Fundamental membrane interactions of copper generated oligomers, profibrils and amyloid fibres

Background:
There are a group of diseases including Mad-cow, and the closely related Alzheimer's disease, that are characterised by protein molecules which stick together to form oligomers and long fibrous accumulations, called amyloid plaques. These are found in the brains of patients (or animals in the case of mad-cow disease) suffering from these diseases. It is this sticking together of specific proteins, in particular amyloid beta peptide (Ab) in the case of Alzheimer's disease, which causes a cascade of events culminating in cell-death and dementia. The small peptide molecule, called Ab, is only 40 or 42 amino acids long but is responsible for the most common of all dementias. There is strong evidence that oligomers of Ab42 are the most toxic to cells. Ab-oligomers are specific bundles of between 5 to 100 Ab molecules bound together. The mechanism by which the oligomers cause cell toxicity is not clearly understood, however, one popular idea involves oligomers damaging the integrity of the celluar membrane wall.

Interestingly, essential minerals (metal ions such as copper) perturb the way and likelihood that Ab will stick together. Genetically modified mice that show symptoms similar to AD, show symptoms more rapidly when copper metabolism is affected. Furthermore, copper is found bound to the amyloid plaques in the brain.

Aims:
The broad aim of this proposal is to investigate the fundamental interaction of different Ab aggregates with cellular membrane walls. We will use essential minerals, in particular copper, which influence the type of Ab aggregate formed, specifically copper stabilises the more toxic oligomeric form of Ab42.

Significance:
Our preliminary observation suggests that well documented differences in the cellular toxicity between Ab40 and Ab42 may be due to the very different ways these two peptides form oligomers or fibres in the presence of copper. The ability of copper to almost exclusively generate oligomers of Ab42, rather than fibres, will facilitate studying this form of Ab42, which is otherwise typically unstable. The effect of copper stabilized Ab-oligomers on cell-membranes will facilitate the generation of the first 3D images of lipid membrane disruption by Ab-oligomers. Cellular studies of copper-Ab-oligomer toxicity will, for the first time, be related to measures of synaptic health in neurons.

Background: There are a range of diseases including Mad-cow and Alzheimer's disease (AD) whose etiology involves proteins that self-associate into oligomers and amyloid fibers. It is this misassembly, of amyloid beta peptide (Ab), in the case of Alzheimer's disease, which causes a cascade of events culminating in cell-death and dementia. Ab is a small peptide 40 or 42 amino acids long. There is strong evidence that oligomers of Ab42, but not Ab40, are the most cytotoxic. The mechanism by which the oligomers are toxic to cells is not clearly understood. One popular hypothesis involves oligomer and protofibre disruption of membrane integrity.

Interestingly metal ions alter Ab fibre formation. Animal models of AD implicate copper ion homeostasis in disease etiology. Furthermore Cu(II) is found bound to Ab within plaques. Cu(II) has a pico-molar affinity for Ab and is therefore capable of coordination Cu(II) at the synapse.

Aims: The broad aim of this proposal is to investigate the fundamental interaction of Ab oligomers, protofibres and fibres with lipid membranes. We will use metal ions, in particular Cu(II), which influence the distribution between these various forms, generating and stabilising the more cytotoxic oligomeric/protofibrillar form of Ab42.

Significance: Our preliminary observations suggest that differences in cytotoxicity between Ab40 and 42 may be due to the very different ways these two peptides misassemble in the presence of Cu(II) ions. The ability of Cu(II) to almost exclusively generate oligomers and protofibres of Ab42, rather than fibres, will facilitate studying this form of Ab42, which is otherwise quite transient in nature. The effect of Cu-Ab-oligomers on liposome models of the bi-layer will facilitate the first 3D structures of lipid membrane disruption by oligomers. Cellular studies of Cu-Ab-oligomer cytotoxicity will, for the first time, be related to measures of synaptic health in the presence of Cu-Ab42 oligomers.

Alzheimer's disease (AD) is the single most common cause of dementia. In the UK alone approximately 800,000 people suffer from Alzheimer's disease, 25 million world-wide. Alzheimer's is the fourth most common cause of death in the western world.

a) Public engagement and dissemination: A key aspect of the dissemination of fundamental research is the publication of original articles and reviews in highly cited journals. To add impact to our research we will endeavour to raise the profile and interest in our research with those involved in drug development, other academics and charities. We will engage the general public with discoveries arising from this project. In the past I have organised an international meeting hosted at Queen Mary, Metals in Neuro-degenerative Disease. Part of the meeting was open to the general public; the meeting was discussed on BBC Radio 4 and had a Nobel Laureate speaking. Furthermore, I have written for a general interest magazine aimed at undergraduates and lay people interested in biochemistry. Queen Mary has a very active Press Office.

b)Pharmaceutical Industry: I would expect our research to have a major impact on the pharmaceutical industry world-wide. Currently pharmaceutical companies are investing heavily in research and development of therapeutics for AD. We will draw the attention of Pharmaceutical Industry to this emerging therapeutic target. Queen Mary has a dedicated research and innovations service through its Research Development and Support Office (RDSO). This department pursues knowledge transfer between academics and Industry and has a successful track record in the commercial exploitation of new research within the university.

c) Research Academics: Our research will also immediately benefit other academics, both those researching AD and also other misfolding diseases, such as TSE, Parkinson's and type II Diabetes. We will ensure dissemination of the knowledge gained from our research by presenting at multi-disciplinary conferences. We will continue to identify individual research groups and share our findings; as well as sending our publications to key colleagues in the field.

d) Charities: UK based charities associated with neurodegeneration, such as Alzheimer's Research UK, are very active. I have been involved in organising an international meeting hosted jointly by the Parkinson Society and the Bioinorganic Discussion Group.

e) Patients and Carers: Alzheimer's Disease currently affects 42% of the UK population through knowing a close friend or family member with the condition. Longer-term beneficiaries of our research will include the patients suffering from Alzheimer's disease, and their carers.

f) Economic beneficiaries: Cost for the treatment and care of dementia is currently £17 billion per year in the UK. It is predicted that this will reach almost £35 billion within 20 years. By researching into this area and collaborating with industry in the production of new therapeutics we can have a major impact.