Prions are our friends

OK, let's see if I can remember what I just read about prion proteins (PrPs) . . . I think I read that they can help us store memories.  Oh yeah, that's right . . . and it turns out that they are needed to maintain the insulating myelin sheath around neurons that enables proper conduction of action potentials.

In my Anatomy & Physiology textbook I define a prion as

a term that is short for “proteinaceous infectious particles,” which are proteins that convert normal proteins of the nervous system into abnormal proteins, causing loss of nervous system function; the abnormal form of the protein also may be inherited; a newly discovered type of pathogen, not much is known about how the prion works; see bovine spongiform encephalopathy, variant Creutzfeldt-Jakob Disease (vCJD)

Well, it turns out that prions are not all bad, after all.  In a recent article in Nature Neuroscience, scientists report that certain prions are needed for the axonal signaling to Schwann cells that is needed to maintain the myelin sheath (pictured) and thus maintain normal conduction of nerve impulses.

In another finding reported in the journal Cell, scientists working with prions in sensory neurons of the sea slug found that the clumping of prions that we previously associated only with prion diseases plays a role in preserving memory.  Typically, when prions clump, they for tangles called amyloid plaques in a cell. Apparently, the clumping of certain prions at synapses increase the length of time that a memory is stored at that synapse.

Researchers also found that the neurotransmitter serotonin promotes the formation of the memory-preserving clumps.

More work needs to be done, of course, but these findings may lead to the discovery of a central role for prions in retaining long-term memories.

Want to know more?

Axonal prion protein is required for peripheral myelin maintenance. 
Bremer, J., et al.
Nature Neuroscience. 24 January 2010. doi:10.1038/nn.2483
[Original research article]

Prion protein is not all bad
Tina Hesman Saey
Science News February 13th, 2010; Vol.177 #4 (p. 17) 
[Summary article describing the role of prions in maintaining the myelin sheath, as well as some general insights on the emerging new view of prions.]

Aplysia CPEB Can Form Prion-like Multimers in Sensory Neurons that Contribute to Long-Term Facilitation
Kausik Si, et al.
Cell Volume 140, Issue 3, 421-435, 5 February 2010
[Original research article included a nifty graphical summary of the central findings.]
Click here for an audio interview with the scientist about this breakthrough

Protein clumps like a prion, but proves crucial for long-term memory
Tina Hesman Saey
Science News web edition : Thursday, February 4th, 2010
[Summary article explaining new research findings and their importance.]