Major prion protein
Major Prion Protein[edit]
The major prion protein (PrP) is a protein that in humans is encoded by the PRNP gene. This protein is most prominently known for its role in the pathogenesis of prion diseases, which are a group of progressive neurodegenerative disorders affecting both humans and animals. These diseases are characterized by the accumulation of an abnormal isoform of the prion protein, known as PrP^Sc, which is infectious and can induce the misfolding of normal cellular prion protein (PrP^C) into the disease-associated form.
Structure[edit]
The major prion protein is a glycoprotein predominantly expressed in the central nervous system, but it is also found in other tissues. It is anchored to the cell membrane by a glycosylphosphatidylinositol (GPI) anchor. The normal cellular form, PrP^C, is rich in alpha-helices, whereas the disease-associated form, PrP^Sc, has a higher beta-sheet content, which contributes to its aggregation and resistance to proteolytic degradation.
Function[edit]
The precise physiological function of PrP^C is not fully understood, but it is believed to play a role in cell signaling, copper metabolism, and protection against oxidative stress. It may also be involved in the maintenance of myelin and the regulation of synaptic function.
Pathogenesis[edit]
Prion diseases, also known as transmissible spongiform encephalopathies (TSEs), occur when PrP^C is converted into PrP^Sc. This conversion can occur sporadically, be inherited due to mutations in the PRNP gene, or be acquired through infection. The accumulation of PrP^Sc leads to the formation of amyloid plaques, neuronal loss, and spongiform changes in the brain tissue.
Genetic Aspects[edit]
The PRNP gene is located on the short arm of chromosome 20 in humans. Mutations in this gene are associated with inherited prion diseases such as Creutzfeldt-Jakob disease, Gerstmann-Sträussler-Scheinker syndrome, and fatal familial insomnia. Polymorphisms in the PRNP gene, such as the methionine/valine polymorphism at codon 129, influence susceptibility to prion diseases.
