Neurodegenerative terms

ß-Amyloid: ß-Amyloid protein causes problems only when it is converted from its normal soluble form to insoluble ß-pleated sheets, which accumulate into neurotoxic amyloid plaques. In its healthy role it is probably involved in stabilising cell walls.

Prions: These are proteins produced by the prion gene and probably have a role in maintaining the electrical activity of cells. In Creutzfeldt-Jakob disease, the normal soluble form changes its configuration by folding up differently, allowing it to form insoluble ß -pleated sheet structures. The protein forms prion plaques that are neurotoxic. The pathological changes are transmissible.

*-Synuclein: This protein is found in Parkinson's disease and dementia with Lewy bodies. Its role in the normal state is unclear. In pathological states this protein forms intraneuronal inclusions (Lewy bodies).

Tau: This protein is found in the microtubules of nerve cells, and its role is to help stabilise them. The role of microtubules is to transport cellular components. In Alzheimer's disease, tau protein becomes hyperphosphorylated and then accumulates into neurofibrillary tangles that disrupt the microtubules. In frontal lobe dementias the balance of different forms of tau protein change, interfering with transportation in the cells.

Parkin: A second protein found in Lewy bodies and implicated in Parkinson's disease.

Ubiquitin: Ubiquitin is associated with proteins that are about to break down. Their usual function is probably to protect proteins. In many dementias an accumulation of ubiquitinated proteins is found--for example, in Lewy bodies.

Glutamine repeats: These are additional repeats of the amino acid glutamine, which when joined to proteins, increase the risk of soluble proteins folding into insoluble ß-pleated sheets. They are commonly found on huntingtin, the abnormal protein found in Huntingdon's disease.

Neuroserpinopathies: Neuroserpin is a protein that is precipitated out to form insoluble inclusions in nerve cells, eventually causing cell death. Familial encephalopathies with neuroserpin inclusion bodies are rare but have been identified in a small number of
families.

Superoxide dismutase 1: This is a natural human antioxidant enzyme that clears free radicals from the brain, maintaining the health of cell membranes.

Abi Berger, BMJ,


studentBMJ 2002;10:259-302 August ISSN 0966-6494