prion protein

pri·on

(prī'on),

An infectious proteinaceous particle of nonnucleic acid composition; the causative agent, either on a sporadic, genetic, or infectious basis, of neurodegenerative diseases in animals, and humans. The latter include the spongiform encephalopathies of kuru, Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker (GSS) syndrome, and fatal familial insomnia. The gene encoding prion protein (PrP) occurs on chromosome 20.

Synonym(s): prion protein

[proteinaceous infectious particle]

Stanley B. Prusiner received the Nobel Prize in Physiology or Medicine in 1997 for his discovery of prions. Prusiner began his research in 1972 to identify the infectious agent of CJD. In 1982 he and his colleagues isolated a protein that was capable of transmitting infection but, unlike all other known pathogens, contained neither DNA nor RNA. Prusiner's term for this protein, prion, was derived from the phrase proteinaceous infectious particle. A gene encoding this protein has been found in all mammals tested, including human beings. The prion protein can occur in either of two structural conformations, one that is normal (but of unknown function), designated PrPc, and one that results in disease, called PrPSc. The normal prion protein is a component of lymphocytes and other cells and is particularly abundant on the cell membranes of central nervous system (CNS) neurons. The PrPSc prion protein is extremely stable and is resistant to proteolysis, organic solvents, and high temperatures. Having been produced or acquired by a suitable host, it can initiate a chain reaction whereby normal PrPc protein is converted into the more stable PrPSc form. After a long, asymptomatic incubation period, the disease-causing PrPSc accumulates to reach neurotoxic levels. Symptoms of prion diseases vary with the parts of the brain affected. All known prion diseases are eventually lethal. Prion diseases are called spongiform encephalopathies because of the histologic appearance of affected cerebral cortex and cerebellum, which display large vacuoles. Probably most mammalian species develop these diseases. Prions are not living, are smaller than viruses, and do not elicit an immune response in either their normal or disease-causing form. Prion diseases besides CJD include kuru (once prevalent among the Fore People of New Guinea, who practiced cannibalism), bovine spongiform encephalopathy (BSE, mad cow disease), and scrapie, a disease of sheep. A new variant of CJD may have arisen through transmission of prions to human beings from cattle infected with BSE. Prion diseases are unique in being both infectious and hereditary. Hereditary forms are due to transmitted mutations in the prion gene, located on chromosome 20 in human beings. GSS disease is a hereditary dementia resulting from a mutation in this gene. Approximately 50 families with GSS mutations have been identified. About 10-15% of cases of CJD are caused by inherited mutations in the prion protein gene. Strains of mice from which this gene has been abolished are immune to prion-caused disease. see Creutzfeldt-Jakob disease, bovine spongiform encephalopathy.

Farlex Partner Medical Dictionary © Farlex 2012

PRNP

A gene on chromosome 20p13 that encodes a membrane glycosyl-phosphatidylinositol-anchored glycoprotein, which aggregates into rod-like structures and contains a highly unstable region of five tandem octapeptide repeats. The exact function of PrP is unknown.

Molecular pathology
PRNP mutations are linked to Creutzfeldt-Jakob disease, fatal familial insomnia, Gerstmann-Straussler disease, Huntington-like disease 1 and kuru.

Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

pri·on pro·tein

(prī'on prō'tēn)

Small, infectious proteinaceous particle, of nonnucleic acid composition; the causative agent of four spongiform encephalopathies in humans: kuru, Creutzfeldt-Jakob disease, Gerstmann-Straüssler-Scheinker syndrome, and fatal familial insomnia. The gene encoding for the PrP is found on chromosome 20.
Synonym(s): prion.

Medical Dictionary for the Health Professions and Nursing © Farlex 2012

prion protein

A protease-resistant sialoglycoprotein that is a normal constituent of the brain. Abnormal forms of the protein are now generally accepted as the causal agents in CREUTZFELDT-JAKOB DISEASE (CJD) and bovine spongiform encephalopathy (BSE). The protein was isolated by Stanley Prusiner in 1982, the term prion (an abbreviation of ‘proteinaceous infectious particle’) being proposed by Prusiner to make the point that it was not a virus. Prion protein (PrP) is found in high concentration in brains affected with spongiform encephalopathy, and forms AMYLOID deposits in these brains. This structurally simple, seemingly-infectious agent of simpler constitution than any virus, is capable of causing a severe and invariably fatal disease of the nervous system. Prions resist sterilization by normal methods and have been spread on surgical instruments and in donated human growth hormone. Prusiner was awarded the Nobel Prize in 1998 for his work on prions. See also PRION PROTEIN DISEASE.

Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005