Synthetic Prion Causes Neurological Disease In Mice
30 Jul 2004
Scientists have produced a prion protein that can trigger the development of a
neurological disorder in mice that is similar to "mad cow" disease, according to a
new study supported by the National Institute on Aging (NIA), a part of the National
Institutes of Health. The findings demonstrate that prions, an unusual class of
infectious proteins, can make copies of themselves without the presence of viral
DNA or RNA, damage brain tissue, and cause neurological diseases.
The work by Nobel Laureate Stanley B. Prusiner, M.D., and colleagues at the
University of California, San Francisco, and Heinrich-Heine Universitat in Germany,
appears in the July 30, 2004, issue of Science. For the study, Dr. Prusiner and his
colleagues produced prion protein fragments in bacteria, folded them into larger
protein structures called amyloid fibrils, and then injected them into the brains of
susceptible mice.
The mice began exhibiting symptoms of disease in their central nervous systems
between 380 and 660 days after they were given the synthetic prion proteins. The
amyloid form of the prion protein, which is thought to cause prion disease, was also
found in the brains of the diseased mice. The researchers then administered brain
extracts from these animals to another group of mice, which subsequently
developed similar symptoms 90 to 150 days later. The disorder seems to be distinct
from that caused by other known strains of prions, suggesting that the synthetic
prion didn't merely activate a pre-existing prion in these mice and that the
synthesized prion protein itself is sufficient to make infectious and disease-causing
prions.
Prusiner received the 1997 Nobel Prize in physiology or medicine for his discovery
of prions. Unlike viruses, bacteria, fungi and parasites, prions contain no DNA or
RNA. Instead, they are a type of protein normally found within cells in humans and
other organisms. In some cases, the structure of prions can change into a disease-
causing form. These abnormal proteins appear to convert other, normal prions to
the abnormal shape. Many scientists now believe this conversion process leads to
several dementing diseases in humans, including Creutzfeldt-Jakob disease.
Similar diseases in animals include bovine spongiform encephalopathy ("mad cow"
disease) in cattle and scrapie in sheep.
Abnormal, misfolded proteins contribute to other age-related neurological diseases
such as Alzheimer's and Parkinson's diseases, and so these new findings may
provide insights into the cause and possible prevention of other brain disorders.
EDS: Andrew Monjan, Ph.D., of the NIA's Neuroscience and Neuropsychology of
Aging Program is available to discuss this finding. For an interview, please phone
301-496-1752.
Contact: Doug Dollemore
[log in to unmask]
301-496-1752
NIH/National Institute on Aging
SOURCE: Medical News Today, UK
http://www.medicalnewstoday.com/medicalnews.php?newsid=11418
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