Cellular interactions with amyloid fibrils: cytotoxic and protective mechanisms

Background
Initially identified in human diseases, amyloid fibrils also perform functional roles in mammalian cells and are being developed as nanomaterials. Understanding how cells respond to amyloid fibrils therefore represents a fundamental biological question. We have shown that amyloid fibrils exhibit length-dependent toxicity, with nanoscale amyloid fibrils being endocytosed into lysosomes, whereupon they inhibit the function of this organelle and disrupt trafficking in the endolysosomal pathway. We have also found that HSP70 can protect against amyloid fibril toxicity. These observations highlight that not only is access to intracellular compartments is important in amyloid toxicity, but also that cellular proteins may protect against the deleterious effects of amyloid.

Objectives
This project will identify cellular proteins in the endolysosomal pathway that bind to amyloid fibrils and determine the role of these interactions in amyloid toxicity.

Novelty
Our data demonstrating that due to their accessibility to extracellular environment, lysosomes represent a key site for amyloid toxicity is a novel finding. Identifying proteins that bind to fibrils will thus provide new insights into both amyloid toxicity and cellular protective responses.

Timeliness
This project aligns with recent genetic studies that have implicated the disruption of lysosome function and trafficking in the endolysosomal pathway as factors in amyloid disease. Moreover the identification of functional amyloids suggests that cells can also protect themselves against the deleterious effects of amyloid fibrils.

Experimental approach

Cells will be incubated with nanoscale fibrils produced from the model amyloid protein beta2-microglobulin; cellular proteins that bind to amyloid fibrils will be isolated in pull-downs and identified by mass spectrometry. The role of fibril-cellular protein interactions will then be examined, by testing whether binding to fibrils impairs the function of proteins in the endolysosomal pathway and/or if protein binding reduces fibril toxicity.