Tau protein and the neurofibrillary pathology of Alzheimer's disease.

Abundant neurofibrillary tangles, neuropil threads and senile plaque neurites constitute the neurofibrillary pathology of Alzheimer's disease. They form in the nerve cells that undergo degeneration in the disease, in which their regional distribution correlates with the degree of dementia. Each lesion contains the paired helical filament (PHF) as its major component. PHFs are composed of the microtubule-associated protein tau in a hyperphosphorylated state. PHF-tau is hyperphosphorylated on all six adult brain isoforms. As a consequence, tau is unable to bind to microtubules and is believed to self-assemble into the PHF. Several candidate protein kinases and protein phosphatases have been identified through in vitro experiments.