A tiny protein called alpha-synuclein has an important role in the damage to the nervous system associated with PD. In PD, alpha-synuclein aggregates, or clumps together, inside nerve cells. The aggregated alpha-synuclein appears to be toxic to nerve cells.
Aggregated alpha-synuclein is found in the substantia nigra and in other regions of the brain impacted by PD.
Aggregated alpha-synuclein can spread from nerve cell to nerve cell like a toxic agent. When taken up in this way, these aggregates induce the formation of increasingly more alpha-synuclein aggregates in nerve cells throughout the brain.
The abnormal aggregation of alpha-synuclein in nerve cells is critical to our understanding of PD. Doctors now use the term synucleinopathy, i.e. an age-related medical condition relating to alpha-synuclein clumping, to frame our understanding of PD.