BSE made a lot of headlines in the ’80s and early ’90s. Now scientists have got new insights into actually the protein that underlies BSE (the prion) and what it does.
Kat Arney: Yes, this isn’t one about mad cow disease but possibly mad fish disease. So BSE, this mad cow disease, and its human equivalent, Creutzfeldt Jakob Disease or CJD, are very rare but very serious degenerative brain diseases. Now we’ve known for over 20 years that they’re caused by rogue protein, this prion protein, and it exists in two different forms or shapes in the brain. Now the healthy, normal shaped protein plays a useful role in the brain, but the rogue form can spread rapidly causing healthy proteins to adopt this abnormal shape and causing disease, but it’s not really clear why we produce this prion protein in the first place, or what its exact function is in the body. But now, new results from German researchers have shed light on the role of the normal prion protein which could explain more about the causes of prion diseases.
Ewan used under CC-BY-NC licence
Chris Smith: It’s quite surprising though, isn’t it, because you’re saying we’ve known about this for a long time, 20 years, why has the real role of this protein only surfaced now?
Kat: Well, it’s been a really tough problem to crack, mainly because, for example, experiments with genetically-modified mice that lack the prion protein have just shown them to be perfectly healthy.
Chris: I guess we infer from that there must be something else which is taking over the role of the missing protein when you get rid of it, but how have the scientists now gone on to solve the problem?
Kat: Well, they’ve used a simpler organism to try and answer this, and writing in this week’s edition of PloS Biology, Edward Málaga-Trillo and his colleagues studied the developing zebra fish. Now, zebra fish are a handy model for these kinds of studies because they’re very quick to grow. Now, scientists injected zebra fish eggs with chemicals called morpholinos. These are a bit like DNA and they block the production of specific proteins. So in this case, they used morpholinos that were specifically designed to target the prion protein, and they found that the zebra fish were unable to develop properly. For example, they didn’t really develop a proper nervous system, and they died.
Chris: But why is that? Why would it have such a dramatic effect when you said earlier that when they removed it from mice the mice didn’t have any ill effects?
Kat: Well, there’s obviously something in mice that’s compensating for the lack of the protein, but that’s not there in the zebra fish, and the researchers showed that other proteins that are normally found at the sites of contact between brain cells disappeared when the prion protein was taken away so the cells couldn’t communicate properly, so it looks like this prion protein is playing some kind of important role in organising cell-to-cell contact, particularly in the brain. So the prion protein’s probably got a similar role in mice or humans, but because we’re a bit more complicated than fish, it hasn’t been possible to tease it out before.
Chris: And going back to where we started this story, which was a mention of BSE and CJD, does it give us any help with insights into those conditions and how we might be able to deal with them?
Kat: Well, this isn’t going to lead to a cure for CJD right now, but it’s certainly an important piece of the jigsaw, and if we can understand what the prion protein normally does, we’ll have more of an idea how it goes wrong in CJD, and, as we discussed a couple of weeks ago, the prion protein may actually play a role in Alzheimer’s Disease, so this is pretty important research for that area too.
Listen to the whole programme, originally broadcast on Radio Five Live, March 2009.
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