Current View of Prions – Prions

by Vincent Racaniello, PhD

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    00:00 Our current view of prions is that the pathogenic prion is a conformational isoform of a normal host protein, so all of us in our central nervous system, produce a protein which is shown in this slide, called PrPc, that stands for prion protein cellular, it's a normal protein, it's found on the surface of neurons and it has a function in our life. The pathogenic protein is a conformational variant of PrPc, we call the conformational variant or the abnormal protein PrPsc , and SC stands for scrapie in honor of the first TSE discovered.

    00:46 If you take this abnormal conformational variant and inject it into an animal, this abnormally folded protein will cause all the animals' normally folded prion protein to misfold and become pathogenic. So it's a really unusual situation where you acquire a little bit of misfolded protein and then that misfolded protein changes your normal protein into a misfolded form and then you develop the prion disease. So on the left of this slide is a picture of what we think the normal protein looks like, PrPc, that's the way the protein folds, on the right is the abnormal protein you can see a different way of it folding, this is PrPsc, that causes these TSEs.

    01:37 There are three types of TSEs that we recognize now, I'd like to explain each of them and how they work. The first is called an infectious or transmissible spongiform encephalopathy and as the name suggests, this can be transmitted from host to host, some examples include kuru, which is a transmissible spongiform encephalopathy discovered in Papua New Guinea, we'll talk about that in a moment. There is also infectious prion diseases transmitted unwittingly by corneal transplants, by hormonal donations, transfusions, or from patients with a TSE called Creutzfeldt-Jacob disease. BSE is a prion disease of cattle which as you'll see is a consequence of feeding the remains of infected animals to cattle as feed. And variant CJD is a human disease acquired by eating BSE beef. So in each of these instances the disease is transmitted from a sick animal, to a healthy one, that's why we call them infectious or transmissible TSEs.

    02:52 The idea of an infectious nature arose from the study of kuru, which is a TSE first discovered in the fore people of New Guinea, so it's a fatal encephalopathy, a TSE first discovered in New Guinea, it's a disease with a long 30 year incubation period. It was initially identified by Carleton Gajdusek, he was an American virologist sent there to study this disease and he found it was spreading through the tribe, mainly via women and children, because when someone in the tribe would die, their brain was fed to the women and children in the tribe as a form of the ceremony for the funeral of that individual. So kuru was only found in women and children. So Gajdusek looked at the data and he made the association between cannibalism and the spread of kuru, he said to them, you need to stop eating the brains in this ritual and eventually he got kuru to stop in the fore people of New Guinea.

    03:59 So it was a disease that spread by cannibalism, that people would die of a transmissible spongiform encephalopathy and by eating their brains they spread the disease to others.

    About the Lecture

    The lecture Current View of Prions – Prions by Vincent Racaniello, PhD is from the course Microbiology: Introduction.

    Included Quiz Questions

    1. The pathogenic prion is a conformational isoform of a normal host protein.
    2. These diseases occur only in humans.
    3. Prions carry a very small genome.
    4. Prions are highly sensitive to UV and ionizing radiation.
    1. Abnormal conformation changes
    2. Chemical changes
    3. Changes in the polarity
    4. Changes in the solubility
    5. Changes in the protein sequence
    1. 3
    2. 1
    3. 2
    4. 4
    5. 5
    1. Papua New Guinea
    2. New Orleans
    3. Ireland
    4. Cambodia
    5. Congo

    Author of lecture Current View of Prions – Prions

     Vincent Racaniello, PhD

    Vincent Racaniello, PhD

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