The clustering (or aggregation) of misfolded proteins is a key feature of many neurodegenerative conditions. These aggregating proteins are collectively referred to as ‘amyloid’ proteins, and the way that they have misfolded allows many copies of these proteins to stick together.
Amyloid proteins are associated with more than 50 medical conditions (from Alzheimer’s, ALS, Huntinton’s and Parkinson’s through to rheumatoid arthritis and diabetes).
In addition to being public enemy no. 1 for their respective conditions, amyloid proteins also share another curious feature:
They glow when exposed to specific wavelengths of light (like near-infrared).
In today’s post, we will look at what we mean by ‘amyloid proteins’, what this new research found, and how this property could be extremely useful in the tracking of Parkinson’s over time.
If you have recently sent me an email, you may not have had a response. I apologise profusely for this, but I have gradually become inundated with questions and requests, and have had a hard time keeping up (in addition: family and day job take priority).
I do get some wonderfully titled emails though, which immediately grab the attention.
For example, the other day I recieved an email entitled:
“So, will my head glow in a disco?”
A brief glance at the contents confirmed suspicions that the sender was referring to this new research report:
Title: Ultraviolet–visible–near-infrared optical properties of amyloid fibrils shed light on amyloidogenesis
Authors: Pansieri J, Josserand V, Lee S-J, Rongier A, Imbert D, Sallanon MM, Kövari E, Dane TG, Vendrely C, Chaix-Pluchery O, Guidetti M, Vollaire J, Fertin A, Usson Y, Rannou P, Coll J-L, Marquette C, & Forge V
Journal: Nature Photonics, published 13th May 2019
Previously researchers have described an intrinsic ultraviolet–visible optical property to amyloid proteins.
What does that mean?
We have previously discussed the importance of the right foods for people with Parkinson’s on this blog – Click here for a good example.
Recently, new data from researchers in Sweden points towards the benefits of a specific component of fish in particular.
It is a protein called β-parvalbumin, which has some very interesting properties.
In today’s post, we discuss what beta-parvalbumin is, review the new research findings, and consider how this new information could be applied to Parkinson’s.
A very old jaw bone. Source: Phys
In 2003, researchers found 34 bone fragments belonging to a single individual in a cave near Tianyuan, close to Beijing (China).
But it was not the beginning of a potential murder investigation.
This was the start of something far more interesting.
Naming the individual “Tianyuan man”, the researchers have subsequently found that “many present-day Asians and Native Americans” are genetically related to this individual. His bones represented one of the oldest set of modern human remains ever found in the eastern Eurasia region.
Tianyuan caves. Source: Sciencemag
But beyond the enormous family tree, when researchers further explored specific details about his jaw bone (or lower mandible as it is called) they found something else that was very interesting about Tianyuan man:
Title: Stable isotope dietary analysis of the Tianyuan 1 early modern human.
Authors: Hu Y, Shang H, Tong H, Nehlich O, Liu W, Zhao C, Yu J, Wang C, Trinkaus E, Richards MP.
Journal: Proc Natl Acad Sci U S A. 2009 Jul 7;106(27):10971-4.
PMID: 19581579 (This research article is OPEN ACCESS if you would like to read it)
In this study, the investigators analysed the carbon and nitrogen isotopes found within bone collagen samples taken from the jaw bone of Tianyuan man. In humans, the carbon and nitrogen isotope values indicate the sources of dietary protein over many years of life.
The researchers found that a substantial portion of Tianyuan man’s diet 40,000 years ago came from freshwater fish.
Interesting preamble, but what does this have to do with Parkinson’s?
In Silicon valley (California), everyone is always looking for the “next killer app” – the piece of software (or application) that is going to change the world. The revolutionary next step that will solve all of our problems.
The title of today’s post is a play on the words ‘killer app’, but the ‘app’ part doesn’t refer to the word application. Rather it relates to the Alzheimer’s disease-related protein Amyloid Precursor Protein (or APP). Recently new research has been published suggesting that APP is interacting with a Parkinson’s disease-related protein called Leucine-rich repeat kinase 2 (or LRRK2).
The outcome of that interaction can have negative consequences though.
In today’s post we will discuss what is known about both proteins, what the new research suggests and what it could mean for Parkinson’s disease.
Seattle. Source: Thousandwonders
In the mid 1980’s James Leverenz and Mark Sumi of the University of Washington School of Medicine (Seattle) made a curious observation.
After noting the high number of people with Alzheimer’s disease that often displayed some of the clinical features of Parkinson’s disease, they decided to examined the postmortem brains of 40 people who had passed away with pathologically confirmed Alzheimer’s disease – that is, an analysis of their brains confirmed that they had Alzheimer’s.
What the two researchers found shocked them:
Title: Parkinson’s disease in patients with Alzheimer’s disease.
Authors: Leverenz J, Sumi SM.
Journal: Arch Neurol. 1986 Jul;43(7):662-4.
Of the 40 Alzheimer’s disease brains that they looked at nearly half of them (18 cases) had either dopamine cell loss or Lewy bodies – the characteristic features of Parkinsonian brain – in a region called the substantia nigra (where the dopamine neurons are located). They next went back and reviewed the clinical records of these cases and found that rigidity, with or without tremor, had been reported in 13 of those patients. According to their analysis 11 of those patients had the pathologic changes that warranted a diagnosis of Parkinson’s disease.
And the most surprising aspect of this research report: Almost all of the follow up studies, conducted by independent investigators found exactly the same thing!
It is now generally agreed by neuropathologists (the folks who analyse sections of brain for a living) that 20% to 50% of cases of Alzheimer’s disease have the characteristic round, cellular inclusions that we call Lewy bodies which are typically associated with Parkinson disease. In fact, in one analysis of 145 Alzheimer’s brains, 88 (that is 60%!) had chemically verified Lewy bodies (Click here to read more about that study).
A lewy body (brown with a black arrow) inside a cell. Source: Cure Dementia
Oh, and if you are wondering whether this is just a one way street, the answer is “No sir, this phenomenon works both ways”: the features of the Alzheimer’s brain (such as the clustering of a protein called beta-amyloid) are also found in many cases of pathologically confirmed Parkinson’s disease (Click here and here to read more about this).
So what are you saying? Alzheimer’s and Parkinson’s disease are the same thing???
This week an interesting new study dealing with the biology of Alzheimer’s was published in the journal Science Translational Medicine. It has drawn a lot of attention as it may be turning our understanding of Alzheimer’s disease on it’s head. If the results are independently replicated and verified, it could potentially have major implications for Parkinson’s disease.
For the last 30 years, a protein called beta-amyloid has been considered one of the bad boys of the most common neurodegenerative condition, Alzheimer’s disease.
What is Alzheimer’s disease?
Alzheimer’s disease is a progressive neurodegenerative condition that can occur in middle or old age. It involves a generalized degeneration of the brain, not localised to specific regions like Parkinson’s disease.
What happens in the Alzheimer’s brain?
In the brain, in addition to cellular loss, Alzheimer’s is characterised by the presence of two features:
- Neurofibrillary tangles
- Amyloid plaques
The tangles are aggregations of a protein called ‘Tau’ (we’ll comeback to Tau in a future post). These tangles reside within neurons initially, but as the disease progresses the tangles can be found in the space between cells – believed to be the last remains of a dying cell.
A normal brain vs an Alzheimer’s affected brain. Source: MMCNeuro
Amyloid plaques are clusters of proteins that sit between cells. A key component of the plaque is beta amyloid. Beta-amyloid is a piece of a larger protein that sits in the outer wall of nerve cells where it has certain functions. In certain circumstances, specific enzymes can cut it off and it floats away.
Beta-Amyloid. Source: Wikimedia
Beta-amyloid is a very “sticky” protein and for a long time it has been believed that free floating beta-amyloid proteins begin sticking together, gradually building up into the large amyloid plaques. And these large plaques were considered to be involved in the neurodegenerative process of Alzheimer’s disease.
So what was discovered this week?
This week a study was published that suggests a new (and positive) function for beta amyloid:
Title: Amyloid-β peptide protects against microbial infection in mouse and worm models of Alzheimer’s disease.
Authors: Kumar DK, Choi SH, Washicosky KJ, Eimer WA, Tucker S, Ghofrani J, Lefkowitz A, McColl G, Goldstein LE, Tanzi RE, Moir RD.
Journal: Sci Transl Med. 2016 May 25;8(340):340ra72.
The researchers took three types of mice:
- genetically normal mice
- mice with no beta amyloid
- mice producing a lot of beta amyloid
They infected all of the mice with the microbe that causes meningitis, and they found that the mice producing a lot of beta amyloid lived significantly longer than other groups of mice. They then repeated the experiment in a species of microscopic worm – called C.elegans – and found similar results. These findings suggested that beta amyloid was having a positive effect in the brain.
But then they noticed something strange.
The mice producing a lot of beta amyloid usually do not develop a lot of protein aggregation until old age, but when the researchers looked in the brains of the mice they infected with meningitis, they found significant levels of aggregation in the mice producing a lot of beta amyloid but at a young age..
This led the researchers to conduct some cell culture experiments in which they watched what was happening to the bacteria and beta amyloid. They found that the beta amyloid was sticking to the bacteria and this was leading to the formation of protein aggregates.
The results of these experiments suggested to the researchers an intriguing possibility that beta amyloid may be playing a protective in the brain – acting as an immune system for the brain – against infection.
Thus the aggregations we see in the brains of people with Alzheimer’s may not be the cause of the cell death associated with the disease, but rather evidence of the ‘brain’s immune system’ trying to fight back against unknown infectious agents. The researcher’s of the study were quick to point out that this antimicrobial action of beta amyloid is simply a new function of the protein, and it may have nothing to do with the disease itself. But it will be interesting to see where this research goes next.
What has this got to do with Parkinson’s disease?
Parkinson’s disease is only definitive diagnosed at the postmortem stage. This is done by microscopic examination of the brain. In the brains of people with Parkinson’s disease, there are protein aggregates calls Lewy bodies. These are densely packed clusters of a protein called ‘alpha synuclein‘.
The brown spot is a Lewy body inside of a brain cell. Source: Cure Dementia
If the results of the study presented above are correct and beta amyloid is a protective protein in the brain against infection, could it not be that alpha synuclein may be playing a similar role? It is a fascinating idea that it will be interesting to test.
What are the implications of the study?
Currently, there are numerous clinical trials for Alzheimer’s disease, involving treatments that act against beta amyloid. If the study presented above is correct, and beta amyloid has a role in protecting the brain, these new treatments in clinical trial may actually be weakening the brain’s ability to fight infection.
Similarly, if alpha synuclein is found to exhibit ‘protective’ properties like beta amyloid, then the alpha synuclein vaccine clinical trials currently underway (in which the body’s immune system is primed to remove free floating alpha synuclein, in an attempt to stop the disease from spreading) may need to be reconsidered. At a minimum, investigations into whether alpha synuclein has antimicrobial properties need to be conducted.
Today’s banner was sourced from PBS.