PRNP and early-onset autosomal dominant Alzheimer disease: Aβ accumulates during pathogenesis of Alzheimer's disease (AD) and PrPC reportedly acts as an inhibitor of β-secretase 1 (Parkin et al., 2007; Whitehouse et al., 2013), thereby reducing the amount of Aβ produced and suggesting that PrPC expression should protect against the development of AD.