prion

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prion

 [pri´on]
any of several pathogenic, transmissible forms of the core of prion protein that cause a group of degenerative diseases of the nervous system known as prion diseases. Prions have a structure different from that of normal prion protein, lack detectable nucleic acid, and do not elicit an immune response.
prion disease any of a group of fatal degenerative diseases of the nervous system caused by abnormalities in the metabolism of prion protein. These diseases are unique in that they may be transmitted genetically as an autosomal dominant trait, or by infection with abnormal forms of the protein (prions). Inherited forms result from mutations in the gene that codes for prion protein; such mutations may also occur sporadically. Hereditary forms include some forms of Creutzfeldt-Jakob disease, Gerstmann-Sträussler syndrome, and fatal familial insomnia. Infectious forms of the disease result from ingestion of infected tissue or the introduction of infected tissue into the body (kuru and some forms of Creutzfeldt-Jakob disease). The latter has occasionally occurred during surgical procedures; it has also occurred as the result of injection of human growth hormone prepared from infected pituitary glands. Prion diseases also occur in animals. Called also transmissible neurodegenerative disease and subacute spongiform or transmissible spongiform encephalopathy.

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.

prion

/pri·on/ (pri´on) any of several transmissible forms of the core of prion protein that cause a group of neurodegenerative diseases. Prions differ in structure from normal prion protein, lack detectable nucleic acid, and do not elicit an immune response.

prion

(prī′ŏn′, prē′-)
n.
A protein particle that is the agent of infection in a variety of neurodegenerative diseases, including bovine spongiform encephalopathy, Creutzfeldt-Jakob disease, and scrapie. Prions are the only known infectious agents that do not contain DNA or RNA. They derive from a normal body protein that becomes irreversibly misfolded, and they proliferate in the body, possibly by acting as a template for further protein misfolding.

prion

[prī′on]
one of several kinds of proteinaceous particles believed to be responsible for transmissible neurodegenerative diseases, including scrapie in sheep and kuru and Creutzfeldt-Jakob disease in humans. Because prions lack detectable nucleic acid, they are not inactivated by the usual procedures for destroying viruses. They also do not trigger an immune response.

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.

prion

Slow spongiform encephalopathy virus Molecular medicine An unconventional 33–35 kD sialoglycoprotein, the smallest known infective particle and implicated in diseases of man–Creutzfeldt-Jakob disease-CJD, fatal familial insomnia, Gerstmann-Straussler-Scheinker syndrome, kuru, and animals–scrapie of sheep and goats, bovine spongiform encephalopathy, transmissible mink encephalopathy, chronic wasting disease of captive mule, deer, elk. See Creutzfeldt-Jakob disease, Protein-only hypothesis.

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.

prion

an infectious PROTEIN particle, devoid of NUCLEIC ACID. Prions are thought to cause certain degenerative diseases of the NERVOUS SYSTEM, for example SCRAPIE in sheep and goats, bovine spongiform encephalopathy (BSE) in cattle, and Creutzfeldt-Jacob disease (CJD) and Gerstmann-Straussler Syndrome (GSS) in humans.

prion

a small protein which is believed capable of infecting cells and causing itself to be replicated, even though it contains no nucleic acid, i.e. it is believed to induce transcription of the gene that codes for the prion protein. In some way the horizontally acquired prion also alters the folding of the expressed protein and it is the altered protein that polymerizes to form fibrils within neurons and causes the spongiform encephalopathy. Aspects of this prion theory remain controversial. Prions can be detected in tissues by infective bioassay, animal inoculation, or by Western blot or immunochemistry. Prions cause spongiform encephalopathies of humans and animals, such as Creutzfeldt-Jakob disease, kuru, scrapie, transmissible mink encephalopathy, feline spongiform encephalopathy, and bovine spongiform encephalopathy.