I am curious about this since this doesn’t seem common among other genetic diseases.
For example I don’t think eating a malignant tumor from a cancer patient would put you at high risk of acquiring cancer yourself. (As far as I am aware)
How come prion disease is different?
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The prion proteins bind to your own normal proteins and cause them to become misfolded which makes them non functional and they themselves become infectious. This leads to a cascade effect where more and more of your proteins become misfolded, especially in the brain leading to a rapid neurological decline. As for tumor cells that we might eat they would all be destroyed or degraded by stomach acid, otherwise if a cancer cell did make it past the digestive system, the immune system would destroy it. Prion proteins are just misfolded proteins to at are native to your body so they don’t get destroyed.
A prion is a name for a misfolded protein. Specifically, it’s a protein that has the ability to cause other proteins to misfold into a similar “wrong” shape. Think of it as a kind of disease that can spread from protein to protein within an organism.
Prion diseases are rare, and are often caused by vital proteins involved in the brain. This can either be due to genetics, a spontaneous misfold event, or from consuming “contaminated” meat with misfolded protein.
Once the protein is in you, it’s kind of game-over. The prion (misfolded protein) will keep causing other proteins to adopt the prion shape, eventually taking over all of the normal protein. In mad cow disease, for example, much of the brain tissue becomes “spongey” and non-functional due to the misfolded proteins.
TL;DR the contaminated meat is the disease, it’s a misfolded protein that can convert other proteins.
Prions are a misfolded protein. All proteins fold or collapse into a compact structure that requires the least amount of energy to maintain. Prions that are misfolded can, in some cases, cause the proteins of the same type to misfold in the same way. This causes a cascading effect where all the proteins of that type misfold. Misfolded proteins don’t or can’t do the job they are meant for. Also, traditional techniques like boiling or cooking are not a high enough temperature to destroy the prion so cooking infected tissue and eating it causes an infection in the animal or person eating it.
Because cancer cells are killed by cooking (and cancer is only dangerous because the cells reproduce too quickly, once the cells are dead the tumors are relatively harmless), but prions can only be deactivated by incineration.
And cancer can be physically transmissible, there is one disease in wild animals (I believe it’s some kind of canid?) where they transmit facial tumors. The infection vector is not a bacteria or a virus, but rather cancer cells that found a way to like outside their original host, and now the cancer cells spread when they fight and bite each other.
So prions are proteins, but they are folded in a weird way.
The reason they are dangerous, is because they force other healthy proteins in your body to fold the same way as them, but your body doesn’t really have a way of undoing the misfolding, which means that they eventually take over all the correctly folded proteins in your body.
Now why they are so dangerous, and transmissible through eating contaminated meat is fairly simple, they are proteins, and therefore can’t be cooked to death like a bacteria or fungus could be
You can get prion disease via genetics, but it isn’t a disease that affects cell DNA itself.
Prion diseases spread throughout the body because the misfolded proteins (the prions) cause surrounding proteins to also misfold. So if these prions get into your body, they spread, whether by eating them, having them come in contact with your tissues somehow (ie contaminated donor tissue), or being predisposed to them genetically.
Proteins aren’t destroyed by being disgested and absorbed by your body, so the prions survive the process. A cancer cell, just like all the other kinds of cells you eat, would be broken down into its parts by your body.
Prions are malformed proteins. They’re not living tissue. They can’t be killed because they’re not alive.
Creutzfeldt-Jakob disease (mad cow disease) is a prime example of a prion.
Eating brain meat from a diseased cow brain will potentially transfer the prions.
It is thought to be a result of cannibalism of feeding, as in cows eating cow ‘meal’ in their diet.
Humans have a lot to learn about nature
If you’ve ever read Vonnegut’s “Cat’s Cradle” you’ll be familiar with “ice nine”, a fictional form of ice that melts not at 32F but at 100-something. It’s introduced to the world and all the world’s water begins to crystallize into this stable form.
Prions are a little like that. They “teach” your normal proteins to fold themselves in the wrong way, and those misfolded proteins cause others to misfold in a cascade that makes your brain not work properly.
A lot of the Orion diseases are not “spread” by humans eating them but instead by using live stock proteins to feed livestock. It can spread to humans eating contaminated meat, especially meats connected to spinal tissues; but the spreading comes from taking live stock offal like spinal and brain tissues, and then mixing it into livestock feed
Prions are misfolded forms of a normal protein found in your body thus are not recognized by the immune system as foreign. A tumor coming from a person or an animal have markers for their own “self” antigens. Those self antigens on the tumor introduced into your body would not be recognized as “self” to your immune system, they would be recognized as foreign. Thus immediately attacked and destroyed by the immune system. Prions are not recognized as foreign, and prions from say mad cow disease are very very similar in sequence to the human form, so are not different enough to be recognized as foreign. But there are sequence differences in prions found in animals and they do matter. Some of the difference in sequence forms a species barrier and hence why humans do not get infected by Scrapie or Chronic Wasting Disease prions.
And you are combining two things that may be causng you some confusion. Most all of human prion diseases are CJD, whereas mad cow disease causes vCJD. Mad cow is acquired as an infection of sorts. However most prion diseases in humans are CJD not vCJD. These can be genetic. People can be born with prion proteins that ultimately will cause CJD. So that is genetic. There is also spontaneous conversion of normal health prions into disease prions. This is not genetic, just something that can happen in rare occasions. So you can get a prion disease like an infection, but in reality most prion disease are due to genetics and spontaneous conversion.
Reddit has a particular fear boner for prion diseases. To try an allay those fears, prion diseases in humans are very rare. Just a few hundred per year in the U.S. It is rare enough that people should not be spending their time worrying about it honestly but reddit spends a lot of time talking prions. It is indeed a nasty disease, but the chance of getting it are just exceptionally low. There are other nasty diseases that are much like prion diseases in a lot of ways such as Alzheimer’s disease. Prions at symptom onset will kill you faster, and Alzheimer’s will take longer. But they both cause brain degeneration with some similarities in symptoms and nastiness. People should not worry about prions, they should worry about Alzheimer’s as their chance of acquiring that is much much much higher than getting a prion disease like CJD.. In the U.S. getting CJD is about 1 in 1 million. If you are 65 years or older your chances of getting Alzheimer’s is 1 in 9. People should worry about that, not CJD.
PrP is a protein that can misfold into a incredibly stable protein called a prion that is impossible to destroy and induces normal PrP to misfold. PrP is more likely to misfold if you have MM alleles instead of MV. Once PrP starts misfolding your brain becomes clogged with misfolded protein and you eventually die.
Alpha Synuclein has also been shown to have a prion form. Misfolding proteins are involved in Parkinson’s Disease, ALS/ MND, FTD and Alzheimer’s but they aren’t infectious like prions.
Cancer cells won’t survive digestion, though cancer can be transmitted by transplants or transfusion.
Prions are misfolded proteins, I don’t know the exact mechanics of this but these misfolded proteins encourage other proper proteins to misfolded themselves. This misfolded orientation make them unable to do their normal task.
The way your immune system works is by “looking” at parts of the stuff that is in your body to check against a database.
Let’s make an analogy that your body is like an office or business. Going into the office there’s a finger print scanner or retinal scanner for the employees to gain access to the office and for the sake of argument let’s say everyone in accounting is a clone of Jim, every red blood cell is a clone of Bob or whatever.
There’s a particular protein that does “something” important for your body let’s call him Frank. So every Frank in your body/office looks exactly the same and Frank is a very diligent employee that’s vital for your brain to work well. One day there’s a weird Frank that shows up at the turnstile to the office, he kind of looks like Frank but he’s dressed like Michael Jackson and is just moonwalking everywhere. He goes up to the retinal scan and finger print scanners and walks right through. Every “normal” Frank that MJ Frank encounters is enamoured by this moon walk and begin to do nothing but Moonwalking instead of their normal tasks. Soon every Frank is vying to be the top MJ impersonator and the office grinds to a halt because the critical TPS reports are all backlogged and the business shuts down.
A bacteria or virus or toxin or something might have tripped up security but MJ Frank IS Frank, just a weirdly behaving Frank. The security system doesn’t identify threats/friendlies by how things behave, they identify based on small unique identifiers (finger prints, retinal scans). Or body’s immune system doesn’t have “smart” security guards that can look at MJ Frank and know they’re acting funny and arrest them, they can only look at certain features and check them against the database.
Prions are not “genetic diseases.” They are little protein programs that screw up your proteins and make them infectious in the same way. In a sense, they act like viruses (which are DNA or RNA based, and thus in a way “genetic”), but they don’t use DNA / RNA to do their damage or spread.
Prions can self-replicate in healthy brain tissue, almost like viruses. It is useful to think of them as highly infectious agents although they are not true life forms. Prions are more dangerous than viruses, because they are immune to things that can kill true viruses. They have to be thoroughly destroyed at the chemical level, down to the last prion molecule, to remove the risk of infection. A single prion molecule, as a misfolded protein, will interact with normal proteins and cause them to become misfolded and spread damage to the organism (such as kuru disease).
but polypeptides will be broken down into individual amino acids and only oligopeptides(di n tripeptides) will be absorbed as such by our intestines. in order to form a secondary structure we need at least 10 amino acids to fold and have a unique structure. then how do we absorb prion proteins from the gut?
Prion diseases are not (usually) genetic. That alone already puts your examples like cancer out. Most prion disease is “sporadic”, meaning it happened spontaneously to an otherwise healthy person who wasn’t exposed to an external source of the prion, it just randomly happened inside them.
But beyond that, prion diseases are a thing that is kind of…beneath the notice of your immune system? That is, even cancer cells have to work VERY hard to avoid being detected by your immune system. That’s why almost all cancer only happens as a result of excessive radiation exposure (=increased mutation rate), old age (=more time for bad mutations to accumulate), or (rarely) as a side effect of certain infections (e g. human papilloma virus).
But proteins? Plain, simple, not even slightly “alive” proteins? Your immune system doesn’t really see them, not normally anyway, and so it doesn’t try to fight them. It’s like if dogs and cats “invaded” a country and started messing everything up. Would the army deploy for such a thing? Would they even notice until it was too late?
Further, it’s worth noting how prion disease spreads, because prions are not self-replicating. Some are infectious, but the “infection” doesn’t mean the protein is manufacturing completely new proteins that look like itself. Instead, it’s that the healthy protein (called PrP^(C)) is found basically all over the place in a mammal’s body, but especially in neural tissue, and this weird misfolded version (PrP^(Sc)) can bump into PrP^(C), latch onto it, and transform it into PrP^(Sc). While PrP^(C) is safe and even healthful, as it appears to reduce sensitivity to various kinds of stress in neural tissue, PrP^(Sc) is more stable and unfortunately quite toxic, and will very slowly warp all the other copies of the regular protein to be the same way.
In simple terms, it just happened to be a bad-luck combination of:
So…yeah. Your body contains untold billions and billions of proteins. Almost all of them lack at least one of the above qualities and thus don’t cause disease. This one single protein won the world’s most terrible lottery.
Prions are rogue proteins that destroy tissue. The odd thing is though not spoken about often it’s detected in about 60 brain surgeries a year. The scary part about that is in the US the most common cause for prion infections is consuming human spinal cord/ nervous/ and brain tissue. Beware of the chili special … lol… funny but not as odd as you might think
Prions are not a genetic disease.
Genetic diseases result from DNA errors embedded in the nucleus of whole cells. Only those cells with the errors are impacted, because their instructions (their genes) are malfunctioning. With cancers, those erroneous cells multiply, and sometimes metastasize/split and flow through the blood through the body, lodging and growing elsewhere, forming tumors. Only the body of origin is really at risk, because those cancer cells hide well among normal cells, because they came from the same body, and the immune system doesn’t know to kill them. Cancers from foreign bodies – even other humans, for example – would have a harder time invading your own body because the body can more easily recognize foreign cells and destroy them. They can’t hide among your own cells.
So even if a cancer cell from organism A somehow miraculously made it through your digestive tract and somehow got past your intestine and into your blood, your body would recognize it as a foreign cell and kill it off because all the cell markers would clearly depict it as foreign. It wouldn’t replicate and hide in your body successfully. But even this above scenario is very unlikely because by cooking meat, you are killing the cells it is composed of. Dead cancer cells can’t replicate anyways.
A prion is a protein that causes other proteins to misfold, which is much smaller than a cell – it’s essentially a complicated molecule. Prions are not alive and do not have genes. They are just molecules. They can’t make other prions on their own, they rely on your cells to make a similar proteins, and then they attach to those proteins and (to oversimplify) bend them out of shape. Then those new misfolded proteins act as prions and bend other proteins out of shape, etc etc.
Prions can’t be as easily attacked by immune cells and there are few markers that could be used to target them. Since they’re made out of otherwise essential body proteins that have been reorganized, attacking them chemically risks harming essential proteins that are functioning properly. And since they aren’t alive, they have very few requirements for survival/continued existence. Essentially, if the meat they come from isn’t cooked at a high enough temperature to denature them (meaning change their folding structure) or decompose them chemically, and assuming your digestive tract and its chemicals don’t alter them either, they can get into your blood and continue to function. Then once they start misfolding your own proteins inside your body, you get a cascading increase of prions inside you.
To try and tl/dr, cancer cells from one organism can’t easily hide in another, making them easy for the immune system to target, and they have to stay alive to continue to cause problems, which is difficult when they are being cooked and eaten. Prions are tiny molecules that are hard for the immune system to target, they aren’t alive, and they’re composed otherwise normal proteins that are hard to attack chemically.
You can’t kill prions because they are not alive. Even an autoclave for surgical scalpels won’t get rid of them, the scalpels must be disposed of. If an animal dies from a prion disease and decomposes the prions can be taken up by the grass (or crops)and passed on to grazing animals that eat that grass years later. I don’t think telling hunters to be careful and use clean knives sounds like sound advice. No one talks about that in CFJ disease prions are in the eyes at high concentrations years before there are recognized CFJ symptoms. And I read those victims have more eye problems years before their brains show symptoms. I think we need more serious research into the dangers.