrus and superior temporal gyrus of autopsied AD and age-matched control brains. Consistent with a role for caspase-3 activation in AD pathology, alphadeltaC(csp)-APP immunoreactivity colocalized with a subset of TUNEL-positive pyramidal neurons in AD brains. AlphadeltaC(csp)-APP immunoreactivity was found in neurons and glial cells, as well as in small- and medium-size particulate elements, resembling dystrophic terminals and condensed nuclei, respectively, in AD and age-matched control brains. There were a larger number of alphadeltaC(csp)-APP immunoreactive elements in the inferior frontal gyrus and superior temporal gyrus of subjects with AD pathology than age-matched controls. AlphadeltaC(csp)-APP immunoreactivity in small and medium size particulate elements were the main component colocalized with 30% of senile plaques in the inferior frontal gyrus and superior temporal gyrus of AD brains. In some control brains, alphadeltaC(csp)-APP immunoreactivity appeared to be associated with a clinical history of metabolic encephalopathy. Our results suggest that apoptosis contributes to cell death resulting from amyloidosis and plaque deposition in AD.