The Good Side of Brain Manglers

Naturally occurring prion proteins may also serve a protective role in the brain. Research shows they may help guard against the damage a stroke can cause when a blood clot cuts off the oxygen supply to the brain. During a stroke, certain receptors in the brain become overactive, letting too much of the mineral sodium into brain cells. Prions, however, seem to make these receptors sluggish. “The presence of [normal prions] seems to dampen the activity of the receptor,” says prion researcher Andrew Steele of the California Institute of Technology in Pasadena, Calif. “When you don’t have normal prions, it tends to be much more easy to damage or lesion the brain.”

Prions may also be linked to Alzheimer’s disease. Oddly enough, scientists remain unsure whether the proteins prevent or facilitate the disease. A July 2007 article in the journal Proceedings of the National Academy of Sciences linked normal prion proteins to a decreased risk of Alzheimer’s. In the disease, protein plaques accumulate on brain cells, and the study found that the presence of high levels of prions prevented the formation of this protein “gunk.” But subsequent research, such as that discussed in Nature in February 2009, has shown that prions may actually mediate the formation of these Alzheimer’s plaques.

“Some say normal prions protect you against Alzheimer’s and others say it’s causing Alzheimer’s,” says MIT’s Jackson. “It’s a total mess. We don’t know what’s what.”

Although the quest to understand prions’ role in the brain remains complicated, more information about these naturally occurring prions may help us understand how to combat diseases that occur when normal prion proteins go wrong. Until now, these infectious agents seemed nearly unstoppable. But as scientists like NYU’s Derkatch work to understand how these proteins form, we may learn how to stop the transformation of good prions into bad.

“It’s not necessarily when the prion is already damaged that it’s the time for looking for the disease,” Derkatch says. Instead, deformed prions could be the result — instead of the cause — of disorders like Mad Cow Disease, she says.

Learning more about what makes prions essential to biological function also could facilitate treatment for prion-based diseases. Without understanding the ins and outs of prion functioning, tinkering with the proteins in the body could negatively affect the body’s other functions. For example, wiping out functional prions in an attempt to stop a case of Mad Cow Disease could result in destroying something that is crucial to normal brain processes, says Derkatch.

It’s clear that normal prions may play a number of roles in the body. And that means there are many avenues of research left to understand the function — and dysfunction — of these ubiquitous proteins.

“They’re just weird, really weird,” says MIT’s Jackson. “There must be a reason we’re making them.”

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