OF THE MIND
TECH INSTRUMENT CENTER
TO BLACK MOUNTAIN
MAY UNLOCK MAD COW DISEASE
SPEECH WASN'T FREE
MAY UNLOCK MAD COW DISEASE
Michele McGuirl calls the prion protein diseases she studies "protein wrecks on the highways of life."
Imagine, she says, nerve cells as highways and prion proteins as cars on those highways. A car has an accident and no one knows why. It rolls over, bends and twists. It no longer has the same shape or the same function. Then a second car speeds down the highway and doesn't see the wreck ahead. It hits the first car, causing a pileup. In prion protein diseases that pileup is called a plaque, and it eventually kills nerve cells — typically causing dementia and death in mammals.
McGuirl studies the cause of the accident. She wants to know why a normal protein already existing in the cell changes its structure and how this causes other proteins to do the same, creating illnesses such as mad cow disease, scrapie and chronic wasting disease.
An assistant professor of biochemistry in UM's Division of Biological Sciences, McGuirl has just finished the first year of a three-year research project funded by the U.S. Department of Defense, which is charged with keeping the food supply safe. The project may lead to more know-ledge about the structures of prion proteins and possibly a field test for the prion protein disease that poses the most threat to human health — mad cow disease.
McGuirl says this research allows for collaboration with University and regional scientists, as well as mentoring to students. It's exactly what she wants to be doing.
"The work is rewarding," she says. "It's nice to be working on a project everyone can relate to. Mad cow disease is of great concern because of the scare in England. People want to know their water and food supply is safe."
Most infectious diseases are caused by viruses, bacteria and parasites invading a cell. For years scientists looked to these outside influences to try to explain diseases such as scrapie (a disease found in sheep), mad cow disease and Creutzfeldt-Jakob disease (a human ailment). They could never make a link. They later found that in these diseases, the disease-causing agent has nothing to do with a microorganism invasion. Instead, the disease was traced back to a structural change in a protein normally found in the brain.
In 1982 researchers discovered prion proteins in the brains of sheep infected with scrapie. Since then, this abnormal form of a simple protein has become associated with a group of related and untreatable diseases. McGuirl's research operates around this theory, called prion protein theory, which suggests that a protein normally found in the brain changes shape, triggering other proteins to convert into a deadly form.
McGuirl and her staff produce prion proteins in a safe laboratory strain of E. coli. When McGuirl's team purifies a protein, it folds into a natural shape. Then, through a chemical process, McGuirl and her team are able to mimic the formation of the abnormal infectious shape of the protein. Using fluorescent compounds as a way to "paint" parts of the substance, McGuirl hopes to figure out which parts of the protein report structural changes in the protein shape. She also hopes to learn about and model the infectious form of the prion protein.
McGuirl says that like scrapie in sheep and chronic wasting disease in elk and deer, mad cow disease has likely been around in small numbers of animals for years. She says there are small but important differences in the prion proteins of humans, cows, sheep and elk. This species barrier protects most members of one species from becoming infected by a sick animal from another species, so it once was common practice to add sheep byproducts to cattle feed.
Then the cattle industry began adding cattle rendering byproducts into its feed. This breeched the species barrier, and during the 1980s and 1990s in England, a few sick cows were able to infect nearly 1 million cattle. This led to the death of 120 people who ate contaminated beef in Britain.
Now, just as scientists have seen infections fade in England, a cow in Washington state was found with the disease in December 2003.
"But the likelihood of infection in the U.S. is very low," McGuirl says, "and I don't see it as a great danger to humans. The rendering process has been changed to avoid feeding dangerous animal byproducts to cattle."
She also isn't afraid to eat beef but avoids beef products such as sausage that have a higher content of spinal material. "Montana is naturally set up to produce safe beef because prion disease can take years to develop after exposure," she says. "Montana beef is awesome because the cattle are range-fed most of their lives and young when slaughtered, so they are not likely to develop the disease."
Originally from Massachusetts, McGuirl moved to Montana to help her mentor set up a lab when he became a professor at Montana State University-Bozeman. He encouraged her to return to school for her doctorate. McGuirl, a single parent, took a little while deciding to go back to school. But with the support of her mentor and colleagues, she did return, and after receiving her doctorate from MSU, McGuirl received a post-doctoral position for two years at the California Institute of Technology. She returned to Montana, but this time to UM to engage in the prion research that allows her to work in the part of the biochemistry field she prefers. After experiencing such an encouraging mentoring relationship, McGuirl is giving back by mentoring the students who work on her team, which include undergraduate, graduate and area high school students.
"I'm always amazed at their enthusiasm," she says. McGuirl hopes her research will help to create a preventative treatment for prion protein diseases or possibly lessen their effects. Hers is fundamental research, she says, but it could be used by other scientists in other clinical trials. Collaboration is a key part of connecting basic research to developing drug therapies, and McGuirl says so far the prion protein research has been a cross-campus collaboration at UM.
"By pulling people together and becoming aware of each other's projects, we have the support to do top-notch research," she says. "This University is growing by leaps and bounds in that respect."