For tau-toxicity in Alzheimer’s disease, Hsp90 has the opposite effect as it stabilizes the toxic soluble oligomers of tau in collaboration with its co-chaperones FKBP51/52 and Aha1; in this case, it prevents the formation of the cytoprotective larger aggregates [172–174]. The gene discussed is HSP90AA1; the disease is early-onset autosomal dominant Alzheimer disease.