[excerpt] Prions may also hold clues to combating common diseases, because they are simply normal proteins that are misfolded. Misfolded proteins, it turns out, cause a host of major ailments, from cancer and diabetes to Alzheimer's and Parkinson's. Proteins are the workhorses of living things; the human body makes at least 50,000 different ones for tasks from building bones and muscle to digesting food and thinking.
As proteins form within cells, their long chains of amino acids fold up like fiendishly intricate origami. Since the 1930s, scientists have known that a protein's folded shape is key to its function, making it possible for hemoglobin to carry oxygen or for collagen to bind together skin. But figuring out how and why proteins fold the way they do has become one of the great, enduring challenges in biochemistry.
It's easy for proteins to get corrupted while folding in the crowded confines of a cell, and misfolded proteins can cause all sorts of trouble.
One example is the P53 protein, the body's frontline warrior against cancer. Misfolded P53s lose their tumor-suppressing power, an error that causes about half of all cancers. Cystic fibrosis, too, is caused by misfolded proteins, as is diabetes. Prions are more malevolent, forcing nearby proteins to misfold, too, unleashing a destructive chain reaction. Although Alzheimer's and Parkinson's are not known to be caused by prions, the disease process, in which brain proteins glom together into plaques, looks remarkably like that of mad cow and other prion diseases. "We're starting to think there may be similarities between many diseases of misfolding," says Jonathan Weissman, a prion researcher at the University of California-San Francisco, "including infectious prion diseases like mad cow and noninfectious diseases like Alzheimer's."
Even a year ago the idea of being able to tame prions, which have no DNA and can survive incineration, seemed laughable. But prions may not be as tough as they seem. Last fall, British researchers used monoclonal antibodies to halt the damage caused by scrapie, a prion disease, in infected mice. And Weissman recently discovered that subtle changes in prions can make them harder to transmit, suggesting that it may be possible to get prions, or Alzheimer's proteins, to fold into less toxic versions.
Read the full article.
