For years, prion diseases like fatal familial insomnia were considered to be pretty unique: one diseased prion protein (PrP) molecule can transmit disease to another PrP molecule, with no virus, no bacterium—no DNA—required.  Before Stanley Prusiner‘s Nobel Prize-winning work showing this was really how diseased PrP spreads, this sort of thing was unheard of in all of human (and animal) disease.

In the past few years, researchers have found proteins that behave similarly in yeast, and new clues that the Aβ protein involved in Alzheimer’s may also spread by protein-to-protein interactions.

The big news this past week has been an impressive new study from UPenn showing the same for Parkinson’s disease as well.  A protein called α-synuclein is central to Parkinson’s disease: plaques of this protein are found in the brains of Parkinson’s patients, and mutations in the SNCA gene encoding this protein can lead to a genetic form of the disease.  In this new study, researchers injected pre-formed α-synuclein fibrils into the brains of mice and then demonstrated that protein aggregation spreads through the brain from this point of the initial “seeding”.  The authors posit that this is how Parkinson’s disease spreads in the human brain as well.

The notion that Parkinson’s may spread throughout the brain just like prion disease—that α-synuclein can act, in short, as a prion—is a huge link between the two diseases.  Last week the Wall Street Journal explained why mad cow disease (a prion disease caused by diseased PrP) might hold the clues to unraveling Parkinson’s, and the Michael J. Fox Foundation for Parkinson’s Research reported on this message as well.

For those of us interested in a cure for prion disease, this is hopeful news.  The discovery of more similarities between prion diseases and the more common neurodegenerative diseases—Alzheimer’s and Parkinson’s—makes it more likely that scientific advances in one disease will help explain things about all of these diseases, and that a treatment strategies developed for one disease might work for others as well.