Alzheimer’s disease is a neurodegenerative disease that is particularly common amongst the elderly. It accounts for about 65% of all cases of dementia, and affects about 6% of people over 65, rising to 50% of people over 85. As the number of elderly people rises, the incidence of Alzheimer’s is expected to increase, quadrupling by 2050. Alzheimer’s leads to memory loss and behavioural change. The cost to society is enormous, with the major burden falling on family members. There is currently no cure. The cause of the disease is generally thought to be a small peptide called Aβ, which is cleaved from a much larger protein of unknown function. Aβ is 40-43 residues long. In solution, it forms fibrils, which aggregate into plaques. Such plaques form the primary diagnosis of Alzheimer’s in post-mortems, but it is generally agreed that the plaques themselves are not the toxic species, which is some earlier stage of Aβ aggregation, generally described as oligomers. However, there is no agreed mechanism for how Aβ oligomers cause the disease.
The project investigates the hypothesis that it is self-association of Aβ oligomers on membrane surfaces that leads to Alzheimer’s. We will use nuclear magnetic resonance (NMR) as the primary tool to investigate this hypothesis, supported by biochemical assays and electron microscopy. The research plan involves:
Expression of Aβ(1-40) in E. coli and purification, using an established methodology
Mutagenesis of Aβ (by polymerase chain reaction) to create single cysteines, which can be used to attach spin labels to Aβ
Measurement of paramagnetic relaxation enhancements (PREs) for wild-type Aβ in the presence of a small amount of spin-labelled Aβ, to establish the geometry of the protofibrils. This will be done using both solution-generated fibrils and membrane-generated fibrils, to investigate the hypothesis that the two fibrils have different morphology (parallel and antiparallel β-sheets, respectively). We will also compare Aβ alone, and Aβ in the presence of membranes, to see if the membranes induce specific types of association.
Measurement of PREs for wild-type Aβ in the presence of spin-labelled small unilamellar vesicles, to establish how it interacts with membrane surfaces. This will be done using 13C-labelled Aβ, to investigate the hypothesis that lysine and aromatic sidechains are important for the interaction
The effect of metal ions and pH on these associations will be investigated, because both of these could be important mediators of the association
Science Graduate School
As a PhD student in one of the science departments at the University of Sheffield, you’ll be part of the Science Graduate School – a community of postgraduate researchers working across biology, chemistry, physics, mathematics and psychology. You’ll get access to training opportunities designed to support your career development by helping you gain professional skills that are essential in all areas of science. You’ll be able to learn how to recognise good research and research behaviour, improve your communication abilities and experience technologies that are used in academia, industry and many related careers. Visit http://www.sheffield.ac.uk/sgs
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