Tau aggregation, the formation of solid deposits of altered tau protein called neurofibrillary tangles, is thought to be the most damaging of the processes underlying Alzheimer’s disease. The earlier accumulation of amyloid-β only sets the stage for the later accumulation of altered tau. When looking at why protein aggregates such as amyloid-β and tau accumulate only in later life, one of many candidate mechanisms is the decline of autophagy that takes place with aging. Autophagy is the name given to a collection of cellular maintenance processes responsible for clearing out damaged structures and other unwanted waste, such as protein aggregates. A range of interventions shown to slow aging in laboratory species involve raised levels of autophagy: if cells are more aggressively maintained, there is less of a chance for damage and dysfunction in cellular processes to spread and cause further harm. The other side of the coin is that lower levels of autophagy mean more metabolic waste, more damaged components, and more downstream consequences.
Early in the course of Alzheimer’s disease, neurons in the brain become clogged with toxic tau proteins that impair and eventually kill the neurons. A new study found that tau accumulates
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