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???
The clustering of a protein called alpha synuclein is one of the cardinal features of the brain of a person with Parkinson’s disease.
Recently published research has demonstrated that tiny antibodies (called nanobodies) derived from llamas (yes, llamas) are very effective at reducing this clustering of alpha synuclein in cell culture models of Parkinson’s disease.
In today’s post, we will discuss the science, review the research and consider what it could all mean for Parkinson’s disease.
Llama. Source: Imagesanimals
Ok, I confess: This post has been partly written purely because I really like llamas. And I’m not ashamed to admit it either.
I mean, look at them! They are fantastic:
Very cute. But what does this have to do with Parkinson’s disease?
Indeed. Let’s get down to business.
This post has also been written because llamas have a very interesting biological characteristic that is now being exploited in many areas of medical research, including for Parkinson’s disease.
Last week at the SoPD, we received an interesting email from reader Gabriel “from Tiana (near Barcelona) (Spain)”. The email brought our attention to an interesting new article that was published in a recent issue of the Journal of Neuroscience.
The research report involves prolyl oligopeptidase (PREP) inhibitors and some pre-clinical data involving a model of Parkinson’s disease.
In today’s post we will review the article and what we know about PREP-inhibitors.
Yes, I know. The obvious first question is:
What is prolil oligoopep..tid… whatever?
It’s really very simple. Prolyl oligopeptidase is a serine protease, that cleaves short peptides containing proline-residue.
Prolyl oligopeptidase (or PREP) is an enzyme that is involved in the making and destruction of certain types of hormones and neuropeptides (Neuropeptides are a group of small molecules used by brain cells to communicate with each other). PREP is required for cutting certain bonds on some of these small molecules, allowing them to function normally or be broken down and recycled.
PREP can be found in cells from most of species – from bacteria to human – suggesting that it has important functions across evolution. In addition, PREP has been associated with amnesia, depression and blood pressure control.
What is has PREP got to do with Parkinson’s disease?
Interestingly, PREP activity changes during the ageing process. It also changes during neurodegenerative conditions, such as Alzheimer’s and Parkinson’s diseases.
Given this situation, several PREP inhibitors were developed during the 1990s, and they were found to have a positive effect on memory and learning in animal models of Alzheimer’s disease (Click here for more on this).
So what is known about PREP in Parkinson’s disease?
Back in 1987, a group of researchers noticed something interesting in the cerebrospinal fluid (the liquid surrounding the brain) of people with Parkinson’s disease:
Title: Post-proline cleaving enzyme in human cerebrospinal fluid from control patients and parkinsonian patients.
Authors: Hagihara M, Nagatsu T.
Journal: Biochem Med Metab Biol. 1987 Dec;38(3):387-91.
When the researchers compared normal healthy subjects with people who have Parkinson’s disease, they found that people with Parkinson’s disease exhibited a marked decrease in the activity of PREP in the cerebrospinal fluid. Interestingly, this decrease was not evident in the blood, suggesting that something was happening in the brain.
This observation was later followed up by other findings, including this journal report:
Title: Prolyl oligopeptidase colocalizes with α-synuclein, β-amyloid, tau protein and astroglia in the post-mortem brain samples with Parkinson’s and Alzheimer’s diseases.
Authors: Hannula MJ, Myöhänen TT, Tenorio-Laranga J, Männistö PT, Garcia-Horsman JA.
Journal: Neuroscience. 2013 Jul 9;242:140-50.
The researchers in this study were investigating where PREP was actually located in the postmortem brain. In people with Parkinson’s disease, they found that a very strong presence of PREP in the substantia nigra (the region which loses dopamine neurons in this condition).
Interestingly, they also noted that PREP was co-localized with the Parkinson’s associated protein alpha synuclein (meaning where they found PREP, they also saw alpha synuclein). It is also interesting to note that they did not see this pattern in the brains of normal healthy controls or people with Alzheimer’s disease.
In 2008, another group found that PREP not only co-localised with alpha synuclein, but it was also doing something quite unexpected:
Title: Prolyl oligopeptidase stimulates the aggregation of alpha-synuclein.
Authors: Brandt I, Gérard M, Sergeant K, Devreese B, Baekelandt V, Augustyns K, Scharpé S, Engelborghs Y, Lambeir AM.
Journal: Peptides. 2008 Sep;29(9):1472-8.
Since alpha synuclein and PREP were in the same locations in the Parkinsonian brain, the researchers in this paper were interested to see if the two protein actually functioned together and required each other to do their respective jobs. What they found, however, when they put the proteins together in cell culture was a surprise: an acceleration in the accumulation (or aggregation) of alpha synuclein.
Aggregation of alpha synuclein is a key feature of the Parkinsonian brain. It is believed to be responsible for the presence of Lewy bodies (the dense circular clusters in cells in the brains of people with Parkinson’s disease) and may be involved in the cell death associated with the condition.
A lewy body (brown with a black arrow) inside a cell. Source: Cure Dementia
With the discovery that PREP is involved with the aggregation of alpha synuclein, the researchers suddenly had a new disease-related target to investigate further. And this is what the new Journal of Neuroscience paper has been explored.
So what was published in the recent Journal of Neuroscience report?
This is Timo.
Dr Timo Myöhänen. Source: University of Helsinki
He’s a dude.
He is also an adjunct professor at the University of Helsinki where he has a research group focused on neurodegenerative disorders. They have a particular interest in PREP and they are the people behind the Journal of Neuroscience research report:
Title: Inhibition of Prolyl Oligopeptidase Restores Spontaneous Motor Behavior in the α-Synuclein Virus Vector-Based Parkinson’s Disease Mouse Model by Decreasing α-Synuclein Oligomeric Species in Mouse Brain.
Authors: Svarcbahs R, Julku UH, Myöhänen TT.
Journal: J Neurosci. 2016 Dec 7;36(49):12485-12497.
Previously Timo and co. have demonstrated that PREP inhibitors can reduce the levels of alpha synuclein in a genetically engineered mouse that produces very higher levels of alpha synuclein (click here to read that report).
In the current study, they modelled Parkinson’s disease in mice using viruses that cause the production of high levels of alpha synuclein in the dopamine neurons (that are affected by Parkinson’s disease). This over-production of alpha synuclein causes problems for the dopamine neurons and some of those cells die off, in effect modelling what is happening in the brains of people with Parkinson’s disease.
Using a PREP inhibitor (KYP-2047, which is crosses the blood–brain barrier), the researchers were able to rescue the behavioural impairment caused by the viral over-production of alpha synuclein. In addition, the administration of the PREP inhibitor reduced the levels of certain types of alpha synuclein in the brain.
The researchers also saw a mild neuroprotective effect with less dopamine neurons dying (perhaps if the study had continued for longer they might have seen a larger difference) and less dopamine dysfunction in the animals that received the PREP inhibitor, suggesting that treatment with the PREP inhibitor protected the dopamine neurons and restored their normal functions.
The critical aspect of this study was that the PREP inhibitor treatment was only given to the animals after the behavioural problems started, and it was still able to provide positive benefits to them. The researchers concluded that these results suggest that PREP inhibitors should be further investigated for Parkinson’s disease.
What does it all mean?
We have had a spate of promising therapies for Parkinson’s disease fail over the last 10-20 years:
- Tocopherol (Parkinson Study Group, 1993)
- Immunophilin (Gold & Nut, 2002)
- Omigapil (TCH346; Olanow et al. 2006)
- CEP1347 (Parkinson Study Group PRECEPT Investigators, 2007)
- Pramipexole (Schapira et al, 2013)
- coenzyme Q10 (Parkinson Study Group QE3 Investigators et al, 2014)
- Cogane (Phytopharm)
- AAV-Neurturin (Ceregene)
Just to name a few…
We desperately need some new and novel targets to help attack this disease, and PREP inhibitors represent a completely new approach. Yes, they are going after alpha synuclein (and the jury is still out as to whether alpha synuclein is a causal agent in the disease), but they are certainly taking a different route.
While the alpha synuclein vaccines and antibodies currently being tested in clinic trials are removing free floating alpha synuclein, PREP inhibitors are stopping alpha synclein from actually aggregating. This is exactly the kind of new approach we are looking for.
Whether PREP inhibitors reducing alpha synuclein aggregation is functionally a good thing for Parkinson’s disease requires further testing. For example, if alpha synuclein is playing an antimicrobial function by aggregating around bacteria/viruses, inhibiting that aggregation might not be a good thing – it might leave us more vulnerable to illness.
But the good news here is that PREP inhibitors represent a new direction for us to explore in the treatment of Parkinson’s disease, and if blocking alpha synuclein aggregation does slow/halt the disease then PREP will definitely be worthy of further investigation.
EDITORIAL NOTE: Full disclosure here, the author of this blog is neither collaborating nor familiar with Dr Timo Myohanen. We just think his research is pretty cool and look forward to seeing where this line of investigation will ultimately lead.
And yes, we’re writing nice things about him in the hope that he won’t mind us borrowing some of the schematics and images from his lab website to better explain what PREP is.
It is very closely associated with Parkinson’s disease, given that people with genetic mutations in the alpha synuclein gene are more vulnerable to the condition, AND the protein is a key component in the disease-related circular aggregations (called ‘Lewy bodies’) in the brain. Recently researchers have identified proteins that may be involved with the transfer of Alpha Synuclein between cells – the method by which the disease is believed to be spreading. By blocking or removing these proteins, the researchers have been able to block the transfer of alpha synuclein.
In this post, we will review the research and discuss what this could mean for Parkinson’s disease.
At the recent annual Society for Neuroscience conference in sunny San Diego, Dr Ravindran Kumaran, a neuroscientist in the laboratory of Professor Mark Cookson (at the National Institute on Aging in Bethesda, Maryland) stood up and presented data about an interesting protein that few people in the audience had ever heard of.
Title: High-content siRNA screen identifies cellular modifiers of pre-formed alpha-synuclein fibril uptake
Authors: Kumarani R, Fernandez D, Werner-Allen JW, Buehler E, Bax A, Lai-Nag M, Cookson MR.
Source: Click here to see the full abstract
Dr Kumaran and his colleagues had systematically removed the function of each gene – one by one – in cell cultures of human cancer cells, and then measured the efficiency of the cells to absorb (or ‘take up’) the Parkinson’s related protein, alpha synuclein. An absolutely laborious task (remember there are over 20,000+ genes), but when they turned off a gene called TM9SF2, something amazing happened:
The cells absorbed 75% less of the free floating alpha synuclein than normal health cells.
This caused a bit of excitement in the Parkinson’s research community. Here was a potential method of blocking the spreading of alpha synuclein.
The funny thing is: few people had ever heard of TM9SF2, and yet Dr Kumaran then showed that TM9SF2 is in the top 3% of all proteins present in the brain. In fact, the highest concentrations of TM9SF2 are in the substantia nigra and other brain regions that are most affected by Parkinson’s disease.
So you can hopefully understand why some people in the Parkinson’s research community thought that this was a wee bit exciting.
Plus, this data presentation came on the back of another study that was published in September which presented another protein (called Lag3) that exhibited a similar ability to reduce the absorption of alpha synuclein:
Title: Pathological α-synuclein transmission initiated by binding lymphocyte-activation gene 3.
Authors: Mao X, Ou MT, Karuppagounder SS, Kam TI, Yin X, Xiong Y, Ge P, Umanah GE, Brahmachari S, Shin JH, Kang HC, Zhang J, Xu J, Chen R, Park H, Andrabi SA, Kang SU, Gonçalves RA, Liang Y, Zhang S, Qi C, Lam S, Keiler JA, Tyson J, Kim D, Panicker N, Yun SP, Workman CJ, Vignali DA, Dawson VL, Ko HS, Dawson TM.
Journal: Science. 2016 Sep 30;353(6307).
In this study, the researchers conducted a screen of 352 proteins that sit on the membrane of cells. They were measuring the level of alpha synuclein binding. They identified three interesting candidates for further investigation, include lymphocyte-activation gene 3 (LAG3), neurexin 1β, and amyloid β precursor-like protein 1 (APLP1).
When the researchers compared the three, they found that by removing LAG3 less alpha synuclein was taken into the cell (by endocytosis) than the other two proteins. In addition, when they increased the amount of LAG3 that a cell produces, they observed a similar increase in the amount of alpha synuclein absorbed by cells.
Next the researchers investigated the transmission of alpha synuclein between brain cells in both normal cells and cells that had no LAG3, and they found not only that LAG3 is required for the transmission, but the absence of LAG3 reduces the damage caused by the transmission.
Finally the researchers used small proteins (antibodies) to bind to and block LAG3, and they observed less transmission and damage caused by alpha synuclein. In their conclusions, the authors pointed out that LAG3 is not the only protein involved with the transmission of alpha synclein – there will be others – but it represents a potential future target for therapeutic intervention in Parkinson’s disease.
So what does this mean?
If the theory of alpha synuclein – that this protein is passed between cells, causing the spread of the disease – is correct, then any agent that can block that transmission should slow down or halt Parkinson’s disease. We have previously talked about vacines and antibodies against alpha synuclein being tested in the clinic (Click here, here and here for more on this), but blocking TM9SF2 and LAG3 represent a new method of preventing the transmission of alpha synuclein. This is very exciting. The more angles of attack that we have for designing a treatment the better our options.
Schematic of how LAG3 may be working. Source: Science
We will be watching the field very closely and will keep you posted as new information comes to hand.
The banner for today’s post is sourced from Keepcalm-o-matic