Absence of abnormal hyperphosphorylation of tau in intracellular tangles in Alzheimer's disease.

Adult human nerve cells contain tau protein, a phosphorylated microtubule-associated protein, that is hyperphosphorylated in the fetus and in patients with Alzheimer's disease. Hyperphosphorylation, which diminishes the microtubule-binding capacity of tau, destabilizes microtubules and may enhance the formation of paired helical filaments that constitute neurofibrillary tangles in Alzheimer's disease. Here, we use phosphorylation-dependent anti-tau antibodies to detect specific epitopes that characterize hyperphosphorylated tau. Our demonstration of intracellular tangles containing full-length tau that are not immunolabeled by these antibodies suggests that hyperphosphorylation of tau is not obligatory in the formation of neurofibrillary tangles in Alzheimer's disease.