Proteins synthesized in a cell have a specific structure and function. When the function of the protein has been carried out, the protein is degraded by different mechanisms in the cell. Misfolded and unfolded proteins are also degraded by these mechanisms. But a failure in these mechanisms in neurons can cause misfolded proteins to accumulate. When these misfolded proteins aggregate beyond a certain limit, they can form inclusion bodies — something like multiple knots in a wire — and can cause neurodegeneration.