What is a prion? And what does it do ?
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Prions are miss-folded proteins. When your body makes proteins they start off as a long chain of amino acids. These amino acids bend and interact with each other to give the protein its 3D shape as well as its function. Prions are proteins which have folded in such a way that they encourage further miss folding of the same protein.
This miss folding ultimately results in lack of function and the cell hosting them to die and eventually the host. There is no known cure and the disease rapidly progresses.
Proteins are the machines of our bodies. Whenever our body needs to do anything, it’s probably a protein that’s doing it.
The shape of the protein is important to it’s function. So if it’s built wrong, it doesn’t work right. If it’s built *really* wrong, it can be actively harmful. Imagine building an internal combustion engine, except oops, it got messed up and the combustion isn’t internal. That’s probably not great for the immediate surroundings. That’s basically what a prion is.
Prions are insanely fascinating!
To start: a prion is a protein. Proteins are the things your DNA has instructions for making, and are the molecular work horses of life. They do everything from digesting foods (enzymes), moving other molecules in or out of the cell (transport proteins), and transmitting signals like nerves (receptors).
Your DNA has instructions for how to make these proteins, but they only get you about halfway there. Once all the pieces are connected in a line, it still has to fold into the right 3D shape. The best metaphor I can think of right now is that the DNA instructions get you to the point of having your cake batter all ready, but you still need to put it into the cake tin(s), bake it, and maybe even add some frosting. (As an ironic aside, cooking/baking usually involves denaturing proteins, which means ruining that careful 3D shape).
Sometimes, proteins fold incorrectly. A misfolded protein cannot do it’s job. In most cases your body can just send that misfolded protein to the recycle bin (proteasome/lysosome), chop it up, and reuse the parts.
Prions are misfolded proteins that somehow have the ability to turn *other*, properly-folded proteins into the same misfolded shape. This not only means those proteins can’t do their intended job, but they might be in the right shape so start going rogue and doing things they aren’t supposed to. As you might guess, prions cause a “chain reaction” – one prion molecule forms, it turns other molecules into that prion, which then go on to turn even more, and so on.
Prions can be spread from one individual to another, making them a form of transmissible/infectious disease. In humans, they often affect the brain specifically. Prion diseases can go undetected for years, all the while cause steadily accumulating damage. Most concerningly, **there are no treatments for prion diseases, and they are almost always fatal.** Honestly, our best defense against prion diseases is just that they are very rare.
One of most well known prion diseases is bovine spongiform encephalopathy, aka “mad cow disease”. It can spread to humans by eating contaminated food, and in humans it is called Creutzfeldt-Jakob disease.
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