What is a prion protein and what makes it abnormal in CJD?
Prion protein (PrP) is a naturally occurring part of the brain and other parts of the body in both humans and other animals. It is an abnormal form of this prion protein that is thought to cause CJD, and becomes ‘infectious’ to other proteins and animals. We don’t yet understand what this prion protein does, but when it is abnormal the protein is resistant to normal breakdown in the cell. The abnormal protein clogs up the cells, killing some of them (especially in the central nervous system, including the brain), which causes sponge-like (‘spongiform’) holes in the tissues. One ‘changed’ prion protein molecule seems to act as a template for change in further molecules of the prion protein. The first abnormal protein molecule might have arisen ‘by chance’ (ie in sporadic CJD), due to a mutation in the genetic code for the protein (ie in familial CJD) or because of exposure to external prion proteins by diet or in healthcare (ie in vCJD).
