<Tr> <Td_colspan="2"> (edit on Wikidata) </Td> </Tr> <P> Prions are misfolded proteins that are associated with several fatal neurodegenerative diseases in animals and humans . It is not known what causes the normal prion protein to misfold; the abnormal 3 - D structure is suspected to confer infectious properties . The word prion derives from' proteinaceous infectious particle' . Prions composed of the prion protein (PrP) are hypothesized as the cause of transmissible spongiform encephalopathies (TSEs), including scrapie in sheep and bovine spongiform encephalopathy (BSE) in cattle--known popularly as "mad cow disease". </P> <P> In humans, prions have been hypothesized as the cause of Creutzfeldt--Jakob disease (CJD) and its variant (vCJD), Gerstmann--Sträussler--Scheinker syndrome, "fatal familial insomnia", and kuru . All known prion diseases in mammals affect the structure of the brain or other neural tissue; all are progressive, have no known effective treatment, and are always fatal . Multiple system atrophy (MSA), a rare human neurodegenerative disease, features a misfolded version of a protein called alpha - synuclein, and is therefore also classifiable as a prion disease . Several yeast proteins have also been identified as having prionogenic properties . </P> <P> The hypothesized role of a protein as an infectious agent stands in contrast to all other known infectious agents such as viruses, bacteria, fungi, and parasites, all of which contain nucleic acids (DNA, RNA, or both). Synthetic prions, created in the laboratory independent of any biological source, have little or no ability to cause infection with TSEs . However, when synthetic prions are administered in combination with cofactors, such as phosphatidylethanolamine and RNA molecules, then this can transmit TSEs . </P>

Where are prions found in the human body