Ca2+ signalling in neurodegeneration and Alzheimer’s disease

Human variants of the ryanodine receptor, the main intracellular calcium ion channel, could be responsible for Alzheimer’s disease. Caenorhabditis elegans provides a powerful genetic system for laboratory study and has a short life span making this species ideal for investigation of this hypothesis.

Full description
Dramatic changes in cytosolic calcium ion concentrations are central to neural excitation. However, intracellular calcium ion levels also have other crucial regulatory roles, vital for the long-term health and function of nerve cells. During nerve cell excitation, the ryanodine receptor is the key channel for controlled release of calcium ions from the principal source, the endoplasmic reticulum. Many variants of the ryanodine receptor present in the human population retain calcium channel function but with modified opening properties which alter cytosolic calcium ion levels. Subtly altered calcium ion concentrations are likely to have negative consequences for nerve cells over time and there is some evidence of a link between ryanodine receptor function and Alzheimer’s disease. Given the lack of success in clinical drug trials aimed at treating this condition, so far, research on alternative explanations for the root cause of Alzheimer’s disease, such as the calcium hypothesis, need to be pursued.

Such a difficult subject to research demands a good experimental model. Caenorhabditis elegans provides a powerful genetic system for laboratory study with a short life span that makes this animal ideal for investigation of age-related conditions like Alzheimer’s disease. Although a nematode may appear only distantly related to us, the remarkable level of conservation between animals at the cell biological and molecular genetic levels means C. elegans is very much relevant.

Through the proposed project, the potential for subtle calcium ion dyshomeostasis, arising from aberrant ryanodine receptor function, to contribute to age-related neuronal degeneration, such as associated with Alzheimer’s Disease, will be assessed. The consequences of minor ryanodine receptor dysfunction, generated through CRISPR-Cas9 genome editing, will be determined with respect to neural function, nerve cell integrity, and amyloid aggregation. Neural function will be assessed with respect to memory and sensory activity. Neural degeneration and synaptic strength will be examined morphologically in GFP-labelled cells and by electron microscopy. Expression of amyloid-beta peptide in C. elegans will allow assessment of consequences for amyloid aggregation. Findings could illuminate mechanisms underlying Alzheimer’s Disease aetiology, could provide further avenues for investigation of the causes of neural degeneration, and could deliver novel strategies for treatment development.