Synphilin-1 is a cytoplasmic protein that is enriched in the neurophil of normal human brain. Although the exact function of synphilin-1 is unknown, it may possibly have a role as a cytoskeletal protein based on the presence of ankyrin-like repeats and an ATP, GTP-binding domain. It has been shown to be novel is its ability to associate in vivo with a-synuclein to form cytoplasmic eosinophilic inclusions. Additionally, it has been observed to be present in Lewy bodies of Parkinson disease, which are composed of a-synuclein. Because synphilin-1 is not found in protein aggregates of Alzheimer’s disease, it appears to be specific for a-synuclein-containing lesions. Synphilin-1 may facilitate the aggregation of a-synuclein into Lewy bodies.