Whats the connection between alzhiemers and prion disease?

Question

would be great to have a biochemistry/molecular aspect as an answer, thankyou

Answer 1

As far as we know, BSE is caused by prions. I have had professors who suspect there is an unknown viral component of BSE/CJD, but so far there is no evidence.

Now, the first answer is right. Both conditions involve the aggregation of proteins. In BSE the proteins are prions that aggregate to the point where they destroy brain cells - hence the sponginess. In Alzheimer's the aggregations create plaques. I don't know the name but I'm sure you can easily find it on wikipedia.

Answer 2

As far as I know the only connection would be that they both affect the brain (and related behavior) and that in both you will see a build up of proteins.

In Alzheimer's the proteins are in the form of plaques that build up on the surface of the brain. In prion diseases the proteins are actually the prions themselves that have an active region that changes existing proteins in the brain into prions causing a spongy appearance of built up proteins within the brain.

Answer 3

BSE *is* prion disease.  Prions are what cause bovine spongiform encephalopathy.  When it happens in humans we call it something else (nvCJD or new variant Creuzfeldt-Jakob Disease), but it's the same thing.

The material that makes the plaques in these diseases is the deformed protein sheets, which are changed from what is called an "alpha-helical" conformation into a "beta-pleated sheet".  These deformed proteins then aggregate into the plaques of BSE or nvCJD.  This is different from the plaques you hear about in Alzheimer's disease, which are mostly fragments of beta-amyloid and tau proteins that clump up outside of neurons.

The common connection between the two diseases that I think you're looking for is that both diseases are associated with protein misfolding.  However, thus far, the pathophysiology appears to be different.  On the other hand, no one really understands why some people get Alzheimer's and others don't (and no one understands how people get sporadic CJD either, the kind that isn't associated with eating tainted meat).  So there's a Nobel Prize opportunity out there for someone.  Why not you?  ;-)

ETA:  Or why not lab rat?  Awesome answer, thanks for the information!

Answer 4

The connection is amyloid. They are both protein folding diseases where amyloid is formed. They both cause the build up of amyloid in the brain and the death of neurons. Other than different symptoms etc, the key biochemical difference is that prion disease involves a different protein and is infectious.

Amyloid is where a particular protein changes its 3D form and folds into a beta-sheet structure. Then other molecules of the same protein do the same thing and they all join into long fibres, called fibrils. These fibrils build up into amyloid plaques and accumulate. Sometimes these plaques directly cause tissue damage, other times they are just a 'marker' that a particular disease is going on in the body.

There are many diseases where you get amyloid - the best known examples are Alzheimer's and prion diseases, but it's also associated with chronic inflammation, certain bone marrow disorders and type 2 diabetes. For each disease, a different specific protein is involved. The effects of the disease depend on what the protein is and where it is found. For example, in AL amyloidosis, the protein is an immunoglobulin light chain, and it can deposit in the kidneys and cause kidney damage. In prion diseases, the protein is prion protein (aka PrP), while in Alzheimer's one of the proteins involved is beta-amyloid peptide. PrP and beta-amyloid peptide are both found in the brain, so that's where the damage is done in those diseases. The diseases affect different regions of the brain and in different ways, so they have very different symptoms. There are different types of prion disease (e.g. CJD, GSS, FFI) which all involve PrP but in different parts of the brain.

Prion diseases are the only known type of infectious amyloid. So if you have an animal with a prion disease and take a bit of its brain tissue and inoculate it into another animal's brain, the second animal will get the disease. This will not happen with Alzheimer's. Prion diseases can also be spread by ingestion (e.g. BSE and CJD). Strictly speaking, most prion researchers don't think it's the prion amyloid fibrils themselves that are infectious, but this is a bit too advanced to worry about in an essay.

EDIT: in that case, have some references!

Amyloidoses: http://www.ncbi.nlm.nih.gov/pubmed/11260...

Prions (by my old PhD supervisor :-D ): http://www.ncbi.nlm.nih.gov/pubmed/11260...