Illustration of the US biologist Irwin Rose (1926-2015). Rose was awarded the 2004 Nobel Prize in Chemistry along with colleagues Avram Hershko and Aaron Ciechanover for their discovery of ubiquitin-mediated protein degradation. Ubiquitin is a regulatory protein found in all eukaryotic cells. When a protein is damaged or old it will be tagged by several ubiquitin molecules, flagging it for degradation. Disruption of the ubiquitin pathway has been implicated in a number of neurodegenerative diseases, including Alzheimers disease and Parkinsons disease, and cancers.