Its primary physiological function is unclear. Has cytoprotective activity against internal or environmental stresses. May play a role in neuronal development and synaptic plasticity. May be required for neuronal myelin sheath maintenance. May play a role in iron uptake and iron homeostasis. Soluble oligomers are toxic to cultured neuroblastoma cells and induce apoptosis (in vitro). Association with GPC1 (via its heparan sulfate chains) targets PRNP to lipid rafts. Also provides Cu(2+) or Zn(2+) for the ascorbate-mediated GPC1 deaminase degradation of its heparan sulfate side chains (By similarity). Monomer and homodimer. Has a tendency to aggregate into amyloid fibrils containing a cross-beta spine, formed by a steric zipper of superposed beta-strands. Soluble oligomers may represent an intermediate stage on the path to fibril formation. Copper binding may promote oligomerization. Spinal cord and brain. Belongs to the prion family.