PRNP and Alzheimer disease: It is recently proposed that the natively folded cellular prion protein (PrPC), which is involved in the development of nervous system through mediation of synaptic and neuroprotective roles [95–100] and promoting neurite outgrowth [101], is an Aβ oligomer receptor and is related to AD by mediating synaptic dysfunction induced via the Aβ oligomers [102].