Autophagy and neurodegeneration.

The proteasome and lysosome are sophisticated apparatuses capable of shredding unnecessary proteins in eukaryotic cells. The proteasome and its partner ubiquitin (which functions as a destination signal for proteolysis) play crucial roles in selective breakdown of not only short-lived regulatory proteins but also abnormal proteins that need to be rapidly eliminated from the cells. It is generally accepted that deficits of the proteasome-ubiquitin system are associated with various neurodegenerative diseases, since ubiquitin-positive inclusions frequently appear in neurons of patients and mice models of neurodegenerative diseases. However, investigators working in the field of neuronal diseases have focused their attention in recent years on autophagy (Greek for "the eating of oneself") following the recent discovery that ablation of autophagy leads to accumulation of ubiquitin-positive inclusions, which are the pathological hallmark of neurodegenerative diseases. Here we discuss the consequences of autophagy deficiency in neurons.