HSP90AA1 and Alzheimer disease: For example, promoted HSP90α facilitates APP processing to Aβ and the aberrant aggregation of Aβ (AD), increases the accumulation of p-tau in neuronal tissue (AD) and mediates the fusion of multivesicular bodies with the plasma membrane and the subsequent release of exosomes, the exosomes containing α-syn aggregates facilitate spreading the aggregates to other cells (PD).