Mechanisms of protein seeding in neurodegenerative diseases.

Most age-associated neurodegenerative diseases involve the aggregation of specific proteins within the nervous system. In Alzheimer disease, the insidious pathogenic process begins many years before the symptoms emerge, and the lesions that characterize the disease—senile plaques and neurofibrillary tangles—ramify systematically through the brain. We review evidence that the -amyloid and tau proteins, which aggregate to form senile plaques and neurofibrillary tangles, respectively, are induced to misfold and self-assemble by a process of templated conformational change that amplifies a toxic species. Recent data also indicate that the spread of these lesions from one site to another is mediated by the cellular uptake, transport, and release of endogenous seeds formed by the cognate proteins. This simple pathogenic principle suggests that the formation, trafficking, and metabolism of pathogenic protein seeds are promising therapeutic targets for Alzheimer disease and other neurodegenerative disorders.