The structural basis for amyloid formation by human apolipoproteins

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Amyloid formation is considered an abnormal state of protein aggregation that accompanies numerous medical conditions, notably Alzheimer disease, Parkinson's disease, the transmissible spongiform encephalopathies (e.g. scrapie, Creutzfeldt-Jakob disease) and metabolic diseases such as diabetes. These diseases involve a variety of normally non-fibrillar proteins with at least 20 human proteins identified as components of different types of amyloid. The current wide publicity given to bovine spongiform encephalopathy (BSE) disease and the potential impact on human health highlights the importance of developing strategies for treating these conditions. The prevalence of apolipoproteins in atherosclerotic amyloid deposits and senile plaques suggests a general propensity for human apolipoproteins to form pathogenic amyloid fibrils. Our recent observations that lipid-free human apolipoprotein C-II (apoC-II) forms ribbon-like fibrils in vitro provides an experimental system to explore this phenomenon. We propose to determine the structural requirements for the formation of amyloid fibrils human apoC-II and whether lipid-free human apolipoproteins form mixed-amyloid fibrils. Future strategies for treatment require better information on amyloid structure, the potential for mixed amyloid formation and the role of in vivo factors such as lipids and macromolecular crowding in regulating amyloid growth.