Growers and Grocers

FYI

Prions are infectious agents that are replicated in the host by copying an aberrant protein structure. They can occur in yeasts, and they cause various neurodegenerative diseases in mammals. The most well-known infection caused by prions is bovine spongiform encephalopathy (BSE, or mad cow disease), which occasionally spreads to humans who eat infected parts of the cow (Figure 25-17) (http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mboc4.figgrp.4636). Isolation of the infectious prions that cause the disease scrapie in sheep, followed by years of painstaking laboratory characterization of scrapie-infected mice, eventually established that the protein itself is infectious.

Intriguingly, the infectious prion protein is made by the host, and its amino acid sequence is identical to a normal host protein. Moreover, the prion and normal forms of the protein are indistinguishable in their posttranslational modifications. The only difference between them appears to be in their folded three-dimensional structure. The misfolded prion protein tends to aggregate, and it has the remarkable capacity to cause the normal protein to adopt its misfolded prion conformation and thereby to become infectious (see Figure 6-89) (http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mboc4.figgrp.1115). This ability of the prion to convert the normal host protein to misfolded prion protein is equivalent to the prion’s having replicated itself in the host. If eaten by another susceptible host, these newly-misfolded prions can transmit the infection.

Feed your head on this topic at (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=Books) and (http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=mboc4.TOC&depth=2)

Or we could just ask our resident scientist.

Thanks for all the info, Nika. What do you think of this supposed controversy about whether or not prions actually cause these things?

A long time ago, some friends of mine discovered a “hardware” virus in certain Macs. Basically, the slots for the prongs of a plug got bent, which then bent the plug, which then bent the slots of new machines. That was the analogy that sprung to mind reading your description of how prions spread; protein structures that affect other protein structures.

Prions are just bloody hard for laypersons to wrap our heads around. The only reason I can get them and actually read about them on a fairly high level is because I was once a pre-veterinary student and thus had to take a bunch of pre-med classes, so I have the background to “get” prions.

Most newspaper articles and magazine articles are woefully inadequate in explaining the subject so that laypersons can understand what they are talking about, probably because most journalists don’t quite get it either. Prions are pretty esoteric wee beasties, and so it is natural that folks get confused by them.

Nika–would you consider writing up a primer for the non-scientificially educated layperson? You have the scientific understanding, but even more important, you have the language skills and the writing ability to potentially translate what you know into a form where more people can understand it.

That would be a very good resource to have on the net.

sure all.. I will see what I can pull together. As with any growing science (a disruptive one too because it breaks some dogmas) some data points in this direction and some in that direction etc.

I agree completely that science reporting is worse than useless! It often confuses and uses unecessary jargon.

Prions are fascinating proto-organismal particles (my words!), I will be glad to put together the 101 on it in relation to our food supply too.

I’m a graduate student working in a lab studying prion disease. I know that Nika is writing up a primer on the subject but I’m happy to offer up my knowledge and try to answer any questions people may have. One thing I did want to mention is in response to the question regarding the controversy over the cause of prion disease. In the past some researchers have argued that prion disease might be caused by a virus. At this point, though, I think that an overwhelming percent of prion researchers(and the published data)support the hypothesis that the infectious agent is indeed the misfolded prion protein. Initially this was a controversial idea because infectious diseases were previously thought to be only caused by agents that contain genetic information (which provides the instructions for replication) such as viruses, parasites, and bacteria. The discovery of this novel mechanism of infection, which doesn’t require genetic information, is one of the reasons why scientists find the field so interesting. I also just wanted to point out that prions in yeast are very different than prions in animals and they pose no risk to humans in the manner that BSE and potentially CWD does.