PRNP and familial Alzheimer disease: Importantly, CYPs and FKBPs facilitate the proper folding and prevent aggregation of human pathogenic proteins such as the prion protein (PrP) and presenilin 1, which is linked with familial Alzheimer's disease (Cohen & Taraboulos, 2003; van de Hoef et al., 2013; Wang et al., 2005).