Prion

A prion ( ) is a misfolded protein that induces folding problems in normal variants of the same protein, leading to cellular death. Prions are responsible for prion diseases, which are fatal and transmissible neurodegenerative diseases affecting animals, including humans. These proteins can misfold sporadically, due to genetic mutations, or through exposure to an already misfolded protein, leading to an abnormal three-dimensional structure that can propagate misfolding in other proteins. The term prion derives from "proteinaceous infectious particle". Unlike other infectious agents such as viruses, bacteria, and fungi, prions do not contain nucleic acids (DNA or RNA). Prions are primarily twisted isoforms of the major prion protein (PrP), a naturally occurring protein with an uncertain function. They are the hypothesized cause of various diseases, including scrapie in sheep, chronic wasting disease (CWD) in deer, bovine spongiform encephalopathy (BSE) in cattle (mad cow disease), and Creutzfeldt–Jakob disease (CJD) in humans. All known prion diseases in mammals affect the structure of the brain or other neural tissues. These diseases are progressive, have no known effective treatment, and are invariably fatal. Most prion diseases were thought to be caused by PrP until 2015 when a prion form of alpha-synuclein was linked to multiple system atrophy (MSA). Misfolded proteins are also linked to other neurodegenerative diseases like Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis (ALS), which have been shown to originate and progress by a prion-like mechanism. Prions are a type of intrinsically disordered protein that continuously changes conformation unless bound to a specific partner, such as another protein. Once a prion binds to another in the same conformation, it stabilizes and can form a fibril, leading to abnormal protein aggregates called amyloids. These amyloids accumulate in infected tissue, causing damage and cell death. The structural stability of prions makes them resistant to...