Alzheimers and Tau proteins

This report on the "spreadable" nature of Alzheimers within the brain is in New Scientist and came to me via Glyn Wainwright on the THINCS forum. It's interesting in it's own right but I rather liked the related paper it linked to about the "contagious" nature of misfolded Tau proteins.

I think it would be reasonable to summarise the abstract as claiming that Tau proteins are non pathogenic structural proteins present inside, and essential to, normal nerve cells. Tau protein aggregates, which are abnormal products, "are observed" outside cells. My assumption is that, as healthy Tau are normally intracellular proteins, they have to be either excreted or exocytosed. Or the cell has to die to released them, before they can be found outside cells. The latter seems the more believable option.

Placing healthy monomer Tau proteins outside neuronal cells in culture does nothing. Placing Tau aggregates outside cells promotes endocytosis of those aggregates and, once endocytosed, the aggregates are directly toxic ("induce fibrillization") to the normal intracellular structural Tau. When this cell then dies it too will release it's abnormal Tau aggregates, which will go on to kill further recipient cells.

OMG its a locally contagious protein! Except it's not, it's a toxic substance which triggers the production of the same toxic substance from healthy tissue on contact.

Where do the original Tau aggregates come from? I suspect that Blaylock would argue they are shrapnel from the death of a neurone killed by catastrophic energy failure, induced by excitotoxins hitting glutamate-receptor sporting cells. This will no doubt involve hyperphosphorylation of Tau and all of the other exciting co factors for Alzheimers. Oh, and might be avoidable by supplying alternative energy molecules such as ketones. The shrapnel is itself neurotoxic and the product of its damage is more of the same neurotoxic shrapnel. This is a chain reaction and Alzheimers then becomes the neurological equivalent of Hiroshima. At this point Blaylock must be feeling quite justified in his views.


The obvious comparison, which is made in the abstract, is to prion proteins as featured in BSE.

If misfolded prion proteins are endocytosed, as Tau proteins are, and are themselves toxic to normal prion proteins, you then have the mirage of a contagious protein.

BSE can be induced in the brain of almost any recipient species by injecting a slurrry from the brain of a BSE case, which contains misfolded prion protein. But what is the trigger for the initial misfolding?

If I was prof Ebringer I might strongly suggest that the original trigger for prion misfolding is an autoimmune attack on myelin basic protein, or a similar structural protein, in the brain. We're not thinking neat and tidy apoptosis here, more like sudden death and spill your contents. Once the misfolding chain reaction is started the progression to BSE via more misfolding and cell death might then follow on, exactly as the Tau aggregates spread.

There is then no need for a contagious protein. In fact, it is easy to "spread" BSE by injecting the ash from incinerated BSE brain (600 deg C in the presence of oxygen. This means incinerated!!!). All you need is for the ash to damage the recipient brain enough to trigger protein misfolding and you have "transmitted" BSE using ash. Thoroughly formalin fixed brain tissue does the job rather better than fresh brain tissue too!

You really have to wonder what is going on here and the Tau "transmission" abstract makes Prof Ebringer and Russell Blaylock look pretty good as proposers of the correct triggers for the respective diseases to me.

Fascinating stuff.

Peter