Calcium/calmodulin-dependent protein kinase II immunostaining is preserved in Alzheimer's disease hippocampal neurons

Alterations in protein phosphorylation may be important in the pathogenesis of Alzheimer's disease and recent observations suggest that a subset of protein kinase pathways may be selectively altered. Calcium/calmodulin-dependent protein kinase II CaM kinase II) is the most abundant protein kinase in the brain and is believed to play an important role in the regulation of synaptic transmission, long-term potentiation and other forms of neuronal plasticity. We have now evaluated brains of individuals with Alzheimer's disease for changes in the distribution and density of immunoreactivity for the alpha subunit of CaM kinase II. CaM kinase II immunoreactivity was found in cytoarchitectural areas and neurons vulnerable to the formation of neurofibrillary angles and senile plaques. Over 80% of neurons bearing neurofibrillary tangles expressed CaM kinase II. Loss of CaM kinase II immunoreactivity was found in CA1, commensurate with neuronal loss in this area. Remaining CA1 neurons, however, had preserved CaM kinase II immunoreactivity. Preservation in the distribution and density of CaM kinase II immunoreactivity was observed in other hippocampal regions and in a multimodal association area, area 20. These results suggest CaM kinase II expression in the Alzheimer's disease brain is unaltered despite marked neuropathological changes.