Role of Transthyretin in Familial Amyloidotic Polyneuropathy
Familial amyloidotic polyneuropathy (FAP) is associated with the misfolding and deposition of the thyroid hormone transport protein transthyretin (TTR). Human TTR is encoded by a single copy gene on the long arm of chromosome 18. Native TTR is a tetramer comprising four identical subunits each of which contains 127 amino acid residues and has a molecular weight of approximately 14 kDa. In FAP, the initial symptom is usually a sensory peripheral neuropathy in the lower limbs, with pain and temperature sensation being the most severely affected, followed by motor impairments later in the course of the disease, causing wasting and weakness. Proteinaceous deposits formed from TTR are found around nerve fibres in FAP. The V30M TTR was first identified as a common underlying genetic variant of FAP. However since then, a large number of mutations have been detected in TTR; many of which are associated with FAP which are evenly distributed over the TTR sequence.
The project builds upon a recent finding from our group (that TTR binds strongly to lipids in the plasma membrane and causes an increase in cell membrane calcium permeability through voltage-gated calcium channels (VGCCs). Our central hypothesis is that in FAP, the build-up of TTR amyloid in peripheral nerves destabilizes Ca2+ homeostasis and leads to neurodegeneration. Our aim is to examine the biochemical mechanisms involved in TTR-induced neuronal dysfunction and neurodegeneration.
This project uses a structural and functional approach to assess TTR neurotoxicity. We are examining the ability of characterised TTR species (monomers, dimers, native tetramers, oligomers and fibrils) to exert pathophysiologic effects in a variety of cell and explant culture systems. Structural studies will employ atomic force microscopy and dynamic light scattering for analysis of TTR aggregation. TTR binding to membranes will be studied using dual polarisation interferometry and surface plasmon resonance spectroscopy. We will examine biochemical and physiological changes in isolated cells (SH-SY5Y neuroblastoma cells, sympathetic neurons) and dorsal root ganglion explants in culture using the techniques of protein biochemistry, calcium indicator dye fluorescence, toxicity assays and electrophysiology.
- Professor David Small (Professorial Fellow)
- Dr Rob Gasperini (Research Fellow)
- Jenny Smith (Research Assistant)