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Prions are a special class of proteins best known as the source for mad cow and other neurodegenerative diseases. Despite this negative reputation, according to a new report in the February 5th issue of the journal Cell, a Cell Press publication, a prion may also have important and very positive roles in brain function. The researchers suggest that a prion-like protein may participate in memory in higher eukaryotes, from sea slugs on up. "The persistence of memory is a fundamental problem," said Kausik Si of Stowers Institute for Medical Research. "Experiences are temporal; they happen once, but somehow must lead to changes in the brain that are somewhat permanent." Those changes must be mediated by molecules, including proteins. "The question is: how can you maintain a stable state with unstable biological molecules," Si said. And now, research conducted by Si in collaboration with Nobel laureate Eric Kandel, suggests that prions may be one solution to that problem. Prions are distinguished by their ability to assume at least two distinct conformational states, one of which is dominant and self-perpetuating. That means that once a protein switches to its "prion state" it has the ability to convert other "non-prion" proteins to that state as well. Therefore, once engaged, the "prion state" is self-renewing and stable.

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