Complex sentence: Prions are proteins that suffer post-translational modification (s) that change their shape so that they no longer perform their cellular functions and instead trigger equivalent modifications in normal proteins, thus creating a cascade of damage that eventually results in significant neurodegeneration.
Split into simpler sentences: Prions are proteins that suffer post-translational modification (s) that change their shape so that they can no longer perform their cellular functions. Worse, they are hypothesized to trigger equivalent modifications in normal proteins, thus creating a cascade of damage that eventually results in significant neurodegeneration.