As I mentioned in an earlier post, some scientific projects have a certain amount of notoriety cued up and waiting for whomever gets to finish line X first. A good example is prion proteins, the cause of a particularly baffling set of illensses that include mad cow and Creutzfelt-Jakob diseases. Unlike any other disease that we know about, prion diseases don’t pass from person to person via a virus or a bacteria or any other sort of living agent but instead constitute a single misfolded protein. The problem is that the single protein can induce other proteins to misfold, which then set off a chain reaction that leaves the brain spongy and riddled with insoluble protein aggregates.
After years of fierce controversy we’ve gained a relatively good idea of how the prion protein (PRP) changes from its innocuous form to the misfolded, disease state. As a result we have a few good pointers for staying healthy. First, don’t eat people. The first known prion disease, kuru, mystified anthropologists who found no infectious reason for the fatal wasting disease afflicting members of a New Guinea tribe of cannibals. As it turns out the acid environment of our stomach is a great place for PRP to slip out of its usual conformation and into the killer state. Similarly, don’t feed cow tissue to cows. The same rule that applies to us applies to them. Finally, you can get it from cows but only if they already have the misfolded protein, so avoid brain tissue of questionable provenance.
The most important thing that we didn’t know, until now, is what exactly PRP does when it isn’t killing people (1).
Harvey Lodish at the Whitehead Institute in Cambridge, Massachusetts, and his co-workers stumbled on one answer when studying mouse stem cells that divide to generate new blood cells. They found that many of these stem cells have prion proteins stuck all over their surfaces.
The team shows that these prions help stem cells from the bone marrow to manufacture more and more new blood cells.
…Stem cells that lacked the prion protein wore out, and were unable to manufacture new cells, long before those that carried working prions. “It’s a first clue to what these proteins might do,” Lodish says, who reports the findings in the Proceedings of the National Academy of Sciences(2).
In a nutshell, we need the prion protein in order to keep our stem cells alive. Some kinds of work can be pretty hard to present to a mixed audience in a way that makes sense and conveys why it’s interesting; these guys have it made. In the global race for stem cell technology score one for America.
(1) link (subscription wall)
(2) Read more here.
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Treat this as an open science thread. Yes, that includes manimals.
Lines
I’ve got a friend that was working on this during the initial phases of the mad-cow terror alert orange phase. This will be great news to the agricultural elite that have been on pins and needles (clean ones).
Thanks for the post, Tim, this is great!
Pb
Tim, nice post about Creutzfelt-Jakob disease–I heard about this years ago from a time traveller… Err, is this an open science fiction thread too? :)
Nutcase
TIM! Good to run into you, man! (This is Smith, from the old Atlantic board.)
Excellent article – and very good work by that team.
Tim F.
Smith, as in JSmith? No shit! Great to see you. Astronomy post coming up.
Nutcase
The same!
“Astronomy post coming up.”
Looking forward to it.
DougJ
Interesting…but can we study this in a way that respects the value of every prion? If not, I don’t think there should be any federal funding for this.
half
Hi Tim! There you are.
ppGaz
In other words, Republican?
Lines
Its obvious that the prions are assisting the terrorists. As such, they don’t fall under Constitutional protections and can be legally spied on at all times. Break out your microscopes, gentlemen, its time to listen in!
Tim F.
DRF! Good lord. Did you know that Elaine has a blog?
Nutcase
Yeah – I read Elaine’s gloom-n-doomfest fairly regularly.
The Disenfranchised Voter
Heh heh.
Krista
How come we never hear the good news about cannibalism?
scs
Yeah I’m still waiting for the public outcry that we feed animal feed to cows under a certain age. I think we also still feed animal feed to pigs and poultry as well, I think. No wonder other countries like Japan don’t want to buy our beef – I don’t blame them.
Anyway, maybe prions will turn out to be the missing step in the fountain of youth, helping us to create more stem cells to stay forever young. Where are prions manufactured in the body anyway, I wonder – in bone marrow?.
demimondian
Two words…on second thought, maybe not.
canuckistani
Prions will be your only defence against…Manimals!
ppGaz
The Prion was named car of the year last year.
demimondian
My _Science News_ came today. It includes a squib on the discovery of prion-form proteins in the muscle of wild deer in North America.
Ick. No more venison sausage for me, I guess.
ppGaz
Wow …. I know a lot of people back in the Midwest who fill their freezers with venison every year.
Is this a serious thing? Should I be telling them about this?
demimondian
Well, I’m not being absurdist — I really did get SN yesterday, and it really did have such a squib. I won’t avoid venison sausage as a result though, since I have venison maybe once a year when I go to an expensive restaurant. If the result is reproduced somewhere else, I might suggest that people have their venison tested before they put it in the freezer.
Fundamnetally, I wouldn’t overread it. I’d treat it as “interesting and worth tracking” for now.
Tim F.
I don’t remember the details, but a prion illness has absolutely devastated deer and elk in some parts of the northern US for some years now. Demi’s article might have the details, or I might remember enough to dig them up myself.
demimondian
Tim’s right — chronic wasting disease (CWD) has become endemic in the deer and elk heards of the northern midwest over the last few years. The reason, by the way, that the result is interesting is that it appears the prions in CWD are dispersed through muscle tissue; the prions in BSE and variant CJD appear to be localized to central nervous system tissue (brain and spinal cord, essentially). That means that eating any meat from a deer or elk with CWD is likely to expose you to the prion, which is not the case for hamburger from downer cattle.
scs
Demi, do you know how if cows get the prions from being fed animal feed, how do elk and deer get it from eating vegetation? I thought you had to be a meat eater to spread prions.
demimondian
scs — that’s an interesting question, and one to which I don’t know an answer. My guess is that there’s probably a lurker here who’s got a good enough veterinary background to be able to speak to that.
Dave
It is a well documented if little known fact, that sheep eat birds. All animals except humans eat the umbilical cord with attachments.
ThomasD
These findings could just as easily serve to undermine the current theories on how prions induce chronic wasting diseases. Previously prions were considered abberent protiens, with no apparent role in normal cellular function. That they actually do play a role in normal cellular activites could indicate that there is some unknown mechanism that renders them pathogenic. The gaps in out knowledge are massive when compared to the meager substance that is known.
Kuru is not the ‘first known prion disease.’ CJD, and scrapie (the sheep version of CWD) were known to be contagious spongiform encephalopathies long before kuru was first seen. Before prion theory the SPEs were often attributed to a ‘slow virus’ although texts often stated that this was a working theory based on the apparent long gestation period of the diseases and the fact that no infectious agent had ever been identified.
The epidemiology surrounding kuru contributed to the development of prion theory, and especially our understanding of how disease amplification may occur. But prion theory remains just that,a theory. The application of this theory to modern animal production techniques (i.e. the elimination of same species animal feed and altered handling of central nervous system material) APPEARS to have postively impacted the transmission and occurence of CWDs but no one really knows for sure.
This new information raises alot more questions than answers.
demimondian
Sporadic CJD is not a spongiform encepalopathy — it lacks the characteristic brain lesions of the alleged prion diseases. Other than that, yes, scrapie has been recorded for many hundreds of years. (In fact, BSE was first reported after CWD, which was first reported in 1962.)
demimondian
scs — You got me curious. Here’s the gold standard answer (from The USDA’s web site)
Tim F.
To clarify what I said, kuru was the first disease for which a prion protein was identified as the vector.
From the biophysics of prion folding we know that the acidic environment of cellular lysosomes promotes the misfolded state, which is why people think that the acidic environment of our gut promotes the misfolding that causes cannibalism-derived prion disorder.
I don’t see any viable theory in which the natural PRP would play no cellular role whatsoever. If that were the case then then genetic drift would have eliminated the gene or modified it beyond pathogenicity. Contrary to that you find conserved PRP in mice, ungulates and humans, making it nearly impossible that the protein would play no positive role. The rare instance of pathogenicity would be enough to eliminate an otherwise useless protein from the genome. For that reason it seemed inevitable that somebody would find a function; the big news here is that the answer landed researchers from one hot field squarely in the middle of a second, and even hotter, line of inquiry. Out of the frying pan and into the fire indeed.
scs
Well thanks to your info, Demi, I think it’s no mystery now. I think I know what the problem may be: Purina Deer Chow. Yes, there’s an actual “Purina Deer Chow”. Here are some of the ingredients:
I wonder what they make the protein out of? Could it be ground up cow offal and spinal cords? I would guess all wild venison eaters should quit it for now.
Vet07
That is incorrect. Sporadic CJD is indeed classified as a spongiform encephalopathy – in fact, it is the most common of the known human TSEs (transmissible spongiform encephalopathies). See ninds.nih.gov/disorders/cjd/detail_cjd.htm or cdc.gov/ncidod/dvrd/prions/resources/BelayE_Annu_Rev_Microbio.pdf for reliable information about spongiform encephalopathies.
I may be the veterinary lurker alluded to earlier: I’m soon entering my 4th year of vet school. What we’ve been taught about CWD transmission is just what the USDA website states: the mode of transmission in deer is unknown at this time. I spent 4 days during my freshman year collecting deer heads from hunters and cutting retropharyngeal lymph nodes out of them to aid in statewide testing efforts for CWD. A total of 9,988 deer were tested that year and all were negative. Subsequent testing has also proven negative.
A recent article with more information on the presence of prions in the skeletal muscle of deer can be found at sciencemag.org/cgi/content/abstract/1122864v1
(First-time poster here – please excuse any formatting mistakes!)
demimondian
Ah. Thanks for the correction.
I was under the impression that sporadic CJD was not demonstrably transmissible, unlike the rarer variant form. (The hereditary form, of course, is not a true TSE.) Also, due to its different course of disease, constained population of victims and distinct lesion etiology (many small voids in localized portions of the cortex instead of the smaller number of large voids distrbuted through the entire brain), I was under the impression that it wasn’t typically believed to be a disease of the same class as the prion diseases, such as vCJD.
But it isn’t my area of study, and I’m certainly willing to be wrong. It’s certainly correct that I misspoke: transmissible or not, all forms of CJD are spongiform encepalopathies.