̽��ֱ�� of Cambridge - Gabriele Kaminski-Schierle

Slow-moving shell of water can make Parkinson’s proteins ‘stickier’

sc604 — Tue, 15 Nov 2022 14:32:31 +0000

When attempting to discover potential treatments for protein misfolding diseases, researchers have primarily focused on the structure of the proteins themselves. However, researchers led by the ̽��ֱ�� of Cambridge have shown that a thin shell of water is key to whether a protein begins to clump together, or aggregate, forming the toxic clusters which eventually kill brain cells.

Using a technique known as Terahertz spectroscopy, the researchers have shown that the movement of the water-based shell surrounding a protein can determine whether that protein aggregates or not. When the shell moves slowly, proteins are more likely to aggregate, and when the shell moves quickly, proteins are less likely to aggregate. ̽��ֱ��rate of movement of the shell is altered in the presence of certain ions, such as salt molecules, which are commonly used in the buffer solutions used to test new drug candidates.

̽��ֱ��significance of the water shell, known as the hydration or solvation shell, in the folding and function of proteins has been strongly disputed in the past. This is the first time the solvation shell has been shown to play a key role in protein misfolding and aggregation, which could have profound implications in the search for treatments. ̽��ֱ��results are reported in the journal Angewandte Chemie International.

When developing potential treatments for protein misfolding diseases such as Parkinson’s and Alzheimer’s disease, researchers have been studying compounds which can prevent the aggregation of key proteins: alpha-synuclein for Parkinson’s disease or amyloid-beta for Alzheimer’s disease. To date however, there are no effective treatments for either condition, which affect millions worldwide.

“It’s the amino acids that determine the final structure of a protein, but when it comes to aggregation, the role of the solvation shell, which sits on the outside of a protein, has been overlooked until now,” said Professor Gabriele Kaminski Schierle from Cambridge’s Department of Chemical Engineering and Biotechnology, who led the research. “We wanted to know whether this water shell plays a role in protein behaviour – it’s been a question in the field for a while, but no one has been able to prove it.”

̽��ֱ��solvation shell slides around on the surface of the protein, acting like a lubricant. “We wondered whether, if the movement of water molecules was slower in the solvation shell of a protein, it could slow the movement of the protein itself,” said Dr Amberley Stephens, the paper’s first author.

To test the role of the solvation shell in the aggregation of proteins, the researchers used alpha-synuclein, the key protein implicated in Parkinson’s disease. Using Teraheartz spectroscopy, a powerful technique to study the behaviour of water molecules, they were able to observe the movement of the water molecules that surround the alpha-synuclein protein.

They then added two different salts in solution to the proteins: sodium chloride (NaCl), or regular table salt, and cesium iodide (CsI). ̽��ֱ��ions in the sodium chloride – Na+ and Cl- – bind strongly to the hydrogen and oxygen ions in water, while the ions in the cesium iodide make much weaker bonds.

̽��ֱ��researchers found that when the sodium chloride was added, the strong hydrogen bonds caused the movement of the water molecules in the solvation shell to slow down. This resulted in slower movement of the alpha-synuclein, and the aggregation rate increased. Conversely, when the cesium iodide was added, the water molecules sped up, and the aggregation rate decreased.

“In essence, when the water shell slows down, the proteins have more time to interact with each other, so they’re more likely to aggregate,” said Kaminski Schierle. “And on the flip side, when the solvation shell moves more quickly, the proteins become harder to catch, so they’re less likely to aggregate.”

“When researchers are screening for an aggregation inhibitor for Parkinson’s disease, they will usually use a buffer composition, but there’s been very little thought on how that buffer is interacting with the protein itself,” said Stephens. “Our results show that you need to understand the composition of the solvent inside the cell in order to mimic the conditions you have in the brain and ultimately end up with an inhibitor that works.”

“It’s so important to look at the whole picture, and that hasn’t been happening,” said Kaminski Schierle. “To effectively test whether a drug candidate will work in a patient, you need to mimic cellular conditions, which means you need to take everything into consideration, like salts and pH levels. ̽��ֱ��failure to look at the whole cellular environment has been limiting the field, which may be why we haven’t yet got an effective treatment for Parkinson’s disease.”

̽��ֱ��research was supported in part by Wellcome, Alzheimer’s Research UK, the Michael J Fox Foundation, and the Medical Research Council (MRC), part of UK Research and Innovation (UKRI). Gabriele Kaminski Schierle is a Fellow of Robinson College, Cambridge.

Reference:
Amberley D Stephens et al. ‘Decreased Water Mobility Contributes to Increased α-Synuclein Aggregation.’ Angewandte Chemie International (2022). DOI: 10.1002/anie.202212063

Water – which makes up the majority of every cell in the body – plays a key role in how proteins, including those associated with Parkinson’s disease, fold, misfold, or clump together, according to a new study.

̽��ֱ��failure to look at the whole cellular environment has been limiting the field, which may be why we haven’t yet got an effective treatment for Parkinson’s disease

Gabriele Kaminski Schierle

Sherbrooke Connectivity Imaging Lab via Getty

Corpus callosum, left-right connections, in a Parkinson's brain

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Alzheimer’s disease causes cells to overheat and ‘fry like eggs’

sc604 — Tue, 31 May 2022 06:00:00 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, used sensors small and sensitive enough to detect temperature changes inside individual cells, and found that as amyloid-beta misfolds and clumps together, it causes cells to overheat.

In an experiment using human cell lines, the researchers found the heat released by amyloid-beta aggregation could potentially cause other, healthy amyloid-beta to aggregate, causing more and more aggregates to form.

In the same series of experiments, the researchers also showed that amyloid-beta aggregation can be stopped, and the cell temperature lowered, with the addition of a drug compound. ̽��ֱ��experiments also suggest that the compound has potential as a therapeutic for Alzheimer’s disease, although extensive tests and clinical trials would first be required.

̽��ֱ��researchers say their assay could be used as a diagnostic tool for Alzheimer’s disease, or to screen potential drug candidates. ̽��ֱ��results are reported in the Journal of the American Chemical Society.

Alzheimer’s disease affects an estimated 44 million people worldwide, and there are currently no effective diagnostics or treatments. In Alzheimer’s disease, amyloid-beta and another protein called tau build up into tangles and plaques – known collectively as aggregates – causing brain cells to die and the brain to shrink. This results in memory loss, personality changes and difficulty carrying out daily functions.

It is a difficult disease to study, since it develops over decades, and a definitive diagnosis can only be given after examining samples of brain tissue after death. It is still not known what kind of biochemical changes inside a cell lead to amyloid-beta aggregation.

In Professor Gabriele Kaminski Schierle’s research group at Cambridge’s Department of Chemical Engineering and Biotechnology, they have been investigating the possible link between temperature and amyloid-beta aggregation in human cells.

̽��ֱ��field of studying temperature changes inside a cell is known as intracellular thermogenesis. It is a new and challenging field: scientists have developed sensors with which temperature changes can be measured, however, no one has ever tried to use these sensors to study conditions such as Alzheimer’s disease.

“Thermogenesis has been associated with cellular stress, which may promote further aggregation,” said Chyi Wei Chung, the study’s first author. “We believe that when there’s an imbalance in cells, like when the amyloid-beta concentration is slightly too high and it starts to accumulate, cellular temperatures increase.”

“Overheating a cell is like frying an egg – as it heats up, the proteins start to clump together and become non-functional,” said Kaminski Schierle, who led the research.

̽��ֱ��researchers used tiny temperature sensors called fluorescent polymeric thermometers (FTPs) to study the link between aggregation and temperature. They added amyloid-beta to human cell lines to kickstart the aggregation process and used a chemical called FCCP as a control, since it is known to induce an increase in temperature.

They found that as amyloid-beta started to form thread-like aggregates called fibrils, the average temperature of the cells started to rise. ̽��ֱ��increase in cellular temperature was significant compared to cells that did not have any amyloid-beta added.

“As the fibrils start elongating, they release energy in the form of heat,” said Kaminski Schierle. “Amyloid-beta aggregation requires quite a lot of energy to get going, but once the aggregation process starts, it speeds up and releases more heat, allowing more aggregates to form.”

“Once the aggregates have formed, they can exit the cell and be taken up by neighbouring cells, infecting healthy amyloid-beta in those cells,” said Chung. “No one has shown this link between temperature and aggregation in live cells before.”

Using a drug that inhibits amyloid-beta aggregation, the researchers were able to pinpoint the fibrils as the cause of thermogenesis. It had previously been unknown whether protein aggregation or potential damage to mitochondria – the ‘batteries’ that power cells – was responsible for this phenomenon.

̽��ֱ��researchers also found that the rise in cellular temperatures could be mitigated by treating them with an aggregation inhibitor, highlighting its potential as a therapeutic for Alzheimer’s disease.

̽��ֱ��laboratory experiments were complemented by computational modelling describing what might happen to amyloid-beta in an intracellular environment and why it might lead to an increase in intracellular temperatures. ̽��ֱ��researchers hope their work will motivate new studies incorporating different parameters of physiological relevance.

̽��ֱ��research was supported in part by Alzheimer’s Research UK, the Cambridge Trust, Wellcome, and the Medical Research Council, part of UK Research and Innovation (UKRI).

Reference:
Chyi Wei Chung et al. ‘Intracellular Aβ42 aggregation leads to cellular thermogenesis.’ Journal of the American Chemical Society (2022). DOI: 10.1021/jacs.2c03599

Researchers have shown that aggregation of amyloid-beta, one of two key proteins implicated in Alzheimer’s disease, causes cells to overheat and ‘fry like eggs.’

No one has shown this link between temperature and aggregation in live cells before

Chyi Wei Chung

Mammalian cell stained with fluorescence polymeric thermometers and falsely-coloured based on temperature gradients.

Yes

Calcium may play a role in the development of Parkinson’s disease

sc604 — Mon, 19 Feb 2018 10:00:00 +0000

̽��ֱ��international team, led by the ̽��ֱ�� of Cambridge, found that calcium can mediate the interaction between small membranous structures inside nerve endings, which are important for neuronal signalling in the brain, and alpha-synuclein, the protein associated with Parkinson’s disease. Excess levels of either calcium or alpha-synuclein may be what starts the chain reaction that leads to the death of brain cells.

̽��ֱ��findings, reported in the journal Nature Communications, represent another step towards understanding how and why people develop Parkinson’s. According to the charity Parkinson’s UK, one in every 350 adults in the UK – an estimated 145,000 in all – currently has the condition, but as yet it remains incurable.

Parkinson’s disease is one of a number of neurodegenerative diseases caused when naturally occurring proteins fold into the wrong shape and stick together with other proteins, eventually forming thin filament-like structures called amyloid fibrils. These amyloid deposits of aggregated alpha-synuclein, also known as Lewy bodies, are the sign of Parkinson’s disease.

Curiously, it hasn’t been clear until now what alpha-synuclein actually does in the cell: why it’s there and what it’s meant to do. It is implicated in various processes, such as the smooth flow of chemical signals in the brain and the movement of molecules in and out of nerve endings, but exactly how it behaves is unclear.

“Alpha-synuclein is a very small protein with very little structure, and it needs to interact with other proteins or structures in order to become functional, which has made it difficult to study,” said senior author Dr Gabriele Kaminski Schierle from Cambridge’s Department of Chemical Engineering and Biotechnology.

Thanks to super-resolution microscopy techniques, it is now possible to look inside cells to observe the behaviour of alpha-synuclein. To do so, Kaminski Schierle and her colleagues isolated synaptic vesicles, part of the nerve cells that store the neurotransmitters which send signals from one nerve cell to another.

In neurons, calcium plays a role in the release of neurotransmitters. ̽��ֱ��researchers observed that when calcium levels in the nerve cell increase, such as upon neuronal signalling, the alpha-synuclein binds to synaptic vesicles at multiple points causing the vesicles to come together. This may indicate that the normal role of alpha-synuclein is to help the chemical transmission of information across nerve cells.

“This is the first time we’ve seen that calcium influences the way alpha-synuclein interacts with synaptic vesicles,” said Dr Janin Lautenschläger, the paper’s first author. “We think that alpha-synuclein is almost like a calcium sensor. In the presence of calcium, it changes its structure and how it interacts with its environment, which is likely very important for its normal function.”

“There is a fine balance of calcium and alpha-synuclein in the cell, and when there is too much of one or the other, the balance is tipped and aggregation begins, leading to Parkinson’s disease,” said co-first author Dr Amberley Stephens.

̽��ֱ��imbalance can be caused by a genetic doubling of the amount of alpha-synuclein (gene duplication), by an age-related slowing of the breakdown of excess protein, by an increased level of calcium in neurons that are sensitive to Parkinson’s, or an associated lack of calcium buffering capacity in these neurons.

Understanding the role of alpha-synuclein in physiological or pathological processes may aid in the development of new treatments for Parkinson’s disease. One possibility is that drug candidates developed to block calcium, for use in heart disease for instance, might also have potential against Parkinson’s disease.

̽��ֱ��research was funded in part by the Wellcome Trust, the Medical Research Council, Alzheimer’s Research UK, and the Engineering and Physical Sciences Research Council.

Reference
Janin Lautenschläger, Amberley D. Stephens et al. ‘C-terminal calcium binding of Alpha-synuclein modulates synaptic vesicle interaction.’ Nature Communications (2018). DOI: 10.1038/s41467-018-03111-4

Researchers have found that excess levels of calcium in brain cells may lead to the formation of toxic clusters that are the hallmark of Parkinson’s disease.

This is the first time we’ve seen that calcium influences the way alpha-synuclein behaves.

Janin Lautenschlӓger

Janin Lautenschläger

Tyrosine hydroxylase positive neuron stained with a synaptic marker

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Researchers identify when Parkinson’s proteins become toxic to brain cells

sc604 — Mon, 14 Mar 2016 19:00:00 +0000

Researchers have used a non-invasive method of observing how the process leading to Parkinson’s disease takes place at the nanoscale, and identified the point in the process at which proteins in the brain become toxic, eventually leading to the death of brain cells.

̽��ֱ��results suggest that the same protein can either cause, or protect against, the toxic effects that lead to the death of brain cells, depending on the specific structural form it takes, and that toxic effects take hold when there is an imbalance of the level of protein in its natural form in a cell. ̽��ֱ��work could help unravel how and why people develop Parkinson’s, and aid in the search for potential treatments. ̽��ֱ��study is published in the journal Proceedings of the National Academy of Sciences.

Using super-resolution microscopy, researchers from the ̽��ֱ�� of Cambridge were able to observe the behaviour of different types of alpha-synuclein, a protein closely associated with Parkinson's disease, in order to find how it affects neurons, and at what point it becomes toxic.

Parkinson’s disease is the second-most common neurodegenerative disease worldwide (after Alzheimer’s disease). Close to 130,000 people in the UK, and more than seven million worldwide, have the disease. Symptoms include muscle tremors, stiffness and difficulty walking. Dementia is common in later stages of the disease.

“What hasn’t been clear is whether once alpha-synuclein fibrils have formed they are still toxic to the cell,” said Dr Dorothea Pinotsi of Cambridge’s Department of Chemical Engineering and Biotechnology, the paper’s first author.

Pinotsi and her colleagues from Cambridge’s Department of Chemical Engineering & Biotechnology and Department of Chemistry, and led by Dr Gabriele Kaminski Schierle, have used optical ‘super-resolution’ techniques to look into live neurons without damaging the tissue. “Now we can look at how proteins associated with neurodegenerative conditions grow over time, and how these proteins come together and are passed on to neighbouring cells,” said Pinotsi.

̽��ֱ��researchers used different forms of alpha-synuclein and observed their behaviour in neurons from rats. They were then able to correlate what they saw with the amount of toxicity that was present.

They found that when they added alpha-synuclein fibrils to the neurons, they interacted with alpha-synuclein protein that was already in the cell, and no toxic effects were present.

“It was believed that amyloid fibrils that attack the healthy protein in the cell would be toxic to the cell,” said Pinotsi. “But when we added a different, soluble form of alpha-synuclein, it didn’t interact with the protein that was already present in the neuron and interestingly this was where we saw toxic effects and cells began to die. So somehow, when the soluble protein was added, it created this toxic effect. ̽��ֱ��damage appears to be done before visible fibrils are even formed.”

̽��ֱ��researchers then observed that by adding the soluble form of alpha-synuclein together with amyloid fibrils, the toxic effect of the former could be overcome. It appeared that the amyloid fibrils acted like magnets for the soluble protein and mopped up the soluble protein pool, shielding against the associated toxic effects.

“These findings change the way we look at the disease, because the damage to the neuron can happen when there is simply extra soluble protein present in the cell – it’s the excess amount of this protein that appears to cause the toxic effects that lead to the death of brain cells,” said Pinotsi. Extra soluble protein can be caused by genetic factors or ageing, although there is some evidence that it could also be caused by trauma to the head.

̽��ֱ��research shows how important it is to fully understand the processes at work behind neurodegenerative diseases, so that the right step in the process can be targeted.

“With these optical super-resolution techniques, we can really see details we couldn’t see before, so we may be able to counteract this toxic effect at an early stage,” said Pinotsi.

̽��ֱ��research was funded by the Medical Research Council, the Engineering and Physical Sciences Research Council, and the Wellcome Trust.

Reference:
Dorothea Pinotsi et. al. ‘Nanoscopic insights into seeding mechanisms and toxicity of α-synuclein species in neurons.’ Proceedings of the National Academy of Sciences (2016). DOI: 10.1073/pnas.1516546113

Observation of the point at which proteins associated with Parkinson’s disease become toxic to brain cells could help identify how and why people develop the disease, and aid in the search for potential treatments.

̽��ֱ��damage appears to be done before visible fibrils are even formed.

Dorothea Pinotsi

Zoomed-in super-resolution (dSTORM) images of the fibrils inside the neuron formed of exogenous ‘’seed’’ fibrils (green) elongated by endogenous α-synuclein (red).

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes