What are Prions?

Encoded by the PRNP gene, prions are proteins that are mainly found on the surface of nerve cells in the brain of all mammals. In its normal form, PrPc (Cellular Prion Protein) is responsible for a multitude of functions that are vital to the processes of the central nervous system, such as the transportation of copper into cells, the protection of neurons, and the formation of synapses. Without PrPc, cells throughout the different body systems will cease to function properly. Despite having many neuroprotective functions, prion proteins can also lead to many neurodegenerative diseases through an alteration in its physical structure.

A PrPSc (Prion Protein Scrapie) is the misfolded form of a normal prion protein. Although both forms of the prion protein are built from the same amino acids, their physical structures are quite different. While a PrPc has an alpha-helix conformation, a PrPSc has a beta-sheet conformation. Once a prion protein becomes misfolded in the brain, it acts as an infectious agent by modifying other alpha-helix proteins into beta-sheet proteins. As more and more PrPc converts to PrPSc, these misfolded proteins will begin to clump together, forming protein deposits that kill brain cells. Holes would eventually form within the brain, resulting in fatal prion diseases: Creutzfeldt-Jakob disease (CJD), Gerstmann- Sträussler-Scheinker syndrome (GSS), fatal familial insomnia (FFI), and kuru. Although rare, these diseases can be acquired genetically or through the consumption of contaminated food, along with the exposure to contaminated medical equipment. It is also possible for a prion protein to suddenly misfold or for a cell to undergo a sudden DNA mutation.

Picture Source: ScienceABC.com