Prions

Wee beasties that cow the public

by Bryan Zepp Jamieson

12/30/03

http://www.zeppscommentaries.com/Science&Environment/prions.htm

You would think Republicans would love prions. Anything that can take a voter and turn him into a drooling, twitching idiot, paranoid and fretful, incapable of doing simple math or making moral judgments on his own, would be just what the GOP wants to see turn up at the polling places.

But it turns out that prions are bad for business, so Republicans don’t like them. America can count itself lucky on that score.

The London Guardian headline writer gleefully described the latest case of mad cow disease that popped up in Washington State as "a billion dollar beef over the nationality of the cow" between the United States and Canada. (Certain papers like to employ headline writers who live in a perpetual state of glee. They are often excellent newspapers, but it’s impossible to read them without wincing.) Leaving aside for the moment, the politics and economics of whether Falling Down Bessie was a Bovine-American or a Bovine-Canadian, the uncertainty of what it means and what happens next is reflective of the general sense of mystery that surrounds prions, and the neuropathological effects they have on life forms.

We aren’t entirely sure if prions actually exist. We aren’t sure what (if they do exist) they are. They have no brain, no spine, no discernable structure and no nucleic acid, no molecular structure, and by way of eliminating the one remaining possibility, have never been appointed to the White House by Antonin Scalia. The only reason we suspect that there is such a thing is because there are a group of diseases (usually neurological) that have no known causative agent, but DO have in common a protein residue, called (reasonably enough) prion protein, or PrP. This protein interacts with the normal proteins found in the DNA of the host animal, and converts it to PrP. Prion protein scrapie (or PrPSc), the more malevolent variation, converts protein strands to PrPSc, thus the "self-replicating" label.

So even though it’s not life as we know it, it’s self-replicating. Since I know little or nothing (most likely nothing) of microbiology, I don’t know exactly why the biologists haven’t simply concluded that this is just some sort of very slow organic chemical reaction. Perhaps they surmise that the prions we can’t see create more prions we can’t see, until there’s so many prions we can’t see anything.

Mad cow disease (bovine spongiform encephalitis) is known as Creutzfeldt-Jakob disease when it affects humans, and scrapie in ruminants other than cows. Since it affects all mammalian life forms, it’s broadly known as "transmissible spongiform encephalopathies," mercifully abbreviated as "TSE."

It was widely believed that in England, where the disease reached proportions of damage large enough to get noticed, it was transmitted among cattle when "animal protein," ie, powdered cow, was added to the food as a supplement, along with the prions, and people caught it from eating cows which had caught the disease.

Cannibalism is frowned upon by biologists, and not just because they consider themselves rather low on the food chain. All meat has various bacteria and viruses, and while meat from species not closely related to oneself doesn’t have many bugs that will find humans appealing, the closer the relationship, the more bugs that like both the meal and the devourer. That’s why it’s important to really cook pork or monkey meat thoroughly. And if the meal is human, then any bugs your dinner had will find you to be an ideal host – and some of those bugs are deadly.

Works the same way for cows, of course. Feed a cow other cows, and it’ll get whatever transmissible diseases the first unfortunate cow had.

The people who run the meat industry thought they had gotten around that by heating the ground up "animal protein" to 600 C and sterilizing it. Turns out prions can survive such inordinately high temperatures, which is odd, since most regular proteins cannot.

Even if prions are the "little man upon the stairs" of microbiology, the class of diseases believed caused by these wee beasties go back in lore for centuries. In sheep, it was called "scrapie" and in cattle, "falling cow disease."

Nor is it unique to cows, or a stranger to North America. It’s been discovered in elk, deer, and bison out in the wild, especially in the Pacific Northwest.

Which leads to an interesting question.

Nobody is feeding elk ground up elk. Deer rarely turn cannibalistic. Bison don’t munch on one another’s droppings.

So how are they catching TSE?

Answer: nobody knows.

This doesn’t take the cattle industry off the hook. Forcing cannibalism on animals for nutritional purposes is still an insanely stupid and eventually very expensive idea, as the British know full well. Our laissez faire regime continues to want this highly competitive and profitable industry to be self-policing on this, and only a complete custard head believes that you can make a money-making industry more honest and responsible by letting it police itself. TSE is a very Republican type of disease.

But in the long run, forcing science to notice these prions might lead to some big advances in biology. What we’re looking at here is a chemical that can reach into the basic DNA of a life form, and alter it to suit itself. In this particular instance, all it does is eat holes in the brain, which is an unfortunate state of affairs for most people. But suppose variations on it are what cause other genetic changes, such as increases in pre-frontal lobes, coloration, webbed toes, and so on.

In short, are prions the basic mechanism of evolution itself? Are they what cause change?

Do they play any role in cancer, a disease that, in many forms, shares the same interesting trait of TSEs of not triggering the body’s immune system?

Could it be that these proteins, now known for their association with a horrible but fortunately rare disease, might be beneficial in fighting cancer and in genetic manipulation?

Until somebody figures out how to put salt on the tail of a prion, nobody knows.

But we have a new mechanism in our understanding of biology, and that’s always beneficial in the long run.

But in the short run, perhaps you should consider cutting back on the hamburgers a bit. Just in case.

Note: some of this information was cribbed from the Nova website, http://www.pbs.org/wgbh/nova/madcow/prions.html The opinions and speculations, however, are entirely mine, and don’t reflect on PBS or Nova.