PRNP (PrP, Prion protein) is a membrane glycosylphosphatidylinositol-anchored glycoprotein prone to forming rod-like structural aggregations. It is thought to engage in antimicrobial and antiviral activity, possibly acting in microbial entrapment and sequestration, and it interacts with amyloid-beta peptide in these innate immunity processes. Misfolded prion proteins cause fatal neurodegenerative diseases such as Creutzfeldt-Jakob disease (also known as Mad Cow Disease), and inherited mutations in PRNP are associated with the genetic form of Creutzfeldt-Jakob disease, fatal familial insomnia, Gerstmann-Straussler disease, Huntington disease-like 1, and kuru. In immunohistochemistry of normal tissue, PRNP has highest cytoplasmic and membranous positivity in the central nervous system, with lower levels of expression in other tissues including the adrenal gland, lung, pancreas, skin, gastrointestinal tract, and in granulocytes. References: Neuropsychiatr Dis Treat. 2018; 14: 2067–2085, PMID: 30147320; J Alzheimers Dis Rep. 2017; 1(1): 263–275, PMID: 30480243;