Immunohistochemical study of synphilin-1 in brains of patients with dementia with Lewy bodies - synphilin-1 is non-specifically implicated in the formation of different neuronal cytoskeletal inclusions.

Dementia with Lewy bodies brains were immunohistochemically investigated using anti-synphilin-1 antibodies. The alpha-synuclein-positive brainstem type and well-defined cortical type Lewy bodies (LB) were positive for synphilin-1, while ill-defined LB and LB-related neurites were negative, suggesting that synphilin-1 does not directly associate with alpha-synuclein. Synphilin-1-positive LB were double-positive for phosphorylated neurofilament. In addition, tau-positive neurofibrillary tangles (NFT) were positive for synphilin-1, while neuropil threads were negative. Immunoelectron microscopically, synphilin-1 was located on filamentous components in cortical type LB and on paired helical filaments in NFT. It is likely that synphilin-1 accumulates in the cell body according to the axonal transport blockage, and associates with abnormal cytoskeltons during the formation of LB or NFT, suggesting that synphilin-1 is non-specifically implicated in the formation of different neuronal cytoskeletal inclusions.