Prions: birth without life.

Days 2,3 of Med School.

So most people have heard of Mad Cow disease.  Caused a meat panic, made England kill a whole bunch of cows, and revealed some creepy practices about feeding cows other cows.  But what many people don't know is the really cool scientific discoveries that came from Mad Cow, and its less glamorous sheep cousin, Scrapie.

When Mad Cow and Scrapie started popping up big time, people were scrambling to identify the causative agent, since it was obviously transmittable from one animal to another.  But they found that beyond even identifying it, they couldn't even kill it.  Anti-bacterials, anti-biotics, anti-virals, extreme heat, everything that would kill any living organism or virus, wouldn't kill whatever was causing Mad Cow.

Eventually, they found that what did stop Mad Cow from spreading was protein denaturing chemicals.  This meant that the Mad Cow infectious agent wasn't a virus, wasn't a bacteria or a microscopic organism, but just a protein.  And not just a protein- a protein that is in everyone's body already.

So here's what happens.  The Prion protein is the protein involved in Mad Cow.  It is a normal protein that is produced in everyone, and is now thought to have some sort of a neuroprotective function.  But it's not a perfectly stable protein.  It can twist, and change its shape a bit.  After it changes its shape, it may bump into another perfectly normal Prion protein.  When it does, it causes that normal Prion to change shape as well.  And so on, in a cascading fashion until there are thousand of millions of misshapen Prions.  When a misshapen Prion from one animal is introduced into another animal, it acts as a seed, initiating this cascade of protein shape changes that causes Mad Cow disease.

It is unclear whether the misshapen Prions are actually poisonous in some way, or if the shape change simply inactivates the good Prions, which may cause a problem if normal Prions are very important in the body.  However, in an interesting twist, very recent research indicates that normal Prions may suppress Beta-secretase, whose action is key in creating the plaques that occur in Alzeheimer's disease.  The plot thickens.