α-Calcium-Calmodulin-Dependent Kinase II is Associated with Paired Helical Filaments of Alzheimer's Disease

Alzheimer's disease (AD) is characterized pathologically by two distinguishable deposits in the brain, namely senile plaques and neurofibrillary tangles (NFT). Senile plaques are composed of fragments of the amyloid precursor protein, whereas NFT are composed primarily of paired-helical filaments (PHF). The latter are in turn composed principally of the microtubule-associated protein, tau. Tau in PHF is highly and unusually phosphorylated but the mechanisms leading to this unusual phosphorylation are not known. Using a combination of immunoblotting and kinase assays, we demonstrate that a discreet set of kinases copurify with PHF. One of these kinases was found by immunoblotting to be α-calcium-calmodulin-dependent kinase II (α-CaM kinase). Immunogold labeling revealed that α-CaM kinase was localized to a novel globular membranelike structure found at the ends of PHF. Since previous studies have shown α-CaM kinase to be involved in memory, its association with PHF may have important implications in understanding memory loss in AD. We also discuss the possibility that the association of α-CaM kinase with PHF may indicate sites where tau protein is converted into PHF.