Nanoinjection as a tool to study alpha-synuclein toxicity inside neurons.

Intraneuronal inclusions known as Lewy bodies are a hallmark of Parkinson's disease. Amyloid fibrils formed by the misfolding of alpha-synuclein are the principal component of Lewy Bodies. However, the role of these fibrils and their oligomeric assembly intermediates in neuronal death is poorly understood.

This is because alpha-synuclein misfolds into amyloid fibrils in the cytoplasm, whereas experimental studies have typically involved adding fibrils and oligomers to the cell culture medium. Although this enables biophysical characterisation of the fibrils and oligomers before addition to the cells, their access to the cytoplasm is limited.

This project will use a single molecule nanoinjection platform to deliver alpha-synuclein fibrils and oligomers into the cytoplasm of neurons. Nanoinjection uses quartz needles (50nm pore diameter), known as nanopipettes, to deliver molecules into cells. The nanopipettes incorporate electrodes and application of a voltage drives the transport of molecules through the pore.

When a protein passes through the nanopipette's pore there is a corresponding disruption in the ion flow, thus the number of proteins delivered into a cell can be quantified. Thus, this project will not only determine whether a-synuclein fibrils or oligomers are toxic in the cytoplasm, but for the first time it will quantify the number of each required to kill a neuron.

Fibrils and oligomers will be made from recombinant a-synuclein, characterised using an array of biophysical techniques, and nanoinjected into neuronal cell lines and primary neurons. To inject cells the nanopipette will be used as a probe for a scanning ion conductance microscope, which will generate a topographical map of the target cell. This information is used to insert the nanopipette into the cell at a pre-defined depth and location.

Application of a voltage will drive the delivery of the fibrils or oligomers into the cell. By monitoring the corresponding disruptions in ion flow, a defined number of oligomers or fibrils will be delivered. The cellular effects of the nanoinjected fibrils and oligomers on cell stress and viability will then be analysed using microscopy-based assays.