A-synucelein

[Mister_X]

This protein really seems to look like the culprit:

http://www.nature.com/news/misfolded-protein-transmits-parkinson-s-from-cell-to-cell-1.11838

[turnip]

Thanks Mr X, it does look like it is the ongoing mechanism, if not the initial cause.
its a bit like the prions in CJD. very very interesting.