filling in the holes. new insights into prion could lead to a better understanding of Creutzfeldt-Jakob disease and related diseases.
prion, misshapen proteins believed to trigger fatal brain diseases, have often baffled scientists. It is unclear how the normal prion proteins become, or how prion entering the body - for example, through contaminated beef - travel to the brain. Now, two independent teams of researchers have found possible answers. Although preliminary, the work could provide clues about how to prevent and treat prion diseases.
In mammals, prions are aberrant forms of a protein called PrP. Prion diseases occur when PrP health contorts in its prion form spontaneously and spreads. But eating meat containing PrP prion apparently can also cause the disease.
Adriano Aguzzi, a neuropathologist at the University of Zurich in Switzerland, and his colleagues were curious how ingested PrP prion ends in the nervous system. His team knew that prions travel to the immune cells in the spleen by the intestinal mucosa. But immune cells that maintain prions, follicular dendritic cells, are far from nerve cells of the spleen. Aguzzi wondered if this separation might explain the long time lag between the consumption of infected meat and become seriously ill. To find out, the group closed the gap using genetically modified mice whose follicular dendritic cells affected nerve cells in the spleen. In these animals, prion disease defined within 30 days after the mice received prion, compared to 80 days in controls.
An ocean away, biochemist Surachai Supattapone at Dartmouth Medical School in Hanover, New Hampshire, was in search of the mysterious "X factor" - the molecules that force normal PrP to adopt a form of prion. He mixed healthy brain tissue with hamster brain tissue infected with prions. Normally healthy tissue infected PrP forces turn into PrP prion. Supattapone tried to add about 20 different molecules, looking for one that has slowed the conversion. He hit the jackpot with enzymes that degrade single-stranded RNA mammal. In high enough doses, enzymes prevented altogether conversion. Adding single-stranded RNA, conversely, stimulated normal PrP prion PrP transformation.
single-stranded RNA "could be the missing cellular factor that is necessary" to convert, says Mick Tuite, a molecular biologist at the University of Kent in Canterbury, UK However, it is not clear how RNA may interact with PrP. Tuite asks whether specific RNA molecules are the culprits. If the specific molecules are at work, he said, it would be much easier to disable and prevent prion form. As for the study of Aguzzi, Supattapone says that "in an elegant way, I think it shows a possible route of entry" by a prion in the nervous system.
Related Sites
Information on prion diseases at the Centers for disease Control and Prevention
UK government home page on the outbreak of "mad cow"
CJD Foundation
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