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.
Science conference. Source: JPL
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
Science conference. Source: JPL
This week over 40,000 neuroscientists from all over the world have gathered for the annual Society for Neuroscience conference in sunny San Diego. It is 5 days of non-stop presentations of scientific results.
One of the presentations made this year was delivered by Dr Russell Kern, executive vice president and chief scientific officer of International Stem Cell Corp (ISCO). It dealt with the controversial on-going stem cell clinical trial in Australia. In the presentation, Dr Kern outlined the study and gave an update on the first patient in the Phase 1 clinical trial, who was transplanted at the end of July. The second patient is scheduled be treated in the next three weeks. A total of 12 are expected to be treated.
During the three months following the first surgery, the attending physicians observed no signs of complications (which is a very good thing). Unfortunately, according to San Diego Union Tribute, Dr Kern is then said to have implied that ‘there are some indications of efficacy in relieving symptoms of the movement disorder’. In addition, Dr Kern suggested that ‘the patient’s handwriting has improved’.
Long time readers of this blog know that we have been extremely critical of this trial from the start (Click here and here to read them). We make no apologise for this. The pre-clinical data that has been presented thus far in no way justifies taking these particular cells to the clinic. We believe it irresponsible. And our opposition is supported by many other researchers in the Parkinson’s research field (Click here for an example).
It defies belief, however, that Dr Kern would suggest to a conference audience or a media outlet that a patient who is 3 months post surgery could be exhibiting functional improvements. It is widely acknowledged in the Parkinson’s disease research field that it takes 2-3 years for the cells (that are transplanted into the brain) to mature and become functional (click here for more on this). In addition, during their preclinical studies Dr Kern and his colleagues observed very little in the way of behavioural improvements 12 months after transplantation (when compared to control conditions), so how is it that they are seeing such rapid improvements in their first human subject?
If Dr Kern’s suggestions of functional improvements are based solely on the unblinded observations of the clinician and the patient, then sharing such information publicly is extremely inappropriate. Unprofessional at best, but potentially unethical. At the very least, any suggestions of functional recovery in cases like these should be supported by brain scans (indicating increases in dopamine activity) and blinded, unbiased investigator scoring. Otherwise any reported outcomes could simply be due to the placebo effect (as the patient knows that he has been transplanted), and thus not valid for a Parkinson’s community desperate to see positive results in a potential therapy.
We also have concerns regarding the financial feasibility of the current study. Shares in ISCO have fallen from their giddy highs of $2.50 a share back in 2010 to a recent all-time low of just $0.055 (valuing the company at less than $6 million). According to their most recent financial statement, the company is burning $343,000 per month (for the year ended December 31, 2015), and the company ended 2015 with a cash position of just over $530,000. They partly resolved this problem in March of this year by issuing more shares (Source), but one does worry that this kind of activity can not be maintained indefinitely.
Here at the SoPD, we are very keen for cell transplantation to become a viable treatment option for people with Parkinson’s disease in the very near future. But the approach must be rigorously tried and tested, and presented to the highest standards before it can be considered feasible. As we have said before, the standards surrounding this particular trial (demonstrated by inappropriate disclosures of information during an ongoing clinical trial) are lacking.
FULL DISCLOSURE – The author of this blog is associated with research groups conducting the current Transeuro transplantation trials and the proposed G-Force embryonic stem cell trials planned for 2018. He has endeavoured to present an unbiased coverage of the news surrounding this current clinical trial, but when unacceptable statements are being made to media outlets, well, he is human and it is difficult to remain unbiased. He shares the concerns of the Parkinson’s scientific community that the research supporting the current Australian trial is lacking in its thoroughness, and will potentially jeopardise future work in this area.
It is important for all readers of this post to appreciate that cell transplantation for Parkinson’s disease is still experimental. Anyone declaring otherwise (or selling a procedure based on this approach) should not be trusted. While we appreciate the desperate desire of the Parkinson’s community to treat the disease ‘by any means possible’, bad or poor outcomes at the clinical trial stage for this technology could have serious consequences for the individuals receiving the procedure and negative ramifications for all future research in the stem cell transplantation area.