Molecular biology of prion diseases

Article Abstract:

Prions are infectious agents that can cause disease, but are not bacteria, fungi, parasites, viroids, or viruses. A review is presented of the molecular biology of prions and of the diseases they can cause in humans and animals. Scrapie is the animal disease caused by prions that has been most extensively studied; it can result in several conditions including bovine spongiform encephalopathy, which is currently wreaking havoc with the beef industry in Great Britain. The discovery of prion protein (PrP), which in humans consists of 253 amino acids, occurred in the early 1980s; the infectious component of the protein has also been identified (PrPSc). PrP genes are located on the short arm of human chromosome 20. The synthesis of PrPSc is described. Disorders in humans known to be caused by prions include kuru, Creutzfeldt-Jakob disease (CJD), and Gerstmann-Straussler-Scheinker (GSS) syndrome; all are degenerative diseases of the central nervous system and can be transmitted to laboratory animals. Familial (inherited) variants of CJD and GSS also exist. Much of the current knowledge about prions has come from studying scrapie in laboratory animals. These findings are summarized and the many unresolved issues concerning prions, such as the ways prion infectivity increases, are discussed. Future research efforts will determine whether PrPSc molecules make up prions entirely or whether other components are also present, and will attempt to identify the significant molecules' crystal structures and structures in solution. At present, no treatments for diseases caused by prions are known. Prenatal testing in families with histories of these disorders allows one way of controlling their genetic proliferation. (Consumer Summary produced by Reliance Medical Information, Inc.)

Nervous system diseases

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A lot of ''excitement'' about neurodegeneration

Article Abstract:

In neurodegenerative diseases, such as Alzheimer's, Parkinson's, and Huntington's diseases, the ability to think or remember is lost because of the destruction of neurons (nerve cells). Research results presented at a recent scientific meeting in Philadelphia showed that if the amino acid neurotransmitters (normal brain chemicals that excite or stimulate nerve impulses) glutamate and aspartate are present in abnormally large amounts, they can kill the neurons that they normally excite. This is thought to occur in the neurodegenerative diseases. In large amounts these substances are known as excitotoxins. Previous research has shown that other chemicals act as excitotoxins, such as quinolic acid, a normal chemical in the brain, which is similar to glutamate, and is thought to kill neurons in Huntington's disease. Others think that L-dopa, a chemical in the brain made during the synthesis of dopamine, is also involved in Huntington's disease. Three different toxins have been shown to be involved in Parkinson's disease, 6-hydroxydopamine, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and amphetamines. It has been shown that in Alzheimer's disease or dementia pugilistica (disease similar to Alzheimer's that is caused by too many blows to the head, such as happens to boxers), the excitatory amino acids are released in large enough quantities to cause destruction of the neurons. It is hoped that scientists can devise ways to protect the neurons against the excitotoxins, such as by developing drugs that block the mechanism of the excitotoxins without affecting normal brain function. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Causes of, Development and progression, Dementia, Alzheimer's disease, Neurons, Huntington's chorea, Huntington's disease, Parkinsonism, Excitatory amino acids

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Spontaneous neurodegeneration in transgenic mice with mutant prion protein

Article Abstract:

Gerstmann-Straussler-Scheinker syndrome (GSS) is a rare brain disease involving degeneration of nerve cells. Patients with GSS develop ataxia (inability to coordinate movement) and dementia (confusion). Prions are infectious particles made up only of protein, with no nucleic acid, which is essential for cell replication. The prion protein PrP is thought to be involved in GSS. The prion gene encoding PrP was experimentally mutated at a specific genetic site and transplanted into transgenic mice (which received the foreign gene at the embryonic stage). This genetic mutation has been shown to be present in patients with GSS and not in other family members who are not affected by the disease. The mice developed neurological disease similar to that seen in GSS and scrapie (a similar disease that develops in sheep). These transgenic mice can be used as an animal model to study GSS. GSS is similar to other neurodegenerative diseases such as Creutzfeldt-Jakob and Alzheimer's diseases. Questions still exist on the role of the prion PrP gene in the diseases, such as how the disease can spread to other animals, without having an agent that can replicate, and whether the prion gene associates with other agents. These questions can be further studied using these transgenic mice. (Consumer Summary produced by Reliance Medical Information, Inc.)

Usage, Genetic aspects, Prions, Prions (Proteins), Creutzfeldt-Jakob disease, Genetically modified mice, Gerstmann-Straussler-Scheinker syndrome

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