alpha-synuclein
noun
al·pha-sy·nu·clein
variants:
or α-synuclein \ ˌal-fə-si-ˈn(y)ü-klē-ən 
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Medical Definition of alpha-synuclein
: a protein that is found primarily in neurons and accumulates to form Lewy bodies in people affected with Parkinson's disease and some forms of dementia
… the pathogenesis of Parkinson's disease involves the abnormal folding, aggregation, and deposition of α-synuclein as key steps in mediating neuronal dysfunction and degeneration.— Mel B. Feany, The New England Journal of Medicine, 4 Nov. 2004
Note: Mutations in the gene encoding alpha-synuclein have been linked to a rare, inherited form of Parkinson's disease.