SPRN (shadow of prion protein), also known as SHO or SHADOO, is a 151 amino acid cytoplasmic protein that is mainly expressed in brain. SPRN is considered a prion-like protein that has PrP(C)-like neuroprotective activity and may act as a modulator for the biological actions of normal and abnormal PrP. In humans, mutations in the gene encoding SPRN may be associated with variant and sporadic Creutzfeldt-Jakob disease, a degenerative neurological disorder that is incurable and invariably fatal.